Department of Orthopaedics, University Medical Center Utrecht, The Netherlands.
Osteoarthritis Cartilage. 2010 Nov;18(11):1487-95. doi: 10.1016/j.joca.2010.08.006. Epub 2010 Aug 17.
In degenerative intervertebral discs (IVDs) collagen type X expression and calcifications have been demonstrated, resembling advanced osteoarthritis (OA), which is associated with hypertrophic differentiation, characterized by the production of collagen type X, Runt-related transcription factor 2 (Runx2), osteoprotegerin (OPG), alkaline phosphatase (ALP) and calcifications.
The aim of this study was to determine if hypertrophic differentiation occurs during IVD degeneration.
IVDs from all Thompson degeneration grades were prepared for histology, extraction of nucleus pulposus (NP) and annulus fibrosis (AF) tissue (N=50) and micro-CT (N=27). The presence of collagen type X, OPG and Runx2 was determined by immunohistochemistry, with OPG levels also determined by Enzyme-linked immunosorbent assay (ELISA). The presence of calcification was determined by micro-CT, von Kossa and Alizarin Red staining.
Immunohistochemical staining for collagen type X, OPG, Runx2 appeared more intense in the NP of degenerative compared to healthy IVD samples. OPG levels correlated significantly with degeneration grade (NP: P<0.000; AF: P=0.002) and the number of microscopic calcifications (NP: P=0.002; AF: P=0.008). The extent of calcifications on micro-CT also correlated with degeneration grade (NP: P<0.001, AF: P=0.001) as did von Kossa staining (NP: P=0.015, AF: P=0.016). ALP staining was only incidentally seen in the transition zone of grades IV and V degenerated IVDs.
This study for the first time demonstrates that hypertrophic differentiation occurs during IVD degeneration, as shown by an increase in OPG levels, the presence of ALP activity, increased immunopositivity of Runx2 and collagen type X.
在退行性椎间盘中（IVD），已经证明存在胶原蛋白 X 的表达和钙化，类似于晚期骨关节炎（OA），其与肥大分化有关，特征为胶原蛋白 X、Runt 相关转录因子 2（Runx2）、骨保护素（OPG）、碱性磷酸酶（ALP）和钙化的产生。
本研究旨在确定肥大分化是否发生在 IVD 退变过程中。
对所有 Thompson 退变分级的 IVD 进行组织学准备，提取髓核（NP）和纤维环（AF）组织（n=50）和 micro-CT（n=27）。通过免疫组织化学法测定胶原蛋白 X、OPG 和 Runx2 的存在，通过酶联免疫吸附试验（ELISA）测定 OPG 水平。通过 micro-CT、von Kossa 和茜素红染色确定钙化的存在。
与健康 IVD 样本相比，退变的 NP 中胶原蛋白 X、OPG、Runx2 的免疫组织化学染色更强烈。OPG 水平与退变分级显著相关（NP：P<0.000；AF：P=0.002）和显微镜下钙化的数量（NP：P=0.002；AF：P=0.008）。micro-CT 上钙化的程度也与退变分级相关（NP：P<0.001，AF：P=0.001），与 von Kossa 染色也相关（NP：P=0.015，AF：P=0.016）。ALP 染色仅在 IV 和 V 级退变的 IVD 过渡区偶尔出现。
本研究首次证明，肥大分化发生在 IVD 退变过程中，这表现为 OPG 水平增加、ALP 活性增加、Runx2 和胶原蛋白 X 的免疫阳性增强。
