THE ROLE OF BCL2 PROTEINS IN CHONDROCYTE BIOLOGY

退行性软骨疾病（骨关节炎，OA）是老年人群发病的主要原因。 一些证据支持这样的概念，即软骨细胞活力降低和基质合成减少或改变（特别是）对生长因子的反应导致OA发病率随年龄增长而增加。 Bcl-2家族包含促凋亡和抗凋亡蛋白。 最近的研究表明Bcl-2蛋白在调节软骨细胞凋亡中的作用。 然而，尚未直接显示Bcl-2在体内调节关节软骨细胞凋亡中起作用，也未系统地检测Bcl-2家族的主要成员在关节软骨中的表达。 除了Bcl-2在调节细胞凋亡中的传统作用之外，现在清楚的是Bcl-2参与控制事件如轴突再生和上皮细胞分化的非细胞凋亡途径的调节。现在有证据表明，这种类型的途径在软骨细胞中起作用，并可能与聚集蛋白聚糖的表达有关。 通过Bcl-2依赖性途径调节聚集蛋白聚糖的机制尚未确定，也没有确定该途径在多大程度上可以调节其他软骨基质基因。 因此，Bcl-2蛋白在调节软骨细胞凋亡和基质基因表达中发挥双重作用的一般假设将通过以下具体目标进行探索：1）通过测量编码胶原蛋白II、IX、IX和IX的mRNA水平，确定响应于血清撤回或反义Bcl-2表达的聚集蛋白聚糖表达的抑制是否是软骨细胞特异性基因表达的协同下调的一部分，Xi、link蛋白等; 2）建立聚集蛋白聚糖降低的机制（和其他基质基因）表达和探针的作用，特定的转录因子（NF κ B）在软骨细胞对血清撤除或反义Bcl-2的反应中; 3）确定Bcl-2主要成员的相关性2通过将这些蛋白在大鼠和人类关节软骨中的表达模式与衰老、凋亡和软骨退变相关联来体内研究;还将确定转基因小鼠模型中Bcl-2表达降低对软骨细胞凋亡和基质基因表达的影响。 这种多方面的实验方法旨在探索Bcl-2蛋白在软骨细胞生物学中的基本作用，并确定对软骨维护和OA发病机制至关重要的机制。

Degenerative cartilage disease (osteoarthritis, OA) is a major contributor to morbidity in the elderly population. Several lines of evidence support the concept that decreased chondrocyte viability and diminished or altered matrix synthesis (especially) in response to growth factors contribute to the increased incidence of OA with aging. The Bcl-2 family contains proteins that are both pro-apoptotic and anti-apoptotic. Recent studies have demonstrated a role for Bcl-2 proteins in regulating chondrocyte apoptosis. However it has not been shown directly that Bcl-2 plays a role in regulating articular chondrocyte apoptosis in vivo, nor has the expression of the major members of the Bcl-2 family been systematically examined in articular cartilage. In addition to the traditional role of Bcl-2 in regulating apoptosis, it is now clear that Bcl-2 is involved in the regulation of non-apoptotic pathways that control events such as axonal regeneration and epithelial cell differentiation. Evidence now exists that this type of pathway is operating in the chondrocyte and may be linked to the expression of aggrecan. The mechanisms that regulate aggrecan through a Bcl-2-dependent pathway have not been determined nor has it been established to what extent this pathway may regulate other cartilage matrix genes. Therefore, the general hypothesis that Bcl-2 proteins play a dual role in regulating both chondrocyte apoptosis and matrix gene expression will be explored through the following specific aims: 1) Determine if the inhibition of aggrecan expression in response to serum withdrawal or anti-sense Bcl-2 expression is part of a coordinate down-regulation of chondrocyte-specific gene expression by measuring mRNA levels coding for collagen II, IX, XI, link protein and others; 2) Establish the mechanism for decreased aggrecan (and other matrix gene) expression and probe the role of a specific transcription factor (NFkappaB) in the chondrocyte response to serum withdrawal or anti-sense Bcl-2; 3) Determine the relevance of the major members of the Bcl-2 in vivo by correlating the expression pattern of these proteins in the articular cartilage of rats and humans with aging, apoptosis and cartilage degeneration; also the effect of reduced Bcl-2 expression in a transgenic mouse model on chondrocyte apoptosis and matrix gene expression will be determined. This multifaceted experimental approach is intended to probe the basic role of Bcl-2 proteins in chondrocyte biology and to identify mechanisms that are important for cartilage maintenance and the pathogenesis of OA.