Platelet factor 4 induces bone loss by inhibiting the integrinα5-FAK-ERK pathway

Background:The effect of platelet factor 4(PF4)on bone marrow mesenchymal stem cells(BMMSCs)and osteoporosis is poorly understood.Therefore,this study aimed to evaluate the effects of PF4-triggered bone destruction in mice and determine the underlying mechanism.Methods:First,in vitro cell proliferation and cell cycle of BMMSCs were assessed using a CCK8 assay and flow cytometry,respectively.Osteogenic differentiation was confirmed using staining and quantification of alkaline phosphatase and Alizarin Red S.Next,an osteoporotic mouse model was established by performing bilateral ovariectomy(OVX).Furthermore,the PF4 concentrations were obtained using enzymelinked immunosorbent assay.The bone microarchitecture of the femur was evaluated using microCT and histological analyses.Finally,the key regulators of osteogenesis and pathways were investigated using quantitative real-time polymerase chain reaction and Western blotting.Results:Human PF4 widely and moderately decreased the cell proliferation and osteogenic differentiation ability of BMMSCs.Furthermore,the levels of PF4 in the serum and bone marrow were generally increased,whereas bone microarchitecture deteriorated due to OVX.Moreover,in vivo mouse PF4 supplementation triggered bone deterioration of the femur.In addition,several key regulators of osteogenesis were downregulated,and the integrinα5-focal adhesion kinase-extracellular signalregulated kinase(ITGA5-FAK-ERK)pathway was inhibited due to PF4 supplementation.Conclusions:PF4 may be attributed to OVX-i nduced bone loss triggered by the suppression of bone formation in vivo and alleviate BMMSC osteogenic differentiation by inhibiting the ITGA5-FAK-ERK pathway.

Antioxidative stress-induced damage in cochlear explants

The imbalance of reactive oxygen species and antioxidants is considered to be an important factor in the cellular injury of the inner ear. At present, great attention has been placed on oxidative stress. However,little is known about fighting oxidative stress. In the current study, we evaluated antioxidant-induced cochlear damage by applying several different additional antioxidants. To determine whether excessive antioxidants can cause damage to cochlear cells, we treated cochlear explants with 50 m M M40403, a superoxide dismutase mimetic, 50 m M coenzyme Q-10, a vitamin-like antioxidant, or 50 m M d-methionine, an essential amino acid and the important antioxidant glutathione for 48 h. Control cochlear explants without the antioxidant treatment maintained their normal structures after incubation in the standard serum-free medium for 48 h, indicating the maintenance of the inherent oxidative and antioxidant balance in these cochlear explants. In contrast, M40403 and coenzyme Q-10-treated cochlear explants displayed significant hair cell damage together with slight damage to the auditory nerve fibers.Moreover, d-methiodine-treated explants exhibited severe damage to the surface structure of hair cells and the complete loss of the spiral ganglion neurons and their peripheral fibers. These results indicate that excessive antioxidants are detrimental to cochlear cells, suggesting that inappropriate dosages of antioxidant treatments can interrupt the balance of the inherent oxidative and antioxidant capacity in the cell.