Cardiovascular disease develops mostly as a result of endothelial dysfunction. Endothelial regeneration may benefit greatly from the presence of circulating endothelial progenitor cells (cEPCs). Low or undetectable thyroid stimulating hormones and normal thyroid hormones are the hallmarks of subclinical thyrotoxicosis (SCT). Despite being linked to increased cardiovascular risk (CVR) and death, the course of treatment for SCT is unknown. Circulating angiogenic cells (CACs) and endothelial progenitor cells (cEPCs) have been found to be diminished in CVR-positive circumstances.

Significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing the effects of abnormalities in thyroid function in patients and risk of cardiovascular disease. In a new study published in Frontiers in Endocrinology, Newcastle University researchers Jason Phowira, Dr. Anuradha Doddaballapur and led by Dr. Jolanta Weaver together with Sherin Bakhashab at King Abdulaziz University investigated wether SCT was linked to abnormally high levels of cEPCs or CACs that would contribute to endothelial dysfunction and ultimately elevated CVR. The authors cultured CACs from peripheral blood mononuclear cells of SCT patients and cEPCs were quantified by flow cytometry and results was compared with controls with matched ages and sex volunteers. Moreover, the research team looked in depth at the molecular mechanisms involved by assessing CAC apoptosis and eNOS expression in response to high T3 concentrations, endothelial function, plasma asymmetric dimethylarginine levels, the in-vitro paracrine function of CACs, and plasma asymmetric dimethylarginine levels.

According to the authors, SCT is linked to a decreased cEPC count and less FMD. Due to the prevalence of SCT in this group of participants, they evaluated SCT subjects in the context of cardiovascular risk factors. It was not possible to grow pro-angiogenic cells (PACs) in-vitro from the patients they studied since they used middle-aged senior participants with CVD risk factors. In order to explore the paradigm of subclinical thyrotoxicosis, PAC cultures were established from healthy persons, while researchers solely looked at CACs and cEPCs from those patients. The authors found that compared to controls, CD34+ cells were dramatically decreased in SCT. After accounting for CVD risk, the SCT state uniquely predicted the decline in cEPCs, demonstrating that the SCT state can be categorised as having an elevated CVD risk. In comparison to controls, the number of CD34+VEGFR+2 cells was considerably lower in SCT group.

Jolanta Weaver and her colleagues for the first time demonstrated the expression of thyroid hormone receptors in PACs, indicating an important function for thyroid hormones in PACs. To simulate in vivo model of SCT, they used an in vitro model of T3 high concentration. They found that eNOS expression was decreased in PACs at higher T3 levels, indicating that greater tissue T3 levels have an impact on eNOS expression in PACs. Moreover, an increase in T3 concentration promoted PAC apoptosis, which may help to explain how cEPC levels are decreased. Their, in-vitro SCT model has also demonstrated that NO may as a role in both the mobilization of cEPC from the bone marrow and endothelial dysfunction. After accounting for age differences, their study found that FMD was considerably lower in SCT individuals (9 subjects in each group) than controls.

In conclusion, decreased cEPC count and FMD are linked to SCT, supporting higher CVR in SCT. Future trials on outcomes are necessary to see whether treating subclinical hyperactive state enhances cardiovascular outcomes. Furthermore, poor vascular health is evident in patients with SCT which is consistent with an elevated risk of cardiovascular disease. Randomized controlled interventional trials are recommended to determine whether the high risk can be reduced.

Tauopathies are neurodegenerative diseases characterized by the abnormal accumulation of tau protein in the brain. Tau is a microtubule-associated protein primarily involved in stabilizing microtubules in neuronal cells. Microtubules are essential components of the cell’s cytoskeleton, playing a critical role in nutrient transport, cell signaling, and neuronal plasticity. In healthy individuals, tau helps maintain the stability of these structures, but in tauopathies, tau proteins become abnormally phosphorylated and accumulate into insoluble aggregates known as neurofibrillary tangles leading to cell death and brain dysfunction. The tauopathies encompass a wide range of disorders, each with its own set of clinical features, though they share the common pathology of tau protein aggregation. These include Alzheimer’s disease (AD) which is the most common tauopathy, where tau pathology coexists with amyloid-beta plaque formation. Neurofibrillary tangles primarily accumulate in the hippocampus and cortical regions, leading to memory loss, cognitive decline, and behavioral changes. Another taupathy disease frontotemporal dementia which is characterized by degeneration in the frontal and temporal lobes of the brain, affecting behavior, language, and movement. Certain subtypes of FTD, such as Pick’s disease, are associated with tau protein accumulation. The precise mechanism by which tau pathology leads to neurodegeneration is not fully understood, but it is believed that the abnormal tau disrupts cellular functions by impairing microtubule stability, interfering with axonal transport, and promoting inflammation and cell death. Currently, there is no cure for tauopathies, and treatment focuses on managing symptoms. Research is ongoing to develop therapies that can reduce tau pathology or prevent tau aggregation. For instance, tau immunotherapies, which aim to clear aggregated tau or prevent its formation using antibodies, are under investigation. Other approaches include targeting tau phosphorylation, enhancing tau clearance mechanisms, and stabilizing microtubules. Understanding tauopathies is critical for developing effective treatments for these debilitating disorders. As research progresses, it is hoped that new insights into tau biology will lead to breakthroughs in preventing and treating these conditions. To address these challenges, a new study published in the Journal of Clinical Investigation and led by Professor Tara  Tracy from the Buck Institute for Research on Aging in California and conducted by Grant Kauwe, Kristeen  Pareja-Navarro, Lei Yao, Jackson  Chen, Ivy Wong, Rowan Saloner, Helen Cifuentes, Alissa L. Nana, Samah Shah, Yaqiao Li, David Le, Salvatore Spina, Lea Grinberg, William Seeley, Joel Kramer, Todd Sacktor, Birgit Schilling, Li Gan, and Kaitlin Casaletto, the authors investigated the impact of pathogenic tau on synaptic plasticity and memory in AD and related tauopathies, highlighting a potential therapeutic approach.

