Cbfa1基因调节骨形成与骨吸收的研究进展

骨的形成与吸收是一个涉及众多的基因和生长因子的复杂过程,凡可使骨形成下降和骨吸收增加的因素都会促进骨质疏松的发生.Cbfa1是成骨细胞分化和成熟的特异性转录因子,研究发现Cbfa1可通过促进骨形成和抑制骨吸收,对骨质疏松的发生、发展起到抑制作用,因此,我们期望随着Cbfa1基因研究的深入将为防治骨质疏松提供新思路.     

核结合因子a1的调控机制

Cbfa1是骨发育过程中调节骨髓基质干细胞向成骨细胞分化和成熟的重要转录因子。Cbfa1的表达水平异常与骨骼系统疾病有关。体内体外实验证实多种通路(如Wnt/LRP5/-catenin,BMP/Smads,1,25-(OH)2-vitaminD3/VDR/VDRE途径)和调节蛋白(Msx2,Dlx5,Twists)在Cbfa1基因表达、活性和随后的骨形成过程中起关键作用。这些发现对调控成骨细胞分化和治疗骨质疏松以及其他伴有骨量改变的疾病治疗提供了新的思路,这些疾病有可能用控制Cbfa1表达来进行治疗。     

Locally administered T cells from mice immunized with lipopolysaccharide (LPS) accelerate LPS-induced bone resorption

T cells play important roles in bone destruction and osteoclastogenesis and are found in chronic destructive bone lesions. Lipopolysaccharide (LPS) is one of several pathological factors involved in inflammatory bone destruction. We previously described the importance of T cells in the inflammatory bone resorption that occurs after repeated LPS administration. However, whether local or systemic T cells are important for inflammatory bone resorption and whether immunization of host animals influences bone resorption remain unclear. The present study examines the effects of local extant T cells from LPS-immunized mice on LPS-induced bone resorption. T cells from LPS-immunized or non-immunized mice were injected together with LPS into the gingival tissues of mice with severe combined immunodeficiency disease that lack both T and B cells. We histomorphometrically evaluated bone resorption at sites of T cell injections and examined the influence of T cells from LPS-immunized mice on osteoclastogenesis in vitro. We found that locally administered T cells from LPS-immunized but not non-immunized mice accelerated LPS-induced bone resorption in vivo. Moreover, T cells from LPS-immunized mice increased osteoclastogenesis in vitro induced by receptor activator of NF-κ B ligand and LPS and anti-tumor necrosis factor (TNF)-α antibody inhibited this increase. These results demonstrated that local extant T cells accelerate inflammatory bone resorption. Furthermore, T cells from LPS-immunized mice appear to elevate LPS-induced bone resorption using TNF-α.     

Gene expression of connective tissue growth factor (CTGF/CCN2) in calcifying tissues of normal and cbfa1-null mutant mice in late stage of embryonic development

Connective tissue growth factor (CTGF/CCN2), one of the most recently described growth factors, is produced by chondrocytes, vascular endothelial cells, and transforming growth factor (TGF)-β-stimulated fibroblasts. CTGF was isolated from a chondrosarcoma-derived chondrocytic cell line, HCS-2/8, and found to be normally expressed in cartilage tissues, especially in hypertrophic chondrocytes, and also to stimulate both the proliferation and the differentiation of chondrocytes in vitro. Therefore, CTGF is thought to be one of the most important regulators of endochondral ossification in vivo. Herein we describe the expression pattern of the ctgf gene in the calcifying tissues of normal developing mouse embryos in comparison with that in core binding factor a1 (Cbfa1)-targeted mutant (cbfa1-null) mouse embryos, in which impaired development and growth were characteristically observed in the skeletal system. After 15 days of development (E15), the expression of ctgf was detected in the zone of hypertrophy and provisional calcification, in which ossification proceeds toward the epiphysis during the skeletal development of the mouse embryo. Furthermore, ctgf was expressed in developing molar and incisal tooth germs around the perinatal stage. However, no expression of the gene was found in the cbfa1-null mouse embryos. These results indicate that CTGF may have certain important roles in the development of the calcifying tissues in the mouse embryo.     

中药骨康含药血清培养脂肪干细胞移植促进骨质疏松性骨折愈合过程中cbfa1和OCN的表达变化

目的 探讨中药骨康含药血清培养脂肪干细胞移植促进骨折愈合过程中骨折端cbfa1和OCN的动态变化。方法 制备中药骨康含药血清并进行脂肪干细胞培养,移植脂肪干细胞到骨折部位,用免疫组化观察骨折部cbfa1和OCN的动态变化。结果 第3 代脂肪干细胞流式鉴定CD90阳性,CD34、CD45低表达。免疫组化观察骨折部cbfa1和OCN的动态变化：第一周干预组Cbfal和OCN组均可见血肿、肉芽组织及纤维性骨痂组织中出现阳性细胞和基质阳性信号,阳性较强,对照组可见阳性细胞和基质阳性信号,阳性较弱,空白组基本上无阳性表达;第二周Cbfal和OCN组均出现软骨岛和新生骨小梁,胶原纤维排列整齐,大量阳性细胞和基质阳性信号,强阳性表达, 对照组骨小梁和软骨岛均出现,但比干预组少,亦出现阳性细胞和基质阳性信号,信号比干预组弱,空白组少见软骨岛和骨小梁,胶原纤维排列混乱,阳性细胞和基质阳性信号亦可见,但比前两组要弱;第四周干预组Cbfal组阳性表达减弱,OCN组继续强阳性表达,对照组两指标均阳性表达,空白组阳性细胞和基质阳性信号存在,阳性程度比以往稍强。结论 通过免疫组化观察骨折部cbfa1和OCN的动态变化,表明脂肪干细胞移植可促进骨质疏松性骨折愈合,而中药骨康含药血清培养脂肪干细胞移植效果更理想。     

