The effect of mesenchymal stem cells combined with polycaprolactone/hydroxyapatite composite scaffold on the healing of ulnar defect in dogs

Abstract

Bone tissue engineering strategy using biodegradable scaffolds combined with mesenchymal stem cells (MSCs) has emerged as a promising alternative treatment for extensive bone defects. The present in vitro study aimed to investigate the interaction between canine MSCs and polycaprolactone/hydroxyapatite (PCL/HA) scaffolds followed by an in vivo evaluation of the efficacy of PCL/HA and MSC loaded PCL/HA scaffolds on the healing of canine ulnar defect in dogs. Viability assay showed that the majority of cells remained viable on day 1 after seeding. An increase in DAPI-stained nuclei density together with a significant increases in total protein concentration (p<0.05) was observed between day 1 and 5 and day 3 and 5 after seeding all of which indicated that cells were capable of proliferation over time. Finally, osteogenic differentiation potential of the seeded cells was confirmed by Alizarin staining on day 14 of induction. Despite the promising in vitro results, neither new bone nor callus formation was observed in defects treated with PCL/HA alone or MSC-loaded PCL/HA scaffold. Defects in both groups were filled with fibrovascular tissue and remnants of the scaffold. Surprisingly, numerous of multinucleate giant cells were also found within defect sites which strongly indicated chronic inflammation.