A novel focus of this research is on KIdney/BRAin (KIBRA), a postsynaptic protein linked to memory and AD risk. KIBRA levels are significantly reduced in AD brains, correlating with cognitive impairment and abnormal tau modifications. Intriguingly, elevated KIBRA levels in cerebrospinal fluid are associated with cognitive decline and tau pathology, suggesting its potential as a biomarker for synaptic dysfunction in tauopathy. The team introduced the concept of synaptic repair via the C-terminus of the KIBRA protein (CT-KIBRA), demonstrating its ability to restore synaptic plasticity and memory in mouse models of tauopathy without altering pathogenic tau levels or preventing tau-induced synapse loss. Mechanistically, CT-KIBRA enhances synaptic function through stabilization of protein kinase Mζ (PKMζ), crucial for maintaining LTP and memory despite tau-mediated pathology. This identifies KIBRA as not only a biomarker but also a foundation for synapse repair mechanisms to counteract cognitive impairment in tauopathy. Further investigations revealed associations between KIBRA levels in human brain and CSF with tau pathology and cognitive impairment, underscoring its relevance across different tauopathies. The study’s innovative approach using a truncated version of KIBRA (CT-KIBRA) to counteract synaptic plasticity and memory impairments in transgenic mouse models of tauopathy, without modifying tau pathology directly, provides a promising therapeutic strategy.

CT-KIBRA’s efficacy in reversing synaptic dysfunction and memory loss, despite the presence of tau pathology, suggests a mechanism that enhances synaptic resilience to tau toxicity. The stabilization of PKMζ by CT-KIBRA, facilitating the maintenance of synaptic plasticity and memory, underscores a targeted approach for cognitive restoration in tauopathies. The new work enhances our understanding of the molecular underpinnings of tau-induced cognitive decline and opens avenues for developing therapies aimed at synaptic repair and cognitive function restoration in neurodegenerative diseases marked by tau pathology. Moreover, the research provided critical insights into how pathological tau disrupts synaptic plasticity, a fundamental process underlying memory formation and learning. By establishing a link between pathogenic tau, the reduction of KIBRA protein levels in the brain, and synaptic dysfunction, the study deepens our understanding of the molecular mechanisms leading to cognitive impairments in tauopathies. Moreover, the discovery that changes in KIBRA levels in the cerebrospinal fluid correlate with cognitive impairment and pathological tau levels in disease highlights its potential as a biomarker for diagnosing and monitoring the progression of tauopathies. Furthermore, identifying KIBRA’s role in modulating synaptic signaling and strength positions it as a promising therapeutic target for restoring cognitive functions in neurodegenerative diseases. Furthermore, the study introduces a novel therapeutic approach using the CT-KIBRA to reverse synaptic dysfunction and memory loss in tauopathy models. This strategy focuses on enhancing synaptic resilience and function without directly altering tau pathology, suggesting a potential treatment pathway that could be complementary to therapies targeting tau and other pathological aggregates directly. By demonstrating that CT-KIBRA can restore synaptic plasticity and cognitive functions in mouse models through the stabilization of protein kinase Mζ (PKMζ), the research lays the groundwork for developing synapse repair mechanisms as a therapeutic avenue. This approach could benefit a wide range of neurodegenerative diseases characterized by synaptic dysfunction and cognitive decline. Additionally, the authors’ findings have implications beyond Alzheimer’s disease, encompassing a spectrum of tauopathies. The ability of CT-KIBRA to improve cognitive functions in models of tauopathy, regardless of the specific tau pathology, suggests a universal strategy that could be applied across different diseases marked by tau accumulation and synaptic impairment. Overall, the study by Professor Tara Tracy and her colleagues demonstrated a link between KIBRA, synaptic dysfunction, and cognitive decline in tauopathies, and proposed a novel and promising therapeutic strategy focused on synaptic repair. The potential to apply the authors’ findings across a range of neurodegenerative conditions will be a step forward in the search for effective treatments for these challenging diseases.

Tissue engineering scaffolds for bone regeneration provide a temporary, three-dimensional structure that supports osteoblast differentiation and formation of new bone tissue. The development and implementation of tissue engineering scaffolds for bone regeneration, despite their potential, face several challenges which researchers and clinicians try to overcome to advance scaffold-based approaches for bone regeneration.  For instance, finding materials that are biocompatible and do not provoke an adverse immune response remains a challenge. Moreover, matching a scaffold’s degradation rate with the rate of new bone formation is critical-if a scaffold degrades too quickly, it may not provide sufficient support for bone growth while too slow a rate of degradation can limit the integration of new bone tissue. Furthermore, methods are needed to actively induce resident stem cells to differentiate into bone-forming cells. Addressing these challenges requires extensive research and innovation in materials science, molecular biology, and engineering. A new study published in Acta Biomaterialia and conducted by Chunxi Ge, Yiming Li, Fashuai Wu, Peter Ma, and led by Professor Renny Franceschi from the University of Michigan School of Dentistry, describes a new approach for activating the osteoblast differentiation of skeletal progenitor cells involving stimulation of the two main collagen receptors in bone, discoidin domain receptor 2 (DDR2) and collagen-binding integrins, using receptor-specific triple-helical peptides. The selective activation of these receptors by their respective peptides, GVMGFO for DDRs and GFOGER for integrins, provided insight into the molecular mechanisms underlying bone formation and also suggested a novel strategy for the development of tissue engineering scaffolds aimed at enhancing bone repair and regeneration.

