Clonal multipotency and effect of long-term in vitro expansion on differentiation potential of human hair follicle derived mesenchymal stem cells.

Hair follicle harbors a rich stem cell pool with mesenchymal lineage differentiation potential. Although previous studies with rodent cells demonstrated that hair follicle sheath and papilla cells possess multi-lineage differentiation potential, human hair follicle derived mesenchymal stem cells (hHF-MSCs) have not been characterized in detail in terms of their multipotency. In addition, it is not clear whether these cells are true stem cells that can differentiate along multiple lineages or whether they represent a collection of progenitor cells with restricted differentiation potential. Here we report that hHF-MSCs are highly proliferative cells that can be maintained in culture for ~45 population doublings before they start to show signs of cellular senescence. Under appropriate culture conditions, hHF-MSCs differentiated along the myogenic, osteogenic, adipogenic and chondrogenic lineages, as demonstrated by kinetic gene expression profiling and functional assays. Interestingly, the differentiation potential decreased with time in culture in a lineage-specific manner. Specifically, myogenesis and chondrogenesis showed a moderate decrease over time; osteogenesis was maximum at intermediate passages and adipogenesis was highly sensitive to long-term culture and was diminished at late passages. Finally, hHF-MSCs were clonally multipotent as the majority of hHF-MSCs clones (73%) demonstrated bi- or tri-lineage differentiation potential. These results suggest that hHF-MSCs may present as an alternative source of easily accessible, autologous stem cells for tissue engineering and regenerative medicine.