The involvement of YAP-TGFβ-SMAD-mediated fibrosis in primary inferior oblique overaction

• Published in: Biochimica et biophysica acta. Molecular basis of disease 2024-12, Vol.1871 (3), p.167620, Article 167620
• Main Authors: Tang, Shiyu, Wen, Chaojuan, Shen, Tao, Zhu, Binbin, Wang, Xiangjun, Wang, Zhonghao, Fu, Licheng, Wen, Yun, Han, Mengya, Kuang, Xielan, Ma, Weixia, Shen, Huangxuan, Yan, Jianhua
• Format: Article
• Language: English
• Subjects: Fibro/adipogenic progenitors; Fibrosis; Primary inferior oblique overaction; YAP-TGFβ-SMAD signaling pathway
• ISSN: 0925-4439; 1879-260X; 1879-260X
• DOI: 10.1016/j.bbadis.2024.167620

This study investigates the involvement of fibrosis in primary inferior oblique overaction (PIOOA), a strabismus characterized by excessive upward eye rotation. First, we identified extensive fibrotic changes in inferior oblique (IO) muscles in PIOOA patients compared to normal controls. A strong positive correlation was clinically established between the severity of PIOOA and the expression of collagen type I alpha 1 chain (COL1A1). COL1A1 levels correlate with preoperative and postoperative clinical grading of PIOOA and the degree of fundus deviation, as measured by disk-foveal angle (DFA). Moreover, immunofluorescence in IO muscle sections of PIOOA patients confirmed activation of fibro/adipogenic progenitors (FAPs) and suggested increased activation of YAP. Interestingly, the TGFβ signaling pathway also exhibited activation, with a notable increase observed in the expression of TGFβ2 in the PIOOA group. Subsequently, we first isolated FAPs from human IO muscles and validated these findings. In vitro, YAP overexpression promoted the differentiation of FAPs into myofibroblasts, exacerbating fibrotic changes. However, knockdown of YAP inhibited the activation of FAPs and fibrogenesis induced by TGFβ2. More importantly, we found TGFβ2 treatment promoted the activation of YAP simultaneously, and the overexpression or inhibition of YAP also affected TGFβ2 production and Smad phosphorylation, indicating a close connection between the two. Remarkably, verteporfin was observed to block both pathways effectively. Taken together, these findings suggest that the YAP-TGFβ-SMAD signaling cascade plays a key role in the pathophysiology of PIOOA through FAP-mediated fibrosis. Targeting these pathways may therefore provide a potential therapeutic strategy for managing PIOOA by alleviating muscle fibrosis. •Identification of extensive fibrotic changes in the inferior oblique (IO) muscle of Primary inferior oblique overaction (PIOOA) patients.•PIOOA severity strongly correlates with COL1A1 expression, emphasizing fibrosis's role.•Discovery of activated Fibro-Adipogenic Progenitors (FAPs) in PIOOA IO muscle, potentially regulated by YAP and TGFβ signaling pathways.•First FAPs Isolation from IO muscles, providing a crucial tool for investigating the pathological mechanisms of PIOOA.•Verteporfin blocks YAP-TGFβ-SMAD pathways, showing potential as a therapy for PIOOA by reducing muscle fibrosis.