Hair Follicle Transplantation for Wound Repair

Chemical Scalp Burn after Hair Coloring-Case Report with Literature Review

Hair dyeing is widely performed around the world. Chemical and thermal burns can result from the components present in brightening and coloring products, as well as the application process. We present a case of a chemical burn after applying hair dye and review the literature on similar cases, the composition of hair dyes, their mechanism of action, and the process of burns. The patient was a 17-year-old girl, who presented to the Dermatology Clinic with a 13 × 10 cm ulcer on the scalp after hair dyeing in a hairdressing salon. General and local treatment was applied, with particular emphasis on specialized dressings. The ulcer site was replaced by an area of scarring after 11 months of treatment. Based on the presented case and the review of the literature, we conclude that hair dye treatments warrant careful attention for potential scalp complications. The diagnostic and therapeutic approach demands a multidisciplinary effort, with ongoing patient-doctor cooperation throughout the treatment, which may complicate and span several months.

Dermal TRPV1 innervations engage a macrophage- and fibroblast-containing pathway to activate hair growth in mice

Pain, detected by nociceptors, is an integral part of injury, yet whether and how it can impact tissue physiology and recovery remain understudied. Here, we applied chemogenetics in mice to locally activate dermal TRPV1 innervations in naive skin and found that it triggered new regenerative cycling by dormant hair follicles (HFs). This was preceded by rapid apoptosis of dermal macrophages, mediated by the neuropeptide calcitonin gene-related peptide (CGRP). TRPV1 activation also triggered a macrophage-dependent induction of osteopontin (Spp1)-expressing dermal fibroblasts. The neuropeptide CGRP and the extracellular matrix protein Spp1 were required for the nociceptor-triggered hair growth. Finally, we showed that epidermal abrasion injury induced Spp1-expressing dermal fibroblasts and hair growth via a TRPV1 neuron and CGRP-dependent mechanism. Collectively, these data demonstrated a role for TRPV1 nociceptors in orchestrating a macrophage and fibroblast-supported mechanism to promote hair growth and enabling the efficient restoration of this mechano- and thermo-protective barrier after wounding.

Cell-homing and immunomodulatory composite hydrogels for effective wound healing with neovascularization

Wound healing in cases of excessive inflammation poses a significant challenge due to compromised neovascularization. Here, we propose a multi-functional composite hydrogel engineered to overcome such conditions through recruitment and activation of macrophages with adapted degradation of the hydrogel. The composite hydrogel (G-TSrP) is created by combining gelatin methacryloyl (GelMA) and nanoparticles (TSrP) composed of tannic acid (TA) and Sr2+. These nanoparticles are prepared using a one-step mineralization process assisted by metal-phenolic network formation. G-TSrP exhibits the ability to eliminate reactive oxygen species and direct polarization of macrophages toward M2 phenotype. It has been observed that the liberation of TA and Sr2+ from G-TSrP actively facilitate the recruitment and up-regulation of the expression of extracellular matrix remodeling genes of macrophages, and thereby, coordinate in vivo adapted degradation of the G-TSrP. Most significantly, G-TSrP accelerates angiogenesis despite the TA's inhibitory properties, which are counteracted by the released Sr2+. Moreover, G-TSrP enhances wound closure under inflammation and promotes normal tissue formation with strong vessel growth. Genetic analysis confirms macrophage-mediated wound healing by the composite hydrogel. Collectively, these findings pave the way for the development of biomaterials that promote wound healing by creating regenerative environment.

Split-Thickness Skin and Dermal Pixel Grafts Can Be Expanded up to 500 Times to Re-Epithelialize a Full-Thickness Burn Wound

Objective: Autologous skin transplantation is limited by donor site availability for patients with extensive burns. The objective of this study was to demonstrate the feasibility and efficacy of split-thickness skin (STS) and dermal pixel grafts (PG) in the treatment of burns. Approach: The study was divided into three arms of validation, expansion, and combination that all followed the same study design. Sixteen deep partial-thickness burns were created on the dorsum of anesthetized pigs. Three days postinjury the burns were debrided and grafted with STS and dermal PGs. The PGs were prepared by harvesting two skin grafts (split-thickness skin graft [STSG] and dermal graft) from the same donor site going down in depth. The grafts were minced to 0.3 × 0.3 × 0.3 mm PGs and suspended in a small volume of hydrogel. Healing was monitored for 6, 10, 14, or 28 days. In the validation study the PGs at 1:2 expansion ratio were transplanted and compared with STSG and untreated controls. The expansion study investigated the maximum expansion potential of the PGs and the combination of the benefits of transplanting STS and dermal PGs together. Results: The validation study showed that when STS and dermal PGs were transplanted in a 1:2 ratio they fully re-epithelialized the wounds in 14 days. The expansion study demonstrated that using expansion ratios up to 1:500 the wounds were re-epithelialized by day 28. The combination study showed that there was no additional benefit to use STS and dermal PGs together. Innovation: Pixel grafting provides expansion ratios greater than conventional STSG. The possibility to harvest both STS and dermal PGs from the same donor area further reduces the need for healthy skin. Conclusion: STSG and dermal grafts can be minced to PGs with preserved viability and expanded up to 500 times to re-epithelialize a wound.

