Lysophosphatidic Acid Analogue rather than Lysophosphatidic Acid Promoted the Bone Formation In Vivo

Lysophosphatidic acid (LPA), a bioactive lipid molecule, has recently emerged as physiological and pathophysiological regulator in skeletal biology. Here we evaluate the effects of LPA on bone formation in vivo in murine femoral critical defect model. Primary femoral osteoblasts were isolated and treated with osteogenic induction conditional media supplemented with 20 μM LPA or LPA analogue. Mineralized nodules were visualized by Alizarin Red S staining. Forty-five C57BL/6 mice underwent unilateral osteotomy. The femoral osteotomy gap was filled with porous scaffolds of degradable chitosan/beta-tricalcium phosphate containing PBS, LPA, or LPA analogue. 2, 5, and 10 weeks after surgery, mice were sacrificed and femurs were harvested and prepared for Micro-Computed Tomography (Micro-CT) and histological analysis. Alizarin Red S staining showed that LPA and LPA analogue significantly enhanced the mineral deposition in osteoblasts. Micro-CT 3D reconstruction images and HE staining revealed that significantly more newly formed bone in osteotomy was treated with LPA analogue when compared to control and LPA group, which was verified by histological analysis and biomechanical characterization testing. In summary, our study demonstrated that although LPA promotes mineralized matrix formation in vitro, the locally administrated LPA was not effective in promoting bone formation in vivo. And bone formation was enhanced by LPA analogue, administrated locally in vivo. LPA analogue was a potent stimulating factor for bone formation in vivo due to its excellent stability.