Role of Keratinocyte Growth Factor in the Differentiation of Sweat Gland-Like Cells From Human Umbilical Cord-Derived Mesenchymal Stem Cells

A review of biomacromolecule-based 3D bioprinting strategies for structure-function integrated repair of skin tissues

When skin is damaged or affected by diseases, it often undergoes irreversible scar formation, leading to aesthetic concerns and psychological distress for patients. In cases of extensive skin defects, the patient's life can be severely compromised. In recent years, 3D printing technology has emerged as a groundbreaking approach to skin tissue engineering, offering promising solutions to various skin-related conditions. 3D bioprinting technology enables the precise fabrication of structures by programming the spatial arrangement of cells within the skin tissue and subsequently printing skin replacements either in a 3D bioprinter or directly at the site of the defect. This study provides a comprehensive overview of various biopolymer-based inks, with a particular emphasis on chitosan (CS), starch, alginate, agarose, cellulose, and fibronectin, all of which are natural polymers belonging to the category of biomacromolecules. Additionally, it summarizes artificially synthesized polymers capable of enhancing the performance of these biomacromolecule-based bioinks, thereby composing hybrid biopolymer inks aimed at better application in skin tissue engineering endeavors. This review paper examines the recent advancements, characteristics, benefits, and limitations of biological 3D bioprinting techniques for skin tissue engineering. By utilizing bioinks containing seed cells, hydrogels with bioactive factors, and biomaterials, complex structures resembling natural skin can be accurately fabricated in a layer-by-layer manner. The importance of biological scaffolds in promoting skin wound healing and the role of 3D bioprinting in skin tissue regeneration processes is discussed. Additionally, this paper addresses the challenges and constraints associated with current 3D bioprinting technologies for skin tissue and presents future perspectives. These include advancements in bioink formulations, full-thickness skin bioprinting, vascularization strategies, and skin appendages bioprinting.

The Molecular Regulatory Mechanism in Multipotency and Differentiation of Wharton's Jelly Stem Cells

Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) are isolated from Wharton's jelly tissue of umbilical cords. They possess the ability to differentiate into lineage cells of three germ layers. WJ-MSCs have robust proliferative ability and strong immune modulation capacity. They can be easily collected and there are no ethical problems associated with their use. Therefore, WJ-MSCs have great tissue engineering value and clinical application prospects. The identity and functions of WJ-MSCs are regulated by multiple interrelated regulatory mechanisms, including transcriptional regulation and epigenetic modifications. In this article, we summarize the latest research progress on the genetic/epigenetic regulation mechanisms and essential signaling pathways that play crucial roles in pluripotency and differentiation of WJ-MSCs.

A volar skin excisional wound model for in situ evaluation of multiple-appendage regeneration and innervation

Background

Promoting rapid wound healing with functional recovery of all skin appendages is the main goal of regenerative medicine. So far current methodologies, including the commonly used back excisional wound model (BEWM) and paw skin scald wound model, are focused on assessing the regeneration of either hair follicles (HFs) or sweat glands (SwGs). How to achieve de novo appendage regeneration by synchronized evaluation of HFs, SwGs and sebaceous glands (SeGs) is still challenging. Here, we developed a volar skin excisional wound model (VEWM) that is suitable for examining cutaneous wound healing with multiple-appendage restoration, as well as innervation, providing a new research paradigm for the perfect regeneration of skin wounds.

Methods

Macroscopic observation, iodine-starch test, morphological staining and qRT-PCR analysis were used to detect the existence of HFs, SwGs, SeGs and distribution of nerve fibres in the volar skin. Wound healing process monitoring, HE/Masson staining, fractal analysis and behavioral response assessment were performed to verify that VEWM could mimic the pathological process and outcomes of human scar formation and sensory function impairment.

