Huang Henry, Veien Eric S, Zhang Hong, Ayers David C, Song Jie
Department of Orthopedics and Physical Rehabilitation, University of Massachusetts Medical School, Worcester, MA, United States of America.
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA, United States of America.
PLoS One. 2016 Jan 27;11(1):e0148088. doi: 10.1371/journal.pone.0148088. eCollection 2016.
Overexpression of Smad ubiquitin regulatory factor 2 (Smurf2) in chondrocytes was reported to cause spontaneous osteoarthritis (OA) in mice. However, it is unclear whether Smurf2 is involved in bone and cartilage homeostasis and if it is required for OA pathogenesis. Here we characterized age-related changes in the bone and articular cartilage of Smurf2-deficient (MT) mice by microCT and histology, and examined whether reduced Smurf2 expression affected the severity of OA upon surgical destabilization of the medial meniscus (DMM). Using immature articular chondrocytes (iMAC) from MT and wild-type (WT) mice, we also examined how Smurf2 deficiency affects chondrogenic and catabolic gene expressions and Smurf2 and Smurf1 proteins upon TGF-β3 or IL-1β treatment in culture. We found no differences in cortical, subchondral and trabecular bone between WT and MT in young (4 months) and old mice (16-24 months). The articular cartilage and age-related alterations between WT and MT were also similar. However, 2 months following DMM, young MT showed milder OA compared to WT (~70% vs ~30% normal or exhibiting only mild OA cartilage phenotype). The majority of the older WT and MT mice developed moderate/severe OA 2 months after DMM, but a higher subset of aged MT cartilage (27% vs. 9% WT) remained largely normal. Chondrogenic gene expression (Sox9, Col2, Acan) trended higher in MT iMACs than WT with/without TGF-β3 treatment. IL-1β treatment suppressed chondrgenic gene expression, but Sox9 expression in MT remained significantly higher than WT. Smurf2 protein in WT iMACs increased upon TGF-β3 treatment and decreased upon IL-1β treatment in a dose-dependent manner. Smurf1 protein elevated more in MT than WT upon TGF-β3 treatment, suggesting a potential, but very mild compensatory effect. Overall, our data support a role of Smurf2 in regulating OA development but suggest that inhibiting Smurf2 alone may not be sufficient to prevent or consistently mitigate post-traumatic OA across a broad age range.
据报道,软骨细胞中Smad泛素调节因子2(Smurf2)的过表达会导致小鼠自发性骨关节炎(OA)。然而,尚不清楚Smurf2是否参与骨骼和软骨的稳态,以及它是否是OA发病机制所必需的。在这里,我们通过显微CT和组织学方法对Smurf2缺陷(MT)小鼠的骨骼和关节软骨的年龄相关变化进行了表征,并研究了在内侧半月板手术不稳定(DMM)后,Smurf2表达降低是否会影响OA的严重程度。使用来自MT和野生型(WT)小鼠的未成熟关节软骨细胞(iMAC),我们还研究了在培养中用TGF-β3或IL-1β处理后,Smurf2缺陷如何影响软骨生成和分解代谢基因表达以及Smurf2和Smurf1蛋白。我们发现,在年轻(4个月)和老年小鼠(16 - 24个月)中,WT和MT之间的皮质骨、软骨下骨和小梁骨没有差异。WT和MT之间的关节软骨及其年龄相关变化也相似。然而,DMM后2个月,与WT相比,年轻的MT表现出较轻的OA(正常或仅表现出轻度OA软骨表型的比例约为70%对30%)。大多数老年WT和MT小鼠在DMM后2个月发展为中度/重度OA,但老年MT软骨中较高比例(27%对WT的9%)在很大程度上仍保持正常。在有/无TGF-β3处理的情况下,MT iMACs中的软骨生成基因表达(Sox9、Col2、Acan)趋势高于WT。IL-1β处理抑制了软骨生成基因表达,但MT中的Sox9表达仍显著高于WT。WT iMACs中的Smurf2蛋白在TGF-β3处理后增加,在IL-1β处理后以剂量依赖方式减少。在TGF-β3处理后,MT中的Smurf1蛋白升高幅度比WT更大,表明存在潜在但非常轻微的补偿作用。总体而言,我们的数据支持Smurf2在调节OA发展中的作用,但表明仅抑制Smurf2可能不足以在广泛的年龄范围内预防或持续减轻创伤后OA。