Focal adhesion protein Kindlin-2 regulates bone homeostasis in mice

Abstract

Our recent studies demonstrate that the focal adhesion protein Kindlin-2 is critical for chondrogenesis and early skeletal development. Here, we show that deleting Kindlin-2 from osteoblasts using the 2.3-kb mouse Col1a1-Cre transgene minimally impacts bone mass in mice, but deleting Kindlin-2 using the 10-kb mouse Dmp1-Cre transgene, which targets osteocytes and mature osteoblasts, results in striking osteopenia in mice. Kindlin-2 loss reduces the osteoblastic population but increases the osteoclastic and adipocytic populations in the bone microenvironment. Kindlin-2 loss upregulates sclerostin in osteocytes, downregulates β-catenin in osteoblasts, and inhibits osteoblast formation and differentiation in vitro and in vivo. Upregulation of β-catenin in the mutant cells reverses the osteopenia induced by Kindlin-2 deficiency. Kindlin-2 loss additionally increases the expression of RANKL in osteocytes and increases osteoclast formation and bone resorption. Kindlin-2 deletion in osteocytes promotes osteoclast formation in osteocyte/bone marrow monocyte cocultures, which is significantly blocked by an anti-RANKLneutralizing antibody. Finally, Kindlin-2 loss increases osteocyte apoptosis and impairs osteocyte spreading and dendrite formation. Thus, we demonstrate an important role of Kindlin-2 in the regulation of bone homeostasis and provide a potential target for the treatment of metabolic bone diseases.Bone Research (2020) 8:2; https://doi.

Kindlin-2 regulates skeletal homeostasis by modulating PTH1R in mice

“… 13 , 36 Interestingly, Kindlin-2 and PTH1R cooperatively regulate not only the osteoblast-mediated bone formation, but also the osteoclast formation in bone. While Kindlin-2 loss in osteoblastic cells increases the basal level osteoclast formation in bone, which is consistent with our previously published results, 30 it abolished the intermittent PTH stimulation of osteoclast formation in bone, which can be partially explained by the fact that intermittent PTH induces expression of RANKL in control but not cKO bones.…”

“… 37 The generation of the Dmp1-Cre; Kindlin-2 f/f mice was previously described. 30 Pth1r f/f mice were previously described, 5 generously provided by Dr. Meiqing Wang (the Fourth Military Medical University, Xi’an, China) 38 and bred to Dmp1-Cre; Kindlin-2 f/f mice to generate Dmp1-Cre; Kindlin-2 f/+ , Dmp1-Cre; Pth1r f/+ , Dmp1-Cre; Kindlin-2 f/+ ; Pth1r f//+ mice and other genotypes for this study. Mice were subjected to daily subcutaneous administration of PTH 1-34 (Bachem) (100 μg/kg body weight) for 28 d. For acute effect of PTH on protein expression in bone, cortical bone shafts were cut into tiny pieces and treated with PTH 1-34 (10 −7 M) for 3 h, followed by western blotting using the indicated antibodies.…”

“… 33 More recently, we demonstrated that Kindlin-2 regulates bone remodeling in mice through modulation of expression of sclerostin and Rankl in osteocytes. 30 …”

Moderate Fluid Shear Stress Regulates Heme Oxygenase-1 Expression to Promote Autophagy and ECM Homeostasis in the Nucleus Pulposus Cells

“…The protein content was detected by Pierce TM BCA Protein Assay Kit (23225; ThermoFisher Scientifc, United States). Western blot analyses were performed as previously described (Cao et al, 2020). Proteins were loaded on sodium dodecyl sulfate-polyacrylamide gel for electrophoresis.…”

“…Immunofluorescence staining was performed according to the method we previously used (Cao et al, 2020). After fixation in 4% paraformaldehyde at room temperature for 10 min, cells were permeabilized in 0.1% triton-100 for 15 min and blocked with 1% bovine serum albumin for 1 h at room temperature.…”