Generation and characterization of multipotent stem cells from established dermal cultures

Laminin fragments conjugated with perlecan's growth factor-binding domain differentiate human induced pluripotent stem cells into skin-derived precursor cells

Deriving stem cells to regenerate full-thickness human skin is important for treating skin disorders without invasive surgical procedures. Our previous protocol to differentiate human induced pluripotent stem cells (iPSCs) into skin-derived precursor cells (SKPs) as a source of dermal stem cells employs mouse fibroblasts as feeder cells and is therefore unsuitable for clinical use. Herein, we report a feeder-free method for differentiating iPSCs into SKPs by customising culture substrates. We immunohistochemically screened for laminins expressed in dermal papillae (DP) and explored the conditions for inducing the differentiation of iPSCs into SKPs on recombinant laminin E8 (LM-E8) fragments with or without conjugation to domain I of perlecan (PDI), which binds to growth factors through heparan sulphate chains. Several LM-E8 fragments, including those of LM111, 121, 332, 421, 511, and 521, supported iPSC differentiation into SKPs without PDI conjugation. However, the SKP yield was significantly enhanced on PDI-conjugated LM-E8 fragments. SKPs induced on PDI-conjugated LM111-E8 fragments retained the gene expression patterns characteristic of SKPs, as well as the ability to differentiate into adipocytes, osteocytes, and Schwann cells. Thus, PDI-conjugated LM-E8 fragments are promising agents for inducing iPSC differentiation into SKPs in clinical settings.

Hypoxia Treatment of Adipose Mesenchymal Stem Cells Promotes the Growth of Dermal Papilla Cells via HIF-1α and ERK1/2 Signaling Pathways

Dermal papilla cells (DPCs) cultured in vitro induce hair follicle formation. Using a hypoxic microenvironment to culture adipose mesenchymal stem cells (ADSCs) can promote hair follicle growth. However, the exact molecular mechanisms underlying this process remain unclear. In this study, ADSCs and DPCs from Arbas Cashmere goats were used. A hypoxic microenvironment promoted the proliferation of ADSCs and increased the pluripotency of ADSCs. The growth factors vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were upregulated in ADSCs in the hypoxia-conditioned medium (Hypo-cm). Hypo-cm also enhanced the ability of DPCs to induce hair follicle formation. Inhibitors of the ERK1/2 signaling pathway caused the expressions of growth factors that increased in hypoxic microenvironments to decrease; moreover, hypoxia-inducible factor-1α (HIF-1α) increased the expression levels of VEGF, bFGF, and PDGF and inhibited the expression of bone morphogenic protein 7 (BMP7). In conclusion, these findings improve the theoretical basis for the development of gene therapy drugs for the treatment of alopecia areata and hair thinning.

Autologously transplanted dermis-derived cells alleviated monobenzone-induced vitiligo in mouse

Vitiligo is a depigmentation disease which affects skin and hair follicles with a prevalence of 0.5-1% worldwide. In this study, we aimed to investigate treatmental potential of dermis-derived cells in monobenzone (MBEH)-induced mouse vitiligo model with light and electron microscopy. MBEH (40%) cream was topically applied to C57BL/6 mice until depigmentation occured in vitiligo and experimental groups. In experimental groups, dermis-derived cells obtained from back skin biopsy samples before induction of vitiligo, were injected intradermally to vitiligo mice. On day 3 and 15 after cell transplantation to experimental groups, skin biopsies were compared with biopsies of control and vitiligo groups. Dermis-derived cells obtained from back skin biopsy samples of experimental groups showed nestin and versican immunoreactivity. Melanin in hair follicles of control group was detected by histochemical stainings (Hematoxylin&Eosin and Fontana-Masson) whereas sparse melanin granules were observed in hair follicles of vitiligo group. In experimental groups, there was an increase in the number of hair follicles with melanin compared to vitiligo group. We observed MART-1 immunoreactive cells mostly around the hair follicles in control group and within dermis in vitiligo group. Electron microscopic investigation showed presence of melanosomes in hair follicles of control group and lacking in vitiligo group. In experimental groups, both type of hair follicles were observed with electron microscope. Our data suggest that autologously transplanted dermis-derived cells may be effective in vitiligo treatment by contrubuting to melanin production.

Facilitation of mouse skin-derived precursor growth and yield by optimizing plating density

Multiple methodologies have been reported to facilitate skin-derived precursor (SKP) growth, but the impact of plating density on SKP growth has not been studied. To determine the optimal plating density, we used six plating densities and two types of flasks for mouse SKP (mSKP) culture. On the 14th day, the number, diameter, and viability of mSKP spheres were compared by morphological assessment and cell counting kit 8, and we found the optimal plating density was 2.5 × 10⁵–5 × 10⁵ cells/mL. In addition, we investigated the correlation between the SKP spheres and the adherent cell colonies in the serum-free culture system. We treated the adherent cell colonies with two culture conditions and characterized the cells generated from two conditions by immunocytochemistry and induced differentiation, respectively. The results elucidated that the adherent cell colonies differentiated into either mSKPs or dermal mesenchymal stem cells under appropriate culture conditions. In conclusion, mSKP spheres differentiated from the adherent cell colonies. The optimal plating density significantly promoted and advanced the proliferation of adherent cell colonies, which optimized mSKP growth and yield. The adherent cell colonies possessed the capacity of differentiating into different types of cells under appropriate culture conditions.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

Plant callus-derived shikimic acid regenerates human skin through converting human dermal fibroblasts into multipotent skin-derived precursor cells

Background

The human skin-derived precursors (SKPs) are a good cell source for regeneration. However, the isolation of SKP from human skin is limited. To overcome this drawback, we hypothesized that the component of plant stem cells could convert human fibroblasts to SKPs.

