Project description:Quiescent adult muscle stem cells (MuSCs) regenerate skeletal muscle upon injury throughout life. However, aged skeletal muscles fail to maintain stem cell quiescence, leading to declines in MuSC number and functionality. Although autophagy plays an important role in the maintenance of MuSC quiescence, how quiescent MuSCs and their autophagy levels are maintained throughout life is largely unknown. The current study reveals how GnRH, a hypothalamic hormone, maintains the quiescence of adult MuSCs by preventing the onset of senescence and how the decline of sex steroids in organismal ageing is implicated in MuSC ageing.
Project description:Quiescent satellite cells, also known as adult muscle stem cells, possess a remarkable ability to regenerate skeletal muscle upon injury throughout life. Although they mainly originate from multipotent stem/progenitors of the somite, the mechanism underlying the establishment of quiescent satellite cell populations is unknown. Here, we show that sex hormones induce Mind bomb-1 (Mib1) expression in myofibers at puberty, which activates Notch signaling in cycling juvenile satellite cells and causes them to be converted into quiescent adult satellite cells. Myofibers lacking Mib1 failed to send Notch signals to juvenile satellite cells, leading to impaired cell cycle exit and depletion. Genetic and inhibitor studies revealed that the hypothalamic-pituitary-gonadal axis drives Mib1 expression in the myofiber niche. Our data show how sex hormones establish quiescent adult satellite cell populations by regulating the myofiber niche at puberty. Microarray analysis of Veh or DHT-injected 10-day-old mice s.c. injected with Veh or DHT. TA muscles were isolated 24 h after the injection.
Project description:Quiescent satellite cells, also known as adult muscle stem cells, possess a remarkable ability to regenerate skeletal muscle upon injury throughout life. Although they mainly originate from multipotent stem/progenitors of the somite, the mechanism underlying the establishment of quiescent satellite cell populations is unknown. Here, we show that sex hormones induce Mind bomb-1 (Mib1) expression in myofibers at puberty, which activates Notch signaling in cycling juvenile satellite cells and causes them to be converted into quiescent adult satellite cells. Myofibers lacking Mib1 failed to send Notch signals to juvenile satellite cells, leading to impaired cell cycle exit and depletion. Genetic and inhibitor studies revealed that the hypothalamic-pituitary-gonadal axis drives Mib1 expression in the myofiber niche. Our data show how sex hormones establish quiescent adult satellite cell populations by regulating the myofiber niche at puberty.
Project description:The goal of our study was to evaluate at the systems-level, the effect of sex hormones on thymic epithelial cells (TECs). To this end, we sequenced the transcriptome of cortical and medullary TECs (cTECs and mTECs) from three groups of 6 month-old mice: males, females and males castrated at four weeks of age. In parallel, we analyzed variations in the size of TEC subsets in those three groups between 1 and 12 months of age. We report that sex hormones have pervasive effects on the transcriptome of TECs: the number of differentially expressed genes was 1,440 in cTECs and 1,783 in mTECs. Sexual dimorphism was particularly conspicuous in cTECs. Male cTECs displayed low proliferation rates that correlated with low expression of Foxn1 and its main targets. Furthermore, male cTECs expressed relatively low levels of genes instrumental in thymocyte expansion (e.g., Dll4) and positive selection (Psmb11 and Ctsl). Nevertheless, cTECs were more abundant in males than females. Accumulation of cTECs in males correlated with differential expression of genes regulating cell survival and cell differentiation. Unexpectedly, we observed that female and male sex hormones repressed promiscuous gene expression in mTECs. Since sex hormones did not affect the expression of Aire per se, they must impinge on the activity of unidentified regulator(s) of promiscuous gene expression in mTECs. The sexual dimorphism of TECs highlighted here may be mechanistically linked to the well-recognized sex differences in susceptibility to infections and autoimmune diseases.
