Hair follicle: a novel source of multipotent stem cells for tissue engineering and regenerative medicine

Human Fibroblast-Derived Matrix Hydrogel Accelerates Regenerative Wound Remodeling Through the Interactions with Macrophages

Herein, a novel extracellular matrix (ECM) hydrogel is proposed fabricated solely from decellularized, human fibroblast-derived matrix (FDM) toward advanced wound healing. This FDM-gel is physically very stable and viscoelastic, while preserving the natural ECM diversity and various bioactive factors. Subcutaneously transplanted FDM-gel provided a permissive environment for innate immune cells infiltration. Compared to collagen hydrogel, excellent wound healing indications of FDM-gel treated in the full-thickness wounds are noticed, particularly hair follicle formation via highly upregulated β-catenin. Sequential analysis of the regenerated wound tissues disclosed that FDM-gel significantly alleviated pro-inflammatory cytokine and promoted M2-like macrophages, along with significantly elevated vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) level. A mechanistic study demonstrated that macrophages-FDM interactions through cell surface integrins α5β1 and α1β1 resulted in significant production of VEGF and bFGF, increased Akt phosphorylation, and upregulated matrix metalloproteinase-9 activity. Interestingly, blocking such interactions using specific inhibitors (ATN161 for α5β1 and obtustatin for α1β1) negatively affected those pro-healing growth factors secretion. Macrophages depletion animal model significantly attenuated the healing effect of FDM-gel. This study demonstrates that the FDM-gel is an excellent immunomodulatory material that is permissive for host cells infiltration, resorbable with time, and interactive with macrophages, where it thus enables regenerative matrix remodeling toward a complete wound healing.

Bioactive Compound-Loaded Nanocarriers for Hair Growth Promotion: Current Status and Future Perspectives

Hair loss (alopecia) has a multitude of causes, and the problem is still poorly defined. For curing alopecia, therapies are available in both natural and synthetic forms; however, natural remedies are gaining popularity due to the multiple effects of complex phytoconstituents on the scalp with fewer side effects. Evidence-based hair growth promotion by some plants has been reported for both traditional and advanced treatment approaches. Nanoarchitectonics may have the ability to evolve in the field of hair- and scalp-altering products and treatments, giving new qualities to hair that can be an effective protective layer or a technique to recover lost hair. This review will provide insights into several plant and herbal formulations that have been reported for the prevention of hair loss and stimulation of new hair growth. This review also focuses on the molecular mechanisms of hair growth/loss, several isolated phytoconstituents with hair growth-promoting properties, patents, in vivo evaluation of hair growth-promoting activity, and recent nanoarchitectonic technologies that have been explored for hair growth.

Potential Natural Products Regulation of Molecular Signaling Pathway in Dermal Papilla Stem Cells

Stem cells have demonstrated significant potential for tissue engineering and repair, anti-aging, and rejuvenation. Hair follicle stem cells can be found in the dermal papilla at the base of the follicle and the bulge region, and they have garnered increased attention because of their potential to regenerate hair as well as their application for tissue repair. In recent years, these cells have been shown to affect hair restoration and prevent hair loss. These stem cells are endowed with mesenchymal characteristics and exhibit self-renewal and can differentiate into diverse cell types. As research in this field continues, it is probable that insights regarding stem cell maintenance, as well as their self-renewal and differentiation abilities, will benefit the application of these cells. In addition, an in-depth discussion is required regarding the molecular basis of cellular signaling and the influence of nature-derived compounds in stimulating the stemness properties of dermal papilla stem cells. This review summarizes (i) the potential of the mesenchymal cells component of the hair follicle as a target for drug action; (ii) the molecular mechanism of dermal papilla stem cells for maintenance of their stem cell function; and (iii) the positive effects of the natural product compounds in stimulating stemness in dermal papilla stem cells. Together, these insights may help facilitate the development of novel effective hair loss prevention and treatment.

Non-Healing Perianal Fistulas: A Clinical Model of Tissue Senescence Impairing Both Tissue Fibrosis and Regenerative Potential

Senescent cells and fibrosis are important components that impact the regenerative capacity of skin, particularly when considering chronic non-healing wounds. Anoderm and perianal fistulas in the setting of Crohn's disease are clinically pathophysiological extremes with consequently different healing processes which impact treatment modalities. This study describes the implications of potential senescence reversing techniques including autologous fat grafting and pharmacologic and immunomodulating agents. Given these findings, the authors propose a future direction of study involving exosomes loaded with senolytics as a method for potentially improving chronic wound healing. In conclusion, this manuscript explores the diversity of skin healing and healing outcomes which supports the future investigation of senotherapeutic agents promoting regenerative processes for non-healing wounds.

Human-derived hair follicle stem cells and hydrogen sulfide on focal cerebral ischemia model: A comparative evaluation of radiologic, neurobehavioral and immunohistochemical results

The present study investigated the effects of intracerebral human-derived hair follicle stem cells (HFBSCs), whether alone or in combination with hydrogen sulfide (H₂S) in a rat model of focal cerebral ischemia. The rats were randomly assigned into 4 groups (n = 10): Control (phosphate buffered saline (PBS)), Group A (at 24 h post-middle cerebral artery occlusion(MCAo), stereotaxic intracerebral, 1,0 × 10⁶, total 10 μL HFBSCs), Group B (3-14 d post-MCAo, intraperitoneal (i.p.), 25 μM/kg/day H₂S), Group AB (HFBSCs + H₂S). Cranial magnetic resonance images were recorded on postoperative 1st and 28th days. Three dimensional analysis was performed to calculate the infarct volumes. Rotarod and cylinder tests were performed after MCAo and finally all rats were euthanized by cardiac perfusion at 28 days after MCAo for immunohistochemical analysis. The reduction in infarct volumes of rats receiving HFBSC was significant. The cranial infarct volume on the postoperative 28th day was significantly higher in the group in which H₂S was administered alone compared to the HFBSC alone group. All animals showed steadily improved spontaneous locomotor activity from day 7 post-MCAo on rotarod test, from day 1 on cylinder test, but showed no significant differences at all times. In all groups, the grading scores of CD34, CD5, CD11b and GFAP immunohistochemical markers did not differ significantly. In conclusion, intracerebral HFBSC treatment after 24 h of ischemic stroke may be an effective way to reduce the cranial infarct volume, whereas H₂S treatment alone or in combination with HFBSC may not be sufficient for ischemic brain injury.

Inhibition of glutaminolysis restores mitochondrial function in senescent stem cells

Mitochondrial dysfunction, a hallmark of aging, has been associated with the onset of aging phenotypes and age-related diseases. Here, we report that impaired mitochondrial function is associated with increased glutamine catabolism in senescent human mesenchymal stem cells (MSCs) and myofibroblasts derived from patients suffering from Hutchinson-Gilford progeria syndrome. Increased glutaminase (GLS1) activity accompanied by loss of urea transporter SLC14A1 induces urea accumulation, mitochondrial dysfunction, and DNA damage. Conversely, blocking GLS1 activity restores mitochondrial function and leads to amelioration of aging hallmarks. Interestingly, GLS1 expression is regulated through the JNK pathway, as demonstrated by chemical and genetic inhibition. In agreement with our in vitro findings, tissues isolated from aged or progeria mice display increased urea accumulation and GLS1 activity, concomitant with declined mitochondrial function. Inhibition of glutaminolysis in progeria mice improves mitochondrial respiratory chain activity, suggesting that targeting glutaminolysis may be a promising strategy for restoring age-associated loss of mitochondrial function.

