Recent progress in hair follicle stem cell markers and their regulatory roles

Hair follicle stem cells(HFSCs)in the bulge are a multipotent adult stem cell population.They can periodically give rise to new HFs and even regenerate the epidermis and sebaceous glands during wound healing.An increasing number of biomarkers have been used to isolate,label,and trace HFSCs in recent years.Considering more detailed data from single-cell transcriptomics technology,we mainly focus on the important HFSC molecular markers and their regulatory roles in this review.

Rat hair follicle stem cells differentiate and promote recovery following spinal cord injury

Emerging studies of treating spinal cord injury （SCI） with adult stem cells led us to evaluate the effects of transplantation of hair follicle stem cells in rats with a compression-induced spinal cord lesion. Here, we proposed a hypothesis that rat hair follicle stem cell transplantation can promote the recovery of injured spinal cord. Compression-induced spinal cord injury was induced in Wistar rats in this study. The bulge area of the rat vibdssa follicles was isolated, cultivated and characterized with nestin as a stem cell marker. 5-Bromo-2＇-deoxyuridine （BrdU） labeled bulge stem cells were transplanted into rats with spinal cord injury. Immunohistochemical staining results showed that some of the grafted cells could survive and differentiate into oligodendrocytes （receptor-interacting protein positive cells） and neuronal-like cells （~lll-tubulin positive cells） at 3 weeks after transplantation. In addition, recovery of hind limb locomotor function in spinal cord injury rats at 8 weeks following cell transplantation was assessed using the Basso, Beattie and Bresnahan （BBB） locomotor rating scale. The results demon- strate that the grafted hair follicle stem cells can survive for a long time period in vivo and differentiate into neuronal- and glial-like cells. These results suggest that hair follicle stem cells can promote the recovery of spinal cord injury.

Hair follicle stem cells: In vitro and in vivo neural differentiation

Hair follicle stem cells(HFSCs) normally give rise to keratinocytes, sebocytes, and transient amplifying progenitor cells. Along with the capacity to proliferate rapidly, HFSCs provide the basis for establishing a putative source of stem cells for cell therapy. HFSCs are multipotent stem cells originating from the bulge area. The importance of these cells arises from two important characteristics, distinguishing them from all other adult stem cells. First, they are accessible and proliferate for long periods. Second, they are multipotent, possessing the ability to differentiate into mesodermal and ectodermal cell types. In addition to a developmental capacity in vitro, HFSCs display an ability to form differentiated cells in vivo. During the last two decades, numerous studies have led to the development of an appropriate culture condition for producing various cell lineages from HFSCs. Therefore, these stem cells are considered as a novel source for cell therapy of a broad spectrum of neurodegenerative disorders. This review presents the current status of human, rat, and mouse HFSCs from both the cellular and molecular biology and cell therapy perspectives. The first section of this review highlights the importance of HFSCs and in vitro differentiation, while the final section emphasizes the significance of cell differentiation in vivo.

miR-21 promotes the differentiation of hair folliclederived neural crest stem cells into Schwann cells

Hair follicle-derived neural crest stem cells can be induced to differentiate into Schwann cells in vivo and in vitro. However, the underlying regulatory mechanism during cell differentiation remains poorly understood. This study isolated neural crest stem cells from human hair folli-cles and induced them to differentiate into Schwann cells. Quantitative RT-PCR showed that microRNA （miR）-21 expression was gradually increased during the differentiation of neural crest stem cells into Schwann cells. After transfection with the miR-21 agonist （agomir-21）, the differentiation capacity of neural crest stem cells was enhanced. By contrast, after transfection with the miR-21 antagonist （antagomir-21）, the differentiation capacity was attenuated. Further study results showed that SOX-2 was an effective target of miR-21. Without compromising SOX2 mRNA expression, miR-21 can down-regulate SOX protein expression by binding to the 3′-UTR of miR-21 mRNA. Knocking out the SOX2 gene from the neural crest stem cells significantly reversed the antagomir-21 inhibition of neural crest stem cells differentiating into Schwann cells. The results suggest that miR-21 expression was increased during the differentiation of neural crest stem cells into Schwann cells and miR-21 promoted the differentiation through down-regu-lating SOX protein expression by binding to the 3′-UTR of SOX2 mRNA.

