scRNAseq RAT DIA WT and DMD 12months

Duchenne muscular dystrophy (DMD) is a fatal muscle-wasting disorder caused by mutations in the Dystrophin gene with no therapeutic option. To bridge the gap between preclinical and therapeutic evaluation studies, we have generated a rat model for DMD that carries an exon 52 deletion (R DMDdel52) causing a complete lack of dystrophin protein. Here we show that R DMDdel52 animals recapitulated human DMD pathophysiological trajectory more faithfully than the mdx mouse model. We report that R DMDdel52 rats displayed progressive and severe skeletal muscle loss associated with fibrotic deposition, fat infiltration and fibre type switch. Early fibrosis was also apparent in the cardiac muscle. These histological modifications led to severe muscle, respiratory and cardiac functional impairments leading to premature death around one year. Moreover, DMD muscle exhibited systemic inflammation with a mixed M1/M2 phenotype. A comparative single cell RNAseq analysis of the diaphragm muscle was performed, revealing cellular populations alteration and molecular modifications in all muscle cell types. We show that DMD fibroadipogenic progenitors produced elevated levels of cartilage oligomeric matrix protein (COMP), a glycoprotein responsible for modulating homeostasis of extracellular matrix, and whose increased concentration correlated with muscle fibrosis both in R DMDdel52 rats and human patients. Fibrosis is a component of tissue remodelling impacting the whole musculature of DMD patients, at the tissue level but most importantly at the functional level. We therefore propose that this specific biomarker can optimize the prognostic monitoring of functional improvement of patients included in clinical trials.杜氏肌营养不良症（Duchenne muscular dystrophy, DMD）是一类由抗肌萎缩蛋白（Dystrophin）基因突变引发的致死性肌肉萎缩性疾病，目前尚无有效治疗方案。为搭建临床前研究与治疗性评估研究之间的桥梁，我们构建了携带外显子52缺失的DMD大鼠模型（R DMDdel52），该模型可完全缺失抗肌萎缩蛋白。 本研究证实，相较于经典mdx小鼠模型，R DMDdel52大鼠能够更真实地重现人类DMD的病理生理进程。研究发现，R DMDdel52大鼠会出现进行性加重的严重骨骼肌丢失，伴随纤维化沉积、脂肪浸润及肌纤维类型转换；心肌组织中同样可见早期纤维化病变。 上述组织学改变会引发严重的肌肉、呼吸与心脏功能障碍，导致受试个体在约1岁时过早死亡。此外，DMD模型的肌肉组织呈现混合M1/M2表型的全身性炎症反应。 我们对膈肌开展了比较单细胞RNA测序（single cell RNAseq）分析，揭示了所有肌肉细胞类型的细胞群异常与分子层面改变。 研究表明，DMD相关的纤维脂肪祖细胞会高表达软骨寡聚基质蛋白（cartilage oligomeric matrix protein, COMP）——该糖蛋白可调控细胞外基质稳态，其浓度升高与R DMDdel52大鼠及人类患者体内的肌肉纤维化程度均呈显著正相关。 纤维化是组织重塑的核心组分，会从组织层面乃至更关键的功能层面累及DMD患者的全身肌肉系统。因此，我们提出该特异性生物标志物可用于优化临床试验中患者功能改善情况的预后监测。