Nestin is a marker of unipotent embryonic and adult progenitors differentiating into an epithelial cell lineage of the hair follicles

Nestin is an intermediate filament protein transiently expressed in neural stem/progenitor cells. We previously demonstrated that outer root sheath (ORS) keratinocytes of adult hair follicles (HFs) in mice descend from nestin-expressing cells, despite being an epithelial cell lineage. This study determined the exact stage when nestin-expressing ORS stem/precursor cells or their descendants appear during HF morphogenesis, and whether they are present in adult HFs. Using Nes-Cre/CAG-CAT-EGFP mice, in which enhanced green fluorescent protein (EGFP) is expressed following Cre-based recombination driven by the nestin promoter, we found that EGFP⁺ cells appeared in the epithelial layer of embryonic HFs as early as the peg stage. EGFP⁺ cells in hair pegs were positive for keratin 14 (K14) and K5, but not vimentin, SOX2, SOX10, or S100 alpha 6. Tracing of tamoxifen-induced EGFP⁺ cells in postnatal Nes-CreERT2/CAG-CAT-EGFP mice revealed labeling of some isthmus HF epithelial cells in the first anagen stage. EGFP⁺ cells in adult HFs were not immunolabeled for K15, an HF multipotent stem cell marker. However, when hairs were depilated in Nes-CreERT2/CAG-CAT-EGFP mice to induce the anagen stage after tamoxifen injection, the majority of ORS keratinocytes in depilation-induced anagen HFs were labeled for EGFP. Our findings indicate that nestin-expressing unipotent progenitor cells capable of differentiating into ORS keratinocytes are present in HF primordia and adult HFs.

3D bioprinting of a gelatin-alginate hydrogel for tissue-engineered hair follicle regeneration

Hair follicle (HF) regeneration remains challenging, principally due to the absence of a platform that can successfully generate the microenvironmental cues of hair neogenesis. Here, we demonstrate a 3D bioprinting technique based on a gelatin/alginate hydrogel (GAH) to construct a multilayer composite scaffold simulating the HF microenvironment in vivo. Fibroblasts (FBs), human umbilical vein endothelial cells (HUVECs), dermal papilla cells (DPCs), and epidermal cells (EPCs) were encapsulated in GAH (prepared from a mixture of gelatin and alginate) and respectively 3D-bioprinted into the different layers of a composite scaffold. The bioprinted scaffold with epidermis- and dermis-like structure was subsequently transplanted into full-thickness wounds in nude mice. The multilayer scaffold demonstrated suitable cytocompatibility and increased the proliferation ability of DPCs (1.2-fold; P < 0.05). It also facilitated the formation of self-aggregating DPC spheroids and restored DPC genes associated with hair induction (ALP, β-catenin, and α-SMA). The dermal and epidermal cells self-assembled successfully into immature HFs in vitro. HFs were regenerated in the appropriate orientation in vivo, which can mainly be attributed to the hierarchical grid structure of the scaffold and the dot bioprinting of DPCs. Our 3D printed scaffolds provide a suitable microenvironment for DPCs to regenerate entire HFs and could make a significant contribution in the medical management of hair loss. This method may also have broader applications in skin tissue (and appendage) engineering. STATEMENT OF SIGNIFICANCE: Hair loss remains a challenging clinical problem that influences quality of life. Three-dimensional (3D) bioprinting has become a useful tool for the fabrication of tissue constructs for transplantation and other biomedical applications. In this study, we used a 3D bioprinting technique based on a gelatin/alginate hydrogel to construct a multi-layer composite scaffold with cuticular and corium layers to simulate the microenvironment of dermal papilla cells (DPCs) in the human body. This new approach permits the controllable formation of self-aggregating spheroids of DPCs in a physiologically relevant extracellular matrix and the initiation of epidermal-mesenchymal interactions, which results in HF formation in vivo. The ability to regenerate entire HFs should have a significant impact on the medical management of hair loss.

Aberrant Bone Regulation in Albright Hereditary Osteodystrophy dueto Gnas Inactivation: Mechanisms and Translational Implications

PURPOSE OF REVIEW

This review highlights the impact of Gnas inactivation on both bone remodeling and the development of heterotopic subcutaneous ossifications in Albright hereditary osteodystrophy (AHO). Here we discuss recent advancements in understanding the pathophysiologic mechanisms of the aberrant bone development in AHO as well as potential translational implications.

RECENT FINDINGS

Gnas inactivation can regulate the differentiation and function of not only osteoblasts but also osteoclasts and osteocytes. Investigations utilizing a mouse model of AHO generated by targeted disruption of Gnas have revealed that bone formation and resorption are differentially affected based upon the parental origin of the Gnas mutation. Data suggest that Gnas inactivation leads to heterotopic bone formation within subcutaneous tissue by changing the connective tissue microenvironment, thereby promoting osteogenic differentiation of tissue-resident mesenchymal progenitors. Observed variations in bone formation and resorption based upon the parental origin of the Gnas mutation warrant future investigations and may have implications in the management and treatment of AHO and related conditions. Additionally, studies of heterotopic bone formation due to Gnas inactivation have identified an essential role of sonic hedgehog signaling, which could have therapeutic implications not only for AHO and related conditions but also for heterotopic bone formation in a wide variety of settings in which aberrant bone formation is a cause of significant morbidity.

Injectable platelet rich fibrin facilitates hair follicle regeneration by promoting human dermal papilla cell proliferation, migration, and trichogenic inductivity

Hair follicle regeneration has been successful in mice but failed in human being for years. Dermal papilla cells, a specialized mesenchymal stem cell derived from dermal papilla within hair follicles, is considered the key cells for hair follicle regeneration function as both regeneration initiator and regulator. Injectable platelet rich fibrin (i-PRF), a novel biomaterial rich in a variety of growth factors and three-dimensional scaffolds, has shown promising effects on tissue regeneration. In this study, we aimed to evaluate the application of i-PRF in human hair follicle regeneration by examining the biological effects of i-PRF on human dermal papilla cells (hDPCs). Biomaterial compatibility, cell viability, proliferation, migration, alkaline phosphatase activity and trichogenic inductivity were assessed after exposing hDPCs to different concentrations of i-PRF extracts. In addition, we investigated the ultrastructure of i-PRF with all cell components filtered. The results revealed that i-PRF possessing excellent biocompatibility and could significantly promote hDPCs proliferation, migration, and trichogenic inductivity. Furthermore, the concentration of i-PRF is able to remarkably influence hDPCs behavior in a dose-dependent pattern. Different concentrations exhibited differential effects on hDPCs behavior. In general, lower concentration promotes cell proliferation better than higher concentration, while higher concentration promotes cell function better reversely. Best concentration for hDPCs in vitro expending is 1% concentration. 20% concentration is optimal for hair follicle regeneration. In summary, our findings concluded that i-PRF facilitates hair follicle regeneration by promoting human dermal papilla cell proliferation, migration, and trichogenic inductivity.

A Beginner's Introduction to Skin Stem Cells and Wound Healing

The primary function of the skin is that of a physical barrier against the environment and diverse pathogens; therefore, its integrity is essential for survival. Skin regeneration depends on multiple stem cell compartments within the epidermis, which, despite their different transcriptional and proliferative capacity, as well as different anatomical location, fall under the general term of skin stem cells (SSCs). Skin wounds can normally heal without problem; however, some diseases or extensive damage may delay or prevent healing. Non-healing wounds represent a serious and life-threatening scenario that may require advanced therapeutic strategies. In this regard, increased focus has been directed at SSCs and their role in wound healing, although emerging therapeutical approaches are considering the use of other stem cells instead, such as mesenchymal stem cells (MSCs). Given its extensive and broad nature, this review supplies newcomers with an introduction to SSCs, wound healing, and therapeutic strategies for skin regeneration, thus familiarizing the reader with the subject in preparation for future in depth reading.

