Teriparatide (human PTH_1–34) compensates for impaired fracture healing in COX-2 deficient mice

Genetic ablation of cyclooxygenase-2 (COX-2) in mice is known to impair fracture healing. To determine if teriparatide (human PTH_1–34) can promote healing of Cox-2-deficient fractures, we performed detailed in vivo analyses using a murine stabilized tibia fracture model. Periosteal progenitor cell proliferation as well as bony callus formation was markedly reduced in Cox-2^−/− mice at day 10 post-fracture. Remarkably, intermittent PTH_1–34 administration increased proliferation of periosteal progenitor cells, restored callus formation on day 7, and enhanced bone formation on days 10, 14 and 21 in Cox-2-deficient mice. PTH_1–34 also increased biomechanical torsional properties at days 10 or 14 in all genotypes, consistent with enhanced bony callus formation by radiologic examinations. To determine the effects of intermittent PTH_1–34 for callus remodeling, TRAP staining was performed. Intermittent PTH_1–34 treatment increased the number of TRAP positive cells per total callus area on day 21 in Cox-2^−/− fractures. Taken together, the present findings indicate that intermittent PTH_1–34 treatment could compensate for COX-2 deficiency and improve impaired fracture healing in Cox-2-deficient mice.