Wu Qiuqian, Wang Meina, Zuscik Michael J, Chen Di, O'Keefe Regis J, Rosier Randy N
Department of Orthopaedics, Center for Musculoskeletal Research, University of Rochester Medical Center, 601 Elmwood Avenue, Box 665, Rochester, New York 14642, USA.
J Orthop Res. 2008 May;26(5):704-12. doi: 10.1002/jor.20563.
Smurf2 is an E3 ubiquitin ligase that targets TGF-beta receptor activated Smad2 and Smad3 for the proteasome in primary articular chondrocytes, thus stimulating their hypertrophic differentiation. Comparatively, how Smurf2 functions in growth plate chondrocytes in a developing long bone is an open question. In this study, we measured the mRNA levels of endogenous Smurf2 and type X collagen in chick growth plate at different embryonic stages to monitor the correlation between the level of Smurf2 expression and chondrocyte maturational stage. We found that high levels of Smurf2 were associated with the differentiative and proliferative stages, while Smurf2 levels were thereafter decreased as the chondrocytes matured toward hypertrophy. In addition, we injected Smurf2-RCAS into chick wing buds at HH stage 20-23 and examined how the ectopic overexpression of Smurf2 in condensing chondrogenic mesenchyme affects the subsequent process of chondrocyte maturation and ossification during embryonic development. Histological analysis showed that overexpression of Smurf2 in a developing wing bud accelerated chondrocyte maturation and endochondral ossification, which may result from a decrease in TGF-beta signaling in the infected chondrocytes with Smurf2-RCAS.
Smurf2是一种E3泛素连接酶，它在原代关节软骨细胞中靶向转化生长因子-β（TGF-β）受体激活的Smad2和Smad3，使其进入蛋白酶体，从而刺激它们的肥大分化。相比之下，Smurf2在发育中的长骨生长板软骨细胞中如何发挥作用仍是一个悬而未决的问题。在本研究中，我们测量了不同胚胎阶段鸡生长板中内源性Smurf2和X型胶原蛋白的mRNA水平，以监测Smurf2表达水平与软骨细胞成熟阶段之间的相关性。我们发现，高水平的Smurf2与分化和增殖阶段相关，而随着软骨细胞向肥大方向成熟，Smurf2水平随后降低。此外，我们在HH阶段20-23将Smurf2-RCAS注射到鸡翼芽中，并研究了在凝聚的软骨形成间充质中Smurf2的异位过表达如何影响胚胎发育过程中软骨细胞成熟和骨化的后续过程。组织学分析表明，在发育中的翼芽中Smurf2的过表达加速了软骨细胞成熟和软骨内骨化，这可能是由于用Smurf2-RCAS感染的软骨细胞中TGF-β信号传导减少所致。
