Therapeutic effects of the stromal vascular fraction and adipose-derived stem cells on osteoarthritis in an experimental rabbit model

Abstract

Background The stromal-vascular fraction (SVF), comprising heterogeneous cell populations and adipose-derived stem cells (ADSCs), has therapeutic potential against osteoarthritis (OA); however, the underlying mechanism remains elusive. This study investigated the therapeutic effects of the heterogeneous cells in rabbit SVF on rabbit chondrocytes and compared them with those of two different ADSCs adjusted for their stem cell content.Methods Animals were divided into control, low-dose ADSCs (lADSC; 1×104 ADSCs), high-dose ADSCs (hADSC; 1×105 ADSCs), and SVF (1×105 SVF) groups. SVF and ADSCs isolated from rabbits were autografted into the knees after OA onset, and the animals were sacrificed 8 and 12 weeks after OA onset. OA progression and synovitis was analyzed by macroscopic and histological analyses, and the expression of collagen type II, SOX9, MMP-13, CD86 (M1) and CD163 (M2) was assessed using immunohistochemical and real-time polymerase chain reaction (RT-PCR). In vitro, chondrocytes were either co-cultured with SVF or lADSCs or alone (control), and the pellet size was evaluated. TGF-β and IL-10 concentrations in the medium were evaluated using an enzyme-linked immunosorbent assay. Additionally, immune-fluorescent double staining was performed for SVF and lADSCs to stain macrophages with F4/80, CD86, and CD163.Results OA progression was significantly suppressed, and synovitis was reduced in the SVF and hADSC groups. Compared to those in the control and lADSC groups, immunohistochemistry and RT-PCR revealed higher expression of collagen type Ⅱ and SOX9, lower expression of MMP-13 in cartilage, lower macrophage M1/M2 ratio, and higher expression of TGF-β, IL-10 in the synovium in the SVF and the hADSC groups. In the SVF group, the pellet size and TGF-β and IL-10 concentrations were significantly higher than those in the control and lADSC groups. Immune-fluorescent double staining revealed a significantly higher number of M2 than M1 macrophages in SVF.Conclusions The therapeutic effects of SVF and hADSCs superior on chondrocytes was superior with enhanced anabolic and inhibited catabolic factors than those of controls and lADSCs. Heterogeneous cells, mainly M2 macrophages in SVF, contributed to the therapeutic effect on chondrocytes and knee joint homeostasis by enhancing the growth factors and chondrocyte protective cytokines secretion.