NANOG Alleviates the Damage of Human Hair Follicle Mesenchymal Stem Cells Caused by H_2O_2 through Activation of AKT Pathway

Objective To explore the protective effect of NANOG against hydrogen peroxide(H_2O_2)-induced cell damage in the human hair follicle mesenchymal stem cells(hHF-MSCs). Methods NANOG was expressed from a lentiviral vector, pLVX-IRES-ZsGreen. NANOG hHF-MSCs and vector hHF-MSCs were treated with 400 μmol/L hydrogen peroxide(H_2O_2) for 2 h, the cell survival rate, cell morphology, ROS production, apoptosis and expression of AKT, ERK, and p21 were determined and compared. Results Our results showed that NANOG could activate AKT and upregulate the expression of p-AKT, but not p-ERK. When treated with 400 μmol/L H_2O_2, NANOG hHF-MSCs showed higher cell survival rate, lower ROS production and apoptosis, higher expression of p-AKT, higher ratio of p-AKT/AKT. Conclusion Our results suggest that NANOG could protect hHF-MSCs against cell damage caused by H_2O_2 through activating AKT signaling pathway.

Detailed Histological Structure of Human Hair Follicle Bulge Region at Different Ages: A Visible Niche for Nesting Adult Stem Cells

In the bulge region of the hair follicle, a densely and concentrically packed cell mass is encircled by the arrector pili muscle (APM), which offers a specilized microenvironment (niche) for housing heterogeneous adult stem cells. However, the detailed histological architecture and the cellular composition of the bulge region warrants intensive study and may have implications for the regulation of hair follicle growth regulation. This study was designed to define the gene-expression pro-files of putative stem cells and lineage-specific precursors in the mid-portions of plucked hair follicles prepared according to the presence of detectable autofluorescence. The structure was also characterized by using a consecutive sectioning technique. The bulge region of the hair follicle with autofluorescence was precisely excised by employing a micro-dissection procedure. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed to identify the gene expression profiles specific for epithelial, melanocyte and stromal stem cells in the bulge region of the hair follicle visualized by autofluorescence. The morphology and its age-dependent changes of bulge region of the hair follicles with autofluorescence segment were also examined in 9 scalp skin specimens collected from patients aged 30 weeks to 75 years, by serial sectioning and immuno-staining. Gene expression profile analysis revealed that there were cells with mRNA transcripts of DctHiTyraseLo-Tyrp1LoMC1RLoMITFLo/K15Hi/NPNTHi in the bulge region of the hair follicle with autofluorescence segments, which differed from the patterns in hair bulbs. Small cell-protrusions that sprouted from the outer root sheath (ORS) were clearly observed at the APM inserting level in serial sections of hair follicles by immunohistological staining, which were characteristically replete with K15+/K19+expressing cells. Likewise, the muscle bundles of APM positive for smooth muscle actin intimately encircled these cell-protrusions, and the occurrence frequency of the cell-protrusions was increased in fetal scalp skin compared with adult scalp skin. This study provided the evidence that the cell-protrusions occurring at the ORS relative to the APM insertion are more likely to be characteristic of the visible niches that are filled with abundant stem cells. The occurrence frequency of these cell-protrusions was significantly increased in fetal scalp skin samples (128%) as compared with the scalp skins of younger (49.4%) and older (25.4%) adults (P<0.01), but difference in the frequency between the two adult groups were not significant. These results indicated that these cell-protrusions function as a niche house for the myriad stem cells and/or precursors to meet the needs of the development of hair follicles in an embryo. The micro-dissection used in this study was simple and reliable in excising the bulge region of the hair follicle with autofluorescence segments dependent on their autofluorescence is of value for the study of stem cell culture.

Adipose Derived Stem Cells and Growth Factors Applied on Hair Transplantation. Follow-Up of Clinical Outcome

Different studies show the need of immature adipose cell to induce the proliferation of bulge stem cells in order to kick off the anagen phase of hair cycle. Furthermore, the adipose derived stem cell, adipose progenitors, and growth factors secreted by mature adipocytes can help the wound healing and the vascular neogenesis. Nowadays, it is not known any protocol of tissue regeneration applied to hair transplantation, especially if aimed to the reconstruction of the main vascular network for the engraftment of transplanted hair and the healing process. The aim of the work is to investigate how the application of autologous cellular suspension obtained by Rigenera system, mechanical fragmentation procedure which allows to obtain a physiological saline solution consisting of a heterogeneous pool of cells rich in adipose derived mesenchymalstem cells and growth factors, helps the wound healing and engraftment of the transplanted hair. During hair restoration surgery, the adipose tissue recovered from the discard of follicular slicing, was processed using the Rigenera system. The obtained cell suspension was applied in the area of hair transplantation, increasing the natural background of adipocyte lineage and raising the amount of growth factors. In addition, the cellular suspension was applied to the suture on the occipital region. The cell population was characterized by FACS. The monthly evaluation of hair transplantation follow-up with photos and the patient’s impressions demonstrates that there is a faster healing of the micro-wound and a continuous growth of the transplanted hair even two months after the procedure, with a shortening of the dormant phase. In conclusion, this new approach aims to integrate regenerative medicine and hair restoration surgery in order to improve the outcome for the patient. It would be wonderful to continue this research to elaborate on the molecular cause behind this satisfying clinical.

