An ideal mesenchymal stem cell (MSC) source for bone tissue engineering has yet to be identified. Such an MSC population would be easily harvested in abundance, with minimal morbidity and with high purity. Our laboratories have identified perivascular stem cells (PSCs) as a candidate cell source. PSCs are readily isolatable (through fluorescent activated cell sorting) from adipose tissue and have been previously shown to be indistinguishable in phenotype and differentiation potential to MSCs.

In the present study we directly compare the bone-forming capability of PSCs to an unsorted population, termed stromal vascular fraction (or SVF). We found that the purified PSCs out-performed the unpurified SVF population in terms of bone formation. This was determined through the use of an intramuscular implantation model. Finally, a novel osteoinductive protein (NELL-1) was shown to synergistic enhance PSC-mediated bone formation. These results suggest that both PSCs alone, or PSCs with NELL-1, have promise for future efforts in stem cell mediated bone repair.