van Meurs J B, van Lent P L, Holthuysen A E, Singer I I, Bayne E K, van den Berg W B
Department of Rheumatology, University Hospital Nijmegen, The Netherlands.
Arthritis Rheum. 1999 Jun;42(6):1128-39. doi: 10.1002/1529-0131(199906)42:6<1128::AID-ANR9>3.0.CO;2-2.
Two major cleavage sites, one mediated by metalloproteinases (MMPs) and the other by an as-yet unidentified enzyme termed aggrecanase, have been observed in aggrecan. To learn more about the relative contribution of these enzymes during cartilage degradation, this study assessed the occurrence of both specific neoepitopes in cartilage during murine arthritis and examined the correlation between neoepitope formation and different aspects of cartilage damage.
Reversible cartilage damage was induced in mice in the zymosan-induced arthritis (ZIA) model, partly irreversible cartilage damage in the antigen-induced arthritis (AIA) model, and irreversible, destructive cartilage damage in the collagen-induced arthritis (CIA) model. Immunolocalization techniques were used to detect the specific C-terminal neoepitopes VDIPEN (MMPS) and NITEGE (aggrecanase).
In normal cartilage from young adult mice, no VDIPEN epitopes were detected, but a limited amount of NITEGE epitopes were already present. During the early phase of proteoglycan (PG) depletion, NITEGE expression was raised substantially in all arthritis models. VDIPEN epitopes were not detected in this early phase of cartilage destruction. When PG depletion progressed toward advanced cartilage damage, VDIPEN epitopes were induced. During ZIA, minimal induction of VDIPEN was observed, whereas in AIA, strong, but partly reversible, VDIPEN staining was evident, and in CIA, an extensive presence and persistence of the MMP-induced neoepitope was seen. When VDIPEN epitopes were intensely present, NITEGE epitopes were greatly reduced at that site in the cartilage.
Presence of VDIPEN epitopes in cartilage correlated with severe cartilage damage, but these epitopes were not detected during early PG degradation. This suggests a limited role for VDIPEN-inducing MMPs in early PG degradation during murine arthritis. In contrast, aggrecanase epitopes were induced before the appearance of VDIPEN epitopes, but they disappeared with progression of cartilage damage.
在聚集蛋白聚糖中已观察到两个主要裂解位点，一个由金属蛋白酶（MMPs）介导，另一个由一种尚未鉴定的名为聚集蛋白聚糖酶的酶介导。为了更多地了解这些酶在软骨降解过程中的相对作用，本研究评估了在小鼠关节炎期间软骨中这两种特定新表位的出现情况，并研究了新表位形成与软骨损伤不同方面之间的相关性。
在酵母聚糖诱导的关节炎（ZIA）模型中诱导小鼠发生可逆性软骨损伤，在抗原诱导的关节炎（AIA）模型中诱导部分不可逆性软骨损伤，在胶原诱导的关节炎（CIA）模型中诱导不可逆的、破坏性软骨损伤。采用免疫定位技术检测特定的C端新表位VDIPEN（MMPs）和NITEGE（聚集蛋白聚糖酶）。
在年轻成年小鼠的正常软骨中，未检测到VDIPEN表位，但已存在少量NITEGE表位。在蛋白聚糖（PG）消耗的早期阶段，所有关节炎模型中NITEGE表达均显著升高。在软骨破坏的早期阶段未检测到VDIPEN表位。当PG消耗进展为严重的软骨损伤时，诱导产生VDIPEN表位。在ZIA期间，观察到VDIPEN的诱导作用最小，而在AIA中，VDIPEN染色强烈但部分可逆，在CIA中，可见MMP诱导的新表位广泛存在且持续存在。当VDIPEN表位大量存在时，软骨中该部位的NITEGE表位大大减少。
软骨中VDIPEN表位的存在与严重的软骨损伤相关，但在早期PG降解过程中未检测到这些表位。这表明在小鼠关节炎早期PG降解过程中，诱导VDIPEN的MMPs作用有限。相比之下，聚集蛋白聚糖酶表位在VDIPEN表位出现之前就被诱导，但随着软骨损伤的进展而消失。
