Cultured human epithelium: human umbilical cord blood stem cells differentiate into keratinocytes under in vitro conditions

A Systematic Review of Stem Cell Differentiation into Keratinocytes for Regenerative Applications

To improve wound healing or treatment of other skin diseases, and provide model cells for skin biology studies, in vitro differentiation of stem cells into keratinocyte-like cells (KLCs) is very desirable in regenerative medicine. This study examined the most recent advancements in in vitro differentiation of stem cells into KLCs, the effect of biofactors, procedures, and preparation for upcoming clinical cases. A range of stem cells with different origins could be differentiated into KLCs under appropriate conditions. The most effective ways of stem cell differentiation into keratinocytes were found to include the co-culture with primary epithelial cells and keratinocytes, and a cocktail of growth factors, cytokines, and small molecules. KLCs should also be supported by biomaterials for the extracellular matrix (ECM), which replicate the composition and functionality of the in vivo extracellular matrix (ECM) and, thus, support their phenotypic and functional characteristics. The detailed efficient characterization of different factors, and their combinations, could make it possible to find the significant inducers for stem cell differentiation into epidermal lineage. Moreover, it allows the development of chemically known media for directing multi-step differentiation procedures.In conclusion, the differentiation of stem cells to KLCs is feasible and KLCs were used in experimental, preclinical, and clinical trials. However, the translation of KLCs from in vitro investigational system to clinically valuable cells is challenging and extremely slow.

Mesenchymal stem cells express epidermal markers in an in vitro reconstructed human skin model

Introduction: In skin traumas, such as burns, epidermal homeostasis is affected, often requiring clinical approaches. Different therapeutic strategies can be used including transplantation, besides the use of synthetic or natural materials with allogeneic cells. In this context, tissue engineering is an essential tool for skin regeneration, and using mesenchymal stem cells (MSC) from the umbilical cord appears to be a promising strategy in regenerative medicine due to its renewal and differentiation potential and hypo immunogenicity. We evaluated the transdifferentiation of MSC from umbilical cord into keratinocytes in three-dimensional (3D) in vitro skin models, using dermal equivalents composed by type I collagen with dermal fibroblasts and a commercial porcine skin decellularized matrix, both cultured at air-liquid interface (ALI). Methods: The expression of epidermal proteins cytokeratins (CK) 5, 14 and 10, involucrin and filaggrin was investigated by real-time PCR and immunofluorescence, in addition to the activity of epidermal kallikreins (KLK) on the hydrolysis of fluorogenic substrates. Results and discussion: The cultivation of MSCs with differentiation medium on these dermal supports resulted in organotypic cultures characterized by the expression of the epidermal markers CK5, CK14, CK10 and involucrin, mainly on the 7^th day of culture, and filaggrin at 10^th day in ALI. Also, there was a 3-fold increase in the KLK activity in the epidermal equivalents composed by MSC induced to differentiate into keratinocytes compared to the control (MSC cultivated in the proliferation medium). Specifically, the use of collagen and fibroblasts resulted in a more organized MSC-based organotypic culture in comparison to the decellularized matrix. Despite the non-typical epithelium structure formed by MSC onto dermal equivalents, the expression of important epidermal markers in addition to the paracrine effects of these cells in skin may indicate its potential use to produce skin-based substitutes.

Nanobiotechnology: Applications in Chronic Wound Healing

Wounds occur when skin integrity is broken and the skin is damaged. With progressive changes in the disease spectrum, the acute wounds caused by mechanical trauma have been become less common, while chronic wounds triggered with aging, diabetes and infection have become more frequent. Chronic wounds now affect more than 6 million people in the United States, amounting to 10 billion dollars in annual expenditure. However, the treatment of chronic wounds is associated with numerous challenges. Traditional remedies for chronic wounds include skin grafting, flap transplantation, negative-pressure wound therapy, and gauze dressing, all of which can cause tissue damage or activity limitations. Nanobiotechnology — which comprises a diverse array of technologies derived from engineering, chemistry, and biology — is now being applied in biomedical practice. Here, we review the design, application, and clinical trials for nanotechnology-based therapies for chronic wound healing, highlighting the clinical potential of nanobiotechnology in such treatments. By summarizing previous nanobiotechnology studies, we lay the foundation for future wound care via a nanotech-based multifunctional smart system.