Methods

Human dermal fibroblasts were treated with shikimic acid, a major component of Sequoiadendron giganteum callus extract. The characteristics of these reprogrammed cells were analyzed by qPCR, western blot, colony-forming assay, and immunofluorescence staining. Artificial human skin was used for CO₂ laser-induced wound experiments. Human tissues were analyzed by immunohistochemistry.

Results

The reprogrammed cells expressed nestin (a neural precursor-specific protein), fibronectin, and vimentin and could differentiate into the ectodermal and mesodermal lineage. Nestin expression was induced by shikimic acid through the mannose receptor and subsequent MYD88 activation, leading to P38 phosphorylation and then CREB binding to the nestin gene promoter. Finally, we confirmed that shikimic acid facilitated the healing of cut injury and enhanced dermal reconstruction in a human artificial skin model. Moreover, in a clinical study with healthy volunteers, plant callus extracts increased the expression of stem cell markers in the basal layer of the epidermis and collagen deposit in the dermis.

Conclusions

These results indicate that shikimic acid is an effective agent for tissue regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02409-3.

Exosomes derived from autologous dermal fibroblasts promote diabetic cutaneous wound healing through the Akt/β-catenin pathway

Diabetic cutaneous wounds are one of the complications of diabetes mellitus (DM) and are difficult to cure at present. Autologous dermal fibroblasts (DFs) have shown great promise in skin regeneration and repair. However, whether exosomes derived from autologous dermal fibroblasts (DF-Ex) can be used to accelerate diabetic cutaneous wound healing is unclear. In this study, human umbilical vein endothelial cells (HUVECs) were treated with high glucose. We found that DF-Ex could reverse the damage produced by high glucose in HUVECs in vitro. A high-fat diet and streptozotocin were used to establish a rat model of type 2 diabetes mellitus (T2DM), and a diabetic cutaneous wound model was established in the T2DM rats. We discovered that subcutaneous injections of DF-Ex could significantly promote re-epithelialization, collagen deposition, skin cell proliferation, angiogenesis and inhibit inflammation to accelerate diabetic cutaneous wound healing. We further explored the underlying mechanism and found that DF-Ex exerted positive effects by activating the Akt/β-catenin pathway. This research revealed that DF-Ex may provide a new treatment strategy for diabetic cutaneous wound healing.

Human Keratinocytes Adopt Neuronal Fates After In Utero Transplantation in the Developing Rat Brain

Human skin contains keratinocytes in the epidermis. Such cells share their ectodermal origin with the central nervous system (CNS). Recent studies have demonstrated that terminally differentiated somatic cells can adopt a pluripotent state, or can directly convert its phenotype to neurons, after ectopic expression of transcription factors. In this article we tested the hypothesis that human keratinocytes can adopt neural fates after culturing them in suspension with a neural medium. Initially, keratinocytes expressed Keratins and Vimentin. After neural induction, transcriptional upregulation of NESTIN, SOX2, VIMENTIN, SOX1, and MUSASHI1 was observed, concomitant with significant increases in NESTIN detected by immunostaining. However, in vitro differentiation did not yield the expression of neuronal or astrocytic markers. We tested the differentiation potential of control and neural-induced keratinocytes by grafting them in the developing CNS of rats, through ultrasound-guided injection. For this purpose, keratinocytes were transduced with lentivirus that contained the coding sequence of green fluorescent protein. Cell sorting was employed to select cells with high fluorescence. Unexpectedly, 4 days after grafting these cells in the ventricles, both control and neural-induced cells expressed green fluorescent protein together with the neuronal proteins βIII-Tubulin and Microtubule-Associated Protein 2. These results support the notion that in vivo environment provides appropriate signals to evaluate the neuronal differentiation potential of keratinocytes or other non-neural cell populations.

Comparative transcriptome analysis of transcultured human skin-derived precursors (tSKPs) from adherent monolayer culture system and tSKPs-derived fibroblasts (tFBs) by RNA-Seq

Transcultured human skin derived precursors (tSKPs) from adherent monolayer culture system have similar characteristics as traditional skin derived precursors (SKPs), making tSKPs a suitable candidate for regenerative medicine. tSKPs can differentiate into fibroblasts. However, little is known about the molecular mechanism of the transition from tSKPs to fibroblasts. Here, we compared the transcriptional profiles of human tSKPs and tSKPs-derived fibroblasts (tFBs) by RNA-Sequence aiming to determine the candidate genes and pathways involving in the differentiation process. A total of 1042 differentially expressed genes (DEGs) were identified between tSKPs and tFBs, with 490 genes up-regulated and 552 genes down-regulated. Our study showed that these DEGs were significantly enriched in tumor necrosis factor signaling pathway, focal adhesion, extracellular matrix-receptor interaction and phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway. A further transcription factors (TFs) analysis of DEGs revealed the significantly down-expressed TFs (p21, Foxo1and Foxc1) in tFBs were mostly the downstream nodes of PI3K-Akt signaling pathway, which suggested PI3K-Akt signaling pathway might play an important role in tSKPs differentiation. The results of our study are useful for investigating the molecular mechanisms in tSKPs differentiation into tFBs, making it possible to take advantage of their potential application in regenerative medicine.

Multipotentiality of skin-derived precursors: application to the regeneration of skin and other tissues

Skin-derived precursors (SKPs) have been described as multipotent dermal precursors. Here, we provide a review of the breadth and depth of scientific literature and studies regarding SKPs, accounting for a large number of scientific publications. Interestingly, these progenitors can be isolated from embryonic and adult skin, as well as from a population of dermal cells cultured in vitro in monolayer. Gathering information from different authors, this review explores different aspects of the SKP theme, such as the potential distinct origins of SKPs in rodents and in humans, and also their ability to differentiate in vitro and in vivo into multiple lineages of different progeny. This remarkable capacity makes SKPs an interesting endogenous source of precursors to explore in the framework of experimental and therapeutic applications in different domains. SKPs are not only involved in the skin's dermal maintenance and support as well as wound healing, but also in hair follicle morphogenesis. This review points out the interests of future researches on SKPs for innovative perspectives that may be helpful in many different types of scientific and medical domains.