Alloplastic Epidermal Skin Substitute in the Treatment of Burns

The goal of burn wound treatment is to ensure rapid epithelialization in superficial burns and the process of rebuilding the lost skin in deep burns. Topical treatment plays an important role. One of the innovations in the field of synthetic materials dedicated to the treatment of burns is epidermal skin substitutes. Since the introduction of Suprathel®, the alloplastic epidermal substitute, many research results have been published in which the authors investigated the properties and use of this substitute in the treatment of wounds of various origins, including burn wounds. Burn wounds cause both physical and psychological discomfort, which is why ensuring comfort during treatment is extremely important. Alloplastic epidermal substitute, due to its biodegradability, plasticity, no need to remove the dressing until healing, and the associated reduction in pain, is an alternative for treating burns, especially in children.

Incorporation of hair follicles in 3D bioprinted models of human skin

Current approaches fail to adequately introduce complex adnexal structures such as hair follicles within tissue engineered models of skin. Here, we report on the use of 3D bioprinting to incorporate these structures in engineered skin tissues. Spheroids, induced by printing dermal papilla cells (DPCs) and human umbilical vein cells (HUVECs), were precisely printed within a pregelled dermal layer containing fibroblasts. The resulting tissue developed hair follicle-like structures upon maturation, supported by migration of keratinocytes and melanocytes, and their morphology and composition grossly mimicked that of the native skin tissue. Reconstructed skin models with increased complexity that better mimic native adnexal structures can have a substantial impact on regenerative medicine as grafts and efficacy models to test the safety of chemical compounds.

Current and Future Developments in Wound Healing

Poor wound healing on the face and neck can lead to significant morbidity and dissatisfaction in facial plastic surgery. With current advances in wound healing management and commercially available biologic and tissue-engineered products, there are several options available to optimize acute wound healing and treat delayed or chronic wounds. This article summarizes some of the key principals and recent developments in wound healing research in addition to potential future advancements in the field of soft tissue wound healing.

Pharmacological YAP activation promotes regenerative repair of cutaneous wounds

Chronic cutaneous wounds remain a persistent unmet medical need that decreases life expectancy and quality of life. Here, we report that topical application of PY-60, a small-molecule activator of the transcriptional coactivator Yes-associated protein (YAP), promotes regenerative repair of cutaneous wounds in pig and human models. Pharmacological YAP activation enacts a reversible pro-proliferative transcriptional program in keratinocytes and dermal cells that results in accelerated re-epithelization and regranulation of the wound bed. These results demonstrate that transient topical administration of a YAP activating agent may represent a generalizable therapeutic approach to treating cutaneous wounds.

An optimized force-triggered density gradient sedimentation method for isolation of pelage follicle dermal papilla cells from neonatal mouse skin

BACKGROUND

The dermal papilla cells are a specialized population of mesenchymal cells located at the base of the hair follicle (HF), which possess the capacity to regulate HF morphogenesis and regeneration. However, lack of cell-type specific surface markers restricts the isolation of DP cells and application for tissue engineering purposes.

METHODS

We describe a novel force-triggered density gradient sedimentation (FDGS) method to efficiently obtain purified follicular DP-spheres cells from neonatal mouse back skin, utilizing only centrifugation and optimized density gradients.

RESULTS

Expression of characteristic DP cell markers, alkaline phosphatase, β-catenin, versican, and neural cell adhesion molecules, were confirmed by immunofluorescence. Further, the patch assays demonstrated that DP cells maintained their hair regenerative capacity in vivo. Compared with current methods, including microdissection and fluorescence-activated cell sorting, the FDGS technique is simpler and more efficient for isolating DP cells from neonatal mouse skin.

CONCLUSIONS

The FDGS method will improve the research potential of neonatal mouse pelage-derived DP cells for tissue engineering purposes.