Constructing skin-equivalents using hair follicle stem cells

Objective： To establish the method of constructing skin-equivalents （SE） using hair follicle stem cells （HFSC）. Methods： K19 positive cells derived from hair were cultivated using serum-free medium KGM and seeded on dermal equivalents （DE）. After the culture between the air-liquid interface for 14 days, SE were harvested and used for evaluation. Results： K19 positive cells chosen as HFSC were located in bulge of out root sheet in hair follicle. Cultivated HFSC could build a fully developed, multi-layered epidermis on the basis of DE, resembling the skin structure. Conclusion： HFSC located in out root sheet can differentiate into kerafinocyte in vitro and be used for SE construction.

Expression of stem cell factor in hair follicl epithelium

The interaction between flair folllcle dermis and its epidermis plays an important role in modulation of the growth and development of t he hair follicle. Stem cell factor (SCF ). which was found in recent years,is a cytokine related to the survival . growl h and development of the hemopoietic stem cells and can exert important biological effects on the development of keratinocytes and melanocytes. In this study, the expression of SCF in the hair follicle spithelium was invesstigated with immunohistochemistry and in situ hybridization. It was found that the gene of the encoded SCF was strongly expressed al a limited area in the middle of the hair follicle epithelium. The protein of SCF was evenly expressed in each part of the hair follicle epithelium. The findings suggest that the expression of SCF in the hair follicle epithelium at the level of molecule is different from thai at the level of protein.

In vitro Differentiation of Adipose-Derived Stem Cells into Hair Cell-Like Cells in Guinea Pigs

Objective Adipose-derived stem cells(ADSCs) are suggested to possess a highly plastic ability to differentiate into several specific cell types in addition to adipocyte lineages, including germ layer tissue-specific cell lineages such as chondrocyte, myocyte, neuronal, and osteoblast lineages. The aim of this study is to establish an in vitro culture technique for ADSCs in an adult guinea pig model that facilitate their differentiation into hair cell-like cells. Materials and Methods Cells from inguinal fat pads in adult guinea pigs were cultured with β-mercaptoethanol, RA, Forskorin, Heregulin, bFGF, BDNF and EGF. Cellular differentiation was examined using immunocytochemistry techniques. Results The ADSCs demonstrated hair cell immunophenotypes with expression of epitopes of the hair cell marker protein myosin Ⅶa. Conclusion ADSCs from adult guinea pig adipose tissue can differentiate into hair cell-like cells when cultured in vitro. ADSCs may serve as seed cells for tissue engineering.

Identification of Bulge Stem Cells in Mouse and Human Hair Follicles

The skin contains various populaions of stem cells, but its characterization has been hampered by lack of markers and unclear location. The hair follicle has a niche for stem cells called a “bulge” which acts as a reservoir of multipotent stem cells. In the study reported here, an immunohistochemical and immunofluorescence analysis was performed on mouse and human tissues in order to determine the possible presence of stem cells of hair follicle through cytokeratin 15 (CK15), CD34, and CD200 markers identified as crucial to the stem cells and to identify the bulge region. Mouse (n = 7) and human (n = 7) skin samples were used. The expression of proteins was determined by the indirect immunoperoxidase technique and a secondary antibody bound to a fluorochrome. The specificity of staining was evaluated by negative controls. The results revealed that the stem cells associated with CD34 and CD200 antibodies were differentially expressed in the interfollicular epidermis, sebaceous glands, and bulge region, indicating that, in mice, CD34 and, in humans, CD200 are more specific than CK15 in detecting bulge cells. It also suggests that CD34 is specific for mouse bulge cells, while CD200 might have specificity for progenitor cells and partially differentiated cells in humans.