Insights into Fibroblast Plasticity: Cellular Communication Network 2 Is Required for Activation of Cancer-Associated Fibroblasts in a Murine Model of Melanoma

Tumor stroma resembles a fibrotic microenvironment, being characterized by the presence of myofibroblast-like cancer-associated fibroblasts (CAFs). In wild-type mice injected with melanoma cells, we show that the stem cell transcription factor Sox2 is expressed by tumor cells and induced in CAFs derived from synthetic fibroblasts. These fibroblasts were labeled postnatally with green fluorescent protein using mice expressing a tamoxifen-dependent Cre recombinase under the control of a fibroblast-specific promoter/enhancer. Conversely, fibroblast activation was impaired in mice with a fibroblast-specific deletion of cellular communication network 2 (Ccn2), associated with reduced expression of α-smooth muscle actin and Sox2. Multipotent Sox2-expressing skin-derived precursor (SKP) spheroids were cultured from murine back skin. Using lineage tracing and flow cytometry, approximately 40% of SKPs were found to be derived from type I collagen-lineage cells and acquired multipotency in culture. Inhibition of mechanotransduction pathways prevented myofibroblast differentiation of SKPs and expression of Ccn2. In SKPs deleted for Ccn2, differentiation into a myofibroblast, but not an adipocyte or neuronal phenotype, was also impaired. In human melanoma, CCN2 expression was associated with a profibrotic integrin alpha (ITGA) 11-expressing subset of CAFs that negatively associated with survival. These results suggest that synthetic dermal fibroblasts are plastic, and that CCN2 is required for the differentiation of dermal progenitor cells into a myofibroblast/CAF phenotype and is, therefore, a therapeutic target in melanoma.

Isolation, Characterization, and Safety Evaluation of Human Skin-Derived Precursors from an Adherent Monolayer Culture System

BACKGROUND

Skin-derived precursors (SKPs) are promising candidates for regenerative medicine. Several studies have transcultured human SKPs (termed tSKPs) from fibroblasts (FBs) expanded in monolayer culture. Herein, we optimized the procedure by treating flasks with poly-2-hydroxyethyl methacrylate (poly-HEMA).

METHODS

tSKPs generated from our adherent monolayer culture system were investigated for protein expression and differentiation capacity. The aggregated cells and the proliferative cells within tSKP spheres were detected by mix-culturing FBs expressing two different fluorescent proteins and BrdU- or EdU-positive cells, respectively. To distinguish tSKPs from FBs, we compared their phenotypes and transcriptomes. The tumorigenicity of tSKPs and FBs was also assessed in our study.

RESULTS

tSKPs expressed Versican, Fibronectin, Vimentin, Sox2, and Nestin. Under appropriate stimuli, tSKPs could differentiate to mesenchymal or neural lineages. While these spheres were heterogeneous populations consisting of both proliferative and aggregated cells, the rate of proliferative cells correlated with a seeding density. tSKPs, isolated from FBs, were distinctive from FBs in cell cycle, marker expression, neural differentiation potential, and transcript profiles despite the two sharing partial similarity in certain properties. As for tumorigenesis, both tSKPs and FBs could be considered as nontumorigenic ex vivo and in vivo.

CONCLUSION

tSKPs were heterogeneous populations presenting similar characteristics as traditional SKPs, while being different from FBs. The potential mixture of FBs in spheres did not affect the biosafety of tSKPs, as both of which had normal karyotype and nontumorigenicity. Taken together, we suggested tSKPs had potential applications in regenerative medicine.

Hair-follicle-associated pluripotent stem cells derived from cryopreserved intact human hair follicles sustain multilineage differentiation potential

The bulge area of the hair follicle contains hair-follicle-associated pluripotent (HAP) stem cells. Here, we present effective cryopreservation procedures of the human hair follicle that preserve the differentiation potential of HAP stem cells. Whole hair follicles isolated from human scalp were cryopreserved by a slow-rate cooling medium and stored in liquid nitrogen. A careful thawing method was used to collect the upper parts of the human hair follicles which were cultured for four weeks in a Dulbecco’s Modified Eagle’s Medium with fetal bovine serum (FBS). Proliferating hair follicle cells were then shifted to DMEM/Ham’s Nutrient Mixture F-12 medium without FBS and allowed to grow for one week. These proliferating cells were able to produce HAP stem cell colonies with multilineage differentiation capacity. They produced keratinocytes, smooth muscle cells, cardiac muscle cells, neurons and glial cells. Interestingly, these cryopreserved hair follicles produced pluripotent HAP stem cell colonies similar to fresh follicles. These findings suggest that the cryopreserved whole human hair follicle preserves the ability to produce HAP stem cells, which will enable any individual to preserve a bank of these stem cells for personalized regenerative medicine.

Characterization of spontaneous spheroids from oral mucosa-derived cells and their direct comparison with spheroids from skin-derived cells

Background

Our group has developed a novel method for spontaneous spheroid formation using a specific low-adherence culture plate with around 90° water contact angle. In this study, this method was applied for oral mucosa-derived cells. First, the feasibility of spontaneous spheroid formation was tested. Next, the characteristics of spontaneous spheroids from oral mucosa- and skin-derived cells were compared with special focus on the stemness and neuronal differentiation capability.

