Sorokina Margarita, Bobkov Danila, Khromova Natalia, Vilchinskaya Natalia, Shenkman Boris, Kostareva Anna, Dmitrieva Renata
Almazov National Medical Research Centre, Saint Petersburg, Russia.
Institute of Cytology, Russian Academy of Sciences, Saint Petersburg, Russia.
Skelet Muscle. 2024 Dec 6;14(1):31. doi: 10.1186/s13395-024-00362-2.
Skeletal muscle resident fibro-adipogenic progenitor cells (FAPs) control skeletal muscle regeneration providing a supportive role for muscle stem cells. Altered FAPs characteristics have been shown for a number of pathological conditions, but the influence of temporary functional unloading of healthy skeletal muscle on FAPs remains poorly studied. This work is aimed to investigate how skeletal muscle disuse affects the functionality and metabolism of FAPs.
Hindlimb suspension (HS) rat model employed to investigate muscle response to decreased usage. FAPs were purified from m. soleus functioning muscle (Contr) and after functional unloading for 7 and 14 days (HS7 and HS14). FAPs were expanded in vitro, and tested for: immunophenotype; in vitro expansion rate, and migration activity; ability to differentiate into adipocytes in vitro; metabolic changes. Crosstalk between FAPs and muscle stem cells was estimated by influence of medium conditioned by FAP's on migration and myogenesis of C2C12 myoblasts. To reveal the molecular mechanisms behind unloading-induced alterations in FAP's functionality transcriptome analysis was performed.
FAPs isolated from Contr and HS muscles exhibited phenotype of MSC cells. FAPs in vitro expansion rate and migration were altered by functional unloading conditions. All samples of FAPs demonstrated the ability to adipogenic differentiation in vitro, however, HS FAPs formed fat droplets of smaller volume and transcriptome analysis showed fatty acids metabolism and PPAR signaling suppression. Skeletal muscle unloading resulted in metabolic reprogramming of FAPs: decreased spare respiratory capacity, decreased OCR/ECAR ratio detected in both HS7 and HS14 samples point to reduced oxygen consumption, decreased potential for substrate oxidation and a shift to glycolytic metabolism. Furthermore, C2C12 cultures treated with medium conditioned by FAPs showed diverse alterations: while the HS7 FAPs-derived paracrine factors supported the myoblasts fusion, the HS14-derived medium stimulated proliferation of C2C12 myoblasts; these observations were supported by increased expression of cytokines detected by transcriptome analysis.
the results obtained in this work show that the skeletal muscle functional unloading affects properties of FAPs in time-dependent manner: in atrophying skeletal muscle FAPs act as the sensors for the regulatory signals that may stimulate the metabolic and transcriptional reprogramming to preserve FAPs properties associated with maintenance of skeletal muscle homeostasis during unloading and in course of rehabilitation.
骨骼肌驻留的成纤维脂肪生成祖细胞（FAPs）控制骨骼肌再生，为肌肉干细胞提供支持作用。在许多病理状况下已显示FAPs特征发生改变，但健康骨骼肌的暂时功能卸载对FAPs的影响仍研究不足。本研究旨在探究骨骼肌废用如何影响FAPs的功能和代谢。
采用后肢悬吊（HS）大鼠模型来研究肌肉对使用减少的反应。从比目鱼肌功能正常的肌肉（对照）以及功能卸载7天和14天后（HS7和HS14）纯化FAPs。FAPs在体外扩增，并进行以下检测：免疫表型；体外扩增率和迁移活性；体外分化为脂肪细胞的能力；代谢变化。通过FAPs条件培养基对C2C12成肌细胞迁移和肌肌生成的影响来评估FAPs与肌肉干细胞之间的相互作用。为揭示卸载诱导的FAPs功能改变背后的分子机制，进行了转录组分析。
从对照和HS肌肉中分离的FAPs表现出间充质干细胞（MSC）的表型。功能卸载条件改变了FAPs的体外扩增率和迁移。所有FAPs样本均显示出体外成脂分化能力，然而，HS FAPs形成较小体积的脂滴，转录组分析显示脂肪酸代谢和PPAR信号传导受到抑制。骨骼肌卸载导致FAPs的代谢重编程：备用呼吸能力降低，在HS7和HS14样本中检测到的OCR/ECAR比值降低，表明氧消耗减少、底物氧化潜力降低以及向糖酵解代谢转变。此外，用FAPs条件培养基处理的C2C12培养物表现出不同的变化：虽然HS7 FAPs衍生的旁分泌因子支持成肌细胞融合，但HS14衍生的培养基刺激C2C12成肌细胞增殖；转录组分析检测到的细胞因子表达增加支持了这些观察结果。
本研究获得的结果表明，骨骼肌功能卸载以时间依赖性方式影响FAPs的特性：在萎缩的骨骼肌中，FAPs充当调节信号的传感器，这些信号可能刺激代谢和转录重编程，以维持卸载期间和康复过程中与骨骼肌稳态维持相关的FAPs特性。
