MSCs seeded on bioengineered scaffolds improve skin wound healing in rats

The inducing effect of epidermal growth factor on acellular dermal matrix in a rat model of skin regeneration

OBJECTIVE

Tissue engineering, a novel approach in dermatology, has resulted in the development of scaffolds as skin substitutes that have accelerated wound healing. The aim of the present study was to synthesise acellular dermal matrix (ADM) as a dermal alternative and assess the effect of human epidermal growth factor (EGF) on the proliferation and migration of seeded fibroblast cells.

METHOD

ADM from fresh, full-thickness human skin was developed and characterised. Next, foreskin fibroblast cells were isolated, cultured and characterised. The fibroblast cells were sown into the ADM in two groups: one with EGF and one without EGF. We assessed the adhesion and proliferation of the cells on the scaffold by scanning electron microscopy, and thiazolyl blue tetrazolium bromide and 4',6-diamidino-2-phenylindole staining. For the animal study, 30 rats were divided into two equal groups at random (ADM, ADM+EGF). Wound healing was assessed macroscopically, histologically and by real-time polymerase chain reaction for Bax and Bcl-2 gene expression.

RESULTS

The ADM characterisation results showed that the scaffold was dense and integral with good stretching. The morphology and phenotype of the isolated fibroblast cells confirmed their identity. The fibroblast cells cultured on the ADM showed proliferation, which improved with the addition of EGF. In the animal model, EGF addition caused significantly (p<0.05) improved wound healing compared with isolated ADM; it also resulted in increased Bcl-2 and reduced Bax expressions.

CONCLUSION

A combination of ADM, fibroblast cells and EGFs could serve as skin substitutes and represent a novel therapeutic methodology for treating burns and hard-to-heal wounds.

Therapeutic Properties of M2 Macrophages in Chronic Wounds: An Innovative Area of Biomaterial-Assisted M2 Macrophage Targeted Therapy

Wound healing is a dynamic, multi-stage process essential for restoring skin integrity. Dysregulated wound healing is often linked to impaired macrophage function, particularly in individuals with chronic underlying conditions. Macrophages, as key regulators of wound healing, exhibit significant phenotypic diversity, ranging from the pro-healing M2 phenotype to the pro-inflammatory M1 phenotype. Imbalances in the M1/M2 ratio or hyperactivation of the M1 phenotype can delay the normal healing. Consequently, strategies aimed at suppressing the M1 phenotype or promoting the shift of local skin macrophages toward the M2 phenotype can potentially treat chronic non-healing wounds. This manuscript provides an overview of macrophages' role in normal and pathological wound-healing processes. It examines various therapeutic approaches targeting M2 macrophages, such as ex vivo-activated macrophage therapy, immunopharmacological strategies, and biomaterial-directed macrophage polarization. However, it also highlights that M2 macrophage therapies and immunopharmacological interventions may have drawbacks, including rapid phenotypic changes, adverse effects on other skin cells, biotoxicity, and concerns related to biocompatibility, stability, and drug degradation. Therefore, there is a need for more targeted macrophage-based therapies that ensure optimal biosafety, allowing for effective reprogramming of dysregulated macrophages and improved therapeutic outcomes. Recent advances in nano-biomaterials have demonstrated promising regenerative potential compared to traditional treatments. This review discusses the progress of biomaterial-assisted macrophage targeting in chronic wound repair and addresses the challenges faced in its clinical application. Additionally, it explores novel design concepts for combinational therapies, such as incorporating regenerative particles like exosomes into dressing materials or encapsulating them in microneedling systems to enhance wound healing rates.

Macrophage Polarization: A Novel Target and Strategy for Pathological Scarring

BACKGROUND

Abnormal scarring imposes considerable challenges and burdens on the lives of patients and healthcare system. Macrophages at the wound site are found to be of great concern to overall wound healing. There have been many studies indicating an inextricably link between dysfunctional macrophages and fibrotic scars. Macrophages are not only related to pathogen destruction and phagocytosis of apoptotic cells, but also involved in angiogenesis, keratinization and collagen deposition. These abundant cell functions are attributed to specific heterogeneity and plasticity of macrophages, which also add an extra layer of complexity to correlational researches.