Methods

Oral mucosal cells were obtained from the palate and buccal mucosa of C57BL/6J mice. Similarly, skin cells were obtained from the back of the same mouse strain. Passage 2–3 cells were inoculated into the specific low-adherence culture plates to form spontaneous spheroids. The effect of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and B27 supplement on spheroid formation and maintenance was assessed. Immunofluorescence and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were performed to investigate the expression of pluripotency markers, cell proliferation and apoptosis markers, and neurogenic differentiation markers.

Results

Using this culture plate, spontaneous spheroid formation was feasible. This process depended on the presence of serum but was independent of the additives such as bFGF, EGF, and B27 supplement, although they improved the efficiency and were essential for spheroid maintenance. This result was confirmed by the higher expression of Caspase7 in the spheroids cultured without the additives than that with the additives. The spheroids from oral mucosa-derived cells expressed stem cell markers, such as Sox2, SSEA1, Oct4, Nanog, and Nestin. The expression of Sox2 in spheroids from oral mucosal cells was higher than that in spheroids from skin-derived cells. Both spheroid-forming cell types had the ability to differentiate into neural and Schwann cells after neurogenic induction, although significantly higher MAP 2, MBP, Nestin, and Nurr1 gene expression was noted in the cells from oral mucosa-derived spheroids.

Conclusions

The results showed that spontaneous spheroids from oral mucosa-derived cells contain highly potent stem cells, which were as good as skin-derived stem cells. The high expression of certain neuronal marker genes suggests an advantage of these cells for regeneration therapy for neuronal disorders.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1283-0) contains supplementary material, which is available to authorized users.

Hydrogel-Based Strategies to Advance Therapies for Chronic Skin Wounds

Chronic skin wounds are the leading cause of nontraumatic foot amputations worldwide and present a significant risk of morbidity and mortality due to the lack of efficient therapies. The intrinsic characteristics of hydrogels allow them to benefit cutaneous healing essentially by supporting a moist environment. This property has long been explored in wound management to aid in autolytic debridement. However, chronic wounds require additional therapeutic features that can be provided by a combination of hydrogels with biochemical mediators or cells, promoting faster and better healing. We survey hydrogel-based approaches with potential to improve the healing of chronic wounds by reviewing their effects as observed in preclinical models. Topics covered include strategies to ablate infection and resolve inflammation, the delivery of bioactive agents to accelerate healing, and tissue engineering approaches for skin regeneration. The article concludes by considering the relevance of treating chronic skin wounds using hydrogel-based strategies.

Flowable Polyethylene Glycol Hydrogels Support the in Vitro Survival and Proliferation of Dermal Progenitor Cells in a Mechanically Dependent Manner

Cell-based therapies have garnered considerable interest largely because of their potential utility for tissue regeneration in a variety of organs, including skin. Designing vehicles that enable optimal delivery and purposeful integration of donor cells within tissues will be critical for their success. Here, we investigate the utility of an injectable, self-polymerizing, fully synthetic hydrogel in supporting the survival, proliferation, and function of cultured adult dermal progenitor cells (DPCs) which may serve as a source of renewable cells to repair severe skin injuries or restore hair growth. We show that modifying the stiffness of these transglutaminase cross-linked poly(ethylene glycol) (TG-PEG) hydrogels significantly alters DPC behavior and phenotype; increasing stiffness promotes their differentiation and migration whereas softer gels maintained them in a proliferative state. We found that 2-3% TG-PEG was optimal to promote cell expansion and survival. Unexpectedly, DPCs grown in all conditions maintained their inductive function and thus generated de novo hair follicles. Our data suggests that TG-PEG hydrogels may be a versatile platform for stem and progenitor cell transplantation and fate specification while maintaining functional competence.

The Human Skin-Derived Precursors for Regenerative Medicine: Current State, Challenges, and Perspectives

Skin-derived precursors (SKPs) are an adult stem cell source with self-renewal and multipotent differentiation. Although rodent SKPs have been discussed in detail in substantial studies, human SKPs (hSKPs) are rarely reported. Understanding the biological properties and possible mechanisms underlying hSKPs has important implications for regenerative medicine particularly clinical applications, as human-derived sources are more suitable for clinical transplantation. The finding that hSKPs derivatives, such as neural and mesodermal progeny, have both in vitro and in vivo function without any genetical modification makes hSKPs a trustable, secure, and accessible resource for cell-based therapy. Here, we provide an overview of hSKPs, describing their characteristics, originations and niches, and potential applications. A comparison between traditional and innovative culture methods used for hSKPs is also introduced. Furthermore, we discuss the challenges and the future perspectives towards the field of hSKPs. With this review, we hope to point out the current stage of hSKPs and highlight the problems that remain in this field.

Bone morphogenetic protein 7-transduced human dermal-derived fibroblast cells differentiate into osteoblasts and form bone in vivo

BACKGROUND

Human dermal-derived fibroblast cells (hDDFCs) are multipotent. Bone morphogenetic proteins (BMPs) are a group of cytokines that promote different developmental processes, including the formation of bone. BMPs can promote hDDFC osteogenesis, but the role of BMP7 in hDDFC osteogenesis in vitro and bone formation in vivo has not been investigated in depth.

MATERIALS AND METHODS

hDDFCs were stably transfected with a human BMP7 recombinant adenovirus and osteogenic differentiation was examined by alkaline phosphatase staining and calcium accumulation. In addition, we measured the expression of osteoblast-related genes. To examine osteogenesis in vivo, we injected C57BL/6 nude mice with adenovirus-transfected hDDFCs in a calcium alginate hydrogel and examined bone formation using soft X-ray, histological, and immunohistochemical analyses.

RESULTS

Our findings showed that adenovirus-mediated BMP7 expression promoted osteogenic differentiation of hDDFCs and enhanced expression of osteoblast-related genes in vitro. Cells infected with BMP7 adenoviruses showed enhanced bone formation and osteoblast-related gene expression in vivo after the injection of hDDFC-hydrogel mixture.

