Chitosan–poly(butylene succinate) scaffolds and human bone marrow stromal cells induce bone repair in a mouse calvaria model

Tissue engineering sustains the need of a three-dimensional (3D) scaffold to promote the
regeneration of tissues in volume. Usually, scaffolds are seeded with an adequate cell population,
allowing their growth and maturation upon implantation in vivo. Previous studies obtained by our
group evidenced significant growth patterns and osteogenic differentiation of human bone marrow
mesenchymal stem cells (hBMSCs) when seeded and cultured on melt-based porous chitosan
fibre mesh scaffolds (cell constructs). Therefore, it is crucial to test the in vivo performance of
these in vitro 3D cell constructs. In this study, chitosan-based scaffolds were seeded and cultured
in vitro with hBMSCs for 3 weeks under osteogenic stimulation conditions and analysed for cell
adhesion, proliferation and differentiation. Implantation of 2 weeks precultured cell constructs in
osteogenic culture conditions was performed into critical cranial size defects in nude mice. The
objective of this study was to verify the scaffold integration and new bone formation. At 8 weeks
of implantation, scaffolds were harvested and prepared for micro-computed tomography (μCT)
analysis. Retrieved implants showed good integration with the surrounding tissue and significant
bone formation, more evident for the scaffolds cultured and implanted with human cells. The results
of this work demonstrated that chitosan-based scaffolds, besides supporting in vitro proliferation
and osteogenic differentiation of hBMSCs, induced bone formation in vivo. Thus, their osteogenic
potential in orthotopic location in immunodeficient mice was validated, evidencing good prospects
for their use in bone tissue-engineering therapies.