Regulatory T cells, or Tregs, regulate immune responses, maintain tolerance to self‐antigens, and prevent autoimmune disease by suppressing/downregulating the activation, proliferation, and cytokine production of immune cells such as CD4+/CD8+ T cells, B‐Lymphocytes, dendritic cells, monocytes, and granulocytes.1 Tregs influence the function of said immune cells through direct mechanisms, such as the secretion of cytokines or the production of enzymes such as granzyme and perforin, and indirect mechanisms, which include alterations to the immune cell microenvironment. Studies have highlighted Treg dysfunction in immune‐related pathologies such as graft vs. host disease and multiple sclerosis2, 3; meanwhile, other preclinical research has underscored the therapeutic potential of Treg modulation in conditions such as autoimmune disease, cancer, and wound healing. Furthermore, the administration of Tregs has been explored as a means to facilitate successful organ transplantation by inducing immunotolerance. To this end, multiple clinical trials are currently evaluating Treg therapy in several disease states. In our first Feature Article published this month in STEM CELLS Translational Medicine , Caplan et al. describe how treatment with human Tregs expanded from umbilical cord blood can modulate the central and peripheral immune responses in a rodent model of traumatic brain injury (TBI) and may improve patient outcomes.4 In a Related Article published recently in STEM CELLS , Li et al. demonstrated that transplanted human induced pluripotent stem cell‐derived mesenchymal stem cells (iPSCs‐MSCs) displayed an immunosuppressive effect in a host vs. graft reaction mouse model through the inhibition of caspase cleavage by secreted factors and an associated upregulation of Tregs.5

The approximately five million hair follicles present in the human body vary in size and shape according to their location, and while no new follicles form after birth, the size of the follicles and hairs continues to change over time. The cells of the hair follicles resident in the dermal layer of mammalian skin regulate hair growth via complex interactions with hormones, neuropeptides, and immune cells. Each hair follicle comprises a lower, middle, and upper segment, with the lower segment undergoing repeated cycles of regression (catagen), resting (telogen), and growth (anagen) phases under the control of bulge‐resident hair follicle stem cells (HFSCs). The dysregulation of the hair follicle growth cycle can prompt hair loss, and while this condition is not life‐threatening, it can induce low self‐esteem and psychological distress in patients.6 Therefore, many have sought to develop safe and effective therapeutic options for hair loss,7 and ongoing complementary studies have sought to fully define the molecular mechanisms controlling the hair follicle cycle to potentially guide the development novel treatment strategies. In our second Feature Article published this month in STEM CELLS Translational Medicine , Tak et al. report that a topical solution of adipose stem cell (ASC) constituent extract may represent a safe and effective means to induce hair regrowth in androgenetic alopecia patients by increasing both hair density and thickness.8 In a Related Article published recently in STEM CELLS , Suen et al. demonstrated that Hes1, a major Notch downstream transcriptional repressor, reinforces Hedgehog signaling to expand and replenish HSFCs to maintain hair cycle homeostasis.9

调节性T细胞或Treg通过抑制/下调免疫细胞（例如CD4 + / CD8 + T细胞，B淋巴细胞，树突状细胞）的活化，增殖和细胞因子产生来调节免疫反应，维持自身抗原耐受性并预防自身免疫性疾病细胞，单核细胞和粒细胞。1 Treg通过直接机制（例如细胞因子的分泌或酶的生成，例如颗粒酶和穿孔素）以及间接机制（包括改变免疫细胞微环境）来影响所述免疫细胞的功能。研究突出了免疫相关病理中的Treg功能异常，例如移植物抗宿主病和多发性硬化症2、3; 同时，其他临床前研究也强调了Treg调节在自身免疫性疾病，癌症和伤口愈合等疾病中的治疗潜力。此外，已经探索了Treg的施用作为通过诱导免疫耐受来促进成功的器官移植的手段。为此，目前多项临床试验正在评估几种疾病状态下的Treg治疗。在本月发表于《STEM细胞转化医学》上的第一篇专题文章中，Caplan等人。描述了从脐带血中扩增的人类Treg的治疗如何在创伤性脑损伤（TBI）的啮齿动物模型中调节中枢和外周免疫反应，并可能改善患者预后。4在最近发表的相关文章中干细胞，李等。证明移植的人诱导的多能干细胞来源的间充质干细胞（iPSCs-MSC）在宿主与移植物反应小鼠模型中通过分泌因子抑制胱天蛋白酶的裂解以及相关的Treg上调显示出免疫抑制作用。5

人体中大约有五百万个毛囊，其大小和形状根据其位置而异，虽然出生后没有新的毛囊形成，但毛囊和毛发的大小会随着时间而不断变化。驻留在哺乳动物皮肤真皮层中的毛囊细胞通过与激素，神经肽和免疫细胞的复杂相互作用来调节毛发生长。每个毛囊包含一个下部，中部和上部，在膨隆驻留的毛囊干细胞（HFSCs）的控制下，下部经历了反复的回归（催化），静息（端源）和生长（生长期）阶段。 ）。毛囊生长周期的失调会促使脱发，尽管这种状况不会危及生命，但会导致患者的自卑感和心理困扰。6因此，许多人寻求开发出用于脱发的安全有效的治疗选择，7并且正在进行的补充研究试图充分定义控制毛囊周期的分子机制，以潜在地指导开发新的治疗策略。Tak等人在本月发表于《STEM细胞转化医学》上的第二篇专题文章中。报告指出，局部应用脂肪干细胞（ASC）提取物的溶液可能代表一种安全有效的方法，可通过增加头发密度和厚度来诱导雄激素性脱发患者的头发再生长。8在最近发表在STEM CELLS中的相关文章中，Suen等。证明Hes1是主要的Notch下游转录阻遏物，可增强刺猬信号，以扩展和补充HSFC，以维持毛发循环的稳态。9