Bone Marrow-Derived Cells and Wound Age Estimation

Appropriate technology as well as specific target cells and molecules are key factors for determination of wound vitality or wound age in forensic practice. Wound examination is one of the most important tasks for forensic pathologists and is indispensable to distinguish antemortem wounds from postmortem damage. For vital wounds, estimating the age of the wound is also essential in determining how the wound is associated with the cause of death. We investigated bone marrow-derived cells as promising markers and their potential usefulness in forensic applications. Although examination of a single marker cannot provide high reliability and objectivity in estimating wound age, evaluating the appearance combination of bone marrow-derived cells and the other markers may allow for a more objective and accurate estimation of wound age.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Tissue engineering strategies combining molecular targets against inflammation and fibrosis, and umbilical cord blood stem cells to improve hampered muscle and skin regeneration following cleft repair

Cleft lip with or without cleft palate is a congenital deformity that occurs in about 1 of 700 newborns, affecting the dentition, bone, skin, muscles and mucosa in the orofacial region. A cleft can give rise to problems with maxillofacial growth, dental development, speech, and eating, and can also cause hearing impairment. Surgical repair of the lip may lead to impaired regeneration of muscle and skin, fibrosis, and scar formation. This may result in hampered facial growth and dental development affecting oral function and lip and nose esthetics. Therefore, secondary surgery to correct the scar is often indicated. We will discuss the molecular and cellular pathways involved in facial and lip myogenesis, muscle anatomy in the normal and cleft lip, and complications following surgery. The aim of this review is to outline a novel molecular and cellular strategy to improve musculature and skin regeneration and to reduce scar formation following cleft repair. Orofacial clefting can be diagnosed in the fetus through prenatal ultrasound screening and allows planning for the harvesting of umbilical cord blood stem cells upon birth. Tissue engineering techniques using these cord blood stem cells and molecular targeting of inflammation and fibrosis during surgery may promote tissue regeneration. We expect that this novel strategy improves both muscle and skin regeneration, resulting in better function and esthetics after cleft repair.

Mesenchymal stem cells differentiate into keratinocytes and express epidermal kallikreins: Towards an in vitro model of human epidermis

Epidermal differentiation is a complex process in which keratinocytes go through morphological and biochemical changes in approximately 15 to 30 days. Abnormal keratinocyte differentiation is involved in the pathophysiology of several skin diseases. In this scenario, mesenchymal stem cells (MSCs) emerge as a promising approach to study skin biology in both normal and pathological conditions. Herein, we have studied the differentiation of MSC from umbilical cord into keratinocytes. MSC were cultured in Dulbecco's modified Eagle's medium (DMEM) (proliferation medium) and, after characterization, differentiation was induced by culturing cells in a defined keratinocyte serum-free medium (KSFM) supplemented with epidermal growth factor (EGF) and calcium chloride ions. Cells cultivated in DMEM were used as control. Cultures were evaluated from day 1 to 23, based on the cell morphology, the expression of p63, involucrin and cytokeratins (KRTs) KRT5, KRT10 and KRT14, by quantitative polymerase chain reaction, Western blot analysis or immunofluorescence, and by the detection of epidermal kallikreins activity. In cells grown in keratinocyte serum-free medium with EGF and 1.8 mM calcium, KRT5 and KRT14 expression was shown at the first day, followed by the expression of p63 at the seventh day. KRT10 expression was detected from day seventh while involucrin was observed after this period. Data showed higher kallikrein (KLK) activity in KSFM-cultured cells from day 11th in comparison to control. These data indicate that MSC differentiated into keratinocytes similarly to that occurs in the human epidermis. KLK activity detection appears to be a good methodology for the monitoring the differentiation of MSC into the keratinocyte lineage, providing useful tools for the better understanding of the skin biology.

Novel trends in application of stem cells in skin wound healing

The latest findings indicate the huge therapeutic potential of stem cells in regenerative medicine, including the healing of chronic wounds. Main stem cell types involved in wound healing process are: epidermal and dermal stem cells, mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and hematopoietic stem cells (HSCs). In the therapy of chronic wounds, they can be administrated either topically or using different matrix like hydrogels, scaffolds, dermal substitutes and extracellular matrix (ECM) derivatives. Stem cells are proven to positively influence wound healing by different direct and indirect mechanisms including residing cells stimulation, biomolecules release, inflammation control and ECM remodelling. MSCs are especially worth mentioning as they can be easily derived from bone-marrow or adipose tissue. Apart from traditional approach of administering living stem cells to wounds, new trends have emerged in recent years. Good healing results are obtained using stem cell secretome alone, for example exosomes or conditioned media. There are also attempts to improve healing potential of stem cells by their co-culture with other cell types as well as by their genetic modifications or pretreatment using different chemicals or cell media. Moreover, stem cells have been tested for novel therapeutic purposes like for example acute burns and have been used in experiments on large animal models including pigs and sheep. In this review we discuss the role of stem cells in skin wound healing acceleration. In addition, we analyse possible new strategies of stem cells application in treatment of chronic wounds.