Results

HFs are limited to the inter-footpads. SwGs are densely distributed in the footpads, scattered in the IFPs. The volar skin is richly innervated. The wound area of the VEWM at 1, 3, 7 and 10 days after the operation is respectively 89.17% ± 2.52%, 71.72% ± 3.79%, 55.09 % ± 4.94% and 35.74% ± 4.05%, and the final scar area accounts for 47.80% ± 6.22% of the initial wound. While the wound area of BEWM at 1, 3, 7 and 10 days after the operation are respectively 61.94% ± 5.34%, 51.26% ± 4.89%, 12.63% ± 2.86% and 6.14% ± 2.84%, and the final scar area accounts for 4.33% ± 2.67% of the initial wound. Fractal analysis of the post-traumatic repair site for VEWM vs human was performed: lacunarity values, 0.040 ± 0.012 vs 0.038 ± 0.014; fractal dimension values, 1.870 ± 0.237 vs 1.903 ± 0.163. Sensory nerve function of normal skin vs post-traumatic repair site was assessed: mechanical threshold, 1.05 ± 0.52 vs 4.90 g ± 0.80; response rate to pinprick, 100% vs 71.67% ± 19.92%, and temperature threshold, 50.34°C ± 3.11°C vs 52.13°C ± 3.54°C.

Conclusions

VEWM closely reflects the pathological features of human wound healing and can be applied for skin multiple-appendages regeneration and innervation evaluation.

Biofabrication of Human Skin with Its Appendages

Much effort has been made to generate human skin organ in the laboratory. Yet, the current models are limited due to the lack of many critical biological and structural features of the skin. Importantly, these in vitro models lack appendages and fail to recapitulate the whole human skin construction. Thus, engineering a human skin with the capacity to generate all components, including appendages, is a major challenge. This review intends to provide an update on the recent efforts underway to regenerate appendage-bearing skin organs based on scaffold-free and scaffold-based bioengineering approaches. Although the mouse skin equivalents containing hair follicles, sebaceous glands, and sweat glands have been established in vitro, there has been limited success in humans. A combination of biofabricated matrices and cell aggregates, such as organoids, can pave the way for generating skin substitutes with human-like biological, structural, and physical features. Accordingly, the formation of human skin organoids and reconstruction of vascularized skin equipped with immune cells prompt calls for more scientific research. The generation of appendage-bearing skin substitutes can be applied in practice for wound healing, hair restoration, and scar treatment.

Small molecules facilitate single factor-mediated sweat gland cell reprogramming

BACKGROUND

Large skin defects severely disrupt the overall skin structure and can irreversibly damage sweat glands (SG), thus impairing the skin's physiological function. This study aims to develop a stepwise reprogramming strategy to convert fibroblasts into SG lineages, which may provide a promising method to obtain desirable cell types for the functional repair and regeneration of damaged skin.

METHODS

The expression of the SG markers cytokeratin 5 (CK5), cytokeratin 10 (CK10), cytokeratin 18 (CK18), carcino-embryonic antigen (CEA), aquaporin 5 (AQP5) and α-smooth muscle actin (α-SMA) was assessed with quantitative PCR (qPCR), immunofluorescence and flow cytometry. Calcium activity analysis was conducted to test the function of induced SG-like cells (iSGCs). Mouse xenograft models were also used to evaluate the in vivo regeneration of iSGCs. BALB/c nude mice were randomly divided into a normal group, SGM treatment group and iSGC transplantation group. Immunocytochemical analyses and starch-iodine sweat tests were used to confirm the in vivo regeneration of iSGCs.

RESULTS

EDA overexpression drove HDF conversion into iSGCs in SG culture medium (SGM). qPCR indicated significantly increased mRNA levels of the SG markers CK5, CK18 and CEA in iSGCs, and flow cytometry data demonstrated (4.18 ± 0.04)% of iSGCs were CK5 positive and (4.36 ± 0.25)% of iSGCs were CK18 positive. The addition of chemical cocktails greatly accelerated the SG fate program. qPCR results revealed significantly increased mRNA expression of CK5, CK18 and CEA in iSGCs, as well as activation of the duct marker CK10 and luminal functional marker AQP5. Flow cytometry indicated, after the treatment of chemical cocktails, (23.05 ± 2.49)% of iSGCs expressed CK5⁺ and (55.79 ± 3.18)% of iSGCs expressed CK18⁺, respectively. Calcium activity analysis indicated that the reactivity of iSGCs to acetylcholine was close to that of primary SG cells [(60.79 ± 7.71)% vs. (70.59 ± 0.34)%, ns]. In vivo transplantation experiments showed approximately (5.2 ± 1.1)% of the mice were sweat test positive, and the histological analysis results indicated that regenerated SG structures were present in iSGCs-treated mice.

