Hair Follicle Stem Cells for Tissue Regeneration

Exosomes from human umbilical cord mesenchymal stem cells promote the growth of human hair dermal papilla cells

Human hair dermal papilla cells (HHDPCs) play a significant role in hair growth. This study found that human umbilical cord mesenchymal stem cell-derived exosomes (UC-MSC-Es) effectively enhanced cell growth of HHDPCs. UC-MSC-Es has a size range of 30-180 nm and expression of CD9, CD63, CD81, CD73, and TSG101. UC-MSC-Es significantly increased cell populations of HHDPCs in the S and G2/M phases. UC-MSC-Es also increased the expression of cell cycle-related proteins, β-catenin, and cyclin D1. Further mechanistic studies demonstrated that UC-MSC-Es promoted the phosphorylation of Akt and GSK-3β, and the inhibition of PI3K and Akt reduced the proliferative effects of UC-MSC-Es. Collectively, these findings suggest that UC-MSC-Es have a potential effect in treating hair loss through modulating PI3K and Akt-dependent pathways in HHDPCs.

Cholesterol promotes hair growth through activating sympathetic nerves and enhancing the proliferation of hair follicle stem cells

The regulatory mechanisms by which cholesterol influences hair regeneration remain incompletely understood. This study investigates the effects of cholesterol on hair follicle stem cells (HFSCs) proliferation and hair regeneration, with a focus on the underlying molecular mechanisms. Subcutaneous cholesterol injections in C57BL/6 mice significantly enhanced hair regeneration by promoting HFSCs proliferation. Hematoxylin and eosin (HE) staining revealed a greater number of hair follicles in the anagen phase in the cholesterol-treated group compared to controls. Immunofluorescence (IF) and BrdU labeling further confirmed that cholesterol significantly stimulated HFSCs proliferation. Mechanistically, cholesterol activated the PKA signaling pathway, leading to the phosphorylation of tyrosine hydroxylase (TH) at the serine 40 residue, which subsequently stimulated the sympathetic nervous system (SNS). SNS activation enhanced HFSCs proliferation and increased the proportion of hair follicles in the anagen phase. Furthermore, sympathetic nerve ablation significantly attenuated the hair regeneration-promoting effects of cholesterol, highlighting the critical regulatory role of SNS in this process. These findings provide key insights into the molecular mechanisms by which cholesterol regulates hair regeneration via the PKA-tyrosine hydroxylase-SNS pathway. Moreover, they suggest potential therapeutic applications targeting cholesterol-mediated signaling pathways to promote hair regeneration.

Bulge-Derived Epithelial Cells Isolated from Human Hair Follicles Using Enzymatic Digestion or Explants Result in Comparable Tissue-Engineered Skin

Hair follicle stem cells, located in the bulge region of the outer root sheath, are multipotent epithelial stem cells capable of differentiating into epidermal, sebaceous gland, and hair shaft cells. Efficient culturing of these cells is crucial for advancements in dermatology, regenerative medicine, and skin model development. This investigation aimed to develop a protocol for isolating enriched bulge-derived epithelial cells from scalp specimens to produce tissue-engineered substitutes. The epithelium, including hair follicles, was separated from the dermis using thermolysin, followed by microdissection of the bulge region. Epithelial stem cells were isolated using enzymatic dissociation to create a single-cell suspension and compared with the direct explant culture and a benchmark method which isolates cells from the epidermis and pilosebaceous units. After 8 days of culture, the enzymatic digestion of microdissected bulges yielded 5.3 times more epithelial cells compared to explant cultures and proliferated faster than the benchmark method. Cells cultured from all methods exhibited comparable morphology and growth rates. The fully stratified epidermis of tissue-engineered skin was similar, indicating comparable differentiation potential. This enzymatic digestion method improved early-stage cell recovery and expansion while maintaining keratinocyte functionality, offering an efficient hair bulge cell-extraction technique for tissue engineering and regenerative medicine applications.

Fetal Skin Wound Healing: Key Extracellular Matrix Components and Regulators in Scarless Healing

Fetal skin at early gestational stage is able to regenerate and heal rapidly after wounding. The exact mechanisms and molecular pathways involved in this process are however still largely unknown. The numerous differences in the skin of the early fetus versus skin in later developmental stages might provide clues for the mechanisms of scarless healing. This review summarizes the differences between mammalian fetal skin and the skin at later developmental phases in healthy and wounded conditions, focusing on extracellular matrix components, which are crucial factors in the microenvironment that direct cells and tissue functions and hence the wound healing process.