The effect of mesenchymal stem cells combined with platelet-rich plasma on skin wound healing

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stem cells that have the potential of proliferation, high self-renewal, and the potential of multilineage differentiation. The differentiation potential of the MSCs in vivo and in vitro has caused these cells to be regarded as potentially appropriate tools for wound healing. After the burn, trauma or removal of the tumor of wide wounds is developed. Although standard treatment for skin wounds is primary healing or skin grafting, they are not always practical mainly because of limited autologous skin grafting.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, PubMed (NLM), LISTA (EBSCO), and Web of Science have been searched.

EVIDENCE SYNTHESIS

For clinical use of the MSCs in wound healing, two key issues should be taken into account: First, engineering biocompatible scaffolds clinical use of which leads to the least amount of side effects without any immunologic response and secondly, use of stem cells secretions with the least amount of clinical complications despite their high capability of healing damage.

CONCLUSION

In light of the MSCs' high capability of proliferation and multilineage differentiation as well as their significant role in modulating immunity, these cells can be used in combination with tissue engineering techniques. Moreover, the MSCs' secretions can be used in cell therapy to heal many types of wounds. The combination of MSCs and PRP aids wound healing which could potentially be used to promote wound healing.

Advances of Stem Cell Therapeutics in Cutaneous Wound Healing and Regeneration

Cutaneous wound healing is a complex multiple phase process, which overlaps each other, where several growth factors, cytokines, chemokines, and various cells interact in a well-orchestrated manner. However, an imbalance in any of these phases and factors may lead to disruption in harmony of normal wound healing process, resulting in transformation towards chronic nonhealing wounds and abnormal scar formation. Although various therapeutic interventions are available to treat chronic wounds, current wound-care has met with limited success. Progenitor stem cells possess potential therapeutic ability to overcome limitations of the present treatments as it offers accelerated wound repair with tissue regeneration. A substantial number of stem cell therapies for cutaneous wounds are currently under development as a result of encouraging preliminary findings in both preclinical and clinical studies. However, the mechanisms by which these stem cells contribute to the healing process have yet to be elucidated. In this review, we emphasize on the major treatment modalities currently available for the treatment of the wound, role of various interstitial stem cells and exogenous adult stem cells in cutaneous wound healing, and possible mechanisms involved in the healing process.

In vitro differentiation of menstrual blood stem cells into keratinocytes: A potential approach for management of wound healing

The skin wounds caused by insults should be treated immediately to restore the functions and integrity. Recent studies suggest that stem cells-based therapies may be applicable in wound healing. Newly defined menstrual blood-derived stem cells (MenSCs) show high rate of cell proliferation and trans-differentiation potency to various cell types. However, MenSCs potential to generate keratinocyte for future therapeutic use of skin lesions has been remained to investigate. We cultivated MenSCs in the presence of isolated foreskin derived-keratinocytes using an indirect co-culture system and evaluated efficiency of this protocol to generate keratinocytes using immunofluorescent staining and Real Time PCR technique. Our results showed that differentiated keratinocytes express epidermal/keratinocytes lineage specific markers such as K14, p63, and involucrin at both mRNA and protein levels. Immunofluorescent staining showed the expression of involucrin and K14 in differentiated cells in contrast to undifferentiated cells. Moreover, mRNA expression levels of K14 (11.1 folds, p = 0.001), p63 (10.23 folds, p = 0.001), and involucrin (2.94 folds, p = 0.001) were higher in differentiated MenSCs compared to non-cocultured cells. Therefore, we firstly presented evidence about differentiation capability of MenSCs into epidermal/keratinocytes lineage. Considering the advantages of MenSCs such as great accessibility, these stem cells are promising for stem cells-based therapies of skin defects.

Stem Cells and Tissue Engineering: Regeneration of the Skin and Its Contents

In this review, the authors discuss the stages of skin wound healing, the role of stem cells in accelerating skin wound healing, and the mechanism by which these stem cells may reconstitute the skin in the context of tissue engineering.

Stem Cells in Skin Wound Healing: Are We There Yet?

Significance: Cutaneous wound healing is a serious problem worldwide that affects patients with various wound types, resulting from burns, traumatic injuries, and diabetes. Despite the wide range of clinically available skin substitutes and the different therapeutic alternatives, delayed healing and scarring are often observed. Recent Advances: Stem cells have arisen as powerful tools to improve skin wound healing, due to features such as effective secretome, self-renewal, low immunogenicity, and differentiation capacity. They represent potentially readily available biological material that can particularly target distinct wound-healing phases. In this context, mesenchymal stem cells have been shown to promote cell migration, angiogenesis, and a possible regenerative rather than fibrotic microenvironment at the wound site, mainly through paracrine signaling with the surrounding cells/tissues. Critical Issues: Despite the current insights, there are still major hurdles to be overcome to achieve effective therapeutic effects. Limited engraftment and survival at the wound site are still major concerns, and alternative approaches to maximize stem cell potential are a major demand. Future Directions: This review emphasizes two main strategies that have been explored in this context. These comprise the exploration of hypoxic conditions to modulate stem cell secretome, and the use of adipose tissue stromal vascular fraction as a source of multiple cells, including stem cells and factors requiring minimal manipulation. Nonetheless, the attainment of these approaches to target successfully skin regeneration will be only evident after a significant number of in vivo works in relevant pre-clinical models.