Expression of osterix inhibits bone morphogenetic protein-induced chondrogenic differentiation of mesenchymal progenitor cells

Osteoblasts and chondrocytes arise from common bipotential mesenchymal progenitor cells. Although the differentiation of these two cell lineages can be induced by treatment with bone morphogenetic proteins (BMPs), the responses of mesenchymal progenitors to BMP differ from cell line to cell line. Here we demonstrate that C3H/10T1/2 cells preferred chondrogenic differentiation, primary bone marrow stroma cells (MSCs) tended to convert to osteoblasts, and ST-2 cells differentiated into both the osteoblastic and chondrocytic lineages simultaneously, suggesting that a molecular switch functions to select cell fate. Osterix, the secondary master regulator of osteoblastogenesis, was induced by BMP at high and low levels in MSCs and ST-2 cells, respectively; in contrast, C3H/10T1/2 cells demonstrated only faint expression. As osterix has been suggested as a negative regulator of chondrogenesis, we hypothesized that the intense chondrocyte differentiation of C3H/10T1/2 cells may have resulted from an absence of osterix. We therefore restored osterix gene expression in C3H/10T1/2 cells using an adenovirus vector. Following BMP treatment, infection with an osterix-encoding virus dramatically inhibited the chondrocytic differentiation of C3H/10T1/2 cells, resulting instead in prominent osteoblast differentiation. These results indicate the chondrogenic potential of C3H/10T1/2 cells was abrogated by osterix expression. Chondrocyte differentiation of MSCs, however, was not enhanced by silencing the osterix gene using lentivirus-mediated shRNA, despite successful suppression of osteoblast differentiation. These results suggest that the low levels of osterix expression remaining after knockdown are sufficient to block chondrogenesis, whereas higher expression may be required to promote osteoblastic differentiation.     

Distribution of TRAP‐positive cells and expression of HIF‐1α, VEGF,and FGF‐2 in the reparative reaction in patients with osteonecrosis of the femoral head

Osteogenesis and angiogenesis are closely associated with the reparative process in bone. In osteonecrosis of the femoral head (ONFH), although the progression of bone resorption by osteoclasts is considered to be followed by femoral head collapse, the reparative reaction remains unknown. In order to investigate the reparative reaction in patients with ONFH, the distribution of TRAP‐ positive cells and expression of HIF‐1α, VEGF, and FGF‐2 were observed in 51 hips in 42 patients. TRAP‐positive cells were detected around the teres insertion and retinaculum in the early radiologic stage, and increased around the new trabecular bone throughout the reparative interface zone in the late collapsed stage. HIF‐1α expression was detected at the fibrosis area and the transitional area, which included the proximal area of the reparative interface zone adjacent to the necrotic zone. VEGF was expressed at the edematous area of the reparative interface zone, while FGF‐2 was detected widely in the reparative interface zone and the normal zone. In the late radiologic stages, HIF‐1α, VEGF, and FGF‐2 were not detected in the necrotic zone, and they acted in angiogenesis in the reparative interface zone, while TRAP‐positive cells increased around the new bone formation in response to remodeling after the collapse. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 694–700, 2009     

New clinical evidence of silodosin,an α1A selective adrenoceptor antagonist,in the treatment for lower urinary tract symptoms

Lower urinary tract symptoms associated with benign prostatic hyperplasia are highly prevalent in older men. Pharmacological treatment is the first‐line treatment for lower urinary tract symptoms associated with benign prostatic hyperplasia. The first choice in the pharmacological treatment for lower urinary tract symptoms associated with benign prostatic hyperplasia is the α₁‐adrenoceptor antagonists. Many α₁‐adrenoceptor antagonists are available in the world. Silodosin is an α₁‐adrenoceptor antagonist developed by Kissei Pharmaceutical, and has a specific selectivity for the α_1A‐adrenoceptor subtype. By antagonizing α_1A‐adrenoceptor in the prostate and urethra, silodosin causes smooth muscle relaxation in the lower urinary tract. As a result of the high affinity for the α_1A‐adrenoceptor than for the α_1B‐adrenoceptor, silodosin minimizes the propensity for blood pressure‐related adverse effects caused by blockade of α_1B‐adrenoceptor. The efficacy and safety of silodosin for treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia was first reported by Japanese investigators in 2006. At present, silodosin is used in many countries. In the present review, we summarize the new clinical evidence for lower urinary tract symptoms associated with benign prostatic hyperplasia and introduce the data supporting the new clinical indications of silodosin.