Lysophosphatidic acid and calcitriol co-operate to promote human osteoblastogenesis: requirement of albumin-bound LPA.

Lysophosphatidic acid (LPA), a pleiotropic signalling lipid is assuming growing significance in osteoblast biology. Although committed osteoblasts from several mammalian species are receptive to LPA far less is known about the potential for LPA to influence osteoblast formation from their mesenchymal progenitors. An essential factor for both bone development and post-natal bone growth and homeostasis is the active metabolite of vitamin D3, calcitriol (D3). Previously we reported how a combination of LPA and D3 synergistically co-operated to enhance the differentiation of immature human osteoblasts. Herein we provide evidence for the formation of human osteoblasts from multiple, primary human bone marrow derived stromal (stem) cells (hBMSCs). Importantly osteoblast development from hBMSCs only occurred when LPA was administered as a complex with albumin, its natural carrier. Collectively our findings support a co-operative role of LPA and D3 in osteoblastogenesis, findings which may aid the development of novel treatment strategies for bone repair.