Vellus hair condition is related to dermal elasticity and facial sagging severity

BACKGROUND

Sagging of facial skin is a critical factor associated with an aged appearance. However, the mechanism of sagging has not been fully elucidated. The facial skin contains vellus hair (fine hair), but the contribution of vellus hair to skin condition and facial aging has yet to be studied.

AIM

We aimed to clarify the influence of vellus hair on the physical properties and sagging severity of facial skin by establishing an evaluation system for vellus hair condition.

METHOD

Photographs were taken to assess the vellus hair condition in the cheek area in 30 middle-aged female volunteers. Skin elasticity was measured with a cutometer and sagging severity was evaluated by using previously established photograph-based grading criteria.

RESULTS

Facial skin vellus hairs were divided into three types: fine, thick, and normal thickness. Based on this observation, we established a 6-grade photograph-based grading system based on the dominant type of vellus hair in the target area and used it to evaluate vellus hair condition at the cheek. We found that vellus hair condition is significantly positively related to skin elasticity parameters Ua/Uf (representing overall elasticity including creep and creep recovery), Ur/Ue (representing net elasticity without viscoelastic creep), and Ur/Uf (ratio of elastic recovery to total deformation). Further, vellus hair condition was significantly negatively correlated to sagging severity.

CONCLUSION

Our results suggest that vellus hair condition positively contributes to the skin's physical properties, and consequently deterioration of the vellus hair condition promotes an aged facial appearance.

Advances and Innovations of 3D Bioprinting Skin

Three-dimensional (3D) bioprinted skin equivalents are highlighted as the new gold standard for alternative models to animal testing, as well as full-thickness wound healing. In this review, we focus on the advances and innovations of 3D bioprinting skin for skin regeneration, within the last five years. After a brief introduction to skin anatomy, 3D bioprinting methods and the remarkable features of recent studies are classified as advances in materials, structures, and functions. We will discuss several ways to improve the clinical potential of 3D bioprinted skin, with state-of-the-art printing technology and novel biomaterials. After the breakthrough in the bottleneck of the current studies, highly developed skin can be fabricated, comprising stratified epidermis, dermis, and hypodermis with blood vessels, nerves, muscles, and skin appendages. We hope that this review will be priming water for future research and clinical applications, that will guide us to break new ground for the next generation of skin regeneration.

Mesenchymal Stem Cells in Burn Wound Management

Mesenchymal stem cells have a known regenerative potential and are used in many indications. They secrete many growth factors, including for fibroblasts (FGF), endothelium (VEGF), as well as 14 anti-inflammatory cytokines, and they stimulate tissue regeneration, promoting the secretion of proteins and glycosaminoglycans of extracellular matrices, such as collagen I, II, III, and V, elastin, and also metalloproteinases. They secrete exosomes that contain proteins, nucleic acids, lipids, and enzymes. In addition, they show the activity of inactivating free radicals. The aim of this study was an attempt to collect the existing literature on the use of stem cells in the treatment of a burn wound. There were 81 studies included in the analysis. The studies differed in terms of the design, burn wound model, source of stem cells, and methods of cellular therapy application. No major side effects were reported, and cellular therapy reduced the healing time of the burn wound. Few case reports on human models did not report any serious adverse events. However, due to the heterogeneity of the evidence, cellular therapy in burn wound treatment remains an experimental method.

Soluble CD83 improves and accelerates wound healing by the induction of pro-resolving macrophages

To facilitate the recovery process of chronic and hard-to-heal wounds novel pro-resolving treatment options are urgently needed. We investigated the pro-regenerative properties of soluble CD83 (sCD83) on cutaneous wound healing, where sCD83 accelerated wound healing not only after systemic but also after topical application, which is of high therapeutic interest. Cytokine profile analyses revealed an initial upregulation of inflammatory mediators such as TNFα and IL-1β, followed by a switch towards pro-resolving factors, including YM-1 and IL-10, both expressed by tissue repair macrophages. These cells are known to mediate resolution of inflammation and stimulate wound healing processes by secretion of growth factors such as epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF), which promote vascularization as well as fibroblast and keratinocyte differentiation. In conclusion, we have found strong wound healing capacities of sCD83 beyond the previously described role in transplantation and autoimmunity. This makes sCD83 a promising candidate for the treatment of chronic- and hard-to-heal wounds.

