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减弱有关。我们选择骨骼肌作为模型系统来研究老化环境对干细胞功能影响的调节机制。老化的骨骼肌具有降低的FGF 2水平和升高的Wnt和TGF 2，导致驻留干细胞（所谓的卫星细胞）增殖减少和再生期间纤维化增加。FGF 2、Wnts和TGF 2的生物利用度由硫酸化硫酸乙酰肝素调节。该提案研究了硫酸乙酰肝素依赖性机制，该机制调节骨骼肌再生期间与年龄相关的环境信号向卫星细胞的传输。第一组实验集中于两种细胞外硫酸乙酰肝素6-O-内硫酸酯酶（Sulfs）在年龄相关信号的生物利用度的差异调节中的作用。硫酶促重塑硫酸乙酰肝素6- 0-硫酸化，从而硫减少Wnt和TGF 2与硫酸乙酰肝素的结合，同时破坏FGF 2与受体的相互作用。因此，假设硫促进年龄增加的Wnt和TGF 2信号传导，同时抑制年龄减少的FGF 2信号传导，导致卫星细胞功能受损。将使用体内再生和体外培养测定的组合，通过比较老年对照、全身性和卫星细胞特异性Sulf双突变小鼠中的肌生成、纤维化和年龄相关再生信号传导的效率来测试该假设。第二组实验将测试在结构和信号功能上与硫缺乏小鼠的硫酸乙酰肝素相似的肝素是否会提高老年环境中骨骼肌再生的效率。这些研究的结果预计将导致发现硫酸和硫酸乙酰肝素依赖性机制，调节卫星细胞和老年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途径。

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.