The team began by synthesizing two collagen mimetic triple-helical peptides; one containing the DDR2-binding sequence GVMGFO (termed GVM), and the other containing the integrin-binding sequence GFOGER (termed GER). To create a surface that mimics the extracellular matrix interactions with cells, the researchers coated tissue culture plates with these peptides or with type I collagen as a control. Cellular responses to peptides were assessed using a preosteoblast cell line (MC3T3-E1 cells), murine bone marrow stromal cells (BMSCs), and primary calvarial osteoblasts from Ddr2 ^flox/flox mice. The authors showed that the GVM peptide stimulated DDR2 phosphorylation at tyrosine 740 (Y740), a marker of DDR2 activation, without affecting integrin signaling while the GER peptide activated focal adhesion kinase (FAK) phosphorylation at tyrosine 397 (Y397), indicative of integrin activation, without influencing DDR2 phosphorylation. Remarkably, the combined application of GVM and GER peptides led to enhanced activation of both DDR2 and FAK/integrin pathways and significantly enhanced osteoblast differentiation. This synergistic effect was blocked in Ddr2-deficient cells, indicating DDR2’s essential role. Moreover, they used quantitative real-time PCR to measure the expression levels of osteoblast differentiation markers, including alkaline phosphatase, osteocalcin, and bone sialoprotein, revealing that peptide treatments modulate these critical markers. They also assessed the degree of mineralization which is a hallmark of osteoblast maturation using Alizarin Red staining. The combined peptides markedly enhanced mineral deposition compared to individual peptides or untreated controls.

According to the authors, the GVM and GER peptides selectively activated DDR2 and integrin pathways, respectively, with the GVM peptide notably stimulating osteoblast differentiation. However together, these peptides synergistically enhanced both DDR2 and integrin signaling, significantly boosting osteoblast differentiation beyond the effects observed with individual peptide treatments. Additionally, the cooperative effect on osteoblast differentiation was dependent on DDR2, which highlights its central role in mediating the synergistic enhancement of bone regeneration by these peptides.  The authors’ findings suggest a novel approach for bone regeneration by combining DDR and integrin-activating peptides to mimic signaling cues of the natural extracellular matrix, which potentially may lead to improved outcomes in bone repair and tissue engineering scaffolds. In conclusion, the study by Professor Renny Franceschi and colleagues is an important step towards understanding and harnessing the molecular mechanisms of bone regeneration. Their finding has profound implications for the development of biomaterials for bone repair. The design of tissue engineering scaffolds incorporating both DDR and integrin-activating peptides could mimic the complex extracellular matrix environment, providing the structural support and also biochemical cues for optimal cell function. These scaffolds could potentially accelerate bone healing, and offer new solutions for bone loss resulting from trauma, surgical resections, or pathological conditions. In a statement to Medicine Innovates, Professor Renny Franceschi said “By mimicking signals normally provided to bone cells from the collagenous extracellular niche, this study points to a new strategy for bone tissue engineering involving coupling collagen mimetic peptides to synthetic scaffolds.”

Bronchopulmonary dysplasia (BPD) is a critical lung pathology that primarily affects premature infants, particularly those who have been exposed to mechanical ventilation and oxygen therapy for extended periods. It causes disruption in lung development and increased risk for future respiratory problems. The pathophysiology of BPD involves inflammation and injury to the lung tissue, which leads to fibrosis, reduced alveolarization and impaired vascular growth. Traditional treatments for BPD focus on supportive care strategies to minimize lung injury and promote lung growth and administering medications to reduce inflammation. Despite advancements in trying to better understand the pathology of BPD, therapeutic interventions remain limited, which call for the need for novel and effective treatment strategies. A new comprehensive and expert opinion review published in the International Journal of Molecular Sciences and authored by Dr. Manuela Marega, Dr. Saverio Bellusci, Dr. Natalia El-Merhie and Dr. Cho-Ming Chao from the Justus Liebig University Giessen alongside Dr. Mira Y Gökyildirim from the University of Rostock and Dr. Valerie Orth from Witten/Herdecke University, the authors carefully analyzed all existing preclinical studies and clinical trials focusing on the use of mesenchymal stem cells (MSCs) and other stem/progenitor cells in  the treatment of BPD.

According to the authors, the etiology of BPD is multifactorial, encompassing pre- and postnatal factors that disrupt lung development and repair mechanisms. Preterm birth itself, by leading to an underdeveloped lung structure requiring mechanical ventilation and supplemental oxygen, sets the stage for hyperoxia-induced inflammation and subsequent abnormal lung development. The disease pathology is characterized by disrupted alveolarization, compromised microvasculature development, fibrosis, and cystic emphysema, driven by imbalances in signaling pathways. They examined existing treatments for BPD, including limited drug therapies like caffeine, vitamin A, and corticosteroids such as dexamethasone. Despite their usage, these treatments often offer limited therapeutic benefits and potential significant side effects, which highlights the need for better therapeutic strategies. This has necessitated the search for alternative therapies, with MSCs emerging as a promising therapeutic candidate due to their role in modulating immune responses and reducing inflammation.

