Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Oxford Road, Manchester M13 9PT, UK.
St George & Sutherland Clinical School, University of New South Wales, Sydney, NSW 2217, Australia.
Int J Mol Sci. 2020 Sep 27;21(19):7143. doi: 10.3390/ijms21197143.
Growth differentiation factor (GDF) family members have been implicated in the development and maintenance of healthy nucleus pulposus (NP) tissue, making them promising therapeutic candidates for treatment of intervertebral disc (IVD) degeneration and associated back pain. GDF6 has been shown to promote discogenic differentiation of mesenchymal stem cells, but its effect on NP cells remains largely unknown. Our aim was to investigate GDF6 signalling in adult human NP cells derived from degenerate tissue and determine the signal transduction pathways critical for GDF6-mediated phenotypic changes and tissue homeostatic mechanisms. This study demonstrates maintained expression of GDF6 receptors in human NP and annulus fibrosus (AF) cells across a range of degeneration grades at gene and protein level. We observed an anabolic response in NP cells treated with recombinant GDF6 (increased expression of matrix and NP-phenotypic markers; increased glycosaminoglycan production; no change in catabolic enzyme expression), and identified the signalling pathways involved in these responses (SMAD1/5/8 and ERK1/2 phosphorylation, validated by blocking studies). These findings suggest that GDF6 promotes a healthy disc tissue phenotype in degenerate NP cells through SMAD-dependent and -independent (ERK1/2) mechanisms, which is important for development of GDF6 therapeutic strategies for treatment of degenerate discs.
生长分化因子 (GDF) 家族成员被认为与健康的核髓核组织的发育和维持有关，使它们成为治疗椎间盘 (IVD) 退变和相关腰痛的有前途的治疗候选物。已经表明 GDF6 促进间充质干细胞的椎间盘分化，但它对 NP 细胞的影响在很大程度上仍然未知。我们的目的是研究来自退变组织的成人人类 NP 细胞中的 GDF6 信号传导，并确定 GDF6 介导的表型变化和组织稳态机制的关键信号转导途径。这项研究表明，在基因和蛋白水平上，GDF6 受体在人类 NP 和纤维环 (AF) 细胞中均保持表达，其表达范围跨越一系列退变等级。我们观察到用重组 GDF6 处理的 NP 细胞表现出合成代谢反应（基质和 NP 表型标志物的表达增加；糖胺聚糖产生增加；代谢酶表达无变化），并确定了参与这些反应的信号通路（SMAD1/5/8 和 ERK1/2 磷酸化，通过阻断研究验证）。这些发现表明，GDF6 通过 SMAD 依赖和非依赖（ERK1/2）机制促进退变 NP 细胞中健康的椎间盘组织表型，这对于开发 GDF6 治疗退变椎间盘的治疗策略很重要。