Electrospun poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite scaffold with unrestricted somatic stem cells for bone regeneration

The combination of scaffolds and cells can be useful in tissue reconstruction. In this study, nanofibrous poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/nanohydroxyapatite (nano-HAp) scaffolds, filled with unrestricted somatic stem cells (USSCs), were used for healing calvarial bone in rat model. The healing effects of these scaffolds, with and without stem cells, in bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting. The results of CT analysis showed that bone regeneration on the scaffolds, and the amounts of regenerated new bone for polymer/nano-HAp scaffold with USSC, was significantly greater than the scaffold without cell and untreated control samples. Therefore, the combination of scaffold especially with USSC could be considered as a useful method for bone regeneration.

Human unrestricted somatic stem cells loaded in nanofibrous PCL scaffold and their healing effect on skin defects

Unrestricted somatic stem cells (USSCs) loaded in nanofibrous polycaprolactone (PCL) scaffolds can be used for skin regeneration when grafted onto full-thickness skin defects of rats. Nanofibrous PCL scaffolds were designed by the electrospinning method and crosslinked with laminin protein. Afterwards, the scaffolds were evaluated by scanning electron microscopy, and physical and mechanical assays. In this study, nanofibrous PCL scaffolds loaded with USSCs were grafted onto the skin defects. The wounds were subsequently investigated 21 days after grafting. Results of mechanical and physical analyses showed good resilience and compliance to movement as a skin graft. In animal models; study samples exhibited the most pronounced effect on wound closure, with statistically significant improvement in wound healing being seen at 21 days post-operatively. Histological examinations of healed wounds from all samples showed a thin epidermis plus recovered skin appendages in the dermal layer for samples with cell. Thus, the graft of nanofibrous PCL scaffolds loaded with USSC showed better results during the healing process of skin defects in rat models.

Stem Cells in Wound Healing: The Future of Regenerative Medicine? A Mini-Review

The increased risk of disease and decreased capacity to respond to tissue insult in the setting of aging results from complex changes in homeostatic mechanisms, including the regulation of oxidative stress and cellular heterogeneity. In aged skin, the healing capacity is markedly diminished resulting in a high risk for chronic wounds. Stem cell-based therapies have the potential to enhance cutaneous regeneration, largely through trophic and paracrine activity. Candidate cell populations for therapeutic application include adult mesenchymal stem cells, embryonic stem cells and induced pluripotent stem cells. Autologous cell-based approaches are ideal to minimize immune rejection but may be limited by the declining cellular function associated with aging. One strategy to overcome age-related impairments in various stem cell populations is to identify and enrich with functionally superior stem cell subsets via single cell transcriptomics. Another approach is to optimize cell delivery to the harsh environment of aged wounds via scaffold-based cell applications to enhance engraftment and paracrine activity of therapeutic stem cells. In this review, we shed light on challenges and recent advances surrounding stem cell therapies for wound healing and discuss limitations for their clinical adoption.

Sweat gland regeneration after burn injury: is stem cell therapy a new hope?

Stem cells are the seeds of tissue repair and regeneration and a promising source for novel therapies. The skin of patients with an extensive deep burn injury is repaired by a hypertrophic scar without regeneration of sweat glands and therefore loses the function of perspiration. Stem cell therapy provides the possibility of sweat gland regeneration. In particular, recent studies have reported the reprogramming of mesenchymal stromal cells into sweat gland-like (SGL) cells. We present an overview of recent researches into sweat gland regeneration with stem cells. Difficulties of sweat gland regeneration after deep burns have been elaborated. The advantage and disadvantage of several stem cell types in sweat gland regeneration have been discussed. Additionally, the possible mechanisms for reprogramming stem cells to SGL cells are summarized. A brief discussion on clinical application of stem cell-derived SGL cells is also presented. This review may possibly provide some implications for sweat gland regeneration.