A significant portion of the authors’ review focused on the therapeutic potential of MSCs. In recent years, the potential for using MSCs as a treatment for BPD has gained interest. The lung hosts various stem/progenitor cells, including basal cells, variant club cells, goblet cells, and alveolar progenitors, each playing a critical role in lung repair and regeneration. They discussed the anti-inflammatory effects of MSCs, their ability to secrete growth factors and cytokines, and their role in promoting tissue repair and regeneration. They emphasized on preclinical studies which indicated MSCs’ potential to contribute to lung injury repair. The mechanisms behind these effects are thought to include the reduction of inflammation, modulation of immune responses, and the promotion of tissue repair processes. Moreover, the review highlighted the importance of further understanding these cells’ biology, their interaction with cytokines and growth factors, and their potential therapeutic roles in treating BPD.

Additionally, the review also included an analysis of animal studies and clinical trials using stem cells or their secretome for BPD treatment. The mechanisms behind these effects are thought to include the reduction of inflammation, modulation of immune responses, and the promotion of tissue repair processes, however, more research is needed to fully understand these therapeutic mechanisms in greater detail. Moreover, there’s a critical need for developing standardized protocols for MSC therapy, including the optimization of cell preparation, dosage, administration timing, and long-term safety. Furthermore, significant knowledge gaps exist regarding the optimal use of MSCs in clinical settings, which necessitates more preclinical and clinical studies that could pave the way for MSC-based therapies in clinical settings. In conclusion, the authors’ expert review highlighted the potential of MSCs as a promising therapeutic option for BPD but also revealed the complexities and challenges that must be addressed first through further research and calls for a deeper understanding of stem cell behavior, the development of standardized therapeutic protocols, and a thorough evaluation of the long-term safety and efficacy of these interventions which ultimately will improve the quality of life for affected infants.

Liver disease treatment is witnessing a revolutionary shift with the advent of innovative therapies targeting cellular regeneration. Vascular Endothelial Growth Factor A (VEGF-A) plays a significant role in liver regeneration, a vital process for maintaining liver function after injury or surgery. VEGF-A is a key protein that primarily promotes angiogenesis, the formation of new blood vessels from pre-existing ones. Growth of new blood vessels ensures an adequate supply of oxygen and nutrients to the regenerating liver tissue. This is essential because the liver has a high metabolic demand, especially during the regeneration process. VEGF-A indirectly supports the proliferation of hepatocytes, the primary functional cells of the liver. By improving blood flow and providing necessary growth factors through enhanced vascular networks, it creates a conducive environment for hepatocyte growth. Liver regeneration involves a controlled inflammatory response. VEGF-A plays a role in modulating this response, which is essential for removing damaged cells and facilitating tissue repair. It also interacts synergistically with other growth factors and cytokines involved in liver regeneration, like Hepatocyte Growth Factor (HGF) and Transforming Growth Factor-beta (TGF-β). These interactions are complex and critical for coordinating the regeneration process. Moreover, VEGF-A directly stimulates the proliferation and survival of endothelial cells, which line the interior surface of blood vessels. This is a key aspect of angiogenesis and hence, liver regeneration. Understanding the role of VEGF-A in liver regeneration has significant clinical implications. It can lead to the development of therapeutic strategies for enhancing liver regeneration in patients with liver diseases or those who have undergone liver resection. In a new study published in Journal CellStemCell led by Professor Valerie Gouon-Evans from Boston Medical School explored a novel approach using Vascular Endothelial Growth Factor A (VEGFA) delivered through lipid nanoparticles (mRNA-LNP), a method that has shown promise in promoting biliary epithelial cell (BEC) to hepatocyte conversion in liver diseases.

The researchers embarked on a meticulous journey to unravel the potential of VEGFA mRNA-LNP in liver regeneration. Their approach involved a series of well-orchestrated experimental models, primarily focusing on mice and zebrafish. The methodology was robust, encompassing various liver injury models, including both acute and chronic conditions induced through specific diets and chemical agents. The application of VEGFA mRNA-LNP was carefully timed and executed, ensuring optimal delivery and efficacy. The study employed cutting-edge techniques like single-cell RNA sequencing and lineage tracing to precisely map the transformation of BECs into hepatocytes. This comprehensive methodological framework was pivotal in establishing a clear and detailed understanding of the cellular mechanisms at play.

The findings of this study mark a pivotal point in liver disease treatment. The ability of VEGFA mRNA-LNP to induce BEC-to-hepatocyte conversion opens a new frontier in regenerative medicine. This approach not only offers a potential alternative to liver transplantation but also sheds light on the intricate cellular mechanisms underlying liver regeneration. The implications of this discovery are vast, extending beyond liver diseases to potentially inform therapies for a range of other conditions where tissue regeneration is crucial. Reflecting on the journey of this research, we see a remarkable transition from theoretical concepts to empirical evidence. The past has been riddled with challenges in liver regeneration, primarily centered around the limited understanding of cellular dynamics and the absence of effective therapeutic agents. This study, however, has pivoted the field into a new era where molecular biology and nanotechnology converge to offer tangible solutions. The utilization of mRNA-LNP technology, especially in the wake of its success in COVID-19 vaccines, has proven to be a game-changer, offering a safe and efficient platform for delivering regenerative molecules like VEGFA.