CONCLUSION

We developed a SG reprogramming strategy to generate functional iSGCs from HDFs by using the single factor EDA in combination with SGM and small molecules. The generation of iSGCs has important implications for future in situ skin regeneration with SG restoration.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Recent Advances in the Application of Two-Dimensional Nanomaterials for Neural Tissue Engineering and Regeneration

The complexity of the nervous system structure and function, and its slow regeneration rate, makes it more difficult to treat compared to other tissues in the human body when an injury occurs. Moreover, the current therapeutic approaches including the use of autografts, allografts, and pharmacological agents have several drawbacks and can not fully restore nervous system injuries. Recently, nanotechnology and tissue engineering approaches have attracted many researchers to guide tissue regeneration in an effective manner. Owing to their remarkable physicochemical and biological properties, two-dimensional (2D) nanomaterials have been extensively studied in the tissue engineering and regenerative medicine field. The great conductivity of these materials makes them a promising candidate for the development of novel scaffolds for neural tissue engineering application. Moreover, the high loading capacity of 2D nanomaterials also has attracted many researchers to utilize them as a drug/gene delivery method to treat various devastating nervous system disorders. This review will first introduce the fundamental physicochemical properties of 2D nanomaterials used in biomedicine and the supporting biological properties of 2D nanomaterials for inducing neuroregeneration, including their biocompatibility on neural cells, the ability to promote the neural differentiation of stem cells, and their immunomodulatory properties which are beneficial for alleviating chronic inflammation at the site of the nervous system injury. It also discusses various types of 2D nanomaterials-based scaffolds for neural tissue engineering applications. Then, the latest progress on the use of 2D nanomaterials for nervous system disorder treatment is summarized. Finally, a discussion of the challenges and prospects of 2D nanomaterials-based applications in neural tissue engineering is provided.

Recent Progress in Engineering Mesenchymal Stem Cell Differentiation

Due to the ability to differentiate into variety of cell types, mesenchymal stem cells (MSCs) hold promise as source in cell-based therapy for treating injured tissue and degenerative diseases. The potential use of MSCs to replace or repair damaged tissues may depend on the efficient differentiation protocols to derive specialized cells without any negative side effects. Identification of appropriate cues that support the lineage-specific differentiation of stem cells is critical for tissue healing and cellular therapy. Recently, a number of stimuli have been utilized to direct the differentiation of stem cells. Biochemical stimuli such as small molecule, growth factor and miRNA have been traditionally used to regulate the fate of stem cells. In recent years, many studies have reported that biophysical stimuli including cyclic mechanical strain, fluid shear stress, microgravity, electrical stimulation, matrix stiffness and topography can also be sensed by stem cells through mechanical receptors, thus affecting the stem cell behaviors including their differentiation potential. In this paper, we review all the most recent literature on the application of biochemical and biophysical cues on regulating MSC differentiation. An extensive literature search was done using electronic database (Medline/Pubmed). Although there are still some challenges that need to be taken into consideration before translating these methods into clinics, biochemical and biophysical stimulation appears to be an attractive method to manipulate the lineage commitment of MSCs.

