School of Biological Sciences, Seoul National University, Seoul, South Korea.
Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
J Cachexia Sarcopenia Muscle. 2021 Feb;12(1):177-191. doi: 10.1002/jcsm.12653. Epub 2020 Nov 27.
With organismal aging, the hypothalamic-pituitary-gonadal (HPG) activity gradually decreases, resulting in the systemic functional declines of the target tissues including skeletal muscles. Although the HPG axis plays an important role in health span, how the HPG axis systemically prevents functional aging is largely unknown.
We generated muscle stem cell (MuSC)-specific androgen receptor (Ar) and oestrogen receptor 2 (Esr2) double knockout (dKO) mice and pharmacologically inhibited (Antide) the HPG axis to mimic decreased serum levels of sex steroid hormones in aged mice. After short-term and long-term sex hormone signalling ablation, the MuSCs were functionally analysed, and their aging phenotypes were compared with those of geriatric mice (30-month-old). To investigate pathways associated with sex hormone signalling disruption, RNA sequencing and bioinformatic analyses were performed.
Disrupting the HPG axis results in impaired muscle regeneration [wild-type (WT) vs. dKO, P < 0.0001; Veh vs. Antide, P = 0.004]. The expression of DNA damage marker (in WT = 7.0 ± 1.6%, dKO = 32.5 ± 2.6%, P < 0.01; in Veh = 13.4 ± 4.5%, Antide = 29.7 ± 5.5%, P = 0.028) and senescence-associated β-galactosidase activity (in WT = 3.8 ± 1.2%, dKO = 10.3 ± 1.6%, P < 0.01; in Veh = 2.1 ± 0.4%, Antide = 9.6 ± 0.8%, P = 0.005), as well as the expression levels of senescence-associated genes, p16 and p21 , was significantly increased in the MuSCs, indicating that genetic and pharmacological inhibition of the HPG axis recapitulates the progressive aging process of MuSCs. Mechanistically, the ablation of sex hormone signalling reduced the expression of transcription factor EB (Tfeb) and Tfeb target gene in MuSCs, suggesting that sex hormones directly induce the expression of Tfeb, a master regulator of the autophagy-lysosome pathway, and consequently autophagosome clearance. Transduction of the Tfeb in naturally aged MuSCs increased muscle mass [control geriatric MuSC transplanted tibialis anterior (TA) muscle = 34.3 ± 2.9 mg, Tfeb-transducing geriatric MuSC transplanted TA muscle = 44.7 ± 6.7 mg, P = 0.015] and regenerating myofibre size [eMyHC tdTomato myofibre cross-section area (CSA) in control vs. Tfeb, P = 0.002] after muscle injury.
Our data show that the HPG axis systemically controls autophagosome clearance in MuSCs through Tfeb and prevents MuSCs from senescence, suggesting that sustained HPG activity throughout life regulates autophagosome clearance to maintain the quiescence of MuSCs by preventing senescence until advanced age.
随着机体衰老，下丘脑-垂体-性腺（HPG）活性逐渐降低，导致包括骨骼肌在内的靶组织的全身功能下降。尽管 HPG 轴在健康寿命中起着重要作用，但 HPG 轴如何系统地预防功能衰老在很大程度上仍是未知的。
我们生成了肌肉干细胞（MuSC）特异性雄激素受体（Ar）和雌激素受体 2（Esr2）双敲除（dKO）小鼠，并通过药理学抑制（Antide）HPG 轴来模拟老年小鼠血清中性激素水平降低。在短期和长期的性激素信号缺失后，对 MuSCs 进行功能分析，并将其衰老表型与老年小鼠（30 月龄）进行比较。为了研究与性激素信号中断相关的途径，进行了 RNA 测序和生物信息学分析。
破坏 HPG 轴会导致肌肉再生受损[野生型（WT）与 dKO，P<0.0001；Veh 与 Antide，P=0.004]。DNA 损伤标志物的表达（WT=7.0±1.6%，dKO=32.5±2.6%，P<0.01；Veh=13.4±4.5%，Antide=29.7±5.5%，P=0.028）和衰老相关的β-半乳糖苷酶活性（WT=3.8±1.2%，dKO=10.3±1.6%，P<0.01；Veh=2.1±0.4%，Antide=9.6±0.8%，P=0.005），以及衰老相关基因 p16 和 p21 的表达水平在 MuSCs 中显著增加，表明遗传和药理学抑制 HPG 轴重现了 MuSCs 的渐进性衰老过程。从机制上讲，性激素信号的缺失降低了 MuSCs 中转录因子 EB（Tfeb）和 Tfeb 靶基因的表达，表明性激素直接诱导自噬-溶酶体途径的主调控因子 Tfeb 的表达，从而促进自噬体清除。天然衰老的 MuSCs 中转导 Tfeb 增加了肌肉质量[对照老年 MuSC 移植前胫骨前肌（TA）肌肉=34.3±2.9mg，Tfeb 转导老年 MuSC 移植 TA 肌肉=44.7±6.7mg，P=0.015]和再生肌纤维大小[eMyHC tdTomato 肌纤维横截面积（CSA）在对照与 Tfeb 之间，P=0.002]，提示在肌肉损伤后。
我们的数据表明，HPG 轴通过 Tfeb 系统地控制 MuSCs 中的自噬体清除，并防止 MuSCs 衰老，这表明终生持续的 HPG 活性通过防止衰老来调节自噬体清除，从而维持 MuSCs 的静止状态，直到老年。
Zotero 插件