Osteogenic potential of human Wharton´s Jelly stem cells on hierarchical starch based scaffolds and its in vivo host response

Nano and micro fiber combined scaffolds have been produced in order to mimic the biophysical structure of natural extracellular matrix (ECM). Herein the strategy was to combine layers of polycaprolactone (PCL) electrospun nanofiber meshes (NFM) every two consecutive layers of starch-polycaprolactone rapid prototyped microfibers (SPCL-RP). Human umbilical cord Wharton´s Jelly stem cells (hWJSCs) were isolated, seeded and cultured for 21 days on hierarchical starch based scaffolds, under osteogenic differentiation conditions, to evaluate the influence of the integrated nanofiber meshes on cell entrapment and on osteogenic differentiation. In vitro biological data confirmed that hierarchical starch-based fibrous scaffolds showed enhanced cell entrapment when compared to RP scaffolds. Furthermore, up-regulation of bone specific genes and calcium phosphate deposition corroborate the hypothesis of a successful osteogenic differentiation of hWJSCs seeded on these scaffolds in vitro.

To study the inflammatory response induced by SPCL-RP scaffolds with or without intercalated PCL nanofiber meshes and NFM alone were evaluated in Wistar rats for 1, 6 and 12 weeks. A thicker fibrous capsule was formed in SPCL microfiber scaffold compared to the NFM alone. Active fibroblasts and giant cells were observed for all 3 types of scaffolds. More granulation tissue was formed in the vicinity of the NFM, which indicates a higher inflammatory response. Microvessels were detected just after 1 week of implantation, increasing in caliber with time course of angiogenesis process. Longer implantation time shows some level of degradation in all types of structures, with decreasing levels of inflammation in microfiber scaffolds and new tissue formation, while in the NFM the inflammation continues developing over time of implantation.