The preclinical and clinical implications of fetal adnexa derived mesenchymal stromal cells in wound healing therapy

Mesenchymal stromal cells (MSCs) isolated from fetal adnexa namely amniotic membrane/epithelium, amniotic fluid and umbilical cord have hogged the limelight in recent times, as a proposed alternative to MSCs from conventional sources. These cells which are identified as being in a developmentally primitive state have many advantages, the most important being the non-invasive nature of their isolation procedures, absence of ethical concerns, proliferation potential, differentiation abilities and low immunogenicity. In the present review, we are focusing on the potential preclinical and clinical applications of different cell types of fetal adnexa, in wound healing therapy. We also discuss the isolation-culture methods, cell surface marker expression, multi-lineage differentiation abilities, immune-modulatory capabilities and their homing property. Different mechanisms involved in the wound healing process and the role of stromal cells in therapeutic wound healing are highlighted. Further, we summarize the findings of the cell delivery systems in skin lesion models and paracrine functions of their secretome in the wound healing process. Overall, this holistic review outlines the research findings of fetal adnexa derived MSCs, their usefulness in wound healing therapy in human as well as in veterinary medicine.

Eccrine Sweat Gland and Its Regeneration: Current Status and Future Directions

Eccrine sweat glands (ESGs) play an important role in temperature regulation by secreting sweat. Insufficiency or dysfunction of ESGs in a hot environment or during exercise can lead to hyperthermia, heat exhaustion, heatstroke, and even death, but the ability of ESGs to repair and regenerate themselves is very weak and limited. Repairing the damaged ESGs and regenerating the lost or dysfunctional ESGs poses a challenge for dermatologists and bum surgeons. To promote and accelerate research on the repair and regeneration of ESGs, we summarized the development, structure and function of ESGs, and current strategies to repair and regenerate ESGs based on stem cells, scaffolds, and possible signaling pathways involved.

3D bioprinting for skin tissue engineering: Current status and perspectives

Skin and skin appendages are vulnerable to injury, requiring rapidly reliable regeneration methods. In recent years, 3D bioprinting has shown potential for wound repair and regeneration. 3D bioprinting can be customized for skin shape with cells and other materials distributed precisely, achieving rapid and reliable production of bionic skin substitutes, therefore, meeting clinical and industrial requirements. Additionally, it has excellent performance with high resolution, flexibility, reproducibility, and high throughput, showing great potential for the fabrication of tissue-engineered skin. This review introduces the common techniques of 3D bioprinting and their application in skin tissue engineering, focusing on the latest research progress in skin appendages (hair follicles and sweat glands) and vascularization, and summarizes current challenges and future development of 3D skin printing.

A Concise Review on Tissue Engineered Artificial Skin Grafts for Chronic Wound Treatment: Can We Reconstruct Functional Skin Tissue In Vitro?

Chronic wounds occur as a consequence of a prolonged inflammatory phase during the healing process, which precludes skin regeneration. Typical treatment for chronic wounds includes application of autografts, allografts collected from cadaver, and topical delivery of antioxidant, anti-inflammatory, and antibacterial agents. Nevertheless, the mentioned therapies are not sufficient for extensive or deep wounds. Moreover, application of allogeneic skin grafts carries high risk of rejection and treatment failure. Advanced therapies for chronic wounds involve application of bioengineered artificial skin substitutes to overcome graft rejection as well as topical delivery of mesenchymal stem cells to reduce inflammation and accelerate the healing process. This review focuses on the concept of skin tissue engineering, which is a modern approach to chronic wound treatment. The aim of the article is to summarize common therapies for chronic wounds and recent achievements in the development of bioengineered artificial skin constructs, including analysis of biomaterials and cells widely used for skin graft production. This review also presents attempts to reconstruct nerves, pigmentation, and skin appendages (hair follicles, sweat glands) using artificial skin grafts as well as recent trends in the engineering of biomaterials, aiming to produce nanocomposite skin substitutes (nanofilled polymer composites) with controlled antibacterial activity. Finally, the article describes the composition, advantages, and limitations of both newly developed and commercially available bioengineered skin substitutes.

