Identification of Sulfs as therapeutic targets for the treatment of age-impaired

描述（由申请人提供）：衰老不可避免地与干细胞再生能力下降有关。我们选择骨骼肌作为模型系统，研究衰老环境对干细胞功能影响的调控机制。衰老的骨骼肌FGF2水平降低，wnt和TGF2水平升高，导致常驻干细胞（所谓的卫星细胞）增殖减少，再生过程中纤维化增加。FGF2、wnt和TGF2的生物利用度受硫酸乙酰肝素的调控。本研究探讨了在骨骼肌再生过程中，与年龄相关的环境信号向卫星细胞传递的依赖于硫酸肝素的机制。第一组实验的重点是两种细胞外硫酸肝素6- o -硫酸内酯酶（Sulfs）在年龄相关信号的生物利用度的差异调节中的作用。硫代酶修饰硫酸肝素6- o -硫化，从而减少wnt和TGF2与硫酸肝素的结合，同时破坏FGF2与受体的相互作用。因此，我们假设硫化物可以促进年龄增强的Wnt和TGF2信号，同时抑制年龄减弱的FGF2信号，从而导致卫星细胞功能受损。这一假设将通过比较衰老对照、系统和卫星细胞特异性硫双突变小鼠的肌肉发生、纤维化和年龄相关再生信号的效率来验证，并结合体内再生和体外培养试验。第二组实验将测试肝素在结构和信号功能上与缺硫小鼠的硫酸肝素相似，是否会提高老年环境下骨骼肌再生效率。这些研究结果有望导致硫和肝素硫酸依赖机制的发现，这些机制调节卫星细胞和衰老肌肉环境之间的信号通信。这些知识可能为预防和治疗年龄受损的肌肉再生开辟新的领域。

DESCRIPTION (provided by applicant): Aging is inevitably associated with diminished regeneration capacity of stem cells. We choose the skeletal muscle as a model system to study mechanisms that regulate the influence from aged environment on stem cell function. Aged skeletal muscle has reduced levels of FGF2 and elevated Wnts and TGF2, leading to decreased proliferation of resident stem cells (so called satellite cells) and increased fibrosis during regeneration. The bioavailability of FGF2, Wnts and TGF2 is regulated by sulfated heparan sulfate. This proposal investigates heparan sulfate-dependent mechanisms that regulate the transmission of age-related environmental signals to satellite cells during skeletal muscle regeneration. The first set of experiments focuses on roles of two extracellular heparan sulfate 6-O-endosulfatases (Sulfs) in differential regulation of the bioavailability of age-related signals. Sulfs enzymatically remodel heparan sulfate 6-O-sulfation, thereby Sulfs reduce Wnts and TGF2 binding to heparan sulfate, while disrupting FGF2 interaction with the receptor. Therefore, Sulfs are hypothesized to promote age-augmented Wnt and TGF2 signaling, while repressing age-reduced FGF2 signaling, leading to impaired function of satellite cells. This hypothesis will be tested by comparing the efficiency of myogenesis, fibrosis and age-related regeneration signaling in aged control, systemic and satellite cell-specific Sulf double mutant mice using a combination of in vivo regeneration and in vitro culture assays. The second set of experiments will test whether heparin, which is similar to heparan sulfate of Sulf-deficient mice in the structure and signaling function, will improve the efficiency of skeletal muscle regeneration in an aged environment. The results of these investigations are expected to lead to the discovery of Sulf- and heparan sulfate-dependent mechanisms that regulate signal communication between satellite cells and the aged muscle environment. Such knowledge may open new venues for prevention and therapy of impaired muscle regeneration by age. PUBLIC HEALTH RELEVANCE: Aging is inevitably associated with diminished capacity of stem cells to regenerate. In the skeletal muscle, age-related changes of environmental signals have a major impact on impaired function of resident stem cells, so-called satellite cells. Disruption of the communication between satellite cells and the aged muscle environment may lead to effective therapies for age-impaired skeletal muscle regeneration. This proposal investigates regulatory mechanisms during the transmission of age-related environmental signals into satellite cells. We have identified two Sulf enzymes that regulate the bioavailability of age-related signals in the regeneration environment and satellite cells. Proposed studies will test whether Sulfs are candidate regulators of the communication between satellite cells and the aged muscle environment. Our findings may open new venues for prevention and therapy of aging-related impairment of skeletal muscle regeneration.