METHODS

This article summarizes current understanding of macrophage polarization in scar formation and several prevention and treatment strategies on pathological scarring related to regulation of macrophage behaviors by utilizing databases such as PubMed, Google Scholar and so on.

RESULTS

There are many studies proving that macrophages participate in the course of wound healing by converting their predominant phenotype. The potential of macrophages in managing hypertrophic scars and keloid lesions have been underscored.

CONCLUSION

Macrophage polarization offers new prevention strategies for pathological scarring. Learning about and targeting at macrophages may be helpful in achieving optimum wound healing.

Exploring the therapeutic potential of different sources of mesenchymal stem cells: a novel approach to combat burn wound infections

The most prevalent and harmful injuries are burns, which are still a major global health problem. Burn injuries can cause issues because they boost the inflammatory and metabolic response, which can cause organ malfunction and systemic failure. On the other hand, a burn wound infection creates an environment that is conducive to the growth of bacteria and might put the patient at risk for sepsis. In addition, scarring is unavoidable, and this results in patients having functional and cosmetic issues. Wound healing is an amazing phenomenon with a complex mechanism that deals with different types of cells and biomolecules. Cell therapy using stem cells is one of the most challenging treatment methods that accelerates the healing of burn wounds. Since 2000, the use of mesenchymal stem cells (MSCs) in regenerative medicine and wound healing has increased. They can be extracted from various tissues, such as bone marrow, fat, the umbilical cord, and the amniotic membrane. According to studies, stem cell therapy for burn wounds increases angiogenesis, has anti-inflammatory properties, slows the progression of fibrosis, and has an excellent ability to differentiate and regenerate damaged tissue. Figuring out the main preclinical and clinical problems that stop people from using MSCs and then suggesting the right ways to improve therapy could help show the benefits of MSCs and move stem cell-based therapy forward. This review's objective was to assess mesenchymal stem cell therapy's contribution to the promotion of burn wound healing.

Mesenchymal stem cell therapy using Pal-KTTKS-enriched carboxylated cellulose improves burn wound in rat model

Despite the great progress in developing wound dressings, delayed wound closure still remains a global challenge. Thus, developing novel wound dressings and employing advanced strategies, including tissue engineering, are urgently desired. The carboxylated cellulose was developed through the in situ synthesis method and further reinforced by incorporating pal-KTTKS to stimulate collagen synthesis and improve wound healing. The developed composites supported cell adhesion and proliferation and showed good biocompatibility. To boost wound-healing performance, adipose-derived mesenchymal stem cells (MSC) were seeded on the pal-KTTKS-enriched composites to be implanted in a rat model of burn wound healing. Healthy male rats were randomly divided into four groups and wound-healing performance of Vaseline gauze (control), carboxylated cellulose (CBC), pal-KTTKS-enriched CBC (KTTKS-CBC), and MSCs seeded on the KTTKS-CBC composites (MSC-KTTKS-CBC) were evaluated on days 3, 7, and 14 post-implantation. In each group, the designed therapeutic dressings were renewed every 5 days to increase wound-healing performance. We found that KTTKS-CBC and MSC-KTTKS-CBC composites exhibited significantly better wound healing capability, as evidenced by significantly alleviated inflammation, increased collagen deposition, improved angiogenesis, and considerably accelerated wound closure. Nevertheless, the best wound-healing performance was observed in the MSC-KTTKS-CBC groups among all four groups. This research suggests that the MSC-KTTKS-CBC composite offers a great deal of promise as a wound dressing to enhance wound regeneration and expedite wound closure in the clinic.

An ADSC-loaded dermal regeneration template promotes full-thickness wound healing

Introduction

Full-thickness wounds lead to delayed wound healing and scarring. Adipose-derived stem cell (ADSC) grafting promotes wound healing and minimizes scarring, but the low efficiency of grafting has been a challenge. We hypothesized that loading ADSCs onto a clinically widely used dermal regeneration template (DRT) would improve the efficacy of ADSC grafting and promote full-thickness wound healing.

