Bone tissue engineering has emerged as one of the leading fields in tissue engineering and regenerative medicine. Its success relies on understanding the interplay between progenitor cells, regulatory signals, and the biomaterials/scaffolds used to deliver them. Subtle changes in scaffold architecture can have significant effects on cellular activity. Optimising the design of bioactive scaffolds is guided by an understanding of the behaviour and responses of cells to their surrounding environment. Pore size is an essential architectural consideration in construct development; therefore, it is crucial to identify the optimal pore size for augmented tissue formation.
Using a series of collagen-glycosaminoglycan (CG) scaffolds with a homogenous mean pore size ranging from 85 µm up to 325 µm, we identified key differences in osteoblast and mesenchymal stem cell (MSC) behaviour in response to pore size. Scaffolds with the largest pore size (325 µm) facilitated superior osteoblast attachment, migration, scaffold infiltration and matrix deposition. MSC response was similar to osteoblasts but cell motility, proliferation, and scaffold infiltration was reduced. This was associated with differences in the profile of integrin subunits (α2) and collagen receptors (CD44), indicating that osteoblasts have a stronger affinity for collagen-glycosaminoglycan scaffolds compared to MSCs.
This study, for the first time within the literature, compares two very different cell types head to head to investigate individual cell behaviour in response to a single parameter. The findings elucidate fundamental mechanisms underlying the differences between the two cell types and highlight the importance of tailoring scaffold micro-architecture and cell type for cell-specific applications.
Murphy CM1,2,3, Duffy GP2,3,4, Schindeler A5,6, O’brien FJ2,3,4.[expand title=”Show Affiliations”]
- School of Medicine & Medical Science, University College Dublin, Dublin, Ireland.
- Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland.
- Trinity Centre for Bioengineering, Trinity College Dublin (TCD), Dublin, Ireland.
- Advanced Materials and Bioengineering Research Centre (AMBER) RCSI & TCD, Dublin, Ireland.
- Orthopaedic Research & Biotechnology Unit the Children’s Hospital at Westmead.
- Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia.
We have previously examined osteoblast behavior on porous collagen-glycosaminoglycan (CG) scaffolds with a range of mean pore sizes demonstrating superior cell attachment and migration in scaffolds with the largest pores (325 μm). Scaffolds provide a framework for construct development; therefore, it is crucial to identify the optimal pore size for augmented tissue formation. Utilizing the same range of scaffolds (85 μm – 325 μm), this study aimed to examine the effects of mean pore size on subsequent osteoblast differentiation and matrix mineralization, and to understand the mechanism by which pore size influences behavior of different cell types. Consequently, primary mesenchymal stem cells (MSCs) were assessed and their behavior compared to osteoblasts.
Results demonstrated that scaffolds with the largest pore size (325 μm) facilitated improved osteoblast infiltration, earlier expression of mature bone markers osteopontin (OPN) and osteocalcin (OCN), and increased mineralization. MSCs responded similarly to osteoblasts whereby cell attachment and scaffold infiltration improved with increasing pore size. However, MSCs showed reduced cell motility, proliferation, and scaffold infiltration compared to osteoblasts. This was associated with differences in the profile of integrin subunits (α2) and collagen receptors (CD44), indicating that osteoblasts have a stronger affinity for collagen-glycosaminoglycan scaffolds compared to MSCs.
In summary, these results reveal how larger pores promote improved cell infiltration, essential for construct development, however the optimal scaffold pore size can be cell type specific. As such, this study highlights a necessity to tailor both scaffold micro-architecture and cell-type when designing constructs for successful bone tissue engineering applications.
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