In conclusion, the study on VEGFA mRNA-LNP as a facilitator of BEC-to-hepatocyte conversion represents a monumental step in liver disease therapy. It exemplifies the power of innovative molecular techniques in deciphering and manipulating biological pathways for therapeutic purposes. This research not only broadens our understanding of liver regeneration but also opens new avenues for treating a myriad of diseases where tissue repair and regeneration are critical. As we stand at the cusp of this new era in medicine, the promise held by such advancements is not just hopeful but transformative, heralding a future where regenerative therapies redefine healthcare and patient outcomes.

Adult stem cells play a pivotal role in maintaining tissue homeostasis and repair throughout an organism’s life. These remarkable cells represent a small but critical pool within adult tissues, responsible for generating mature progeny and ensuring the continuous renewal of vital structures. To accomplish this task effectively, adult stem cells have developed a unique strategy – reversible quiescence.

In a new study published in the peer-reviewed Journal Neuroscience, PhD candidate Laura Blasco-Chamarro and Professor Isabel Fariñas from the University of Valencia in Spain have shed light on the fascinating world of reversible quiescence in adult stem cells (aNSCs). This research explores the dynamic state of aNSCs and its crucial role in tissue regeneration and disease. The study discusses the complexities of aNSCs, their activation and quiescence, and their contribution to the maintenance of various tissues, emphasizing the importance of this knowledge for potential therapeutic applications.

Cellular quiescence, in the context of adult stem cells, refers to a reversible state where cells temporarily exit the cell cycle and stop dividing while retaining the ability to resume proliferation when necessary. Unlike other non-proliferative conditions such as postmitotic differentiation or cellular senescence, quiescence equips these cells with the capacity to reactivate and contribute to tissue regeneration.

Quiescence is not a universal trait of all adult stem cells; it varies depending on the tissue in which they are found. Some stem cells can exist in either a quiescent or an activated state, with the proportions of these states adapted to the tissue’s specific needs. For instance, the intestine and the epidermis, exposed to constant environmental challenges, contain rapidly dividing stem cells, while skeletal muscle stem cells remain quiescent until tissue injury necessitates their activation.

Recent advancements in single-cell transcriptomic analysis have unveiled the unique molecular signature of quiescent stem cells. These cells display lower metabolic activity, reduced translation rates, and downregulated genes associated with DNA replication, cell-cycle progression, proliferation, and mitochondrial function. Despite not actively dividing, quiescent stem cells maintain metabolic activity to conserve energy and resources, preparing to respond to activating cues when required. This specialized molecular signature results from the interplay of tissue-specific stem cell transcription factors and discernible epigenetic modifications, highlighting the complexity of transcriptional regulation.

Remarkably, the levels of RNA and proteins within quiescent stem cells can differ significantly, indicating the pivotal role of post-transcriptional mechanisms in orchestrating and controlling the dormant state. Processes like translation repression and protein degradation are crucial for preserving quiescence. Additionally, autophagy and lysosomal pathways contribute to proteostasis and support quiescent stem cell function.

Recent studies have uncovered a surprising level of heterogeneity within quiescent stem cell populations. In some cases, stem cells can exist in different depths of quiescence, transitioning between shallow and deep quiescent states in response to specific cues. This variability raises intriguing questions about the role of primed or alerted stem cells, which exhibit characteristics between quiescent and activated states, in different tissues.

The identification and isolation of quiescent stem cells have been challenging but are essential for advancing our understanding of these cells and their potential therapeutic applications. Recent efforts have employed fluorescence-activated cell sorting (FACS) and surface markers to isolate subsets of quiescent and activated stem cells. This technology, combined with deep RNA sequencing, has enabled researchers to distinguish between different depths of quiescence.

Culturing quiescent stem cells in vitro remains a significant challenge, but recent progress has been made in modeling their behavior. By treating stem cells with specific signaling pathways, such as the bone morphogenetic protein (BMP) pathway, researchers have induced quiescence-like states that closely resemble their in vivo counterparts. These models provide valuable insights into the regulation of quiescence in vitro.

The study also discusses the quiescence of neural stem cells (NSCs) in the adult brain, a population of long-lasting cells that sustain the generation of new neurons, astrocytes, and oligodendrocytes throughout an organism’s lifespan. The heterogeneity of NSCs within the neurogenic niche is highlighted, as well as their distinct responses to various cues.

Aging has been shown to affect NSCs in the brain, leading to a progressive reduction in neurogenic output. While the number of proliferative cells decreases with age, active NSCs exhibit efficient cell cycle re-entry and transient expansion before lineage progression. However, recent studies suggest that aging leads to an increased proportion of NSCs with a quiescence-related molecular signature, rendering them less responsive to activation signals. This shift towards deeper quiescence ultimately results in diminished neurogenesis in the elderly.

Furthermore, the role of quiescence in tumorigenesis is explored, particularly in the context of glioblastoma, a highly malignant brain tumor. Glioblastoma has been linked to subependymal NSCs in both rodents and humans, and glioma stem cells (GSCs) share similarities with NSCs. Understanding the molecular mechanisms that govern quiescence may provide insights into the initiation, progression, and resistance of glioblastoma, paving the way for innovative therapeutic approaches.