Irx1 mechanisms for oral epithelial basal stem cell plasticity during reepithelialization after injury

The oral mucosa undergoes daily insults, and stem cells in the epithelial basal cell layer regenerate gingiva tissue to maintain oral health. The Iroquois Homeobox 1 (IRX1) protein is expressed in the stem cell niches in human/mouse oral epithelium and mesenchyme under homeostasis. We found that Irx1+/- heterozygous (Het) mice have delayed wound closure, delayed morphological changes of regenerated epithelium, and defective keratinocyte proliferation and differentiation during wound healing. RNA-Seq analyses between WT and Irx1+/- mice at 3 days postinjury (dpi) found impaired epithelial migration and decreased keratinocyte-related genes upon injury. IRX1-expressing cells are found in the gingival epithelial basal cell layer, a stem cell niche for gingival maintenance. IRX1-expressing cells are also found in cell niches in the underlying stroma. IRX1 activates SOX9 in the transient amplifying layer to increase cell proliferation, and EGF signaling is activated to induce cell migration. Krt14CreERT lineage tracing experiments reveal defects in the stratification of the Irx1+/- HET mouse oral epithelium. IRX1 is primed at the base of the gingiva in the basal cell layer of the oral epithelium, facilitating rapid and scarless wound healing through activating SOX9 and the EGF signaling pathway.

Epidermal stem cells: skin surveillance and clinical perspective

The skin epidermis is continually influenced by a myriad of internal and external elements. At its basal layer reside epidermal stem cells, which fuels epidermal renovation and hair regeneration with powerful self-renewal ability, as well as keeping diverse signals that direct their activity under surveillance with quick response. The importance of epidermal stem cells in wound healing and immune-related skin conditions has been increasingly recognized, and their potential for clinical applications is attracting attention. In this review, we delve into recent advancements and the various physiological and psychological factors that govern distinct epidermal stem cell populations, including psychological stress, mechanical forces, chronic aging, and circadian rhythm, as well as providing an overview of current methodological approaches. Furthermore, we discuss the pathogenic role of epidermal stem cells in immune-related skin disorders and their potential clinical applications.

Enhancing hair regeneration: Recent progress in tailoring nanostructured lipid carriers through surface modification strategies

BACKGROUND AND PURPOSE

Hair loss is a prevalent problem affecting millions of people worldwide, necessitating innovative and efficient regrowth approaches. Nanostructured lipid carriers (NLCs) have become a hopeful option for transporting bioactive substances to hair follicles because of their compatibility with the body and capability to improve drug absorption.

REVIEW APPROACH

Recently, surface modification techniques have been used to enhance hair regeneration by improving the customization of NLCs. These techniques involve applying polymers, incorporating targeting molecules, and modifying the surface charge.

KEY RESULTS

The conversation focuses on how these techniques enhance stability, compatibility with the body, and precise delivery to hair follicles within NLCs. Moreover, it explains how surface-modified NLCs can improve the bioavailability of hair growth-promoting agents like minoxidil and finasteride. Furthermore, information on how surface-modified NLCs interact with hair follicles is given, uncovering their possible uses in treating hair loss conditions.

CONCLUSION

This review discusses the potential of altering the surface of NLCs to customize them for enhanced hair growth. It offers important information for upcoming studies on hair growth.

Epigenetic regulation and factors that influence the effect of iPSCs-derived neural stem/progenitor cells (NS/PCs) in the treatment of spinal cord injury

Spinal cord injury (SCI) is a severe neurological disorder that causes neurological impairment and disability. Neural stem/progenitor cells (NS/PCs) derived from induced pluripotent stem cells (iPSCs) represent a promising cell therapy strategy for spinal cord regeneration and repair. However, iPSC-derived NS/PCs face many challenges and issues in SCI therapy; one of the most significant challenges is epigenetic regulation and that factors that influence this mechanism. Epigenetics refers to the regulation of gene expression and function by DNA methylation, histone modification, and chromatin structure without changing the DNA sequence. Previous research has shown that epigenetics plays a crucial role in the generation, differentiation, and transplantation of iPSCs, and can influence the quality, safety, and outcome of transplanted cells. In this study, we review the effects of epigenetic regulation and various influencing factors on the role of iPSC-derived NS/PCs in SCI therapy at multiple levels, including epigenetic reprogramming, regulation, and the adaptation of iPSCs during generation, differentiation, and transplantation, as well as the impact of other therapeutic tools (e.g., drugs, electrical stimulation, and scaffolds) on the epigenetic status of transplanted cells. We summarize our main findings and insights in this field and identify future challenges and directions that need to be addressed and explored.

The emerging progress on wound dressings and their application in clinic wound management

BACKGROUND

In addition to its barrier function, the skin plays a crucial role in maintaining the stability of the body's internal environment and normal physiological functions. When the skin is damaged, it is important to select proper dressings as temporary barriers to cover the wound, which can exert significant effects on defence against microbial infection, maintaining normal tissue/cell functions, and coordinating the process of wound repair and regeneration. It now forms an important approach in clinic practice to facilitate wound repair.

SEARCH STRATEGIES

We conducted a comprehensive literature search using online databases including PubMed, Web of Science, MEDLINE, ScienceDirect, Wiley Online Library, CNKI, and Wanfang Data. In addition, information was obtained from local and foreign books on biomaterials science and traumatology.