A three-dimensional bioprinting technique, based on a gelatin/alginate hydrogel, for the tissue engineering of hair follicle reconstruction

Hair loss remains a challenging clinical problem that influences the quality of life. Three-dimensional (3D) bioprinting has become a valuable tool for fabricating tissue constructs for transplantation and other biomedical applications. Although some simple organs, such as skin and cartilage, have been successfully simulated, it remains challenging to make hair follicles (HFs), which are highly complex organs. The tissue engineering of human HFs has been a long-standing challenge, and progress with this has lagged behind that with other lab-grown tissues. This is principally due to a lack of availability of a platform that can successfully recapitulate the microenvironmental cues required to maintain the requisite cellular interactions for hair neogenesis. In this study, we used a 3D bioprinting technique based on a gelatin/alginate hydrogel to construct a multilayer composite scaffold with cuticular and corium layers to simulate the microenvironment of dermal papilla cells (DPCs) in the human body. This new approach permits the controllable formation of self-aggregating spheroids of DPCs in a physiologically relevant extracellular matrix and the initiation of epidermal-mesenchymal interactions, which results in HF formation in vivo. In conclusion, our 3D-bioprinted multilayer composite scaffold prepared using a gelatin/alginate hydrogel provides a suitable 3D microenvironment for DPCs to induce HF formation. The ability to regenerate entire HFs should have a significant impact on the medical management of hair loss. This method may also have critical applications for skin tissue engineering, with its appendages, for other purposes.

Hair Follicle Stem Cells for Tissue Regeneration

With the positive outcomes of various cell therapies currently under pre-clinical and clinical studies, there is a significant interest in novel stem cell sources with unique therapeutic properties. Studies over the past two decades or so demonstrated the feasibility to isolate multipotent/pluripotent stem cells from hair follicles. The easy accessibility, high proliferation and differentiation ability as well as lack of ethical concerns associated with this stem cell source make hair follicle stem cells (HFSCs) attractive candidate for cell therapy and tissue engineering. This review discusses the various stem cell types identified in rodent and human hair follicles and ongoing studies on the potential use of HFSCs for skin, bone, cardio-vascular, and nerve tissue engineering.

Hair follicle stem cells promote cutaneous wound healing through the SDF-1α/CXCR4 axis: an animal model

OBJECTIVE

An appropriate source of adult stem cells for therapeutic use is stem cells deriving from the hair follicle bulge. Following injury, ischaemic tissues produce a variety of cytokines and growth factors that are essential for tissue repair. This study sought to investigate the temporal effects of hair follicle bulge stem cells (HFSCs) on cutaneous wound healing in rats using the SDF-1α/CXCR4 axis.

METHOD

HFSCs obtained from rat vibrissa, labeled with DiI and then special markers, were detected using flow cytometry. The animals were divided into five groups: control (non-treated, n=18), sham (PBS, n=18), AMD (treated with AMD3100, n=18), HFSC + AMD (treated with HFSCs + AMD3100, n=18) and HFSC (treated with HFSCs, n=18). A full-thickness excisional wound model was created and DiI-labeled HFSCs were injected around the wound bed. Wound healing was recorded with digital photographs. The animals were sacrificed 3, 7 and 14 days after the surgery and were used for histological (H&E, Masson's trichrome staining) and molecular (ELISA and q-PCR) assays.

RESULTS

The flow cytometry results demonstrated that HFSCs were CD34-positive, nestin-positive, but Kr15-negative. The morphological analysis of the HFSC-treated wounds showed accelerated wound closure. The histological analysis of the photomicrographs exhibited more re-epithelialisation and dermal structural regeneration in the HFSC-treated wounds compared with the control group. In the HFSC + AMD group, the histological parameters improved on the same days, but showed a significant decrease compared with the HFSC group in all the days assayed. In the AMD group, there was a significant reduction in the noted parameters. qRT-PCR and ELISA showed a high expression level of SDF-1α, CXCR4 and VEGFR-2 in the HFSC-treated wounded skin tissue, but the expression of CXCR4 and VEGFR-2 showed a significant reduction in the HFSC + AMD group compared with the HFSC group.

CONCLUSIONS

Based on the findings of this study, HFSC transplantation affects wound closure parameters and the expression of SDF-1α and CXCR4. As the SDF-1α expression level increases in the injured area, the HFSCs contribute to wound repair through the SDF-1α/CXCR4 axis. This result is extremely valuable because it raises the possibility of wounds healed by isolating autologous HFSCs from the patient.

Establishment of an Efficient Primary Culture System for Human Hair Follicle Stem Cells Using the Rho-Associated Protein Kinase Inhibitor Y-27632

Background

Hair follicle tissue engineering is a promising strategy for treating hair loss. Human hair follicle stem cells (hHFSCs), which play a key role in the hair cycle, have potential applications in regenerative medicine. However, previous studies did not achieve efficient hHFSC expansion in vitro using feeder cells. Therefore, there is a need to develop an efficient primary culture system for the expansion and maintenance of hHFSCs.

Methods

The hHFSCs were obtained by two-step proteolytic digestion combined with microscopy. The cell culture dishes were coated with human fibronectin and inoculated with hHFSCs. The hHFSCs were harvested using a differential enrichment procedure. The effect of Rho-associated protein kinase (ROCK) inhibitor Y-27632, supplemented in keratinocyte serum-free medium (K-SFM), on adhesion, proliferation, and stemness of hHFSCs and the underlying molecular mechanisms were evaluated.

Results

The hHFSCs cultured in K-SFM, supplemented with Y-27632, exhibited enhanced adhesion and proliferation. Additionally, Y-27632 treatment maintained the stemness of hHFSCs and promoted the ability of hHFSCs to regenerate hair follicles in vivo. However, Y-27632-induced proliferation and stemness in hHFSCs were conditional and reversible. Furthermore, Y-27632 maintained propagation and stemness of hHFSCs through the ERK/MAPK pathway.

Conclusion

An efficient short-term culture system for primary hHFSCs was successfully established using human fibronectin and the ROCK inhibitor Y-27632, which promoted the proliferation, maintained the stemness of hHFSCs and promoted the ability to regenerate hair follicles in vivo. The xenofree culturing method used in this study provided a large number of high-quality seed cells, which have applications in hair follicle tissue engineering and stem cell therapy.

A systematic review of the scalp donor site for split-thickness skin grafting

Split-thickness skin grafting (STSG) is the gold standard for coverage of acute burns and reconstructive wounds. However, the choice of the donor site for STSG varies among surgeons, and the scalp represents a relatively under-utilized donor site. Understanding the validity of potential risks will assist in optimizing wound management. A comprehensive literature search was conducted of the PubMed database to identify studies evaluating scalp skin grafting in human subjects published between January 1, 1964 and December 31, 2019. Data were collected on early and late complications at the scalp donor site. In total, 27 articles comparing scalp donor site complications were included. The selected studies included analyses of acute burn patients only (21 of 27 articles), mean total body surface area (20 of 27), age distribution (22 of 27), sex (12 of 27), ethnicity (5 of 27), tumescent technique (21 of 27), depth setting of the dermatome (24 of 27), number of harvests (20 of 27), mean days of epithelization (18 of 27), and early and late complications (27 of 27). The total rate of early complications was 3.82% (117 of 3,062 patients). The total rate of late complications was 5.19% (159 of 3,062 patients). The literature on scalp skin grafting has not yet identified an ideal surgical technique for preventing donor site complications. Although scalp skin grafting provided superior outcomes with fewer donor site complications, there continues to be a lack of standardization. The use of scalp donor sites for STSG can prevent early and late complications if proper surgical planning, procedures, and postoperative care are performed.

