Identification and characterization of human skeletal stem cell-like cells derived from infrapatellar fat pad

Abstract

Background Skeletal stem cells (SSCs) have attracted extensive attention for their crucial role in bone accrual and therapeutical values. The substantial unmet cellular need of regenerative medicine and tissue engineering calls for identification of a novel source for human SSC isolation, or even skeletal stem cell-like cells (SSCLCs). Methods hSSCLCs were isolated through enzyme-digestion and fluorescent-activated cell sorting (FACS) from human tissues including placenta, cord blood, Wharton’s Jelly and various adipose depots. Proportion of hSSCLCs in all those tissues were compared through flow cytometry. For adipose tissue, immunofluorescent staining was also employed to substantiate our flow results. In vitro CFU-F assay, chondrogenic and osteogenic assays were performed to assess self-renewal and multipotency for differentiation of hSSCLCs. Transcriptomic profiling of adipose-derived hSSCLCs was achieved through scRNA-seq. Results Here, we illustrated that adipose tissues contain a satisfying abundancy of hSSCLCs, especially infrapatellar fat pad (IPFP), but not fetal tissues. Moreover, we discovered IPFP-derived hSSCLCs display intact self-renewal and a marked elevation in chondrogenic and osteogenic differentiation. Transcriptomically comparing IPFP-hSSCLCs and dorsal adipose depot (DSAT)-derived hSSCLCs through scRNA-seq, we further demonstrated IPFP-hSSCLCs are less differentiated but more motivated in expressing transcriptomes related to chondrogenic and osteogenic differentiation. Conclusion Our study first identified adipose tissue as an alternative but encouraging source for isolating hSSCLCs with intact SSC properties which might be promising in treating diseases related to bone and/or cartilage defects.