Handheld instrument for wound-conformal delivery of skin precursor sheets improves healing in full-thickness burns

The current standard of care for patients with severe large-area burns consists of autologous skin grafting or acellular dermal substitutes. While emerging options to accelerate wound healing involve treatment with allogeneic or autologous cells, delivering cells to clinically relevant wound topologies, orientations, and sizes remains a challenge. Here, we report the one-step in situ formation of cell-containing biomaterial sheets using a handheld instrument that accommodates the topography of the wound. In an approach that maintained cell viability and proliferation, we demonstrated conformal delivery to surfaces that were inclined up to 45° with respect to the horizontal. In porcine pre-clinical models of full-thickness burn, we delivered mesenchymal stem/stromal cell-containing fibrin sheets directly to the wound bed, improving re-epithelialization, dermal cell repopulation, and neovascularization, indicating that this device could be introduced in a clinical setting improving dermal and epidermal regeneration.

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.

Chemically Defined Conditions Mediate an Efficient Induction of Mesodermal Lineage from Human Umbilical Cord- and Bone Marrow- Mesenchymal Stem Cells and Dental Pulp Pluripotent-Like Stem Cells

The human umbilical cord Wharton's Jelly- and the bone marrow- mesenchymal stem cells (WJ-MSCs and BM-MSCs, respectively) and the newly identified dental pulp pluripotent-like stem cells (DPPSCs) are new sources for stem cells with prospective use in cell regeneration and therapy. These cells are self-renewable, can be differentiated into several lineages, and can potentiate the immune responses. We hypothesized that three-dimensional (3D) culture conditions and directed differentiation using specific signaling regulators will enhance an efficient generation of mesoderm (MD) lineage independent from the origin or source of the stem cells. For a period of 3-days, cell aggregates were generated in a serum-free media containing ascorbic acid, retinoic acid, and keratinocyte growth factor; sonic hedgehog and bone morphogenic protein-4 signaling were inhibited using small molecules. In all cell types used, the biochemical and molecular analysis revealed a time course-dependent induction of the mesodermal, but not endodermal or ectodermal makers. In this study, we utilized a novel and efficient serum-free protocol to differentiate WJ-MSCs, BM-MSCs, and DPPSCs into MD-cells. Successful development of an efficient differentiation protocol can further be utilized and expanded on to obtain MD- derivative cell lineages.

Sweat gland organoids contribute to cutaneous wound healing and sweat gland regeneration

Sweat glands perform a vital thermoregulatory function in mammals. Like other skin components, they originate from epidermal progenitors. However, they have low regenerative potential in response to injury. We have established a sweat gland culture and expansion method using 3D organoids cultures. The epithelial cells derived from sweat glands in dermis of adult mouse paw pads were embedded into Matrigel and formed sweat gland organoids (SGOs). These organoids maintained remarkable stem cell features and demonstrated differentiation capacity to give rise to either sweat gland cells (SGCs) or epidermal cells. Moreover, the bipotent SGO-derived cells could be induced into stratified epidermis structures at the air−liquid interface culture in a medium tailored for skin epidermal cells in vitro. The SGCs embedded in Matrigel tailored for sweat glands formed epithelial organoids, which expressed sweat-gland-specific markers, such as cytokeratin (CK) 18 and CK19, aquaporin (AQP) 5 and αATP. More importantly, they had potential of regeneration of epidermis and sweat gland when they were transplanted into the mouse back wound and claw pad with sweat gland injury, respectively. In summary, we established and optimized culture conditions for effective generation of mouse SGOs. These cells are candidates to restore impaired sweat gland tissue as well as to improve cutaneous skin regeneration.

Developing a Novel and Convenient Model for Investigating Sweat Gland Morphogenesis from Epidermal Stem Cells

