HMGB2介导ACL损伤后软骨细胞表型异常的分子机制研究

Osteoarthritis (OA) is the most prevalent form of arthritis in the world and is becoming a major public health concern due to the progressive aging of population. Presently, the pathogenesis of OA remains unclear. Recent studies found that HMGB2, a member of the non-histone chromosomal high mobility group protein family, is specifically expressed in mature cartilage surface and its expression level tends to decrease with cell senescence. Therefore, it is thought that HMGB2 is closely related to aging and it has since become a hot spot of senile OA etiology. In our previous studies, abnormal differentiated phenotypes were found in anterior cruciate ligament (ACL)-injured OA chondrocytes. Furthermore, we found that the expression of HMGB2 decreased while the apoptosis-related gene Bcl-2 and Bax increased. We hypothesize that ACL injury leads to the instability of knee biomechanics and the long-term abnormal stress leads to the dysdifferentiation of chondrocyte. This may further disturb the autocrine and paracrine signaling pathways of chondrocyte and lead to the degradation of cartilage matrix. Whether this had a relation with presenility or apoptosis? Presently, studies on effect of HMGB2 on chondrocyte proliferation, differentiation, senescence, apoptosis are still just beginning. For instance, the underlying molecular mechanisms and the regulation of downstream signaling pathways are rarely reported. We intend to start with mechanical factors and influence factors of aging and focus on effect of HMGB2 on hypertrophy differentiation, catabolism, anabolism, and cell apoptosis of ACL-injured OA chondrocytes. Our findings may provide new theoretical supports for the pathogenesis of cartilage degenerative diseases.

OA发病机制至今未明，已成为医学界亟待攻克的学术难题。最新研究发现：HMGB2特异性表达于成熟软骨表层，且随年龄增长表达呈减少趋势，认为与软骨细胞衰老密切相关，已成为老年性OA病因学的研究热点。前期研究中，我们发现ACL损伤性OA的软骨细胞见异常分化表型，HMGB2表达也呈减少趋势，且有凋亡相关基因Bcl-2和Bax的高表达。我们推测：由于ACL损伤致膝关节力学不稳，在长期异常应力刺激下软骨细胞发生异常分化，干扰了软骨细胞的自分泌和旁分泌，导致软骨基质降解。这是否还与早衰、凋亡密切相关呢？目前，国内外学者就HMGB2在软骨细胞增殖、分化、衰老和凋亡过程中所起作用的研究尚处于起步阶段，相关分子机制和信号通路的调节作用更是鲜有报道。因此，我们拟从力学因素和影响衰老的因素入手，研究HMGB2对ACL损伤后OA软骨细胞肥大化分化、分解合成代谢及细胞凋亡的影响，以期为软骨退行性病变提供新的理论支持。

本课题针对ACL损伤后膝骨性关节炎发病率高、发病机制复杂等特点，以及衰老与OA发病关系影响强度难以确定的瓶颈问题。以新近发现的、在成熟软骨表层特异表达的、与衰老密切相关的HMGB2基因为研究对象，利用分子生物学技术和形态学方法，研究HMGB2对软骨细胞异常分化的影响。研究过程中，我们发现ACL损伤后OA软骨细胞呈去分化表型，HMGB2表达有减少趋势。另通过人体miRNA芯片研究成果，利用系统生物学研究手段，提取已证实的OA和衰老均密切相关基因，并将miRNA靶基因在上述基因中逐一指认，利用计算机辅助软件计算这些重要miRNAs之间的协同作用。将已确定的与OA和衰老均有协同作用的miRNAs转染OA细胞模型，发现加入抗衰协同治疗因子miR29a可明显改善OA软骨细胞分泌表型，并能有效抑制HMGB2表达的减少。下一步我们将针对HMGB2对维持软骨细胞稳定表型所起具体调节作用机制进行研究，以期为生物学、医学研究者有针对性地进行OA防治提供新的研究数据和结果。