Application of stems cells in wound healing--an update

Wound healing is a complex but well-orchestrated tissue repair process composed of a series of molecular and cellular events conducted by various types of cells and extracellular matrix. Despite a variety of therapeutic strategies proposed to accelerate the healing of acute and/or chronic wounds over the past few decades, effective treatment of chronic nonhealing wounds still remains a challenge. Due to the recent advances in stem cell research, a dramatic enthusiasm has been drawn to the application of stem cells in regenerative medicine. Both embryonic and adult stem cells have prolonged self-renewal capacity and are able to differentiate into various tissue types. Nevertheless, use of embryonic stem cells is limited, owing to ethical concerns and legal restrictions. Adult stem cells, which could be isolated from bone marrow, umbilical cord blood, adipose tissue, skin and hair follicles,are being explored extensively to facilitate the healing of both acute and chronic wounds. The current article summarizes recent research on various types of stem cell-based strategies applied to improve wound healing. In addition, future directions of stem cell-based therapy in wound healing have also been discussed. Finally, despite its apparent advantages, limitations and challenges of stem cell therapy are discussed.

Regeneration of full-thickness skin defects using umbilical cord blood stem cells loaded into modified porous scaffolds

In this study, we have demonstrated the ability of cord blood (CB)-derived unrestricted somatic stem cells (USSCs) and chitosan-modified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffold to promote skin regeneration. Afterward, the scaffolds were evaluated by structural, microscopic, physical, and mechanical assays and cell culture analyses. Results of structural, physical, and mechanical analyses also showed a good resilience and compliance with movement as a skin graft. Cellular experiments showed a better cell adhesion, growth, and proliferation inside the modified scaffolds compared with unmodified ones. In animal models with histological examinations, all groups, excluding the control group especially the groups treated with stem cells, exhibited the most pronounced effect on wound closure, with the statistically significant improvement in wound healing being seen at postoperative day 21. These data suggest that chitosan-modified PHBV scaffold loaded with CB-derived USSCs could significantly contribute to wound repair and be potentially used in the tissue engineering.

Bone reconstruction in rat calvarial defects by chitosan/hydroxyapatite nanoparticles scaffold loaded with unrestricted somatic stem cells

Calcium phosphates are one of the biomaterials that are used for bone regeneration. In this study, Hydroxyapatite (HAp) nanoparticles with chitosan gel filled with unrestricted somatic stem cells (USSCs) were used for healing calvarial bone in rat model. The healing effects of these injectable scaffolds with and without stem cells for bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting. The results of CT analysis showing bone regeneration on the scaffolds, also the amounts of regenerated new bone for USSC scaffold was significantly greater than the scaffold without cell and untreated controls. Therefore, the combination of scaffold especially with USSC is considered as a useful method for bone regeneration.

Bone formation in calvarial defects by injectable nanoparticular scaffold loaded with stem cells

OBJECTIVE

Calcium phosphates are one of biomaterials that are used for bone regeneration. In this study, calcium phosphate nanoparticles such as hydroxyapatite (HA)/fluorapatite (FA),with chitosan gel filled with unrestricted somatic stem cells (USSCs) were used for healing calvarial bone in rat model.

METHODS

The healing effects of these injectable scaffolds, with and without stem cells, in bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting.

RESULTS

The results of CT analysis showed that bone regeneration on the scaffolds, and the amounts of regenerated new bone for USSC scaffold were significantly greater than the scaffold without cell and untreated controls.

CONCLUSION

Therefore, the combination of scaffold especially with USSC could be considered as a useful method for bone regeneration.

The healing effect of unrestricted somatic stem cells loaded in collagen-modified nanofibrous PHBV scaffold on full-thickness skin defects

Unrestricted somatic stem cells (USSCs) loaded in nanofibrous PHBV scaffold can be used for skin regeneration when grafted into full-thickness skin defects of rats. Nanofibrous PHBV scaffolds were designed using electrospinning method and then, modified with the immobilized collagen via the plasma method. Afterward, the scaffolds were evaluated using scanning electron microscopy, physical and mechanical assays. In this study; nanofibrous PHBV scaffolds loaded with and without USSCs were grafted into the skin defects. The wounds were subsequently investigated at 21 days after grafting. Results of mechanical and physical analyses showed good resilience and compliance to movement as a skin graft. In animal models; all study groups excluding the control group exhibited the most pronounced effect on wound closure, with the statistically significant improvement in wound healing being seen on post-operative Day 21. Histological and immunostaining examinations of healed wounds from all groups, especially the groups treated with stem cells, showed a thin epidermis plus recovered skin appendages in the dermal layer. Thus, the graft of collagen-coated nanofibrous PHBV scaffold loaded with USSC showed better results during the healing process of skin defects in rat model.