Methods

ADSCs from human adipose tissue were isolated, expanded, and labeled with a cell tracker. Labeled ADSCs were loaded onto the DRT. The viability, the location of ADSCs on the DRT, and the abundance of ADSCs in the wound area were confirmed using CCK8 and fluorescence microscopy. Full-thickness wounds were created on Bama minipigs, which were applied with sham, ADSC, DRT, and ADSC-DRT. Wounds from the four groups were collected at the indicated time and histological analysis was performed. RNA-seq analysis was also conducted to identify transcriptional differences among the four groups. The identified genes by RNA-seq were verified by qPCR. Immunohistochemistry and western blotting were used to assess collagen deposition. In vitro, the supernatant of ADSCs was used to culture fibroblasts to investigate the effect of ADSCs on fibroblast transformation into myofibroblasts.

Results

ADSCs were successfully isolated, marked, and loaded onto the DRT. The abundance of ADSCs in the wound area was significantly greater in the ADSC-DRT group than in the ADSC group. Moreover, the ADSC-DRT group exhibited better wound healing with improved re-epithelialization and denser collagen deposition than the other three groups. The RNA-seq results suggested that the application of the integrated ADSC-DRT system resulted in the differential expression of genes mainly associated with extracellular matrix remodeling. In vivo, wounds from the ADSC-DRT group exhibited an earlier increase in type III collagen deposition and alleviated scar formation. ADSCs inhibited the transformation of fibroblasts into myofibroblasts, along with increased levels of CTGF, FGF, and HGF in the supernatant of ADSCs. Wounds from the ADSC-DRT group had up-regulated expressions of CTGF, HGF, FGF, and MMP3.

Conclusion

The integral of ADSC-DRT increased the efficacy of ADSC grafting, and promoted full-thickness wound healing with better extracellular matrix remodeling and alleviated scar formation.

Revolutionizing dermatology: harnessing mesenchymal stem/stromal cells and exosomes in 3D platform for skin regeneration

Contemporary trends reveal an escalating interest in regenerative medicine-based interventions for addressing refractory skin defects. Conventional wound healing treatments, characterized by high costs and limited efficacy, necessitate a more efficient therapeutic paradigm to alleviate the economic and psychological burdens associated with chronic wounds. Mesenchymal stem/stromal cells (MSCs) constitute cell-based therapies, whereas cell-free approaches predominantly involve the utilization of MSC-derived extracellular vesicles or exosomes, both purportedly safe and effective. Exploiting the impact of MSCs by paracrine signaling, exosomes have emerged as a novel avenue capable of positively impacting wound healing and skin regeneration. MSC-exosomes confer several advantages, including the facilitation of angiogenesis, augmentation of cell proliferation, elevation of collagen production, and enhancement of tissue regenerative capacity. Despite these merits, challenges persist in clinical applications due to issues such as poor targeting and facile removal of MSC-derived exosomes from skin wounds. Addressing these concerns, a three-dimensional (3D) platform has been implemented to emend exosomes, allowing for elevated levels, and constructing more stable granules possessing distinct therapeutic capabilities. Incorporating biomaterials to encapsulate MSC-exosomes emerges as a favorable approach, concentrating doses, achieving intended therapeutic effectiveness, and ensuring continual release. While the therapeutic potential of MSC-exosomes in skin repair is broadly recognized, their application with 3D biomaterial scenarios remains underexplored. This review synthesizes the therapeutic purposes of MSCs and exosomes in 3D for the skin restoration, underscoring their promising role in diverse dermatological conditions. Further research may establish MSCs and their exosomes in 3D as a viable therapeutic option for various skin conditions.

