Adipose-Derived Perivascular Stem Cells Heal Critical Size Mouse Calvarial Defects
Adipose tissue has attracted great interest as an alternative stem cell source with the same multipotent properties as mesenchymal stem cells (MSCs). However, the stromal vascular fraction (SVF) of adipose tissue contains a heterogeneous population of cells, which hamper its regenerative ability. We previously purified human adipose-derived Perivascular Stem Cells (PSCs) from SVF and showed that PSCs were capable of making significantly more bone compared to the SVF when implanted in the mouse muscle. Objectives: To evaluate the effectiveness of PSCs in the healing of mouse critical-size calvarial defects. Methods: Critical size (3mm) defects were created in the parietal bone of 50 adult SCID mice. Defects were either treated with an apatite coated PLGA scaffold alone, scaffold with human SVF or scaffold with human PSCs. Healing was monitored by live MicroCT scans at 0,2,4 and 6 weeks post injury. At 8 weeks postoperative, subjects were sacrificed and high-resolution microCT scanning was performed to observe total bone formation followed by histological analysis. Immunohistochemistry was performed to study expression of key osteogenic markers such as Osteopontin (OPN), Osteocalcin (OCN), Bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF). Results: PSCs resulted in a significantly more healing of the defect sites (69%) as opposed to 25% healing in the SVF models at 6 weeks. H&E staining revealed that the PSC group showed more and higher quality new bone in comparison with the SVF samples. Immunohistochemical staining of the defect sites showed that PSCs induced significant increases in osteogenic growth factor elaboration (BMP2, VEGF), significant evidence of OPN+, OCN+ osteogenesis, and ultimately significant calvarial defect re-ossification. Conclusion: Our results indicate that adipose-derived PSCs are a new cell source for future efforts in skeletal regenerative medicine. Further research to investigate PSCs induced healing in larger animals is needed to further unfold the haling potential of PSCs and understand its mechanism of action.