mechanical signaling via ion channels and neuronal transmitter-receptors

本课题主要研究骨组织中离子通道之一的起搏通道（HCN）。HCN 1定位于破骨细胞分泌酸的皱褶边缘区域周围。为了阐明HCN的作用，雇用了HCN 1缺陷型小鼠。研究了HCN 3在成骨细胞中的作用。1：在HCN 1缺陷型小鼠中，与野生型（WT）相比，HCN 1-KO中的骨小梁质量和骨小梁数量的结构参数显著较低，而骨小梁分离显著较高。骨形成的组织形态计量学指标（MAR和BFR/BS）和再吸收2：膜片钳记录显示，尽管幅度与WT相同，但HCN 1缺乏降低了超极化激活电流的激活速率，可能是因为其他HCN亚型保持完整。通过转染基因过表达HCN 3增强WT成骨细胞的增殖，如通过总细胞数测量的。4：HCN 4基因敲低后，骨钙素Ih显著降低，提示骨钙素Ih可由HCN 1和HCN 4产生。HCN 1-KO高骨转换可能是基于细胞功能障碍。HCN 1可以调节破骨细胞的酸分泌和分化。此外，缺乏HCN 1上调成骨细胞中HCN 3的表达。HCN 3可能有助于成骨细胞骨形成。

Our study focused on one of ion channels, pacemaker channel (HCN) in bone. HCN1 is localized around ruffled border area where osteoclast secretes acid. To elucidate the role of HCNs, HCN1 deficient mice were hired. The role of HCN3 in osteoblasts was investigated.1 : In HCN1-deficient mice, trabecular bone mass and the structural parameter of Trabecular Number were significantly lower, whereas Trabecular Separation was significantly higher, in HCN1-KO than in wild type (WT). Histomorphometiric indices of bone formation (MAR and BFR/BS) and resorption (Oc.S/BS and Oc.N/BS) were increased.2 : Patch clamp recordings showed that HCN1-deficiency decreased the activation rate of the hyperpolarization-activated current although the amplitude was same as WT, probably because other HCN subtypes remained intact.3 : Overexpression of HCN3 by transfecting the gene enhanced proliferation of WT-osteoblasts as measured by total cell number.4 : Osteoclastic Ih was significantly reduced by knockdown of HCN4, suggesteing that osteoclastic Ih could be generated from HCN1 and HCN4.The high bone turnover in HCN1-KO was likely to be based on cellular dysfunctions. HCN1 could modulate acid secretion and differentiation in osteoclasts. In addition, lack of HCN1 upregulated expression of HCN3 in osteoblasts. HCN3 may contribute to osteoblastic bone formation.