Three-dimensional bioprinting of tissue-engineered skin: Biomaterials, fabrication techniques, challenging difficulties, and future directions: A review

As an emerging new manufacturing technology, Three-dimensional (3D) bioprinting provides the potential for the biomimetic construction of multifaceted and intricate architectures of functional integument, particularly functional biomimetic dermal structures inclusive of cutaneous appendages. Although the tissue-engineered skin with complete biological activity and physiological functions is still cannot be manufactured, it is believed that with the advances in matrix materials, molding process, and biotechnology, a new generation of physiologically active skin will be born in the future. In pursuit of furnishing readers and researchers involved in relevant research to have a systematic and comprehensive understanding of 3D printed tissue-engineered skin, this paper furnishes an exegesis on the prevailing research landscape, formidable obstacles, and forthcoming trajectories within the sphere of tissue-engineered skin, including: (1) the prevalent biomaterials (collagen, chitosan, agarose, alginate, etc.) routinely employed in tissue-engineered skin, and a discerning analysis and comparison of their respective merits, demerits, and inherent characteristics; (2) the underlying principles and distinguishing attributes of various current printing methodologies utilized in tissue-engineered skin fabrication; (3) the present research status and progression in the realm of tissue-engineered biomimetic skin; (4) meticulous scrutiny and summation of the extant research underpinning tissue-engineered skin inform the identification of prevailing challenges and issues.

Decellularized Placental Sponge Seeded with Human Mesenchymal Stem Cells Improves Deep Skin Wound Healing in the Animal Model

Skin injuries lead to a large burden of morbidity. Although numerous clinical and scientific strategies have been investigated to repair injured skin, optimal regeneration therapy still poses a considerable obstacle. To address this challenge, decellularized extracellular matrix-based scaffolds recellularized with stem cells offer significant advancements in skin regeneration and wound healing. Herein, a decellularized human placental sponge (DPS) was fabricated using the decellularization and freeze-drying technique and then recellularized with human adipose-derived mesenchymal cells (MSCs). The biological and biomechanical properties and skin full-thickness wound healing capacity of the stem cells-DPS constructs were investigated in vitro and in vivo. The DPS exhibited a uniform 3D microstructure with an interconnected pore network, 89.21% porosity, a low degradation rate, and good mechanical properties. The DPS and MSCs-DPS constructs were implanted in skin full-thickness wound models in mice. An accelerated wound healing was observed in the wounds implanted with the MSCs-DPS construct when compared to DPS and control (wounds with no treatment) during 7 and 21 days postimplantation follow-up. In the MSCs-DPS group, the wound was completely re-epithelialized, the epidermis layer was properly organized, and the dermis and epidermis' bilayer structures were restored after 7 days. Our findings suggest that DPS is an excellent carrier for MSC culture and delivery to skin wounds and now promises to proceed with clinical evaluations.

Targeting estrogen signaling and biosynthesis for aged skin repair

Non-healing skin wounds are disproportionally prevalent in older adults. Current treatments do not account for the particularities of aged skin and result in inadequate outcomes. Overall, healing chronic wounds in the elderly remains a major unmet clinical need. Estrogens play a critical role in reproduction but also have important actions in non-reproductive organs. Estrogen biosynthesis and signaling pathways are locally activated during physiological wound healing, processes that are inhibited in elderly estrogen-deprived skin. Estrogen deprivation has been shown to be a critical mediator of impaired wound healing in both postmenopausal women and aged men, and topical estrogen application reverses age-associated delayed wound healing in both elderly men and women. These data indicate that adequate estrogen biosynthesis and properly regulated estrogen signaling pathways are essential for normal wound healing and can be targeted to optimize tissue repair in the elderly. However, due to fundamental questions regarding how to safely restore estrogen signaling locally in skin wounds, there are currently no therapeutic strategies addressing estrogen deficiency in elderly chronic wounds. This review discusses established and recent literature in this area and proposes the hypothesis that estrogen plays a pleiotropic role in skin aging and that targeting estrogen signaling and biosynthesis could promote skin repair in older adults.