Comparative characterization and osteogenic / adipogenic differentiation of mesenchymal stem cells derived from male rat hair follicles and bone marrow

Clinical applications of cell therapy and tissue regeneration under different conditions need a multiplicity of adult stem cell sources. Up to date, little is available on the comparative isolation, characterization, proliferation, rapid amplification, and osteogenic/adipogenic differentiation of rat mesenchymal stem cells (MSCs) isolated from living bulge cells of the hair follicle (HF) and bone marrow (BM) from the same animal. This work hopes to use HF-MSCs as an additional adult stem cell source for research and application. After reaching 80% confluence, the cell counting, viability %, and yields of HF-MSCs and BM-MSCs were nearly similar. The viability % was 91.41 ± 2.98 and 93.11 ± 3.06 while the cells yield of initial seeding was 33.15 ± 2.76 and 34.22 ± 3.99 and of second passage was 28.76 ± 1.01 and 29.56 ± 3.11 for HF-MSCs and BM-MSCs respectively. Clusters of differentiation (CDs) analysis revealed that HF-MSCs were positively expressed CD34, CD73 and CD200 and negatively expressed CD45. BM-MSCs were positively expressed CD73 and CD200 and negatively expressed of CD34 and CD45. The proliferation of HF-MSCs and BM-MSCs was determined by means of incorporation of Brd-U, population doubling time (PDT) assays and the quantity of formazan release. The percentage of Brd-U positive cells and PDT were relatively similar in both types of cells. The proliferation, as expressed by the quantity of formazan assay in confluent cells, revealed that the quantity of release by BM-MSCs was slightly higher than HF-MSCs. Adipogenic differentiated BM-MSCs showed moderate accumulation of oil red-O stained lipid droplets when compared to that of HF-MSCs which exhibited high stain. The total lipid concentration was significantly higher in adipogenic differentiated HF-MSCs than BM-MSCs (P < 0.05). It was found that activity of bone alkaline phosphatase and calcium concentration were significantly higher (P < 0.01 and P < 0.05 respectively) in osteogenic differentiated BM-MSCs than that of HF-MSCs. The present findings demonstrate that the HF-MSCs are very similar in most tested characteristics to BM-MSCs with the exception of differentiation. Additionally; no issues have been reported during the collection of HF-MSCs. Therefore, the HF may represent a suitable and accessible source for adult stem cells and can be considered an ideal cell source for adipogenesis research.

Molecular Mechanisms of Hair Growth and Regeneration: Current Understanding and Novel Paradigms

Hair is a defining feature of mammals and has critical functions, including protection, production of sebum, apocrine sweat and pheromones, social and sexual interactions, thermoregulation, and provision of stem cells for skin homeostasis, regeneration, and repair. The hair follicle (HF) is considered a "mini-organ," consisting of intricate and well-organized structures which originate from HF stem and progenitor cells. Dermal papilla cells are the main components of the mesenchymal compartments in the hair bulb and are instrumental in generating signals to regulate the behavior of neighboring epithelial cells during the hair cycle. Mesenchymal-epithelial interactions within the dermal papilla niche drive HF embryonic development as well as the postnatal hair growth and regeneration cycle. This review summarizes the current understanding of HF development, repair, and regeneration, with special focus on cell signaling pathways governing these processes. In particular, we discuss emerging paradigms of molecular signaling governing the dermal papilla-epithelial cellular interactions during hair growth and maintenance and the recent progress made towards tissue engineering of human hair follicles.

Regeneration of skin appendages and nerves: current status and further challenges

Tissue-engineered skin (TES), as an analogue of native skin, is promising for wound repair and regeneration. However, a major drawback of TES products is a lack of skin appendages and nerves to enhance skin healing, structural integrity and skin vitality. Skin appendages and nerves are important constituents for fully functional skin. To date, many studies have yielded remarkable results in the field of skin appendages reconstruction and nerve regeneration. However, patients often complain about a loss of skin sensation and even cutaneous chronic pain. Restoration of pain, temperature, and touch perceptions should now be a major challenge to solve in order to improve patients’ quality of life. Current strategies to create skin appendages and sensory nerve regeneration are mainly based on different types of seeding cells, scaffold materials, bioactive factors and involved signaling pathways. This article provides a comprehensive overview of different strategies for, and advances in, skin appendages and sensory nerve regeneration, which is an important issue in the field of tissue engineering and regenerative medicine.

Isolating Dermal Papilla Cells from Human Hair Follicles Using Microdissection and Enzyme Digestion

The dermal papilla (DP) is a cluster of mesenchymal cells located at the bottom of the hair follicle. Cells within the DP interact with numerous other cell types within the follicle, including epithelial stem cells, matrix cells, and melanocytes, regulating their function. The diameter of the DP is directly proportional to the width of the hair shaft, and a decrease in both cell number and DP size is observed in hair loss conditions such as androgenetic alopecia. Conversely, microdissected ex vivo DP can instruct growth of de novo hair follicles. The study of DP cells and their role in human hair growth is often hampered by the technical challenge of DP isolation and culture. Here we describe a method used within our research group for isolating DP from human hair follicles.

Bioactive Molecules for Skin Repair and Regeneration: Progress and Perspectives

Skin regeneration is a vexing problem in the field of regenerative medicine. A bioactive molecule-based strategy has been frequently used in skin wound healing in recent years. Bioactive molecules are practical tools for regulating cellular processes and have been applied to control cellular differentiation, dedifferentiation, and reprogramming. In this review, we focus on recent progress in the use of bioactive molecules in skin regenerative medicine, by which desired cell types can be generated in vitro for cell therapy and conventional therapeutics can be developed to repair and regenerate skin in vivo through activation of the endogenous repairing potential. We further prospect that the bioactive molecule-base method might be one of the promising strategies to achieve in situ skin regeneration in the future.

Simultaneous two-layer harvesting of scalp split-thickness skin and dermal grafts for acute burns and postburn scar deformities

BACKGROUND

The scalp, an excellent donor site for thin skin grafts, presents a limited surface but is rich in stem cells. The purpose of this study was to test a double harvesting procedure from the scalp and to evaluate the capacity of the dermal layer.

METHODS

Two layers corresponding to a split-thickness skin graft (SSG) and a split-thickness dermal graft (SDG) were harvested from the scalp using a Zimmer dermatome during the same procedure. Healing of the scalp donor site, reason for recipient site grafting, and the percentage of graft loss were evaluated.

RESULTS

Fourteen patients, comprising six men and eight women with a mean age of 34.2 years, were treated according to our protocol. The most common reason for a recipient site graft was a postburn scar deformity (10/14 patients). The mean area of scalp SSGs was 151.8 cm2. The mean area of scalp SDGs was 88.2 cm2. The mean healing time of scalp donors was 9.9 days. The only donor complication was a tufted scar deformity.