CONCLUSIONS

Taken together, our data indicate that BMP7 significantly promotes hDDFC osteogenesis, and confirm that infecting hDDFCs with BMP7-expressing adenoviruses is a useful tool for bone tissue engineering.

Rapid isolation and expansion of skin-derived precursor cells from human primary fibroblast cultures

Skin-derived precursor (SKP) cells have self-renewal and multipotent abilities and are found in the dermis. SKP cells have been isolated previously from pre-established dermal fibroblast cultures. In these procedures, long-term culture and low yield remain the crucial aspects requiring improvement. In this study, we exposed pre-established dermal fibroblasts to 30-min acid stress prior to isolating SKP cells (termed pH-SKP) and compared the yield to the previously published trypsin- and no-stress methods. Spheroid formation was confirmed and analyzed at days 3, 5 and 7. Stemness was investigated by immunohistochemistry for the stem cell markers Nestin, CD9, vimentin and NG2. Multipotency was investigated by differentiation into adipocytes, smooth muscle cells and fibroblasts. The pH-SKP spheroid yield at day 5 was four- and threefold higher than those obtained using trypsin- and no-stress methods, respectively. The expression of stem cell markers Nestin, CD9, vimentin and NG2 were significantly expressed in pH-SKPs compared to the fibroblast origin. Successful pH-SKP spheroid formation and differentiation were achieved and validated in 11 distinct human primary fibroblast lines. These results demonstrate that acute acidic stress treatment of dermal fibroblast cultures greatly improves SKP isolation, growth, yield and multipotency compared to previous methods.

Summary: Exposure of human dermal fibroblast cultures to a short period of acidic stress results in rapid isolation of skin-derived precursor (SKP) cells under the three-dimensional SKP culture conditions.

Human bone marrow harbors cells with neural crest-associated characteristics like human adipose and dermis tissues

Adult neural crest stem-derived cells (NCSC) are of extraordinary high plasticity and promising candidates for use in regenerative medicine. Several locations such as skin, adipose tissue, dental pulp or bone marrow have been described in rodent, as sources of NCSC. However, very little information is available concerning their correspondence in human tissues, and more precisely for human bone marrow. The main objective of this study was therefore to characterize NCSC from adult human bone marrow. In this purpose, we compared human bone marrow stromal cells to human adipose tissue and dermis, already described for containing NCSC. We performed comparative analyses in terms of gene and protein expression as well as functional characterizations. It appeared that human bone marrow, similarly to adipose tissue and dermis, contains NESTIN⁺ / SOX9⁺ / TWIST⁺ / SLUG⁺ / P75^NTR+/ BRN3A⁺/ MSI1⁺/ SNAIL1⁺ cells and were able to differentiate into melanocytes, Schwann cells and neurons. Moreover, when injected into chicken embryos, all those cells were able to migrate and follow endogenous neural crest migration pathways. Altogether, the phenotypic characterization and migration abilities strongly suggest the presence of neural crest-derived cells in human adult bone marrow.

Use of Patterned Collagen Coated Slides to Study Normal and Scleroderma Lung Fibroblast Migration

Systemic sclerosis (SSc) is a spreading fibrotic disease affecting the skin and internal organs. We aimed to model pathogenic fibroblast migration in SSc in order to identify enhancing factors, measure the effect of migrating cells on underlying extracellular matrix (ECM) and test possible therapeutic inhibitors. Novel patterned collagen substrates were used to investigate alignment and migration of skin and lung fibroblasts from SSc patients and healthy controls. Normal lung but not skin fibroblasts consistently elongated and aligned with underlying collagen and migrated dependent on PDGF or serum. SSc lung fibroblasts remained growth factor dependent, did not migrate more rapidly and were less restricted to alignment of the collagen. Multiple collagen proline and lysine-modifying enzymes were identified in SSc but not control fibroblast extracellular matrix preparations, indicating differential levels of ECM modification by the diseased cells. Profiling of migrating cells revealed a possible SCF/c-Kit paracrine mechanism contributing to migration via a subpopulation of cells. Heparin, which binds ligands including PDGF and SCF, and imatininib which blocks downstream tyrosine kinase receptors, both inhibited lung fibroblast migration individually but showed synergy in SSc cells. Pathologic lung fibroblasts from SSc patients modify ECM during migration but remain growth factor dependent and sensitive to inhibitors.

Insight into skin cell-based osteogenesis: a review

For decades, researchers have been fascinated by the strategy of using cell therapy for bone defects; some progress in the field has been made. Owing to its ample supply and easy access, skin, the largest organ in the body, has gained attention as a potential source of stem cells. Despite extensive applications in skin and nerve regeneration, an increasing number of reports indicate its potential use in bone tissue engineering and regeneration. Unfortunately, few review articles are available to outline current research efforts in skin-based osteogenesis. This review first summarizes the latest findings on stem cells or progenitors in skin and their niches and then discusses the strategies of skin cell-based osteogenesis. We hope this article elucidates this topic and generates new ideas for future studies.