Neural, adipocyte and hepatic differentiation potential of primary and secondary hair follicle stem cells isolated from Arbas Cashmere goats

Background

Arbas Cashmere goats are excellent domestic breeds with high yields of wool and cashmere. Their wool and cashmere can bring huge benefits to the livestock industry. Our studies intend to more fully understand the biological characteristics of hair follicle stem cells (HFSCs) in order to further explore the mechanisms of wool and cashmere regular regeneration. And they have been increasingly considered as promising multipotent cells in regenerative medicine because of their capacity to self-renew and differentiate. However, many aspects of the specific growth characteristics and differentiation ability of HFSCs remain unknown. This study aimed to further explore the growth characteristics and pluripotency of primary hair follicle stem cells (PHFSCs) and secondary hair follicle stem cells (SHFCs).

Results

We obtained PHFSCs and SHFSCs from Arbas Cashmere goats using combined isolation and purification methods. The proliferation and vitality of the two types of HFSCs, as well as the growth patterns, were examined. HFSC-specific markers and genes related to pluripotency, were subsequently identified. The PHFSCs and SHFSCs of Arbas Cashmere goat have a typical cobblestone morphology. Moreover, the PHFSCs and SHFSCs express HFSC surface markers, including CD34, K14, K15, K19 and LGR5. We also identified pluripotency-associated gene expression, including SOX2, OCT4 and SOX9, in PHFSCs and SHFSCs. Finally, PHFSCs and SHFSCs displayed multipotent abilities. PHFSCs and SHFSCs can be directed to differentiate into adipocyte-like, neural-like, and hepatocyte-like cells.

Conclusions

In conclusion, this study confirmed that the biological characteristics and differentiation potential of PHFSCs and SHFSCs from Arbas Cashmere goats. These findings broaden and refine our knowledge of types and characteristics of adult stem cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03420-3.

3D printing of skin equivalents with hair follicle structures and epidermal-papillary-dermal layers using gelatin/hyaluronic acid hydrogels

Recent advances in three-dimensional (3D) bioprinting technologies enabled the fabrication of sophisticated live 3D tissue analogs. Although various hydrogel-based bioink has been reported, the development of advanced bioink materials that can reproduce the composition of native extracellular matrix (ECM) accurately and mimic the intrinsic property of laden cells is still challenging. In this work, 3D printed skin equivalents incorporating hair follicle structures and epidermal-papillary-dermal layers are fabricated with gelatin methacryloyl (GelMA)/hyaluronic acid (HA) MA (HAMA) hydrogel (GelMA/HAMA) bioink. The composition of collagen and glycosaminoglycan (GAG) of native skin was recapitulated by adjusting the combination of GelMA and HAMA. The GelMA/HAMA bioink was proven to have excellent viscoelastic and physicochemical properties, 3D printability, cytocompatibility, and functionality to maintain the hair inductive potency and facilitated spontaneous hair pore development. Overall, we suggest that the GelMA/HAMA hydrogels can be promising candidates as bioinks for the 3D printing of skin equivalents with epidermal-papillary-dermal multi-layers and hair follicle structures, and they might serve as a useful model in skin tissue engineering and regeneration.

The Therapeutic Role of ADSC-EVs in Skin Regeneration

Large skin defects caused by burns, unhealing chronic wounds, and trauma, are still an intractable problem for clinicians and researchers. Ideal skin regeneration includes several intricate and dynamic stages of wound repair and regeneration of skin physiological function. Adipose-derived stem cells (ADSCs), a type of mesenchymal stem cells (MSCs) with abundant resources and micro-invasive extraction protocols, have been reported to participate in each stage of promoting skin regeneration via paracrine effects. As essential products secreted by ADSCs, extracellular vesicles (EVs) derived from ADSCs (ADSC-EVs) inherit such therapeutic potential. However, ADSC-EVs showed much more clinical superiorities than parental cells. ADSC-EVs carry various mRNAs, non-coding RNAs, proteins, and lipids to regulate the activities of recipient cells and eventually accelerate skin regeneration. The beneficial role of ADSCs in wound repair has been widely accepted, while a deep comprehension of the mechanisms of ADSC-EVs in skin regeneration remains unclear. In this review, we provided a basic profile of ADSC-EVs. Moreover, we summarized the latest mechanisms of ADSC-EVs on skin regeneration from the aspects of inflammation, angiogenesis, cell proliferation, extracellular matrix (ECM) remodeling, autophagy, and oxidative stress. Hair follicle regeneration and skin barrier repair stimulated by ADSC-EVs were also reviewed. The challenges and prospects of ADSC-EVs-based therapies were discussed at the end of this review.