CONCLUSIONS

Skin defects in the scalp of donors healed faster and led to less scarring than defects at other donor sites. Scalp SDGs needed 10 days for adequate epithelization. The scalp was the best donor site for SSGs and SDGs for burn reconstructive patients.

A crucial role of fibroblast growth factor 2 in the differentiation of hair follicle stem cells toward endothelial cells in a STAT5-dependent manner

Fibroblast growth factor (FGF2) is reported to affect the proliferation, differentiation, and survival abilities of stem cells. In this study, we hypothesize that FGF2 might promote the differentiation of hair follicle stem cell (HFSCs) into endothelial cells (ECs), in a manner dependent on STAT5 activation. We first treated human HFSCs with recombinant human FGF2 to determine the involvement of FGF2 in the differentiation of HFSCs. Then the expression of EC-specific markers including von Willebrand factor (vWF), VE-cadherin, CD31, FLT-1, KDR and Tie2 was evaluated using immunofluorescence and flow cytometry, while the expression of HFSC-specific markers such as K15, K19, Lgr5, Sox9 and Lhx2 was determined by flow cytometry. Next, in vitro tube formation was performed to confirm the function of FGF2, and low-density lipoprotein (LDL) uptake by ECs and HFSCs was studied by Dil-acetylated LDL assay. In addition, we transduced FGF2-treated HFSCs with constitutive-active or dominant-negative STAT5A adenovirus vectors. FGF2 up-regulated the expression of EC-specific markers, and promoted the differentiation of HFSCs into ECs, tube formation and LDL uptake. The phosphorylated STAT5 was translocated into the nucleus of HFSCs after FGF2 treatment, but this translocation was blocked by the dominant-negative STAT5A mutant. FGF2 increased the differentiation potential through the activation of STAT5 in vivo. Taken together, we find that FGF2 promotes the differentiation of HFSCs into ECs via activated STAT5, which gives a new perspective on the role of FGF2 in the development of ischemic vascular disease.

In vitro Differentiation of Hair Follicle Stem Cell into Keratinocyte by Simvastatin

Background

Hair follicle stem cells (HFSCs) located in the bulge area has shown to be highly proliferative and could differentiate into neurons, glia, smooth muscle cell, and melanocytes in vitro. Simvastatin is an HMG-CoA reductase inhibitor that exerts pleiotropic effects beyond simple low-density lipoprotein lowering and has a similar impact on the differentiation of bone marrow stromal cells and peripheral blood mononuclear cells. The present study examined the hypothesis that the application of simvastatin would induce the HFSCs differentiation into keratinocyte.

Methods

The bulge of the hair follicle was anatomized, and HFSCs were cultivated. The flow cytometry and immunocytochemical staining for detection of nestin, CD34, and Kr15 biomarkers were performed before differentiation. In order to hasten the HFSCs differentiation to keratinocyte, HFSCs were treated with 1 µM, 2 µM, and 5 µM of simvastatin daily for a week. After differentiation, the flow cytometry and immunocytochemical staining were performed with Kr15 and Kr10 biomarkers, and the MTT assay was carried out as an index of cell viability and cell growth.

Results

Our results showed that bulge of HFSCs were nestin and CD34 positive and Kr15 negative. Simvastatin significantly increased the viability of HFSCs (p < 0.05) at the concentration of 5 µM. In addition, the percentages of keratinocyte-differentiated cells treated with 5 µM of simvastatin showed a significant increase compared to all other treated groups (p < 0.05).

Conclusion

Our findings demonstrate that 5 µM of simvastatin could induce HFSCs differentiation into keratinocyte.

Restoring extracellular matrix synthesis in senescent stem cells

Collagen type III (COL3) is one of the 3 major collagens in the body, and loss of expression or mutations in the COL3 gene have been associated with the onset of vascular diseases such the Ehlers-Danlos syndrome. Previous work reported a significant reduction of COL3 in tissues such as skin and vessels with aging. In agreement, we found that COL3 was significantly reduced in senescent human mesenchymal stem cells and myofibroblasts derived from patients with Hutchinson-Gilford progeria syndrome, a premature aging syndrome. Most notably, we discovered that ectopic expression of the embryonic transcription factor Nanog homeobox (NANOG) restored COL3 expression by restoring the activity of the TGF-β pathway that was impaired in senescent cells. RNA sequencing analysis showed that genes associated with the activation of the TGF-β pathway were up-regulated, whereas negative regulators of the pathway were down-regulated upon NANOG expression. Chromatin immunoprecipitation sequencing and immunoprecipitation experiments revealed that NANOG bound to the mothers against decapentaplegic (SMAD)2 and SMAD3 promoters, in agreement with increased expression and phosphorylation levels of both proteins. Using chemical inhibition, short hairpin RNA knockdown, and gain of function approaches, we established that both SMAD2 and SMAD3 were necessary to mediate the effects of NANOG, but SMAD3 overexpression was also sufficient for COL3 production. In summary, NANOG restored production of COL3, which was impaired by cellular aging, suggesting novel strategies to restore the impaired extracellular matrix production and biomechanical function of aged tissues, with potential implications for regenerative medicine and anti-aging treatments.-Rong, N., Mistriotis, P., Wang, X., Tseropoulos, G., Rajabian, N., Zhang, Y., Wang, J., Liu, S., Andreadis, S. T. Restoring extracellular matrix synthesis in senescent stem cells.

An important role of podoplanin in hair follicle growth

Podoplanin (PDPN) is a glycoprotein that is expressed by various cell types, including keratinocytes, fibroblasts, and lymphatic endothelial cells. We found that PDPN is expressed in the hair follicle (HF) keratinocyte region and HF stem cell area during the late anagen phase but not during the telogen phase in mice. Importantly, keratinocyte-specific PDPN deletion in mice (K5-Cre;PDPN^flox/flox) promoted anagen HF growth after depilation-induced HF regeneration as compared to control mice. RNA sequencing, followed by gene ontology analysis, showed down-regulation of focal adhesion and extracellular matrix interaction pathways in HF stem cells isolated from K5-Cre;PDPN^flox/flox mice as compared to control mice. Furthermore, HF keratinocytes isolated from K5-Cre;PDPN^flox/flox mice exhibited a decreased ability to interact with collagen type I in cell adhesion assays. Taken together, these results show that PDPN deletion promotes HF cycling, possibly via reduced focal adhesion and concomitantly enhanced migration of HF stem cells towards the bulb region. They also indicate potential new therapeutic strategies for the treatment of conditions associated with hair loss.

The Role of CDR1as in Proliferation and Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells

Mesenchymal stem cells derived from human umbilical cord (hucMSCs) are considered a promising tool for regenerative medicine. circRNAs as newly discovered noncoding RNAs are involved in multiple biological processes. However, little has been known about the function of circRNAs in the proliferation and differentiation of hucMSCs. In this study, we selected several circRNAs expressed in MSCs from circBase and found that CDR1as expression level was markedly significant. We observed that, compared with that of uninduced hucMSCs, the CDR1as expression level of induced hucMSCs decreased with cell induction differentiation. By using siRNA to knock down CDR1as of hucMSCs, we discovered that proliferation was inhibited but the apoptosis increased. In addition, we found that the expression of stemness transcription factors (STFs) was downregulated after CDR1as knockdown and the adipogenesis and osteogenesis potential of hucMSCs was impaired. Our findings suggest that CDR1as takes a part in maintaining proliferation and differentiation of hucMSCs, providing clues for MSC modification and further for stem cell therapy and tissue regeneration.