The study of reversible quiescence in adult stem cells represents a fascinating journey into the intricacies of tissue regeneration, aging, and disease. The molecular signatures, post-transcriptional mechanisms, and heterogeneity of quiescent stem cells offer profound insights into their regulation and potential applications in regenerative medicine. Understanding the role of quiescence in neural stem cells and its implications for the aging brain and glioblastoma underscores the importance of this research in addressing critical challenges in neuroscience and medicine.

Osteoarthritis (OA) is a pervasive and incapacitating musculoskeletal disorder that affects approximately 300 million people worldwide. Its cardinal symptom is chronic pain, which, if inadequately managed, can lead to reduced joint function, compromised sleep quality, and long-term disability. Conventional pharmacological treatments such as nonsteroidal anti-inflammatory drugs and opioids often fall short in providing adequate pain relief and may entail undesirable side effects with chronic use. Consequently, OA pain management remains a formidable challenge that necessitates the development of disease-specific analgesics.

Peripheral nociceptive input plays a pivotal role in OA pain, as evidenced by reduced pain following intra-articular lidocaine injections. Studies in rodent models have further underlined the significance of nociceptor activity in OA pain, showing early sensitization of knee-innervating neurons. Consequently, identifying key molecules implicated in OA pain development and targeting them for treatment has become a priority. One such target is nerve growth factor (NGF), targeting of which with sequestering monoclonal antibodies has shown promise in preclinical models and clinical trials, but has faced challenges in humans due to the risk of inducing rapid OA progression; anti-NGF antibodies are however licensed for treating OA in cats and dogs.

In the quest for disease-modifying OA therapies, mesenchymal stem/stromal cell (MSC) therapy has emerged as a promising avenue. Clinical trials have demonstrated pain relief and improved joint function in OA patients receiving MSC treatment. MSCs exert their effects through paracrine mechanisms, leading to analgesic and anticatabolic effects in OA-affected joints. However, it remains unclear whether MSCs directly affect nociceptive input. To address this gap in knowledge, a recent study led by Professor Ewan St. John Smith and his team (Dr Minji Ai, Dr William Hotham, Dr Luke Pattison, Qingxi Ma, and Dr Frances Henson) at the University of Cambridge investigated the potential of both MSCs and extracellular vesicles derived from MSCs (MSC-EVs) in modulating nociception in OA-affected joints.

The authors used a mouse model of destabilization of the medial meniscus (DMM) to induce OA-like joint pathology. They assessed pain-related behaviors using various tests, including the rotarod test, burrowing behavior analysis, and continuous monitoring of activity patterns. Their results demonstrated that untreated DMM-operated mice exhibited pain-related behavioral changes, such as reduced rotarod performance, decreased burrowing activity, and disrupted rest patterns during the lights-on period. These changes indicated the presence of chronic pain, akin to the sleep disturbances observed in OA patients.

The researchers found that DMM-operated mice treated with either MSCs or MSC-EVs did not exhibit significant differences in pain-related behaviors compared to the sham group. These treated mice displayed similar rotarod performance, burrowing activity, and rest patterns during the lights-on period as the sham-operated mice. Moreover, no significant improvements in joint damage were observed in MSC- or MSC-EV–treated DMM-operated mice, suggesting that the pain relief provided by these treatments was not due to a reduction in gross joint pathology. To investigate the potential underlying mechanisms, the researchers then examined the excitability of knee-innervating dorsal root ganglion (DRG) sensory neurons. These neurons play a pivotal role in nociception, and their hyperexcitability has been associated with driving joint pain. In untreated DMM-operated mice, knee-innervating DRG neurons displayed hyperexcitability characterized by depolarized resting membrane potential, reduced action potential firing threshold, and altered action potential properties. This hyperexcitability was normalized in both MSC- and MSC-EV–treated DMM-operated mice. Furthermore, they explored  if MSC-EVs can normalize NGF-induced DRG neuron hyperexcitability in vitro. In a series of experiments, DRG neurons were exposed to NGF, leading to hyperexcitability. However, when DRG neurons were incubated with MSC-EVs together with NGF, hyperexcitability did not occur, indicating that MSC-EVs can counteract NGF-induced hyperexcitability.

In conclusion, the study led by Dr Minji Ai offers a compelling glimpse into the future of pain management in OA and potentially other chronic pain conditions. By targeting nociceptive pathways through the modulation of sensory neuron excitability, MSCs and MSC-EVs represent a new frontier in pain therapeutics, offering hope for millions of individuals suffering from debilitating pain associated with OA and other chronic pain disorders. One key point of future research for Professor Ewan St. John Smith’s team  is to determine how MSC-EVs evoke their analgesic effects. Further research and clinical trials are warranted to harness the full potential of these innovative approaches and bring relief to those in need.

Endothelial-to-hematopoietic transition (EHT) is a fundamental transdifferentiation event that involves the transformation of hemogenic endothelial cells (HECs) into definitive HSCs. The research sheds light on the various external signaling cues and transcriptional regulatory networks that govern HEC specification and hematopoietic cell emergence. One of the key factors in this process is the runt family transcription factor Runx1, which is essential for EHT. The Runx1 is essential for EHT, and its expression distinguishes HECs from non-HECs. Moreover, ectopic RUNX1 expression in non-HECs is sufficient to convert them into HECs. However, the conversion efficiency is highly dependent on the developmental timing of the ectopic expression and other additional factors modulate the competency for RUNX1 to initiate EHT.