Autologous vs. allogenic mesenchymal progenitor cells for the reconstruction of critical sized segmental tibial bone defects in aged sheep

Mesenchymal progenitor cells (MPCs) represent an attractive cell population for bone tissue engineering. Their special immunological characteristics suggest that MPCs may be used in allogenic applications. The objective of this study was to compare the regenerative potential of autologous vs. allogenic MPCs in an ovine critical size segmental defect model. Ovine MPCs were isolated from bone marrow aspirates, expanded and cultured with osteogenic medium for 2weeks before implantation. Autologous and allogenic transplantation was performed using the cell-seeded scaffolds and unloaded scaffolds, while the application of autologous bone grafts served as a control group (n=6). Bone healing was assessed 12weeks after surgery by radiology, microcomputed tomography, biomechanical testing and histology. Radiology, biomechanical testing and histology revealed no significant differences in bone formation between the autologous and allogenic groups. Both cell groups showed more bone formation than the scaffold alone, whereas the biomechanical data showed no significant differences between the cell groups and the unloaded scaffolds. The results of the study suggest that scaffold-based bone tissue engineering using allogenic cells offers the potential for an off-the-shelf product. Thus the results of this study serve as an important baseline for translation of the assessed concepts into clinical applications.

An update review of stem cell applications in burns and wound care

The ultimate goal of the treatment of cutaneous burns and wounds is to restore the damaged skin both structurally and functionally to its original state. Recent research advances have shown the great potential of stem cells in improving the rate and quality of wound healing and regenerating the skin and its appendages. Stem cell-based therapeutic strategies offer new prospects in the medical technology for burns and wounds care. This review seeks to give an updated overview of the applications of stem cell therapy in burns and wound management since our previous review of the “stem cell strategies in burns care”.

Adipose tissue can be generated in vitro by using adipocytes from human fat tissue mesenchymal stem cells seeded and cultured on fibrin gel sheet

The current study has developed an innovative procedure to generate ex novo fat tissue by culturing adipocytes from human fat tissue mesenchymal stem cells (hFTMSCs) on fibrin gel sheet towards applications in medicine and cosmetology. Fibrin gel has been obtained by combining two components fibrinogen and thrombin collected by human peripheral blood. By this procedure it was possible to generate blocks of fibrin gel containing adipocytes within the gel that show similar features and consistency to human fat tissue mass. Results were assessed by histological staining methods, fluorescent immune-histochemistry staining as well photos by scanning electron microscopy (SEM) to demonstrate the adhesion and growth of cells in the fibrin gel. This result opens a real possibility for future clinical applications in the treatment of reconstructive and regenerative medicine where the use of stem cell may eventually be a unique solution or in the field of aesthetic medicine where autograft fat stem cells may grant for a safer and better outcome with long lasting results.

Using stem cells in skin regeneration: possibilities and reality

Tissue-engineered skin has a long history of clinical applications, yet current treatments are not capable of completely regenerating normal, uninjured skin. Nonetheless, the field has experienced a tremendous development in the past 10 years, encountering the summit of tissue engineering (TE) and the arising of stem cell research. Since then, unique features of these cells such as self-renewal capacity, multi-lineage differentiation potential, and wound healing properties have been highlighted. However, a realistic perspective of their outcome in skin regenerative medicine applications is still absent. This review intends to discuss the directions that adult and embryonic stem cells (ESCs) can take, strengthening the skin regeneration field. Distinctively, a critical overview of stem cells' differentiation potential onto skin main lineages, along with a highlight of their participation in wound healing mechanisms, is herein provided. We aim to compile and review significant work to allow a better understanding of the best skin TE approaches, enabling the embodiment of the materialization of a new era in skin regeneration to come, with a conscious overview of the current limitations.

Combined gene and stem cell therapy for cutaneous wound healing

In current medical practice, wound therapy remains a clinical challenge and much effort has been focused on the development of novel therapeutic approaches for wound treatment. Gene therapy, initially developed for treatment of congenital defects, represents a promising option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines have shown the most potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, and liposomal vectors. Besides advances stemming from breakthroughs in recombinant growth factors and bioengineered skin, there has been a significant increase in the understanding of stem cell biology in the field of cutaneous wound healing. A variety of sources, such as bone marrow, umbilical cord blood, adipose tissue and skin/hair follicles, have been utilized to isolate stem cells and to modulate the healing response of acute and chronic wounds. Recent data have demonstrated the feasibility of autologous adult stem cell therapy in cutaneous repair and regeneration. Very recently, stem cell based skin engineering in conjunction with gene recombination, in which the stem cells act as both the seed cells and the vehicle for gene delivery to the wound site, represents the most attractive field for generating a regenerative strategy for wound therapy. The aim of this article is to discuss the use and the potential of these novel technologies in order to improve wound healing capacities.