Sweat glands developed from the embryonic epidermis. To elucidate the underlying mechanisms of morphogenesis, a reliable in vitro test system for bioactive screening must be developed. Here, we described a novel and convenient model by coculturing embryonic tissue and epidermal stem cells (ESCs) using Transwell insert for evaluating the effects of soluble morphogens on sweat gland morphogenesis in vitro. Using this coculture system, morphological alteration, histological features, and specific markers were observed. Initial experiments revealed that ESCs cocultured with embryonic paw pad (EPP) tissue demonstrated glandular structure and cytokeratin 8 (K8) and cytokeratin 18 (K18) positive, while ESCs cocultured with embryonic dorsal skin demonstrated “sea snail” structure and K8, K18 negative. Moreover, bone morphogenetic protein 4 (BMP4) and epidermal growth factor (EGF) concentrations were detected in the medium of the EPP group. BMP receptor inhibitor could effectively block the ESC differentiation to sweat glands, while EGF receptor blocker did not show the effect. Our results showed clear benefits of this novel and convenient model in terms of in vitro-in vivo correlation. It was an appropriate alternative for screening of potential bioactives regulating the sweat gland morphogenesis mechanism.

Endowing iPSC-Derived MSCs with Angiogenic and Keratinogenic Differentiation Potential: A Promising Cell Source for Skin Tissue Engineering

Induced pluripotent stem cells (iPSC) hold tremendous potential for personalized cell-based therapy for skin regeneration. Aiming to establish human iPSCs as a potential cell source for skin tissue engineering, we expect to obtain an epidermal-like cell line with angiogenic and keratinogenic differentiation potential via inducing iPSC-derived mesenchymal stem cells (iPSC-MSCs) with basic fibroblast growth factor (bFGF) and/or keratinocyte growth factor (KGF). The results show that iPSC-MSCs were successfully induced with a positive FGFR/KGFR expression on the cell surface. BFGF/KGF induction could significantly increase the expression of vascularization marker CD31 and keratinization marker CK10, respectively, while when combined together, although CD31 and CK10 were still positively expressed, their expressions were lower than that of the single induction group, suggesting that the effects of the two growth factors interfered with each other. This cell line with angiogenic and keratinogenic differentiation potential provides a promising new source of cells for the construction of well vascularized and keratinized tissue engineered skin, furthermore establishing an effective strategy for iPSC-based therapy in skin tissue engineering.

Human umbilical cord mesenchymal stem cells improve irradiation-induced skin ulcers healing of rat models

Irradiation-induced skin ulcers can be resultant from nuclear accident or reaction to radiation therapy of tumor and is intractable for healing. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have been considered to be the potential therapeutic tools for tissue regeneration. However, the underlying mechanisms are still not well understood. This study aims to investigate the effects of hUC-MSCs on irradiation-induced skin ulcers healing and the related mechanisms. The ulcers were induced by irradiating the skin of adult SD rats. The ulcers of SD rats were treated with vehicle or hUC-MSCs donated from mother giving birth. The ulcer healing was measured by imaging the healing rate and the H&E staining. CD31 and VEGF expression was measured with immunohistochemistry assay. iTRAQ proteomics analysis was used to analyze the signaling pathway. The results showed that hUC-MSCs improved healing of irradiation-induced skin ulcers in vivo using a rat model of skin ulcer. Transplantation of hUC-MSCs promoted keratin generation and keratinocytes proliferation of ulcer areas. Furthermore, the results demonstrated that hUC-MSCs increased expression of CD31 and VEGF in ulcers and promoted neovascularization. iTRAQ proteomics analysis results indicated that PI3K/Akt signaling pathway involved in hUC-MSCs-mediated repairing of irradiation-induced skin ulcer. In conclusion, human umbilical cord mesenchymal stem cells promoted neovascularization and re-epithelization, and improved healing of irradiation-induced skin ulcers. This healing improvement may be conducted through activating the PI3K/Akt signaling pathway, however, which needs to be proven by the further investigations.

