Tissue-specific mesenchymal stem cell-dependent osteogenesis in highly porous chitosan-based bone analogs

Among conventional fabrication techniques, freeze-drying process has widely been investigated for polymeric implants. However, the understanding of the stem cell progenitor-dependent cell functionality modulation and quantitative analysis of early osseointegration of highly porous scaffolds have not been explored. Here, we developed a novel, highly porous, multimaterial composite, chitosan/hydroxyapatite/polycaprolactone (CHT/HA/PCL). The in vitro studies have been performed using mesenchymal stem cells (MSCs) from three tissue sources: human bone marrow-derived MSCs (BM-MSCs), adipose-derived MSCs (AD-MSCs), and Wharton's jelly-derived MSCs (WJ-MSCs). Although cell attachment and metabolic activity [3-4,5-dimethylthiazol-2yl-(2,5 diphenyl-2H-tetrazoliumbromide) assay] were ore enhanced in WJ-MSC-laden CHT/HA/PCL composites, scanning electron microscopy, real-time gene expression (alkaline phosphatase [ALP], collagen type I [Col I], osteocalcin [OCN], and bone morphogenetic protein 4 [BMP-4]), and immunostaining (COL I, β-CATENIN, OCN, and SCLEROSTIN [SOST]) demonstrated pronounced osteogenesis with terminal differentiation on BM-MSC-laden CHT/HA/PCL composites only. The enhanced cell functionality on CHT/HA/PCL composites was explained in terms of interplay among the surface properties and the optimal source of MSCs. In addition, osteogenesis in rat tibial model over 6 weeks confirmed a better ratio of bone volume to the total volume for BM-MSC-laden composites over scaffold-only and defect-only groups. The clinically conformant combination of 3D porous architecture with pore sizes varying in the range of 20 to 200  μm together with controlled in vitro degradation and early osseointegration establish the potential of CHT/HA/PCL composite as a potential cancellous bone analog.