Induction of Skin-Derived Precursor Cells from Human Induced Pluripotent Stem Cells

The generation of full thickness human skin from dissociated cells is an attractive approach not only for treating skin diseases, but also for treating many systemic disorders. However, it is currently not possible to obtain an unlimited number of skin dermal cells. The goal of this study was to develop a procedure to produce skin dermal stem cells from induced pluripotent stem cells (iPSCs). Skin-derived precursor cells (SKPs) were isolated as adult dermal precursors that could differentiate into both neural and mesodermal progenies and could reconstitute the dermis. Thus, we attempted to generate SKPs from iPSCs that could reconstitute the skin dermis. Human iPSCs were initially cultured with recombinant noggin and SB431542, an inhibitor of activin/nodal and TGFβ signaling, to induce neural crest progenitor cells. Those cells were then treated with SKP medium that included CHIR99021, a WNT signal activator. The induction efficacy from neural crest progenitor cells to SKPs was more than 97%. No other modifiers tested were able to induce those cells. Those human iPSC-derived SKPs (hiPSC-SKPs) showed a similar gene expression signature to SKPs isolated from human skin dermis. Human iPSC-SKPs differentiated into neural and mesodermal progenies, including adipocytes, skeletogenic cell types and Schwann cells. Moreover, they could be induced to follicular type keratinization when co-cultured with human epidermal keratinocytes. We here provide a new efficient protocol to create human skin dermal stem cells from hiPSCs that could contribute to the treatment of various skin disorders.

Quality and exploitation of umbilical cord blood for cell therapy: Are we beyond our capabilities?

There is increasing interest in identifying novel stem cell sources for application in emerging cell therapies. In this context, umbilical cord blood (UCB) shows great promise in multiple clinical settings. The number of UCB banks has therefore increased worldwide, with the objective of preserving potentially life-saving cells that are usually discarded after birth. After a rather long and costly processing procedure, the resultant UCB-derived cell products are cryopreserved until transplantation to patients. However, in many cases, only a small proportion of administered cells engraft successfully. Thus, can we do any better regarding current UCB-based therapeutic approaches? Here we discuss concerns about the use of UCB that are not critically pondered by researchers, clinicians, and banking services, including wasting samples with small volumes and the need for more reliable quality and functional controls to ensure the biological activity of stem cells and subsequent engraftment and treatment efficacy. Finally, we appeal for collaborative agreements between research institutions and UCB banks in order to redirect currently discarded small-volume UCB units for basic and clinical research purposes. Developmental Dynamics 245:710-717, 2016. © 2016 Wiley Periodicals, Inc.

Sphere-Derived Multipotent Progenitor Cells Obtained From Human Oral Mucosa Are Enriched in Neural Crest Cells

: Although isolation of oral mucosal stromal stem cells has been previously reported, complex isolation methods are not suitable for clinical application. The neurosphere culture technique is a convenient method for the isolation of neural stem cells and neural crest stem cells (NCSCs); neurosphere generation is a phenotype of NCSCs. However, the molecular details underlying the isolation and characterization of human oral mucosa stromal cells (OMSCs) by neurosphere culture are not understood. The purpose of the present study was to isolate NCSCs from oral mucosa using the neurosphere technique and to establish effective in vivo bone tissue regeneration methods. Human OMSCs were isolated from excised human oral mucosa; these cells formed spheres in neurosphere culture conditions. Oral mucosa sphere-forming cells (OMSFCs) were characterized by biological analyses of stem cells. Additionally, composites of OMSFCs and multiporous polylactic acid scaffolds were implanted subcutaneously into immunocompromised mice. OMSFCs had the capacity for self-renewal and expressed neural crest-related markers (e.g., nestin, CD44, slug, snail, and MSX1). Furthermore, upregulated expression of neural crest-related genes (EDNRA, Hes1, and Sox9) was observed in OMSFCs, which are thought to contain an enriched population of neural crest-derived cells. The expression pattern of α2-integrin (CD49b) in OMSFCs also differed from that in OMSCs. Finally, OMSFCs were capable of differentiating into neural crest lineages in vitro and generating ectopic bone tissues even in the subcutaneous region. The results of the present study suggest that OMSFCs are an ideal source of cells for the neural crest lineage and hard tissue regeneration.

SIGNIFICANCE

The sphere culture technique is a convenient method for isolating stem cells. However, the isolation and characterization of human oral mucosa stromal cells (OMSCs) using the sphere culture system are not fully understood. The present study describes the isolation of neural crest progenitor cells from oral mucosa using this system. Human OMSCs form spheres that exhibit self-renewal capabilities and multipotency, and are enriched with neural crest-derived cells. These oral mucosa sphere-forming cells can generate ectopic bone tissue in vivo. Therefore, the results of the present study show that the sphere culture system can be applied, without the need for complex isolation techniques, to produce multipotent spheres with the properties of neural crest stem cells. Furthermore, a convenient strategy is demonstrated for the isolation and culture of human OMSCs that could have clinical applications.

Giant Panda (Ailuropoda melanoleuca) Buccal Mucosa Tissue as a Source of Multipotent Progenitor Cells

Since the first mammal was cloned, the idea of using this technique to help endangered species has aroused considerable interest. However, several issues limit this possibility, including the relatively low success rate at every stage of the cloning process, and the dearth of usable tissues from these rare animals. iPS cells have been produced from cells from a number of rare mammalian species and this is the method of choice for strategies to improve cloning efficiency and create new gametes by directed differentiation. Nevertheless information about other stem cell/progenitor capabilities of cells from endangered species could prove important for future conservation approaches and adds to the knowledge base about cellular material that can be extremely limited. Multipotent progenitor cells, termed skin-derived precursor (SKP) cells, can be isolated directly from mammalian skin dermis, and human cheek tissue has also been shown to be a good source of SKP-like cells. Recently we showed that structures identical to SKPs termed m-SKPs could be obtained from monolayer/ two dimensional (2D) skin fibroblast cultures. Here we aimed to isolate m-SKPs from cultured cells of three endangered species; giant panda (Ailuropoda melanoleuca); red panda (Ailurus fulgens); and Asiatic lion (Panthera leo persica). m-SKP-like spheres were formed from the giant panda buccal mucosa fibroblasts; whereas dermal fibroblast (DF) cells cultured from abdominal skin of the other two species were unable to generate spheres. Under specific differentiation culture conditions giant panda spheres expressed neural, Schwann, adipogenic and osteogenic cell markers. Furthermore, these buccal mucosa derived spheres were shown to maintain expression of SKP markers: nestin, versican, fibronectin, and P75 and switch on expression of the stem cell marker ABCG2. These results demonstrate that giant panda cheek skin can be a useful source of m-SKP multipotent progenitors. At present lack of sample numbers means that we can only postulate why we were unable to obtain m-SKPs from the lion and red panda cultures. However the giant panda observations point to the value of archiving cells from rare species, and the possibilities for later progenitor cell derivation.