Repair of Peripheral Nerve Sensory Impairments via the Transplantation of Bone Marrow Neural Tissue-Committed Stem Cell-Derived Sensory Neurons

The present study aimed to investigate the efficacy of transplantation of bone marrow neural tissue-committed stem cell-derived sensory neuron-like cells for the repair of peripheral nerve sensory impairments in rats. Bone marrow was isolated and cultured to obtain the neural tissue-committed stem cells (NTCSCs), and the differentiation of these cells into sensory neuron-like cells was induced. Bone marrow mesenchymal stem cells (BMSCs), bone marrow NTCSCs, and bone marrow NTCSC-derived sensory neurons (NTCSC-SNs) were transplanted by microinjection into the L4 and L5 dorsal root ganglions (DRGs) in an animal model of sensory defect. On the 2nd, 4th, 8th, and 12th week after the transplantation, the effects of the three types of stem cells on the repair of the sensory functional defect were analyzed via behavioral observation, sensory function evaluation, electrophysiological examination of the sciatic nerve, and morphological observation of the DRGs. The results revealed that the transplanted BMSCs, NTCSCs, and NTCSC-SNs were all able to repair the sensory nerves. In addition, the effect of the NTCSC-SNs was significantly better than that of the other two types of stem cells. The general posture and gait of the animals in the sensory defect model exhibited evident improvement over time. Plantar temperature sensitivity and pain sensitivity gradually recovered, and the sensation latency was reduced, with faster sensory nerve conduction velocity. Transplantation of NTCSC-SNs can improve the repair of peripheral nerve sensory defects in rats.

A Human Skin Model Recapitulates Systemic Sclerosis Dermal Fibrosis and Identifies COL22A1 as a TGFβ Early Response Gene that Mediates Fibroblast to Myofibroblast Transition

: Systemic sclerosis (SSc) is a complex multi-system autoimmune disease characterized by immune dysregulation, vasculopathy, and organ fibrosis. Skin fibrosis causes high morbidity and impaired quality of life in affected individuals. Animal models do not fully recapitulate the human disease. Thus, there is a critical need to identify ex vivo models for the dermal fibrosis characteristic of SSc. We identified genes regulated by the pro-fibrotic factor TGFβ in human skin maintained in organ culture. The molecular signature of human skin overlapped with that which was identified in SSc patient biopsies, suggesting that this model recapitulates the dermal fibrosis characteristic of the human disease. We further characterized the regulation and functional impact of a previously unreported gene in the setting of dermal fibrosis, COL22A1, and show that silencing COL22A1 significantly reduced TGFβ-induced ACTA2 expression. COL22A1 expression was significantly increased in dermal fibroblasts from patients with SSc. In summary, we identified the molecular fingerprint of TGFβ in human skin and demonstrated that COL22A1 is associated with the pathogenesis of fibrosis in SSc as an early response gene that may have important implications for fibroblast activation. Further, this model will provide a critical tool with direct relevance to human disease to facilitate the assessment of potential therapies for fibrosis.

Dynamic Nestin expression during hair follicle maturation and the normal hair cycle

Nestin, a type-VI intermediate filament protein, serves as a marker for neural stem cells, and is also known to be expressed in follicle stem cells. Hair follicles go through repeated cycles of anagen (growth), catagen (regression) and telogen (quiescence) throughout the life of mammals following morphogenesis. In the present study it was demonstrated that in mice, the maturation of hair follicles includes the period between morphogenesis and the first anagen (4 weeks of age). Skin samples from Nestin‑green fluorescent protein (GFP)+ mice at different hair follicle stages were collected, and immunostaining for Nestin and Ki67 was performed. It was identified that during morphogenesis, Nestin‑GFP expression was rarely detected and it gradually increased during maturation (0‑4 weeks) in hair follicle dermal cells. In mature hair follicle dermal cells, Nestin and the proliferation marker Ki67 were highly expressed in anagen, while during telogen, they were markedly decreased. Additionally, lineage tracing data demonstrated that peri‑follicular Nestin+ cells during morphogenesis differentiated into cluster of differentiation 31+ cells.

Differential correlations between maternal hair levels of tobacco and alcohol with fetal growth restriction clinical subtypes

Maternal exposure to tobacco and alcohol is a known cause, among others, for fetal growth restriction (FGR). Clinically, FGR can be subclassified into two forms: intrauterine growth restriction (IUGR) and small for gestational age (SGA), based on the severity of the growth retardation, and abnormal uterine artery Doppler or cerebro-placental ratio. This study aimed at investigating any differential correlation between maternal exposures to these toxins with the two clinical forms of FGR. Therefore, a case-control study was conducted in Barcelona, Spain. Sixty-four FGR subjects, who were further subclassified into IUGR (n = 36) and SGA (n = 28), and 89 subjects matched appropriate-for-gestational age (AGA), were included. The levels of nicotine (NIC) and ethyl glucuronide (EtG), biomarkers of tobacco and alcohol exposure, respectively, were assessed in the maternal hair in the third trimester. Our analysis showed 65% of the pregnant women consumed alcohol, 25% smoked, and 19% did both. The odds ratios (ORs) of IUGR were 21 times versus 14 times for being SGA with maternal heavy smoking, while with alcohol consumption the ORs for IUGR were 22 times versus 37 times for the SGA group. The differential correlations between these toxins with the two subtypes of FGR suggest different mechanisms influencing fetal weight. Our alarming data of alcohol consumption during pregnancy should be considered for further confirmation among Spanish women.

The Hair Follicle: An Underutilized Source of Cells and Materials for Regenerative Medicine

The hair follicle is one of only two structures within the adult body that selectively degenerates and regenerates, making it an intriguing organ to study and use for regenerative medicine. Hair follicles have been shown to influence wound healing, angiogenesis, neurogenesis, and harbor distinct populations of stem cells; this has led to cells from the follicle being used in clinical trials for tendinosis and chronic ulcers. In addition, keratin produced by the follicle in the form of a hair fiber provides an abundant source of biomaterials for regenerative medicine. In this review, we provide an overview of the structure of a hair follicle, explain the role of the follicle in regulating the microenvironment of skin and the impact on wound healing, explore individual cell types of interest for regenerative medicine, and cover several applications of keratin-based biomaterials.

Generation of full-thickness skin equivalents using hair follicle-derived primary human keratinocytes and fibroblasts

Skin equivalents are increasingly used as human-based test systems for basic and preclinical research. Most of the established skin equivalents are composed of primary keratinocytes and fibroblasts, isolated either from excised human skin or juvenile foreskin following circumcisions. Although the potential of hair follicle-derived cells for the generation of skin equivalents has been shown, this approach normally requires microdissections from the scalp for which there is limited subject compliance or ethical approval. In the present study, we report a novel method to isolate and cultivate keratinocytes and fibroblasts from plucked hair follicles that were then used to generate skin equivalents. The procedure is non-invasive, inflicts little-pain, and may allow easy access to patient-derived cells without taking punch biopsies. Overall, minor differences in morphology, ultrastructure, expression of important structural proteins, or barrier function were observed between skin equivalents generated from hair follicle-derived or interfollicular keratinocytes and fibroblasts. Interestingly, improved basal lamina formation was seen in the hair follicle-derived skin equivalents. The presented method here allows easy and non-invasive access to keratinocytes and fibroblasts from plucked hair follicles that may be useful particularly for the generation of skin disease equivalents.