Stem cell therapies for recessive dystrophic epidermolysis bullosa

Human epidermis is composed of a stratified squamous epithelium that provides a mechanical barrier against the external environment and which is renewed every 3-4 weeks by resident stem cells in the epidermis. However, in the inherited skin fragility disorder, recessive dystrophic epidermolysis bullosa (RDEB), there is recurrent trauma-induced subepidermal blistering that disrupts epidermal homeostasis and is likely to deplete the epidermal stem cell pool. This review article discusses the nature of epidermal stem cells and other stem cell populations in the skin, as well as other possible extracutaneous sources of stem cells, that might have physiological or therapeutic relevance to cell therapy approaches for RDEB. Strategies to identify, create and use cells with multipotent or pluripotent properties are explored and current clinical experience of stem cell therapy in RDEB is reviewed. There is currently no single optimal therapy for patients with RDEB, but cell therapy technologies are evolving and hold great potential for modifying disease severity and improving quality of life for people living with RDEB.

Dedifferentiation derived cells exhibit phenotypic and functional characteristics of epidermal stem cells

Differentiated epidermal cells can dedifferentiate into stem cells or stem cell-like cells in vivo. In this study, we report the isolation and characterization of dedifferentiation-derived cells. Epidermal sheets eliminated of basal stem cells were transplanted onto the skin wounds in 47 nude athymic (BALB/c-nu/nu) mice. After 5 days, cells negative for CK10 but positive for CK19 and β₁-integrin emerged at the wound-neighbouring side of the epidermal sheets. Furthermore, the percentages of CK19 and β₁-integrin⁺ cells detected by flow cytometric analysis were increased after grafting (P < 0.01) and CK10⁺ cells in grafted sheets decreased (P < 0.01). Then we isolated these cells on the basis of rapid adhesion to type IV collagen and found that there were 4.56% adhering cells (dedifferentiation-derived cells) in the grafting group within 10 min. The in vitro phenotypic assays showed that the expressions of CK19, β₁-integrin, Oct4 and Nanog in dedifferentiation-derived cells were remarkably higher than those in the control group (differentiated epidermal cells) (P < 0.01). In addition, the results of the functional investigation of dedifferentiation-derived cells demonstrated: (1) the numbers of colonies consisting of 5–10 cells and greater than 10 cells were increased 5.9-fold and 6.7-fold, respectively, as compared with that in the control (P < 0.01); (2) more cells were in S phase and G2/M phase of the cell cycle (proliferation index values were 21.02% in control group, 45.08% in group of dedifferentiation); (3) the total days of culture (28 days versus 130 days), the passage number of cells (3 passages versus 20 passages) and assumptive total cell output (1 × 10⁵ cells versus 1 × 10¹² cells) were all significantly increased and (4) dedifferentiation-derived cells, as well as epidermal stem cells, were capable of regenerating a skin equivalent, but differentiated epidermal cells could not. These results suggested that the characteristics of dedifferentiation-derived cells cultured in vitro were similar to epidermal stem cells. This study may also offer a new approach to yield epidermal stem cells for wound repair and regeneration.

Human umbilical cord blood cells form epidermis in the skin equivalent model

Recently, human embryonic stem cells have been differentiated in vitro into functional epidermal keratinocytes. Here, we demonstrated that these cells can be generated also from non-embryonic, human umbilical cord blood (hUCB) cells that have the potential to differentiate into cells of non-hematopoietic lineage. Human UCB mono-nucleated cells were cultivated in monolayer and in three-dimensional skin equivalent cultures and assayed for the presence of phenotype-specific markers. Our results determined that after one month of culturing in serum containing medium, the hUCB cells produced morphologically homogeneous colonies of epithelial cells expressing keratinocyte-specific markers. They also formed stratified epidermis in organ cultures that contained sporadic CD1a-positive cells within the accurate strata. We concluded that hUCB cells have the capacity to differentiate into functional epidermal keratinocytes and may serve as a source of high-quality keratinocytes for clinical applications.

Stem cell therapy for cystic fibrosis: current status and future prospects

Although cystic fibrosis (CF), an autosomal recessive disease caused by mutations in the gene encoding for the CF transmembrane conductance regulator (CFTR), seems a good candidate for gene therapy, 15 years of intense investigation and a number of clinical trials have not yet produced a viable clinical gene-therapy strategy. In addition, the duration of gene expression has been shown to be limited, only lasting 1-4 weeks. Therefore, alternative approaches involve the search for, and use of, stem cell populations. Bone marrow contains different stem cell types, including hematopoietic stem cells and multipotent mesenchymal stromal cells. Numerous studies have now demonstrated the ability of hematopoietic stem cells and mesenchymal stromal cells to home to the lung and differentiate into epithelial cells of both the conducting airways and the alveolar region. However, engraftment of bone marrow-derived stem cells into the airways is a very inefficient process. Detailed knowledge of the cellular and molecular determinants governing homing to the lung and transformation of marrow cells into lung epithelial cells would benefit this process. Despite a very low level of engraftment of donor cells into the nose and gut, significant CFTR mRNA expression and a measurable level of correction of the electrophysiological defect were observed after transplantation of wild-type marrow cells into CF mice. It is uncertain whether this effect is due to the presence of CFTR-expressing epithelial cells derived from donor cells or to the immunomodulatory role of transplanted cells. Finally, initial studies on the usefulness of umbilical cord blood and embryonic stem cells in the generation of airway epithelial cells will be discussed in this review.