In a new study published in the peer-reviewed Journal Development, led by Dr. Yuki Sato and a team of researchers from Kyushu University in collaboration with Okayama University, discussed the complexity of hematopoietic cell development. Specifically, their study focused on the phenomenon of EHT, which is pivotal in the formation of HSCs during embryogenesis. This process has long fascinated scientists and clinicians alike, and their finding provided novel insights into the underlying mechanisms.

A notable observation made by the researchers is the involvement of vacuoles in the cell rounding process, a crucial step during EHT. It is known that Runx1-deficient embryos lack vacuole-like organelles with specific structures in their prospective HECs. These cells also display irregular cell flattening, further suggesting the significance of vacuoles in the cell rounding process. While vacuoles are well-known for their role in regulating cell morphology and size in plant cells in response to osmotic pressure, their role in animal development, particularly in EHT, was less understood. The study also highlighted the presence of Aquaporin (AQP) family proteins, which are responsible for water transport in cell and vacuole membranes. These AQPs, particularly AQP1, are implicated in various cellular processes, such as cell migration, tumor invasion, and epithelial-to-mesenchymal transition (EMT).

The authors found that AQP1 is localized in the plasma and vacuole membranes of endothelial cells during the EHT process. This localization was found in HECs and hematopoietic cells, indicating a role for AQP1 throughout this developmental stage. Additionally, AQP1 expression decreased after EHT completion, suggesting that its role is temporally regulated. The researchers used AQP1 overexpression experiments and observed that it led to increased vacuole size and significant cell rounding. This finding suggests that AQP1 plays a critical role in promoting cell rounding by facilitating water permeation into vacuoles.

Moreover, they demonstrated that AQP1 overexpression induces ectopic cell rounding and detachment from the endothelium. This is a remarkable finding as it suggests that excess AQP1 expression can drive cellular responses similar to those observed during EHT, even in non-HEC endothelial cells. The authors successfully provided evidence of these ectopically rounded cells entering the circulation, further emphasizing the profound impact of AQP1 on cell behavior during development. The study extends beyond avian embryos, as the in vitro experiments involving quail embryo-derived presomitic mesoderm reaffirm the role of AQPs in vacuole formation and cell rounding. It also shows that AQP1 expression is associated with an upregulation of genes related to HEC and hematopoietic cell specification.

One interesting findings of the study is the redundancy of AQP channels. While AQP1 was the focus of their study, the presence of AQP5, AQP8, and AQP9 in the endothelium adds complexity to the picture. The authors showed that multiple AQP knockouts in HECs result in the failure of morphological EHT, highlighting the collective importance of AQP activity in the process. This finding challenges the idea that EHT is solely dependent on a single AQP channel. Dr. Yuki Sato and colleagues conducted comprehensive analyses to investigate Runx1’s role in avian embryos. While the role of Runx1 has been extensively studied in the context of EHT in mouse embryos, its function in avian embryos had remained less explored. This study indicates that Runx1 may not be essential for cell morphological changes during EHT in avian embryos, providing some clues into species-specific variations in hematopoietic development. The authors concluded with a proposed model of AQP-mediated transcellular water transport. This model suggests that AQP channels facilitate the movement of water across cells, playing a crucial role in EHT and the regulation of cell morphology. Taken together, Yuki Sato et al study provides a number of significant findings, first it advances our knowledge on hematopoietic development. Secondly, their findings reveal the mechanisms of EHT, highlighting the critical role of AQP1 and the redundancy of AQP channels in the process. Moreover, the findings will pave they way for future investigations into the therapeutic applications of AQPs in hematopoietic disorders and other developmental processes.

The basal cell layer contains dendritic pigment-producing cells called melanocytes. Although all melanocytes have the ability to synthesize melanin and originate from same embryonic cells known as neural crest cells (NCC), their individual roles in each target location go much beyond just producing melanin. The embryonic progenitors of the pigment-producing melanocytes found in the skin, meninges, heart, and ears are called melanoblasts. Melanocytes’ life cycle involves various steps comprising lineage specification from embryonic neural crest cells, migration and proliferation of melanoblasts, differentiation of melanoblasts into melanocytes, their maturation, transport of mature melanosomes to keratinocytes, and eventual cell death. While hair melanocytes pass away at the end of the 3–8 year long hair cycle, epidermal melanocytes have a long lifespan.

Some studies have shown the possibility and prospects of mesenchymal stem cells used in tissue engineering skin. The establishment of tissue-engineered skin could solve the problems of cells, scaffolds, and growth stimulation signals. The human hair bulge contains melanoblasts, which have been defined as the amelanotic precursor cells of melanocytes. They serve as a source of stem cells for the periodic hair cycle. They may develop first from neural crest cells or secondarily from Schwann cell precursors, another type of NCC-derived cell. Previous published reports reveal that there is a major difference in functional characteristics of melanocytes between mice and human. One significant distinction is that in mice, amelanotic melanoblasts are seen not only in the hair bulge but also in the epidermis (non-hairy part). This prompts the question of whether the interfollicular epidermis of humans also has a population of amelanotic melanoblasts that would serve as a comparable source of stem cells.