Investigation of Transcriptional Gene Profiling in Normal Murine Hair Follicular Substructures Using Next-Generation Sequencing to Provide Potential Insights Into Skin Disease

Skin diseases, including hair-related diseases and neoplasia, are a major public health problem. While their prevalence is increasing, their treatment options are limited. Researchers have tried to investigate the genes and signal pathways underlying hair follicles (HFs) to develop genetically targeted therapies through microarrays, which represent an appropriate modality for the analysis of small genomes. To enable the comprehensive transcriptome analysis of large and/or complex transcriptomes, we performed RNA-seq using next-generation sequencing (NGS). We isolated interfollicular keratinocytes (IFKs), HFs, and dermal fibroblasts including dermal papilla cells (DFs-DPCs) from normal C57BL/6 murine skin, transplanted combinations of these samples into nude mice, and followed the mice over time. Sustained hair growth was supported by HFs and DFs-DPCs. We then investigated the pathways and the relevant gene ontology associated with any identified differentially expressed genes (DEGs). In addition, in the culture and flow cytometry (FCM), the HFs had a more quiescent cell cycle pattern than did the IFKs and DFs-DPCs. Therefore, the representative cell cycle-related gene expression of IFKs, HFs, and DFs-DPCs was analyzed by NGS. Our study will allow researchers to further investigate the potential interactions and signaling pathways that are active in HF-related diseases and cancer and may aid in future bioengineering applications.

Impact of umbilical cord blood-derived mesenchymal stem cells on cardiovascular research

Over the years, cell therapy has become an exciting opportunity to treat human diseases. Early enthusiasm using adult stem cell sources has been tempered in light of preliminary benefits in patients. Considerable efforts have been dedicated, therefore, to explore alternative cells such as those extracted from umbilical cord blood (UCB). In line, UCB banking has become a popular possibility to preserve potentially life-saving cells that are usually discarded after birth, and the number of UCB banks has grown worldwide. Thus, a brief overview on the categories of UCB banks as well as the properties, challenges, and impact of UCB-derived mesenchymal stem cells (MSCs) on the area of cardiovascular research is presented. Taken together, the experience recounted here shows that UCBMSCs are envisioned as attractive therapeutic candidates against human disorders arising and/or progressing with vascular deficit.

Mesenchymal stromal cells for sphincter regeneration

Stress urinary incontinence (SUI), defined as the involuntary loss of considerable amounts of urine during increased abdominal pressure (exertion, effort, sneezing, coughing, etc.), is a severe problem to the individuals affected and a significant medical, social and economic challenge. SUI is associated with pelvic floor debility, absence of detrusor contraction, or a loss of control over the sphincter muscle apparatus. The pathology includes an increasing loss of muscle cells, replacement of muscular tissue with fibrous tissue, and general aging associated processes of the sphincter complex. When current therapies fail to cure or improve SUI, application of regeneration-competent cells may be an alternative therapeutic option. Here we discuss different aspects of the biology of mesenchymal stromal cells, which are relevant to their clinical applications and for regenerating the sphincter complex. However, there are reports in favor of and against cell-based therapies. We therefore summarize the potential and the risks of cell-based therapies for the treatment of SUI.

A review of adipocyte lineage cells and dermal papilla cells in hair follicle regeneration

Alopecia is an exceedingly prevalent problem effecting men and women of all ages. The standard of care for alopecia involves either transplanting existing hair follicles to bald areas or attempting to stimulate existing follicles with topical and/or oral medication. Yet, these treatment options are fraught with problems of cost, side effects, and, most importantly, inadequate long-term hair coverage. Innovative cell-based therapies have focused on the dermal papilla cell as a way to grow new hair in previously bald areas. However, despite this attention, many obstacles exist, including retention of dermal papilla inducing ability and maintenance of dermal papilla productivity after several passages of culture. The use of adipocyte lineage cells, including adipose-derived stem cells, has shown promise as a cell-based solution to regulate hair regeneration and may help in maintaining or increasing dermal papilla cells inducing hair ability. In this review, we highlight recent advances in the understanding of the cellular contribution and regulation of dermal papilla cells and summarize adipocyte lineage cells in hair regeneration.

Neural-competent cells of adult human dermis belong to the Schwann lineage

Resident neural precursor cells (NPCs) have been reported for a number of adult tissues. Understanding their physiological function or, alternatively, their activation after tissue damage or in vitro manipulation remains an unsolved issue. Here, we investigated the source of human dermal NPCs in adult tissue. By following an unbiased, comprehensive approach employing cell-surface marker screening, cell separation, transcriptomic characterization, and in vivo fate analyses, we found that p75NTR⁺ precursors of human foreskin can be ascribed to the Schwann (CD56⁺) and perivascular (CD56⁻) cell lineages. Moreover, neural differentiation potential was restricted to the p75NTR⁺CD56⁺ Schwann cells and mediated by SOX2 expression levels. Double-positive NPCs were similarly obtained from human cardiospheres, indicating that this phenomenon might be widespread.