Isolation, Cultivation, and Morphological Characteristics of Hair Follicle Adult Stem Cells in the Bulge Region in Mouse and Human

Skin contains various populations of stem cells (SCs). Among these are hair follicle stem cells (HFSCs) in the bulge region. The behavior of HFSCs deserves to be widely studied due to the benefits to be derived from their identification, isolation, and amplification. Skin samples of newborn mice (n = 32) and human adults (n = 10) were used, and the bulge region was isolated and cultured. The isolation and characterization of cells were conducted through immunocytochemistry and immunofluorescence, using mainly CD34 and CD200 monoclonal antibodies. Initially, cells grew slowly from the explant around the bulge region, accruing cells with different morphology in both mouse and human, latter being mostly polygonal;the mouse cells reaching confluence faster (5 to 7 days) than the human (12 to 15 days). It was possible to isolate into subcultures cells with small size (10 - 13 μm diameter), round-shape, scant cytoplasm, central prominent nucleus and with nucleolus, which formed colonies, maintaining their phenotype in a high proportion (77% - 83% and 91% in mouse and human, respectively), without showing changes in their morphology during almost 7 months in the mouse cells, and a month and a half in the human. These results demonstrate that the selection, the isolation, and the conditioned mediums allowed population increases of bulge cells and indicate that cultured cells may retain their sternness in that they maintained their phenotypic characteristics, expressed specific markers for SCs, and showed a high proliferative capacity for long periods. Hair follicles, in mice and humans, are important repositories of multipotent stem cells, due to their tendency to differentiate into keratinocytes. Human HFSCs, obtained by depilation, preserve their potential for proliferation and prove to be easily accessible. This suggests that the bulge cells may present an alternative source of autologous stem cells for tissue engineering and regenerative medicine.

绒毛用羊毛囊干细胞研究进展

产毛(绒)量是绒毛用羊主要的经济性状,毛(绒)的质量和产量受毛囊发育的影响。众所周知,毛囊控制羊毛(绒)的生长,而毛囊干细胞决定着毛囊形态的发生。因此,文章从绒毛用羊毛囊干细胞的分离培养方法、鉴定、增殖与分化等方面的相关研究进展进行了综合阐述,为进一步开展毛囊生长发育的分子调控机制研究、选育绒毛性状优良的绒毛生产用羊提供参考资料。

ⅩⅦ型胶原蛋白在脱发中的作用机制研究进展

脱发是一种较为常见的皮肤疾病,其发病率逐年上升,并呈年轻化趋势发展,困扰着越来越多人的生活,以进行性毛囊微型化、毛发生长期缩短为特点,导致毛发附着松散容易脱落。ⅩⅦ型胶原蛋白是一种跨膜蛋白,位于表皮基底膜区的半桥粒,维持表皮真皮之间的紧密连接。近期研究发现,ⅩⅦ型胶原蛋白参与毛发生长,调节毛发相关细胞的静息与活化。若缺失ⅩⅦ型胶原蛋白可通过DNA损伤效应累积、表皮细胞极性失衡以及抑制干细胞竞争导致脱发。本文将对ⅩⅦ型胶原蛋白在脱发中的作用机制予以综述,为毛发再生领域研究提供方向。

不同胚层来源成体干细胞修复周围神经损伤

背景:成体干细胞疗法是周围神经损伤修复与再生领域的研究热点之一。中胚层被视为成体干细胞的理想来源,间充质干细胞具有获得率高、来源广、增殖快等优异性能。而外胚层来源成体干细胞,尤其是神经嵴干细胞,具有神经源性,越来越受到研究人员的关注。目的:对来自外胚层和中胚层的多功能成体干细胞在周围神经损伤修复与再生中的作用及机制进行简要综述,探究不同来源成体干细胞的研究进展与应用前景,并结合临床研究,探讨成体干细胞疗法潜在的应用价值以及亟待解决的问题。方法:第一作者于2024年2月应用计算机在PubMed和SinoMed数据库检索2001年12月至2024年2月相关文献,以“ectodermal stem cells,mesenchymal stem cells,peripheral nerve injury,repair,regeneration”为英文检索词,以“外胚层干细胞、间充质干细胞、周围神经损伤、修复、再生”为中文检索词,最终纳入69篇文献进行分析论述。结果与结论:①外胚层来源成体干细胞具有优异的分化和再生潜能,尤其是毛囊神经嵴干细胞、嗅干细胞、牙外胚层干细胞等,具有神经源性,可在体外表达神经特异性标志物,但目前缺少临床试验研究。②中胚层来源成体干细胞种类多、易获得及纯化,其中骨髓间充质干细胞和脐带间充质干细胞在周围神经损伤修复的应用疗效及安全性方面有相关临床试验支持,能改善感觉及运动神经传导,且在随访中未出现并发症和明显不良反应。骨髓间充质干细胞的获取需行侵入性外科手术且要求患者与捐赠者骨髓配型吻合,应用受到一定限制;而脐带间充质干细胞虽无需侵入性获取,但分离较困难且表型不稳定。③内胚层来源成体干细胞常难以在体外生长,应用受限,目前应用于临床的可能性低。④综合来看,骨髓间充质干细胞仍为周围神经损伤干细胞治疗的首选细胞,适用于无外科手术禁忌且符合配型要求的情况,其次为脐带间充质干细胞,辅以分离方法的改进和表型稳定性的提高策略。⑤牙外胚层干细胞以及脂肪间充质干细胞具有较高应用潜能,有待进一步临床试验,其他外胚层、中胚层来源成体干细胞各以其优异特性在动物及细胞实验研究中具有显著优势。