In a new study conducted by Swiss scientists at the University Children’s Hospital Zurich, University of Zurich: Dr. Katarzyna Michalak-Micka, Dr. Vanessa Buchler, Natalia Zapiorkowska-Blumer, PD Dr. Thomas Biedermann and PD Dr. Agnes S. Klar conducted elegant molecular and cellular studies to characterize melanocyte subpopulations in the interfollicular human epidermis. The research team  looked at whether the interfollicular epidermis of humans  contains populations of mature and precursor melanocytes. Authors performed confocal imaging of triple immunofluorescence co-staining for cKit, CD90, HMB45 and Laminin 5 to image mature and progenitor melanocytes in the epidermal basement membrane. Knowledge of melanocyte population homoeostasis and its recovery after injury significantly depends on the accurate identification and detailed characterization of the many melanocyte cell groups. The current investigation found three distinct kinds of melanocytes subpopulations in the human interfollicular epidermis: cKit⁺CD90^–, cKit⁺CD90⁺, and cKitCD90⁺. The discovery of the Kit tyrosine kinase receptor (cKit) as a marker uniquely expressed in mature, melanin-producing melanocytes is noteworthy. The research work is now published in the journal Cell Reports.

The researchers showed that only cKitCD90⁺ cells are melanocyte progenitor cells, whereas cKit⁺CD90^– cells are pigmented melanocytes that have undergone full differentiation. Additional in vivo studies using pigmented dermo-epidermal replacements demonstrated that melanocyte cKit expression is crucial for the pigmentation of skin grafts in vivo (melDESSs). They observed that while cKit⁺CD90^– melanocytes had the maximum degree of melanin expression, cKit⁺CD90⁺ cells had a moderate quantity of melanin, and cKitCD90⁺ cells barely produced any melanin pigment in the corresponding melDESSs. According to recent findings, cKit signaling is necessary for the differentiation of human interfollicular melanocytes.

In conclusion, these findings provide critical insights into the variety of melanocytes in the human interfollicular epidermis and their capacity for differentiation. The authors claim that the interfollicular epidermis of humans has a pool of progenitor melanocytes made up of cKitCD90⁺ cells. In the typical human skin, authors successfully differentiated between cKit⁺CD90^–, cKit⁺CD90⁺, and cKitCD90⁺ melanocyte subpopulations

Skin grafting is one of the most promising approaches to heal extensive wounds. The discoveries of the Swiss scientists also enable skin-tone customization, making it a significant advancement in the therapeutic application of pigmented human bio-engineered skin grafts.

Moreover, the findings of this study could pave the way for new treatment methods for severe skin disease including vitiligo, postinflammatory hypopigmentation, albinism, piebaldism, melasm, hypomelanosis, and café-au-lait macules.

Mesenchymal stem cells (MSC) are multipotent adult stem cells that are present in multiple tissues including umbilical cord, bone marrow and fat tissue. MSCs can self-renew by dividing and can differentiate into multiple tissues including bone, cartilage, adipose tissue, and connective tissue. Platelet-derived growth factor (PDGF) isoforms are important signaling molecules for different types of mesenchymal cells, and these isoforms stimulate the proliferation, migration and survival of cells including MSCs. The PDGF family consists of two transmembrane receptor tyrosine kinase subunits (PDGF receptor alpha [α-PDGFR] and PDGF receptor beta [β-PDGFR]) and four ligands (PDGF A, B, C, and D). Little is currently known about how PDGF controls the differentiation of MSCs into certain lineages.

In a new study published in the Journal of Biological Chemistry: Tri Pham, Abdo Najy, and led by Professor Hyeong-Reh Choi Kim from Wayne State University School of Medicine and the Barbara Ann Karmanos Cancer Institute demonstrated that PDGF D stimulates the differentiation of human bone marrow mesenchymal stem cells (hBMSCs) into osteoblasts and prevents hBMSC differentiation into adipocytes.

The research team reported the unique function of PDGF D in bone formation by concurrently promoting the commitment of osteoblastic differentiation of BMSCs while blocking their commitment to adipogenesis using the growth factor domain dimers of recombinant PDGF D (rPDGF D) proteins. This is the first study to show that PDGF may control MSC development into a certain lineage directly. Importantly, the authors offer proof that PDGF D-activated β-PDGFR inhibits MSCs from differentiating into adipocytes by preserving the actin cytoskeleton and downregulating the expression of adipogenic genes. PDGF D facilitates remodeling of the actin cytoskeleton, coupled with the manifestation of osteogenic gene expression. According to the authors, PDGF D induces hBMSCs to differentiate into osteoblasts via increasing cytoskeleton tension, presumably involving networks of RhoA-ROCK-MCL-actin.

The authors further reported that PDGF D induces massive polyubiquitination of β-PDGFR mediated by the E3 ligase HUWE1 and demonstrated that HUWE1 expression is critical for PDGF D regulation of hBMSCs’ osteogenic differentiation. Even in the absence of a ubiquitin-proteasome system inhibitor, HUWE1-mediated polyubiquitination of β-PDGFR was easily detected by immunoblot analysis of whole cell lysates. Contrary to the Cbl family, HUWE1-mediated β-PDGFR extends the protein stability of β-PDGFR and its osteogenic signals by keeping β-PDGFR on the cell surface. The findings clearly illustrated the functional significance of HUWE1 in the regulation of PDGFR-mediated osteogenic differentiation of hBMSCs. Taken together, the discovery made by Professor Hyeong-Reh Kim and her research team widens our understanding on the detailed molecular mechanism by which PDGF D controls the commitment of hBMSCs to the osteoblastic lineage and opens up the potential of the use of rPDGF D for promoting bone repair and regeneration.