Neuropilin 1 Mediates Keratinocyte Growth Factor Signaling in Adipose-Derived Stem Cells: Potential Involvement in Adipogenesis

Adipogenesis is regulated by a complex network of molecules, including fibroblast growth factors. Keratinocyte growth factor (KGF) has been previously reported to promote proliferation on rat preadipocytes, although the expression of its specific receptor, FGFR2-IIIb/KGFR, is not actually detected in mesenchymal cells. Here, we demonstrate that human adipose-derived stem cells (ASCs) show increased expression of KGF during adipogenic differentiation, especially in the early steps. Moreover, KGF is able to induce transient activation of ERK and p38 MAPK pathways in these cells. Furthermore, KGF promotes ASC differentiation and supports the activation of differentiation pathways, such as those of PI3K/Akt and the retinoblastoma protein (Rb). Notably, we observed only a low amount of FGFR2-IIIb in ASCs, which seems not to be responsible for KGF activity. Here, we demonstrate for the first time that Neuropilin 1 (NRP1), a transmembrane glycoprotein expressed in ASCs acting as a coreceptor for some growth factors, is responsible for KGF-dependent pathway activation in these cells. Our study contributes to clarify the molecular bases of human adipogenesis, demonstrating a role of KGF in the early steps of this process, and points out a role of NRP1 as a previously unknown mediator of KGF action in ASCs.

Targeting ectodysplasin promotor by CRISPR/dCas9-effector effectively induces the reprogramming of human bone marrow-derived mesenchymal stem cells into sweat gland-like cells

BACKGROUND

Patients with a deep burn injury are characterized by losing the function of perspiration and being unable to regenerate the sweat glands. Because of their easy accession, multipotency, and lower immunogenicity, bone marrow-derived mesenchymal stem cells (BM-MSCs) represent as an ideal biological source for cell therapy. The aim of this study was to identify whether targeting the promotor of ectodysplasin (EDA) by CRISPR/dCas9-effector (dCas9-E) could induce the BM-MSCs to differentiate into sweat gland-like cells (SGCs).

METHODS

Activation of EDA transcription in BM-MSCs was attained by transfection of naive BM-MSCs with the lenti-CRISPR/dCas9-effector and single-guide RNAs (sgRNAs). The impact of dCas9-E BM-MSCs on the formation of SGCs and repair of burn injury was identified and evaluated both in vitro and in a mouse model.

RESULTS

After transfection with sgRNA-guided dCas9-E, the BM-MSCs acquired significantly higher transcription and expression of EDA by doxycycline (Dox) induction. Intriguingly, the specific markers (CEA, CK7, CK14, and CK19) of sweat glands were also positive in the transfected BM-MSCs, suggesting that EDA plays a critical role in promoting BM-MSC differentiation into sweat glands. Furthermore, when the dCas9-E BM-MSCs with Dox induction were implanted into a wound in a laboratory animal model, iodine-starch perspiration tests revealed that the treated paws were positive for perspiration, while the paws treated with saline showed a negative manifestation. For the regulatory mechanism, the expression of downstream genes of NF-κB (Shh and cyclin D1) was also enhanced accordingly.

CONCLUSIONS

These results suggest that EDA is a pivotal factor for sweat gland regeneration from BM-MSCs and may also offer a new approach for destroyed sweat glands and extensive deep burns.

Gene-activated matrix/bone marrow-derived mesenchymal stem cells constructs regenerate sweat glands-like structure in vivo

It is a significant challenge to regenerate full-thickness skin defects with sweat glands. Various skin substitutes have been developed to resolve this issue with minimal success. In this study, to yield a novel construct for in situ regeneration of sweat glands, the collagen-chitosan porous scaffold was combined with Lipofectamine 2000/pDNA-EGF complexes to obtain the gene-activated scaffold (GAS), which was then seeded with bone marrow-derived mesenchymal stem cells (BM-MSCs). The porous scaffold functionalized as a reservoir for the incorporated gene complexes which were released in a sustained manner. The seeded BM-MSCs were transfected in situ by the released complexes and specially differentiated into sweat gland cells in vitro under the induction of the expressed epidermal growth factor (EGF). Application in vivo of the GAS/BM-MSCs constructs on the full-thickness skin defects of SD rats confirmed that GAS/BM-MSCs could accelerate the wound healing process and induce the in situ regeneration of the full-thickness skin with sweat gland-like structures. Analyzed by immunohistochemical staining, RT-qPCR and Western-blotting, the levels of the major sweat gland markers such as carcino-embryonic antigen (CEA), cytokeratin 8 (CK8) and cytokeratin 14 (CK14) were all up-regulated, indicating that GAS/BM-MSCs can facilitate the regeneration of sweat glands-like structure in vivo.

