Department of Orthopaedics, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences,Third Hospital of Shanxi Medical University, Tongji Shanxi Hospital, Taiyuan, Shanxi Province, 030032, People's Republic of China.
Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Taiyuan, Shanxi Province, 030001, People's Republic of China.
BMC Musculoskelet Disord. 2024 Jun 15;25(1):467. doi: 10.1186/s12891-024-07578-9.
The present study evaluated whether the lack of histone deacetylase 4 (HDAC4) increases endoplasmic reticulum stress-induced chondrocyte apoptosis by releasing activating transcription factor 4 (ATF4) in human osteoarthritis (OA) cartilage degeneration.
Articular cartilage from the tibial plateau was obtained from patients with OA during total knee replacement. Cartilage extracted from severely damaged regions was classified as degraded cartilage, and cartilage extracted from a relatively smooth region was classified as preserved cartilage. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining was used to detect chondrocyte apoptosis. HDAC4, ATF4, and C/EBP homologous protein (CHOP) expression levels were measured using immunohistochemistry staining and real-time quantitative PCR. Chondrocytes were transfected with HDAC4 or HDAC4 siRNA for 24 h and stimulated with 300 µM HO for 12 h. The chondrocyte apoptosis was measured using flow cytometry. ATF4, CHOP, and caspase 12 expression levels were measured using real-time quantitative PCR and western blotting. Male Sprague-Dawley rats (n = 15) were randomly divided into three groups and transduced with different vectors: ACLT + Ad-GFP, ACLT + Ad-HDAC4-GFP, and sham + Ad-GFP. All rats received intra-articular injections 48 h after the operation and every three weeks thereafter. Cartilage damage was assessed using Safranin O staining and quantified using the Osteoarthritis Research Society International score. ATF4, CHOP, and collagen II expression were detected using immunohistochemistry, and chondrocyte apoptosis was detected using terminal deoxynucleotidyl transferase dUTP nick end labeling staining.
The chondrocyte apoptosis was higher in degraded cartilage than in preserved cartilage. HDAC4 expression was lower in degraded cartilage than in preserved cartilage. ATF4 and CHOP expression was increased in degraded cartilage. Upregulation of HDAC4 in chondrocytes decreased the expression of ATF4, while the expression of ATF4 was increased after downregulation of HDAC4. Upregulation of HDAC4 decreased the chondrocyte apoptosis under endoplasmic reticulum stress, and chondrocyte apoptosis was increased after downregulation of HDAC4. In a rat anterior cruciate ligament transection OA model, adenovirus-mediated transduction of HDAC4 was administered by intra-articular injection. We detected a stronger Safranin O staining with lower Osteoarthritis Research Society International scores, lower ATF4 and CHOP production, stronger collagen II expression, and lower chondrocyte apoptosis in rats treated with Ad-HDAC4.
The lack of HDAC4 expression partially contributes to increased ATF4, CHOP, and endoplasmic reticulum stress-induced chondrocyte apoptosis in OA pathogenesis. HDAC4 attenuates cartilage damage by repressing ATF4-CHOP signaling-induced chondrocyte apoptosis in a rat model of OA.
本研究评估了在人骨关节炎（OA）软骨退变中，缺乏组蛋白去乙酰化酶 4（HDAC4）是否通过释放激活转录因子 4（ATF4）增加内质网应激诱导的软骨细胞凋亡。
在全膝关节置换术中从 OA 患者的胫骨平台获取关节软骨。从严重受损区域提取的软骨被归类为降解软骨，而从相对光滑区域提取的软骨被归类为保存软骨。末端脱氧核苷酸转移酶 dUTP 缺口末端标记染色用于检测软骨细胞凋亡。使用免疫组织化学染色和实时定量 PCR 测量 HDAC4、ATF4 和 C/EBP 同源蛋白（CHOP）的表达水平。用 HDAC4 或 HDAC4 siRNA 转染软骨细胞 24 小时，并用 300µM HO 刺激 12 小时。用流式细胞术测量软骨细胞凋亡。用实时定量 PCR 和 Western blot 测量 ATF4、CHOP 和 caspase 12 的表达水平。雄性 Sprague-Dawley 大鼠（n=15）随机分为三组，并转导不同的载体：ACLT+Ad-GFP、ACLT+Ad-HDAC4-GFP 和 sham+Ad-GFP。所有大鼠在手术后 48 小时内接受关节内注射，此后每 3 周注射一次。用番红 O 染色评估软骨损伤，并采用骨关节炎研究协会国际评分进行定量。用免疫组织化学检测 ATF4、CHOP 和胶原 II 的表达，用末端脱氧核苷酸转移酶 dUTP 缺口末端标记染色检测软骨细胞凋亡。
降解软骨中的软骨细胞凋亡高于保存软骨。降解软骨中的 HDAC4 表达低于保存软骨。降解软骨中的 ATF4 和 CHOP 表达增加。软骨细胞中 HDAC4 的上调降低了 ATF4 的表达，而 HDAC4 的下调增加了 ATF4 的表达。内质网应激下，HDAC4 的上调降低了软骨细胞凋亡，而 HDAC4 的下调增加了软骨细胞凋亡。在大鼠前交叉韧带切断性 OA 模型中，通过关节内注射给予腺病毒介导的 HDAC4 转导。我们发现，用 Ad-HDAC4 处理的大鼠的番红 O 染色更强，骨关节炎研究协会国际评分更低，ATF4 和 CHOP 产物更少，胶原 II 表达更强，软骨细胞凋亡更低。
HDAC4 表达缺失部分导致 OA 发病机制中 ATF4、CHOP 和内质网应激诱导的软骨细胞凋亡增加。在 OA 大鼠模型中，HDAC4 通过抑制 ATF4-CHOP 信号诱导的软骨细胞凋亡，减轻软骨损伤。