Tissue engineering potential of human dermis-isolated adult stem cells from multiple anatomical locations

Abundance and accessibility render skin-derived stem cells an attractive cell source for tissue engineering applications. Toward assessing their utility, the variability of constructs engineered from human dermis-isolated adult stem (hDIAS) cells was examined with respect to different anatomical locations (foreskin, breast, and abdominal skin), both in vitro and in a subcutaneous, athymic mouse model. All anatomical locations yielded hDIAS cells with multi-lineage differentiation potentials, though adipogenesis was not seen for foreskin-derived hDIAS cells. Using engineered cartilage as a model, tissue engineered constructs from hDIAS cells were compared. Construct morphology differed by location. The mechanical properties of human foreskin- and abdominal skin-derived constructs were similar at implantation, remaining comparable after 4 additional weeks of culture in vivo. Breast skin-derived constructs were not mechanically testable. For all groups, no signs of abnormality were observed in the host. Addition of aggregate redifferentiation culture prior to construct formation improved chondrogenic differentiation of foreskin-derived hDIAS cells, as evident by increases in glycosaminoglycan and collagen contents. More robust Alcian blue staining and homogeneous cell populations were also observed compared to controls. Human DIAS cells elicited no adverse host responses, reacted positively to chondrogenic regimens, and possessed multi-lineage differentiation potential with the caveat that efficacy may differ by anatomical origin of the skin. Taken together, these results suggest that hDIAS cells hold promise as a potential cell source for a number of tissue engineering applications.

Epidermal E-Cadherin Dependent β-Catenin Pathway Is Phytochemical Inducible and Accelerates Anagen Hair Cycling

Unlike the epidermis, which regenerates continually, hair follicles anchored in the subcutis periodically regenerate by spontaneous repetitive cycles of growth (anagen), degeneration (catagen), and rest (telogen). The loss of hair follicles in response to injuries or pathologies such as alopecia endangers certain inherent functions of the skin. Thus, it is of interest to understand mechanisms underlying follicular regeneration in adults. In this work, a phytochemical rich in the natural vitamin E tocotrienol (TRF) served as a productive tool to unveil a novel epidermal pathway of hair follicular regeneration. Topical TRF application markedly induced epidermal hair follicle development akin to that during fetal skin development. This was observed in the skin of healthy as well as diabetic mice, which are known to be resistant to anagen hair cycling. TRF suppressed epidermal E-cadherin followed by 4-fold induction of β-catenin and its nuclear translocation. Nuclear β-catenin interacted with Tcf3. Such sequestration of Tcf3 from its otherwise known function to repress pluripotent factors induced the plasticity factors Oct4, Sox9, Klf4, c-Myc, and Nanog. Pharmacological inhibition of β-catenin arrested anagen hair cycling by TRF. This work reports epidermal E-cadherin/β-catenin as a novel pathway capable of inducing developmental folliculogenesis in the adult skin.

NANOG Restores Contractility of Mesenchymal Stem Cell-Based Senescent Microtissues

Mesenchymal stem cells (MSCs) have been extensively used in the field of tissue engineering as a source of smooth muscle cells (SMCs). However, recent studies showed deficits in the contractile function of SMCs derived from senescent MSCs and there are no available strategies to restore the contractile function that is impaired due to cellular or organismal senescence. In this study, we developed a tetracycline-regulatable system and employed micropost tissue arrays to evaluate the effects of the embryonic transcription factor, NANOG, on the contractility of senescent MSCs. Using this system, we show that expression of NANOG fortified the actin cytoskeleton and restored contractile function that was impaired in senescent MSCs. NANOG increased the expression of smooth muscle α-actin (ACTA2) as well as the contractile force generated by cells in three-dimensional microtissues. Interestingly, NANOG worked together with transforming growth factor-beta1 to further enhance the contractility of senescent microtissues. The effect of NANOG on contractile function was sustained for about 10 days after termination of its expression. Our results show that NANOG could reverse the effects of stem cell senescence and restore the myogenic differentiation potential of senescent MSCs. These findings may enable development of novel strategies to restore the function of senescent cardiovascular and other SMC-containing tissues.

Hair Follicle Generation by Injections of Adult Human Follicular Epithelial and Dermal Papilla Cells into Nude Mice

Objective

Dermal papilla and hair epithelial stem cells regulate hair formation and the growth cycle. Damage to or loss of these cells can cause hair loss. Although several studies claim to reconstitute hairs using rodent cells in an animal model, additional research is needed to develop a stable human hair follicle reconstitution protocol. In this study, we have evaluated hair induction by injecting adult cultured human dermal papilla cells and a mixture of hair epithelial and dermal papilla cells in a mouse model.

Materials and Methods

In this experimental study, discarded human scalp skins were used to obtain dermal papilla and hair epithelial cells. After separation, cells were cultured and assessed for their characteristics. We randomly allocated 15 C57BL/6 nude mice into three groups that received injections in their dorsal skin. The first group received cultured dermal papilla cells, the second group received a mixture of cultured epithelial and dermal papilla cells, and the third group (control) received a placebo [phosphate-buffered saline (PBS-)].

Results

Histopathologic examination of the injection sites showed evidence of hair growth in samples that received cells compared with the control group. However, the group that received epithelial and dermal papilla cells had visible evidence of hair growth. PKH tracing confirmed the presence of transplanted cells in the new hair.

Conclusion

Our data showed that injection of a combination of adult human cultured dermal papilla and epithelial cells could induce hair growth in nude mice. This study emphasized that the combination of human adult cultured dermal papilla and epithelial cells could induce new hair in nude mice.

A Selective Cell Population from Dermis Strengthens Bone Regeneration

Finding appropriate seed cells for bone tissue engineering remains a significant challenge. Considering that skin is the largest organ, we hypothesized that human bone morphogenetic protein receptor type IB (BmprIB)+ dermal cells could have enhanced osteogenic capacity in the healing of critical-sized calvarial defects in an immunodeficient mouse model. In this study, immunohistochemical staining revealed that BmprIB was expressed throughout reticular dermal cells; the positive expression rate of BmprIB was 3.5% ± 0.4% in freshly separated dermal cells, by flow cytometry. Furthermore, in vitro osteogenic capacity of BmprIB+ cells was confirmed by osteogenic-related staining and marker gene expression compared with unsorted dermal cells. In vivo osteogenic capacity was demonstrated by implantation of human BmprIB+ cell/coral constructs in the treatment of 4-mm diameter calvarial defects in an immunodeficient mouse model compared with implantation of unsorted cell/coral constructs and coral scaffold alone. These results indicate that the selective cell population BmprIB from human dermis is a promising osteogenic progenitor cell that can be a large-quantity and high-quality cell source for bone tissue engineering and regeneration. Stem Cells Translational Medicine 2017;6:306-315.

Regeneration of hair and other skin appendages: A microenvironment-centric view

Advances in skin regeneration have resulted in techniques and products that have allowed regeneration of both the dermis and epidermis. Yet complete skin regeneration requires the adnexal skin structures. Thus it is crucial to understand the regenerative potential of hair follicles where genetic, nutritional, and hormonal influences have important effects and are critical for skin regeneration. The follicular stem cell niche serves as an anatomical compartment, a structural unit, a functional integrator, and a dynamic regulator necessary to sustain internal homeostasis and respond to outside stimuli. In particular, mechanics such as pressure, compression, friction, traction, stretch, shear, and mechanical wounding can influence hair loss or growth. Relevant niche signaling pathways such as Wnt, bone morphogenetic protein, fibroblast growth factor, Shh, and Notch may yield potential targets for therapeutic interventions.

