The effect of diminished osteogenic signals on reduced osteoporosis recovery in aged mice and the potential therapeutic use of adipose-derived stem cells

Adipose-derived stem cells (ADSCs) have been shown to be pluoripotent and explored for their usage in tissue engineering. Previously, we have established a cell-based approach comprised of platelet-enriched plasma and osteo-progenitor cells for treating osteoporosis in an ovariectomized-senescence-accelerated mice (OVX-SAMP8) model. In the present study, we intend to explore the feasibility of using ADSCs as a cell-based therapeutic approach for treating osteoporosis, and to examine the effects of aging on the pluoripotency of ADSCs and the efficiency of bone formation both in vitro and in vivo. Flow cytometry was used to characterize ADSCs isolated from young and aged female SAMP8 mice and showed that the highly positive expression of surface markers such as CD44 and CD105 and negative for CD34 and CD45. Therefore, to compare the aging effects on the growth kinetics and differentiation potential of young and aged ADSCs, we found that there was a significant decline in both the proliferation rate (approximately 13.3%) and osteo-differentiation potential in aged ADSC. Subsequently, young and aged ADSCs were transplanted into the bone marrow of osteoporotic mice (OVX-SAMP8) to evaluate their bone formation ability. ADSC transplants were shown effective in restoring bone mineral density in the right/left knees, femurs and spine, 4 months post-transplantation; mice which received young ADSC transplants showed significantly higher bone regeneration(an average of 24.3% of improved BMD) over those received aged ADSCs. In conclusion, these findings showed that aging impedes osteoporosis-ameliorating potential of ADSC by diminishing osteogenic signal, and that ADSC could be used as a potential cell-based therapy for osteoporosis.