Effect of Stromal Vascular Fractions on Angiogenesis of Injected Diced Cartilage

OBJECTIVES: This study explored the effect of adipose-derived stromal vascular fractions (SVFs) on angiogenesis in injected autologous diced cartilage. METHODS: Stromal vascular fractions were extracted by enzymatic digestion. Cartilage grafts were harvested from 1 side of the auricular cartilage of New Zealand rabbit and then diced to a size of 1.0 mm(3). The grafts were divided into 2 groups. The control group was diced cartilage mixed with culture medium, and the experimental group was diced cartilage mixed with SVFs. The 2 groups of composite grafts were subcutaneously implanted on both sides of the back of each rabbit. After 4, 12 and 24 weeks, the tissue structure, number of blood vessels, and angiogenic factors in the grafts were observed. RESULTS: The SVFs conformed to the current standard of the biological evaluation. Under an inverted microscope, the number of layers of chondrocytes in the experimental group was higher than that in the control group at 4 weeks. A small number of inflammatory cells and blood vessels were observed around the cartilage grafts. At 12 and 24 weeks, the volume of tissue was increased gradually by general observation. And a large number of chondrocytes were observed microscopically, whereas the number of inflammatory cells decreased. And meanwhile additional new blood vessels were observed. Immunohistochemical analysis of CD31 showed that the number of capillaries in the control group was significantly lower than that in the experimental group at 4, 12 and 24 weeks. Further, the expression of Hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) mRNA and protein were measured by RT-PCR and Western bloting, respectively. The results showed that the mRNA expression of VEGF and HIF-1α in the experimental group was increased. The mRNA level remained higher than that of the control group at 24 weeks (P < 0.05). And the relative expression levels of VEGF and HIF-1α protein in the experimental group were higher than those in the control group at 4, 12 and 24 weeks (P < 0.05). CONCLUSION: Autologous diced cartilage mixed with adipose-derived SVFs can promote angiogenesis when transplanted by injection. Further research showed that SVFs could increase the expression levels of VEGF and HIF-1α in the grafts, which may be part of the mechanism that SVFs promoted the angiogenesis of diced cartilage.