No abstract

Therapeutic study, Level IV.

No abstract

The hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathway is involved in skeletal development, bone repair, and postmenopausal osteoporosis. Inhibitors of prolyl hydroxylases (PHD) enhance vascularity, increase callus formation in a stabilized fracture model, and activate the HIF-1α/VEGF pathway. This study examined the effects of estrogen on the HIF-1α/VEGF pathway in osteoblasts and whether PHD inhibitors can protect from bone loss in postmenopausal osteoporosis. Osteoblasts were treated with estrogen, and expressions of HIF-1α and VEGF were measured at mRNA (qPCR) and protein (Western blot) levels. Further, osteoblasts were treated with inhibitors of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, and levels of VEGF mRNA and protein expression were detected. In addition, ovariectomized rats were treated with PHD inhibitors, and bone microarchitecture and bone mechanical strength were assessed using micro-CT and biomechanical analyses (lower ultimate stress, modulus, and stiffness). Blood vessel formation was measured with India Ink Perfusion and immunohistochemistry. Estrogen, in a dose- and time-dependent manner, induced VEGF expression at both mRNA and protein levels and enhanced HIF-1α protein stability. Further, the estrogen-induced VEGF expression in osteoblasts involved the PI3K/Akt pathway. PHD inhibitors increased bone mineral density, bone microarchitecture and bone mechanical strength, and promoted blood vessel formation in ovariectomized rats. In conclusion, estrogen and PHD inhibitors activate the HIF-1α/VEGF pathway in osteoblasts. PHD inhibitors can be utilized to protect bone loss in postmenopausal osteoporosis by improving bone vascularity and angiogenesis in bone marrow.

Background/Aims: Chondrocyte apoptosis is largely responsible for cartilage degeneration in osteoarthritis (OA). Interleukin-1 beta (IL-1β) is widely used as a chondrocyte apoptosis-inducing agent, while lactoferrin (LF) is an anabolic reagent which has the potential to inhibit chondrocyte apoptosis. We assessed the effects of LF on cartilage degeneration in IL-1β-induced chondrocytes and in a rat model of OA, and explored the potential molecular mechanisms involved. Methods: Human articular chondrocytes (HACs) were treated with IL-1β alone or in combination with LF. MTT and flow cytometric assays were used to detect changes after treatment with LF. Western blotting was used to examine the relevant molecules regulating apoptosis. Results: We found that IL-1β reduced the viability of HACs, whereas 200 μg/mL of LF significantly counteracted the inhibitory effect of IL-1β. LF significantly inhibited IL-1β-induced HAC apoptosis. The protein expression of the apoptotic markers Caspase-3 and PARP was also significantly reduced in the LF treatment group when analyzed by western blotting. Furthermore, we found that LF triggered CREB1 phosphorylation in IL-1β-induced HAC apoptosis through AKT1 signaling. In addition, LF promoted the repair of articular cartilage damage in a rat OA model with elevated p-CREB levels. Conclusions: These studies suggest that LF has an anti-apoptotic effect on IL-1β-induced chondrocytes, and thus may be a promising novel therapeutic agent for OA.