RESULTS

This review focuses on the efficacy and principles of functional dressings for anti-bacteria, anti-infection, anti-inflammation, anti-oxidation, hemostasis, and wound healing facilitation; and analyses the research progress of dressings carrying living cells such as fibroblasts, keratinocytes, skin appendage cells, and stem cells from different origins. We also summarize the recent advances in intelligent wound dressings with respect to real-time monitoring, automatic drug delivery, and precise adjustment according to the actual wound microenvironment. In addition, this review explores and compares the characteristics, advantages and disadvantages, mechanisms of actions, and application scopes of dressings made from different materials.

CONCLUSION

The real-time and dynamic acquisition and analysis of wound conditions are crucial for wound management and prognostic evaluation. Therefore, the development of modern dressings that integrate multiple functions, have high similarity to the skin, and are highly intelligent will be the focus of future research, which could drive efficient wound management and personalized medicine, and ultimately facilitate the translation of health monitoring into clinical practice.

The Potential of miR-21 in Stem Cell Differentiation and its Application in Tissue Engineering and Regenerative Medicine

MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two important types of non-coding RNAs that are not translated into protein. These molecules can regulate various biological processes, including stem cell differentiation and self-renewal. One of the first known miRNAs in mammals is miR-21. Cancer-related studies have shown that this miRNA has proto-oncogene activity and is elevated in cancers. However, it is confirmed that miR-21 inhibits stem cell pluripotency and self-renewal and induces differentiation by targeting various genes. Regenerative medicine is a field of medical science that tries to regenerate and repair damaged tissues. Various studies have shown that miR-21 plays an essential role in regenerative medicine by affecting stem cell proliferation and differentiation. In this review, we will discuss the function of miR-21 in regenerative medicine of the liver, nerve, spinal cord, wound, bone, and dental tissues. In addition, the function of natural compounds and lncRNAs will be analyzed as potential regulators of miR-21 expression in regenerative medicine.

Global Research Status and Trends in Hair Follicle Stem Cells: a Bibliometric Analysis

BACKGROUND

Hair follicle stem cells (HFSCs) are derived from the bulge region and are important autologous stem cell sources. Bibliometric is a statistical method that quantitatively analyses the research papers concerned about one special topic. This study aims to estimate the research status and trends of HFSCs worldwide by bibliometric analyses.

METHODS

Data were obtained from the Web of Science by searching keywords related to HFSCs. Publication distributions stratified by countries/regions, institutions, journals, and authors were systematically assessed. The frequency of keywords was assessed, and bibliometric mapping was employed to describe the development of HFSC research.

RESULTS

A total of 458 publications that met our screening criteria were included in this study, consisting of 423 (92.4%) articles and 35 (7.6%) reviews. The United States of America (USA) ranked first in the number of publications at 146 (31.9%), followed by China at 130 (28.4%), which is consistent with the rank of the H-index. Author keywords were classified into three clusters, namely, basic study, applied study, and biomarker; average publication time of keywords in applied study cluster is later than basic study cluster. The keywords "bulge", "nestin", and "skin" are the top three most frequent keywords in basic studies; "differentiation", "proliferation", and "alopecia" are the top three most frequent keywords in applied studies. With respect to the latest research hotspots, "apoptosis" and "tissue engineering" are relatively new keywords.

CONCLUSIONS

The USA and China were the most productive countries for research on HFSCs. The focus of keywords gradually shifted from basic study to applied study. Research on the differentiation/proliferation of HFSCs and the role of HFSCs in alopecia have been recent research focuses. Apoptosis and tissue engineering are recommended as promising research hotspots. Our study provides profound insights into the research history, current status, and future trend of HFSCs.

Bacterial cellulose/soybean protein isolate composites with promoted inflammation inhibition, angiogenesis and hair follicle regeneration for wound healing

Soybean protein, as a safe and low-cost alternative to animal protein, attracts increasing attention in wound healing. In the present study, beta-conglycinin (7S) and glycinin (11S) with high solubility were obtained through separation of soybean protein. Afterward, 7S or 11S modified bacterial cellulose (BC) composites were produced by self-assembly method. Results confirmed the successful self-assembly of soybean protein isolates on the nanofibers of BC. The surface roughness and hydrophilicity of BC/7S and BC/11S decreased compared with native BC. Soybean protein could be steadily released from BC/7S and BC/11S and BC/11S released more soybean proteins than BC/7S. In vitro, BC/7S and BC/11S supported fibroblasts attachment and promoted fibroblasts proliferation and type I collagen expression. In vivo, BC/7S and BC/11S facilitated wound healing and collagen deposition, enhanced angiogenesis and hair follicle regeneration, as well as reduced scar formation and inflammation in full-thickness skin wounds of rats. Moreover, wounds treated with BC/11S showed a faster wound healing rate and more collagen depositions than those of BC/7S, which may be attributed to the larger considerable amount of soybean protein released by BC/11S. These results indicate that BC/7S and BC/11S are potential candidates for wound dressings.