Fig. 3

The osteogenic potential of old MDSCs remained significantly lower compared to young MDSCs, after BMP4 transduction. A Transduction efficiency of BMP4/GFP transduction for both young and old MDSCs. The efficiency of BMP4/GFP transduction on both young and old MDSCs is less than 100%. After cell sorting based on GFP positivity, GFP positive cells is at 100% for both young and old MDSCs. B BMP4 secretion level of young and old MDSCs after GFP cells sorting. No significant difference on the secretion levels of BMP4 between young and old MDSCs/BMP4/GFP. C–D Osteogenic differentiation of monolayer culture for young and old BMP4/GFP-transduced MDSCs. ALP positive staining area (purple pixel) is significantly lower in the old MDSC group compared to young MDSCs group. **P < 0.05. E–G qPCR analysis of Alp, Col1, and Osx.*P<0.05, **P<0.01. H–I MicroCT scan for osteogenic pellets of BMP4/GFP transduced MDSCs. Old MDSCs/BMP4/GFP could undergo osteogenic differentiation as demonstrated by mineralization using microCT scanning. However, the mineralized pellet volume of old MDSCs/BMP4/GFP was significantly smaller than young MDSCs/BMP4/GFP-transduced despite expressing similar levels of BMP4 at around 30 ng/million cells/24 h.**P < 0.01