Project description:The project aims to elucidate mechanisms driving P. aeruginosa response to sex steroids hormones. An experiment involving Co-immunoprecipitation combined with Mass spectroscopy was performed to identify P. aeruginosa proteins binding to estradiol and /testosterone.
Project description:Women’s aging is characterized by menopausal loss of ovarian function, which has been suggested as a contributing factor to aging-related muscle deterioration and predisposes to the metabolic dysfunctions. However, the underlying molecular mechanisms have remained unknown. To identify mechanisms, we utilized muscle samples from 24 pre- and postmenopausal women, established proteome-wide profiles and identified upstream regulators and downstream cellular pathways associated with the differences in age, menopausal status and use of hormone replacement therapy (HRT). None of the premenopausal women used hormonal medication while the postmenopausal women were monozygotic twin-sister pairs who were either current HRT users or had never used HRT. The proteomic analyses resulted in the quantification of 762 muscle proteins of which 158 were for the first time associated with female muscle aging. The Ingenuity Pathway Analysis pinpointed 17β-estradiol as a potential upstream regulator of the observed differences in the major downstream pathways including dysregulated cell death and glycolysis pathways. The results increase knowledge on the factors related to skeletal muscle signaling and aging. This is of importance, since the role of female sex hormones in the regulation of muscle cell signaling has been under appreciated and scarcely studied as compared to vast amount of data on male sex hormones and skeletal muscle. Our results clearly demonstrate the also female sex hormones and HRT should be considered as potential active players and an intervention targets to promote women’s muscular health.
Project description:It is well-established that women are disproportionately affected by Alzheimer’s disease (AD). The mechanisms underlying this sex-specific disparity are not fully understood, but several factors that are often associated-including interactions of sex hormones, genetic factors, and the gut microbiome-likely contribute to the disease's etiology. Here, we have examined the role of sex hormones and the gut microbiome in mediating A amyloidosis and neuroinflammation in APPPS1-21 mice. We report that postnatal gut microbiome perturbation in female APPPS1-21 mice leads to an elevation in levels of circulating estradiol. Early stage ovariectomy (OVX) leads to a reduction of plasma estradiol that is correlated with a significant alteration of gut microbiome composition and reduction in A pathology. On the other hand, supplementation of OVX-treated animals with estradiol restores A burden and influences gut microbiome composition. The reduction of A pathology with OVX is paralleled by diminished levels of plaque-associated MGnD-type microglia while estradiol supplementation of OVX-treated animals leads to a restoration of activated microglia around plaques. In summary, our investigation elucidates the complex interplay between sex-specific hormonal modulations, gut microbiome dynamics, metabolic perturbations, and microglial functionality in the pathogenesis of Alzheimer's disease.
Project description:The female sex hormone estrogens plays a critical role in maintaining muscle mass and muscle stem cell (MuSCs) functions. However, it is still unclear about downstream pathways of estrogens including its receptors that are expressed in both skeletal muscle tissue and MuSCs. To study the specific role of estrogen receptor β (ERβ), one of two main types of estrogen receptors, in skeletal muscle and MuSCs, we generated muscle-specific ERβ-knockout (mKO) mice and muscle stem cell-specific ERβ-knockout (scKO) mice. Here, we show that muscle-specific ERβ-deficient induced decreased muscle strength and fast-type muscle mass in young female mice. Furthermore, muscle stem cell-specific ERβ-deficient young female mice but not male exhibited impaired muscle regeneration ability after acute muscle injury, accompanied by a decreased proliferation rate of muscle stem cells. RNA sequencing analysis showed that the loss of ERβ in muscle stem cells changes the expression of cell cycle associated genes and niche component factors including laminin and collagen. Thus, our characterization of mKO and scKO mice indicate that the estrogen-ERβ pathway is a sex-specific regulatory mechanism that controls both skeletal muscle mass and the proliferation of muscle stem cell in females and could be of importance in a therapeutic context.