Can hematopoietic stem cells be an alternative source for skin regeneration?

In the past few years, the plasticity of adult cells in several post-natal tissues has attracted special attention in regenerative medicine. Skin is the largest organ in the body. Adult skin consists of epidermis, dermis and appendages such as hair and glands that are linked to the epidermis but project deep into the dermal layer. Stem cell biology of skin has been a focus of increasing interest in current life science. Committed stem cells with a limited differentiation potential for regeneration and repair of epidermis have been known for decades. Recent studies further found that adult skin tissues contain cell populations with pluripotent characteristics. Multipotent stem cells from skin with and without hair follicles, both in epidermal and dermal tissues, can differentiate and generate multiple cell lineages. Especially, the hematopoietic system in epidermal and dermal tissue, like skin, may be a local, acceptable reservoir of various adult stem cell populations. Given their easy accessibility, such stem cells can provide an experimental model not only for skin biology but also for studying the epithelial-mesenchymal cell interactions of organs other than the skin. This review presents an overview of recent advances in research into skin repair and regeneration involving stem cells from epidermis, dermis, and bone marrow. In particular, we focus on the possible use of blood stem cells as an alternative resource for research advances in skin biology.

Composite tissue engineering on polycaprolactone nanofiber scaffolds

Tissue engineering has largely focused on single tissue-type reconstruction (such as bone); however, the basic unit of healing in any clinically relevant scenario is a compound tissue type (such as bone, periosteum, and skin). Nanofibers are submicron fibrils that mimic the extracellular matrix, promoting cellular adhesion, proliferation, and migration. Stem cell manipulation on nanofiber scaffolds holds significant promise for future tissue engineering. This work represents our initial efforts to create the building blocks for composite tissue reflecting the basic unit of healing. Polycaprolactone (PCL) nanofibers were electrospun using standard techniques. Human foreskin fibroblasts, murine keratinocytes, and periosteal cells (4-mm punch biopsy) harvested from children undergoing palate repair were grown in appropriate media on PCL nanofibers. Human fat-derived mesenchymal stem cells were osteoinduced on PCL nanofibers. Cell growth was assessed with fluorescent viability staining; cocultured cells were differentiated using antibodies to fibroblast- and keratinocyte-specific surface markers. Osteoinduction was assessed with Alizarin red S. PCL nanofiber scaffolds supported robust growth of fibroblasts, keratinocytes, and periosteal cells. Cocultured periosteal cells (with fibroblasts) and keratinocytes showed improved longevity of the keratinocytes, though growth of these cell types was randomly distributed throughout the scaffold. Robust osteoinduction was noted on PCL nanofibers. Composite tissue engineering using PCL nanofiber scaffolds is possible, though the major obstacles to the trilaminar construct are maintaining an appropriate interface between the tissue types and neovascularization of the composite structure.

Interferon-gamma-induced neuronal differentiation of human umbilical cord blood-derived progenitors

Human umbilical cord blood (HUCB) provides a source of progenitors for cell therapy. We isolated and characterized an HUCB-derived population of progenitors (HUCBNP), differentiated toward neuronal phenotype by human neuroblastoma-conditioning medium (CM) and nerve growth factor (NGF), which have been found to confer neuroprotection toward hypoxia-mediated neuronal injury. This study investigated whether interferon-gamma (IFN-gamma) contributes to HUCBNP differentiation. IFN-gamma was detected in the CM used for the induction of differentiation of HUCBNP and a neutralizing antibody of IFN-gamma significantly inhibited either IFN-gamma or CM-induced differentiation. Transcriptome analysis of CM-differentiated HUCBNP, identified 86 genes as highly upregulated, among them 25 were IFN-induced (such as 2',5'-oligoadenylate synthetase 1 and 2, IFN-induced protein and transmembrane proteins, STAT1 (IFN-gamma-receptor signal transducer and activator of transcription) and chemokine C-X-C motif ligand 5). Treatment of HUCBNP with human recombinant IFN-gamma, inhibited cell proliferation in a dose-dependent manner. IFN-gamma (1-100 ng/ml) enhanced neuronal differentiation, expressed by neurite outgrowths and increased expression of the neuronal markers beta-tubulin III, microtubule-associated protein 2, neuronal nuclei, neurofilament M and neuronal-specific enolase. IFN-gamma additively cooperated with NGF to induce the differentiation of HUCBNP. These data indicate that IFN-gamma promotes neuronal differentiation of HUCB-derived progenitors, proposing its use in future protocols towards cell therapy.