NANOG Reverses the Myogenic Differentiation Potential of Senescent Stem Cells by Restoring ACTIN Filamentous Organization and SRF-Dependent Gene Expression

Cellular senescence as a result of organismal aging or progeroid diseases leads to stem cell pool exhaustion hindering tissue regeneration and contributing to the progression of age related disorders. Here we discovered that ectopic expression of the pluripotent factor NANOG in senescent or progeroid myogenic progenitors reversed cellular aging and restored completely the ability to generate contractile force. To elicit its effects, NANOG enabled reactivation of the ROCK and Transforming Growth Factor (TGF)-β pathways-both of which were impaired in senescent cells-leading to ACTIN polymerization, MRTF-A translocation into the nucleus and serum response factor (SRF)-dependent myogenic gene expression. Collectively our data reveal that cellular senescence can be reversed and provide a novel strategy to regain the lost function of aged stem cells without reprogramming to the pluripotent state. Stem Cells 2017;35:207-221.

Isolation and characterization of hair follicle stem cells from Arbas Cashmere goat

In this study, highly purified hair follicle stem cells from Arbas Cashmere goat (gHFSCs) were isolated using enzyme digestion and adhesion to type IV collagen. The biological characteristics of the gHFSCs were identified by morphological observation, growth curve, markers assay and differentiation in vitro. The gHFSCs were in small cell size with typical cobblestone morphology, good adhesion and high refractive index. Immunocytochemistry staining showed the cells were expressing Krt15, Krt19, CD34, Itgβ1 and Krt14. Cell growth curve indicated that cultured gHFSCs had strong proliferation ability. Krt14 and CD34 were high expressed at the mRNA level, respectively, 39.68 and 24.37 times of the Cashmere goat keratinocytes, and krt15 expression was 5.62 times and itgβ1 expression was 1.81 times higher (p < 0.01). Western blot detected the expression of all the above markers. After osteogenic induction, the cells were positive for Von Kossa staining and expressed Osteocalcin. Sulfated proteoglycans in cartilaginous matrices were positively stained by Alcian blue after chondrogenic induction and COL2A1 was expressed. In myogenic induction, Hoechst 33342 staining evidenced cytoplasm fusion and positive expression of MyoG was detected by immunocytochemistry.

Prevention of Cutaneous Penetration and CD1c+ Uptake of Pollen Allergens by a Barrier-Enhancing Formulation

Recent studies have shown that pollen proteins can penetrate the impaired skin barrier of atopic patients and exacerbate their disease. In the presented study the effect of a topically applied barrier-enhancing formulation was investigated for its preventive effect on the uptake of pollen allergens into CD1c+ epidermal cells. The pollen proteins were fluorescence labelled and applied on barrier-disrupted excised human skin. CD1c+ cells were selected after magnetic cell sorting and analysed using laser scanning microscopy. In untreated disrupted skin, 81% of the CD1c+ cells contained the fluorescence-labelled pollen allergens. In formulation-pretreated skin only 12% of the CD1c+ cells showed an uptake of pollen allergens. These results encourage the treatment of atopic patients with barrier-enhancing formulations to reduce the impact of pollen on air-exposed skin areas and hence the exacerbation of cutaneous symptoms.

Isolation, expansion and neural differentiation of stem cells from human plucked hair: a further step towards autologous nerve recovery

Stem cells from the adult hair follicle bulge can differentiate into neurons and glia, which is advantageous for the development of an autologous cell-based therapy for neurological diseases. Consequently, bulge stem cells from plucked hair may increase opportunities for personalized neuroregenerative therapy. Hairs were plucked from the scalps of healthy donors, and the bulges were cultured without prior tissue treatment. Shortly after outgrowth from the bulge, cellular protein expression was established immunohistochemically. The doubling time was calculated upon expansion, and the viability of expanded, cryopreserved cells was assessed after shear stress. The neuroglial differentiation potential was assessed from cryopreserved cells. Shortly after outgrowth, the cells were immunopositive for nestin, SLUG, AP-2α and SOX9, and negative for SOX10. Each bulge yielded approximately 1 × 10⁴ cells after three passages. Doubling time was 3.3 (±1.5) days. Cellular viability did not differ significantly from control cells after shear stress. The cells expressed class III β-tubulin (TUBB3) and synapsin-1 after 3 weeks of neuronal differentiation. Glial differentiation yielded KROX20- and MPZ-immunopositive cells after 2 weeks. We demonstrated that human hair follicle bulge-derived stem cells can be cultivated easily, expanded efficiently and kept frozen until needed. After cryopreservation, the cells were viable and displayed both neuronal and glial differentiation potential.

Utility of Scalp Hair Follicles as a Novel Source of Biomarker Genes for Psychiatric Illnesses

BACKGROUND

Identifying beneficial surrogate genetic markers in psychiatric disorders is crucial but challenging.

METHODS

Given that scalp hair follicles are easily accessible and, like the brain, are derived from the ectoderm, expressions of messenger RNA (mRNA) and microRNA in the organ were examined between schizophrenia (n for first/second = 52/42) and control subjects (n = 62/55) in two sets of cohort. Genes of significance were also analyzed using postmortem brains (n for case/control = 35/35 in Brodmann area 46, 20/20 in cornu ammonis 1) and induced pluripotent stem cells (n = 4/4) and pluripotent stem cell-derived neurospheres (n = 12/12) to see their role in the central nervous system. Expression levels of mRNA for autism (n for case/control = 18/24) were also examined using scalp hair follicles.

RESULTS

Among mRNA examined, FABP4 was downregulated in schizophrenia subjects by two independent sample sets. Receiver operating characteristic curve analysis determined that the sensitivity and specificity were 71.8% and 66.7%, respectively. FABP4 was expressed from the stage of neurosphere. Additionally, microarray-based microRNA analysis showed a trend of increased expression of hsa-miR-4449 (p = .0634) in hair follicles from schizophrenia. hsa-miR-4449 expression was increased in Brodmann area 46 from schizophrenia (p = .0007). Finally, we tested the expression of nine putative autism candidate genes in hair follicles and found decreased CNTNAP2 expression in the autism cohort.

CONCLUSIONS

Scalp hair follicles could be a beneficial genetic biomarker resource for brain diseases, and further studies of FABP4 are merited in schizophrenia pathogenesis.

MicroRNAs in skin tissue engineering

35.2 million annual cases in the U.S. require clinical intervention for major skin loss. To meet this demand, the field of skin tissue engineering has grown rapidly over the past 40 years. Traditionally, skin tissue engineering relies on the "cell-scaffold-signal" approach, whereby isolated cells are formulated into a three-dimensional substrate matrix, or scaffold, and exposed to the proper molecular, physical, and/or electrical signals to encourage growth and differentiation. However, clinically available bioengineered skin equivalents (BSEs) suffer from a number of drawbacks, including time required to generate autologous BSEs, poor allogeneic BSE survival, and physical limitations such as mass transfer issues. Additionally, different types of skin wounds require different BSE designs. MicroRNA has recently emerged as a new and exciting field of RNA interference that can overcome the barriers of BSE design. MicroRNA can regulate cellular behavior, change the bioactive milieu of the skin, and be delivered to skin tissue in a number of ways. While it is still in its infancy, the use of microRNAs in skin tissue engineering offers the opportunity to both enhance and expand a field for which there is still a vast unmet clinical need. Here we give a review of skin tissue engineering, focusing on the important cellular processes, bioactive mediators, and scaffolds. We further discuss potential microRNA targets for each individual component, and we conclude with possible future applications.