Epithelial-Mesenchymal Interaction in Hair Regeneration and Skin Wound Healing

Interactions between epithelial and mesenchymal cells influence hair follicles (HFs) during embryonic development and skin regeneration following injury. Exchanging soluble molecules, altering key pathways, and extracellular matrix signal transduction are all part of the interplay between epithelial and mesenchymal cells. In brief, the mesenchyme contains dermal papilla cells, while the hair matrix cells and outer root sheath represent the epithelial cells. This study summarizes typical epithelial–mesenchymal signaling molecules and extracellular components under the control of follicular stem cells, aiming to broaden our current understanding of epithelial–mesenchymal interaction mechanisms in HF regeneration and skin wound healing.

Type 2 Diabetic Mellitus Inhibits Skin Renewal through Inhibiting WNT-Dependent Lgr5+ Hair Follicle Stem Cell Activation in C57BL/6 Mice

BACKGROUND

Hair follicles are important accessory organs of the skin, and it is important for skin renewal and performs variety of important functions. Diabetes can cause several dermatoses; however, its effect on hair follicles is unclear. The purpose of this study was to investigate the effect of type II diabetes (T2DM) on the hair follicles of mice.

METHODS

Seven-week-old male C57BL/6 littermate mice were divided into two groups. The treatment group was injected with streptozotocin (STZ) to induce T2DM, and the control group was parallelly injected with the same dose of buffer. Seven days after injection, the back is depilated to observe the hair follicle regeneration. Hair follicle regeneration was observed by naked eyes and HE staining. The proliferation of the skin cells was observed by PCNA and K14 staining. The altered genes were screened by RNA sequencing and verified by qRT-PCR. In addition, Lgr5 + GFP/mTmG transgenic mice were used to observe the effect of T2DM on Lgr5 hair follicle stem cells (HFSC). And the expression of WNT4 and WNT8A were measured by Western Blot.

RESULTS

T2DM inhibited hair follicle regeneration. Compared to control mice, T2DM mice had smaller hair follicles, reduced skin thickness, and less expression of PCNA and K14. RNA sequencing showed that the two groups had significant differences in cell cycle and proliferation-related pathways. Compared with the control mice, the mRNA expression of Lgr4, Lgr5, Wnt4, and Wnt8a was decreased in the T2DM group. Moreover, T2DM inhibited the activation of Lgr5 HFSC and the expression of WNT4 and WNT8A.

CONCLUSIONS

T2DM inhibited hair follicle regeneration and skin cells proliferation by inhibiting WNT-dependent Lgr5 HFSC activation. This may be an important reason for the reduction of skin renewal ability and the formation of chronic wounds caused by diabetes. It is important for the treatment of chronic diabetic wounds and the development of tissue engineering.

Hair Follicle Grafting Therapy Promotes Re-Emergence of Critical Skin Components in Chronic Nonhealing Wounds

An exploding public health crisis is the exponential growth in the incidence of chronic nonhealing ulcers associated with diseases such as diabetes. Various modalities have been developed to stimulate wound closure that is otherwise recalcitrant to standard clinical treatments. However, these approaches primarily focus on the process of re-epithelialization and are often deficient in regenerating the full spectrum of structures necessary for normal skin function. Autologous hair follicle grafting is a recent therapy to stimulate the closure of such nonhealing wounds, and we observed effects beyond the epidermis to other important components of the dermis. We found that hair follicle grafting facilitated the reappearance of various undifferentiated and differentiated layers of the epidermis with the restoration of epidermal junctions. In addition, other important structures that are critical for cutaneous health and function such as the blood and lymph vasculature, nerve fibers, and sweat gland structures were restored in postgrafted wounds. Interestingly, both immune cells and inflammatory signals were substantially decreased, indicating a reduction in the chronic inflammation that is a hallmark of nonhealing wounds. Our observation that punch wounds created on the postgrafted area likewise healed suggests that this is a self-sustaining long-term therapy for patients with chronic wounds.

Hair Transplantation: Basic Overview

Modern hair restoration surgery is based on a technique known as follicular unit transplantation in which follicular units (FUs) are the exclusive structures used as hair grafts. In Part 1 of this two-part review, we describe how the techniques employed in hair transplantation have evolved into their present forms. Anatomic concepts of specific relevance for dermatologists are discussed, including the distribution and ex-vivo morphology of scalp FUs. Male androgenetic alopecia and female pattern hair loss are the most common reasons for hair loss consultations with dermatologists and will be the primary focus of this review. However, as not all hair disorders are suitable for transplantation, this review will also describe which scalp conditions are amenable to surgery and which are not. In addition, guidelines are provided to help dermatologists better define good or bad candidates for hair transplantation. Finally, other conditions for which hair transplantation surgery is indicated are reviewed.