Differentiation of human umbilical cord Wharton's jelly-derived mesenchymal stem cells into endometrial cells

BACKGROUND

Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) are a novel and promising strategy for tissue engineering because of their ability to differentiate into many cell types. We characterized the differentiation of WJ-MSCs into endometrial epithelial cell (EEC)-like and endometrial stromal cell (ESC)-like cells and assessed the effect of 17β-estradiol and 8-Br-cAMP on the differentiation system.

METHODS

WJ-MSCs were treated in two ways to differentiate into EEC-like and ESC-like cells respectively: cocultured with ESCs in control/differentiation medium (17β-estradiol, growth factors); and cultured in control/differentiation medium (8-Br-cAMP alone or 8-Br-cAMP plus 17β-estrogen and growth factors). Three signaling pathway inhibitors (SB203580, PD98059, H89) were used to investigate the mechanism of WJ-MSC differentiation into ESC-like cells. Immunofluorescence, western blot and flow cytometry analyses were used to analyze expression of epithelial markers and stromal cell markers. Enzyme-linked immunosorbent assays were used to test the production of secretory proteins associated with the differentiation of ESC-like cells.

RESULTS

17β-estradiol at 1 μM downregulated vimentin and CD13 and upregulated cytokeratin and CD9 proteins, promoting the differentiation of WJ-MSCs into EEC-like cells in the coculture system. 8-Br-cAMP at 0.5 mM upregulated vimentin and CD13 and downregulated CK and CD9, promoting the differentiation of WJ-MSCs into ESC-like cells. Prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP1) were upregulated and the protein kinase A (PKA) signaling pathway was activated, whereas extracellular signal-regulated (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) were not affected.

CONCLUSIONS

17β-estradiol at 1 μM is a good inducer for facilitating the differentiation of WJ-MSCs into EEC-like cells. 8-Br-cAMP plus estrogen and growth factors can induce the differentiation of WJ-MSCs into ESC-like cells. During the differentiation of WJ-MSCs into ESC-like cells, PRL and IGFBP1 were upregulated by the treatment and the PKA signaling pathway was activated, whereas ERK1/2 and p38 MAPK were not affected. These findings suggest a promising approach to the treatment of endometrial damage and other endometrial diseases and suggest new applications for WJ-MSCs in clinical practice.

Defined three-dimensional culture conditions mediate efficient induction of definitive endoderm lineage from human umbilical cord Wharton's jelly mesenchymal stem cells

Background

Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) are gaining increasing interest as an alternative source of stem cells for regenerative medicine applications. Definitive endoderm (DE) specification is a prerequisite for the development of vital organs such as liver and pancreas. Hence, efficient induction of the DE lineage from stem cells is crucial for subsequent generation of clinically relevant cell types. Here we present a defined 3D differentiation protocol of WJ-MSCs into DE cells.

Methods

WJ-MSCs were cultured in suspension to generate spheroids, about 1500 cells each, for 7 days. The serum-free differentiation media contained specific growth factors, cytokines, and small molecules that specifically regulate signaling pathways including sonic hedgehog, bone morphogenetic protein, Activin/Wnt, and Notch.

Results

We obtained more than 85 % DE cells as shown with FACS analysis using antibodies directed against the DE marker CXCR4. In addition, biochemical and molecular analysis of bona-fide DE markers revealed a time-course induction of Sox17, CXCR4, and FoxA2. Focused PCR-based array also indicated a specific induction into the DE lineage.

Conclusions

In this study, we report an efficient serum-free protocol to differentiate WJ-MSCs into DE cells utilizing 3D spheroid formation. Our approach might aid in the development of new protocols to obtain DE-derivative lineages including liver-like and pancreatic insulin-producing cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0426-9) contains supplementary material, which is available to authorized users.