Vital roles of stem cells and biomaterials in skin tissue engineering

Tissue engineering essentially refers to technology for growing new human tissue and is distinct from regenerative medicine. Currently, pieces of skin are already being fabricated for clinical use and many other tissue types may be fabricated in the future.Tissue engineering was first defined in 1987 by the United States National Science Foundation which critically discussed the future targets of bioengineering research and its consequences. The principles of tissue engineering are to initiate cell cultures in vitro, grow them on scaffolds in situ and transplant the composite into a recipient in vivo. From the beginning, scaffolds have been necessary in tissue engineering applications. Regardless, the latest technology has redirected established approaches by omitting scaffolds. Currently, scientists from diverse research institutes are engineering skin without scaffolds. Due to their advantageous properties, stem cells have robustly transformed the tissue engineering field as part of an engineered bilayered skin substitute that will later be discussed in detail. Additionally, utilizing biomaterials or skin replacement products in skin tissue engineering as strategy to successfully direct cell proliferation and differentiation as well as to optimize the safety of handling during grafting is beneficial. This approach has also led to the cells' application in developing the novel skin substitute that will be briefly explained in this review.

Inner ear hair cell regeneration A look from the past to the future

Most recent studies on regeneration of inner ear hair cells focus on use of stem cells, gene therapy and neurotrophic factors. Cochlear gene therapy has been successfully used in the treatment of neu- rosensory hearing loss. This suggests that cochlear hair cell regeneration is possible. The objective of this paper is to review research and clinical application of inner near hair cell regeneration.

毛囊微型化发生的机制与最新研究进展

雄激素性脱发(androgenetic alopecia,AGA)又称为脂溢性脱发,是临床上最常见的脱发类型,毛囊微型化是该病发生发展过程中的重要特征。目前研究已发现有很多原因可诱导毛囊微型化的发生,一方面通过促使患者头皮毛囊真皮乳头细胞(dermal papilla cell,DPC)分泌毛囊抑制因子、DPC发生凋亡和自噬障碍,另一方面通过毛周微循环形成障碍、毛囊干细胞的过度耗竭及真皮鞘细胞的丢失与纤维化进一步加剧了AGA的发生发展,最终导致患者的毛发由最初的终毛逐渐转换为细小的毳毛。本综述从不同角度探讨毛囊微型化的病因与机制,为未来对AGA的有效治疗提供帮助。

毛发色素脱失发生机制的研究进展

毛发色素脱失是常见的毛发疾病之一,主要致病因素包括基因突变、心理和氧化应激、代谢和营养异常等,上述因素导致的黑色素合成减少是毛发色素脱失最主要的病理特征。不同于皮肤中的黑色素持续合成,毛发黑色素仅在毛囊生长期合成,该阶段毛囊色素单位中成熟的黑素细胞异常凋亡,或酪氨酸酶活性降低以及黑素小体转运障碍均可导致黑色素合成减少。而作为毛囊成熟黑素细胞“储存库”的黑素细胞干细胞的完全耗竭将会导致不可逆性的毛发色素脱失。因此,深入研究毛囊黑素细胞系的功能,有望全面揭示毛发色素脱失的发生机制。

Atoh1调控毛细胞再生与分化的研究进展

哺乳动物耳蜗毛细胞受损后无法再生,从而造成听力障碍。Atoh1是bHLH转录因子家族中的一员,是正性调控毛细胞再生与分化的关键因子之一。研究发现,Atoh1可与其上游调控基因(Eya1、Six1、Sox2)和下游调节基因(Gfi,Pou4f3,Barhl1)协同作用,调节多种细胞信号转导通路(如Notch,Wnt/β-catenin,SHH,FGF等),诱导耳蜗毛细胞再生。干细胞具有分化成毛细胞样细胞的潜能,该过程依赖Atoh1的表达。因此,调控Atoh1依赖性耳祖细胞或干细胞的定向分化,将为毛细胞损害的临床治疗提供新途径。