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Human dermis-derived cultures show two types of SOX2⁺ cells: Schwann and perivascular

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p75NTR⁺CD56⁺ Schwann cells are responsible for neural progeny

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SOX2 expression levels regulate the neural competence of dermal precursors

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p75NTR⁺CD56⁺ neural precursor cells similarly arise from human cardiospheres

Stem cells in dermatology

Preclinical and clinical research have shown that stem cell therapy could be a promising therapeutic option for many diseases in which current medical treatments do not achieve satisfying results or cure. This article describes stem cells sources and their therapeutic applications in dermatology today.

Exogenous connective tissue growth factor preserves the hair-inductive ability of human dermal papilla cells

Connective tissue growth factor influences human dermal papilla cells' hair inductive ability through several signaling pathways.

Therapeutic Implications of Newly Identified Stem Cell Populations From the Skin Dermis

Skin, the largest organ of the body, is a promising reservoir for adult stem cells. The epidermal stem cells and hair follicle stem cells have been well studied for their important roles in homeostasis, regeneration, and repair of the epidermis and appendages for decades. However, stem cells residing in dermis were not identified until the year 2001, when a variety of stem cell subpopulations have been isolated and identified from the dermis of mammalian skin such as neural crest stem cells, mesenchymal stem cell-like dermal stem cells, and dermal hematopoietic cells. These stem cell subpopulations exhibited capabilities of self-renewing, multipotent differentiating, and immunosuppressive properties. Hence, the dermis-derived stem cells showed extensive potential applications in regenerative medicine, especially for wound healing/tissue repair, neural repair, and hematopoietic recovery. Here we summarized current research on the stem cell subpopulations derived from the dermis and aimed to provide a comprehensive review on their isolation, specific markers, differentiation capacity, and the functional activities in homeostasis, regeneration, and tissue repair.

Characterization of mesenchymal progenitor cell populations directly derived from human dermis

Mesenchymal stem cell (MSC) and progenitor cell (MPC) populations in human dermis remain poorly characterized, despite their importance to wound repair and the pathogenesis of many skin diseases. To identify MSC/MPC populations in human dermis we developed an 11-marker flow cytometry technique that enabled sorting of mesenchymal cell populations for functional assays, using adipose-derived stem cells (ASCs) from human adipose tissue as a positive control. Two populations of dermal cells had similar phenotypes to ASCs: both were CD34(+) CD73(+) CD105(-)/low, and lacked expression of c-kit (CD117) and hematopoietic or vascular markers (CD31, CD45, CD146, and HLA-DR). However, whereas ASCs were CD36(+/-) CD90(+), dermal mesenchymal progenitor cells (DMPCs) were split between a dominant CD36(-) CD90(+) population (DMPC1) and a small CD36(+) CD90(-) population (DMPC2). Both these populations were capable of differentiating into adipocytes, but only DMPC1 localized to a perivascular location, similar to that reported for ASCs. Re-gating of the flow cytometry data revealed that both DMPC1 and DMPC2 were part of CD45(-) CD73(+) CD146(-) populations with variable expression of CD34. This suggests that CD34 may not be a stable marker of DMPC populations in human dermis, consistent with data from MSCs in human bone marrow, and with the loss of CD34 we observed from both ASCs and DMPCs on cell culture. These data enable future study of DMPCs in health and disease, and may also explain why some mesenchymal cell lines derived from human dermis exhibit characteristics of MSCs.

Novel in vitro culture condition improves the stemness of human dermal stem/progenitor cells

Cell therapy using adult stem cells has emerged as a potentially new approach for the treatment of various diseases. Therefore, it is an essential procedure to maintain the stemness of adult stem cells for clinical treatment. We previously reported that human dermal stem/progenitor cells (hDSPCs) can be enriched using collagen type IV. However, hDSPCs gradually lose their stem cell properties as in vitro passages continue. In the present study, we developed optimized in vitro culture condition to improve the stemness of these hDSPCs. To evaluate whether the stemness of hDSPCs is well sustained in various culture conditions, we measured the expression levels of SOX2, NANOG, and S100B, which are well-known representative dermal progenitor markers. We observed that hDSPCs grown in three-dimensional (3D) culture condition had higher expression levels of those markers compared with hDSPCs grown in two-dimensional (2D) culture condition. Under the 3D culture condition, we further demonstrated that a high glucose (4.5 g/L) concentration enhanced the expression levels of the dermal progenitor markers, whereas O(2) concentration did not affect. We also found that skin-derived precursor (SKP) culture medium was the most effective, among various culture media, in increasing the dermal progenitor marker expression. We finally demonstrated that this optimized culture condition enhanced the expression level of human telomerase reverse transcriptase (hTERT), the proliferation, and the multipotency of hDSPCs, an important characteristic of stem cells. Taken together, these results suggested that this novel in vitro culture condition improves the stemness of hDSPCs.

Isolation of multipotent nestin-expressing stem cells derived from the epidermis of elderly humans and TAT-VHL peptide-mediated neuronal differentiation of these cells

A specialized population of cells residing in the hair follicle is quiescent but shows pluripotency for differentiating into epithelial-mesenchymal lineage cells. Therefore, such cells are hoped to be useful as implantable donor cells for regenerative therapy. Recently, it was reported that intracellular delivery of TAT-VHL peptide induces neuronal differentiation of skin-derived precursors. In the present study, we successfully isolated multipotent stem cells derived from the epidermis of elderly humans, characterized these cells as being capable of sphere formation and strong expression of nestin, fibronectin, and CD34 but not of keratin 15, and identified the niche of these cells as being the outer root sheath of the hair follicles. In addition, we showed that TAT-VHL peptide induced their neuronal differentiation in vitro, and confirmed by fluorescence immunohistochemistry the neuronal differentiation of such peptide-treated cells implanted into rodent brains. These multipotent nestin-expressing stem cells derived from human epidermis are easily accessible and should be useful as donor cells for neuronal regenerative cell therapy.