Supporting wound healing by mesenchymal stem cells (MSCs) therapy in combination with scaffold, hydrogel, and matrix; State of the art

Non-healing wounds impose a huge annual cost on the survival of different countries and large populations in the world. Wound healing is a complex and multi-step process, the speed and quality of which can be changed by various factors. To promote wound healing, compounds such as platelet-rich plasma, growth factors, platelet lysate, scaffolds, matrix, hydrogel, and cell therapy, in particular, with mesenchymal stem cells (MSCs) are suggested. Nowadays, the use of MSCs has attracted a lot of attention. These cells can induce their effect by direct effect and secretion of exosomes. On the other hand, scaffolds, matrix, and hydrogels provide suitable conditions for wound healing and the growth, proliferation, differentiation, and secretion of cells. In addition to generating suitable conditions for wound healing, the combination of biomaterials and MSCs increases the function of these cells at the site of injury by favoring their survival, proliferation, differentiation, and paracrine activity. In addition, other compounds such as glycol, sodium alginate/collagen hydrogel, chitosan, peptide, timolol, and poly(vinyl) alcohol can be used along with these treatments to increase the effectiveness of treatments in wound healing. In this review article, we take a glimpse into the merging scaffolds, hydrogels, and matrix application with MSCs therapy to favor wound healing.

Assessment of the quality of the healing process in experimentally induced skin lesions treated with autologous platelet concentrate associated or unassociated with allogeneic mesenchymal stem cells: preliminary results in a large animal model

Regenerative medicine for the treatment of skin lesions is an innovative and rapidly developing field that aims to promote wound healing and restore the skin to its original condition before injury. Over the years, different topical treatments have been evaluated to improve skin wound healing and, among them, mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) have shown promising results for this purpose. This study sought to evaluate the quality of the healing process in experimentally induced full-thickness skin lesions treated with PRP associated or unassociated with MSCs in a sheep second intention wound healing model. After having surgically created full-thickness wounds on the back of three sheep, the wound healing process was assessed by performing clinical evaluations, histopathological examinations, and molecular analysis. Treated wounds showed a reduction of inflammation and contraction along with an increased re-epithelialization rate and better maturation of the granulation tissue compared to untreated lesions. In particular, the combined treatment regulated the expression of collagen types I and III resulting in a proper resolution of the granulation tissue contrary to what was observed in untreated wounds; moreover, it led to a better maturation and organization of skin adnexa and collagen fibers in the repaired skin compared to untreated and PRP-treated wounds. Overall, both treatments improved the wound healing process compared to untreated wounds. Wounds treated with PRP and MSCs showed a healing progression that qualitatively resembles a restitutio ad integrum of the repaired skin, showing features typical of a mature healthy dermis.

Wound healing by transplantation of mesenchymal stromal cells loaded on polyethylene terephthalate scaffold: Implications for skin injury treatment

BACKGROUND

Several clinical studies have shown that cellular therapy based on mesenchymal stromal cells (MSCs) transplantation may accelerate wound healing. One major challenge is the delivery system used for MSCs transplantation. In this work, we evaluated the capacity of a scaffold based on polyethylene terephthalate (PET) to maintain the viability and biological functions of MSCs, in vitro. We examined the capacity of MSCs loaded on PET (MSCs/PET) to induce wound healing in an experimental model of full-thickness wound.

METHODS

Human MSCs were seeded and cultured on PET membranes at 37 °C for 48 h. Adhesion, viability, proliferation, migration, multipotential differentiation and chemokine production were evaluated in cultures of MSCs/PET. The possible therapeutic effect of MSCs/PET on the re-epithelialization of full thickness wounds was examined at day 3 post-wounding in C57BL/6 mice. Histological and immunohistochemical (IH) studies were performed to evaluate wound re-epithelialization and the presence of epithelial progenitor cells (EPC). As controls, wounds without treatment or treated with PET were established.

RESULTS

We observed MSCs adhered to PET membranes and maintained their viability, proliferation and migration. They preserved their multipotential capacity of differentiation and ability of chemokine production. MSCs/PET implants promoted an accelerated wound re-epithelialization, after three days post-wounding. It was associated with the presence of EPC Lgr6⁺ and K6⁺.

DISCUSSION

Our results show that MSCs/PET implants induce a rapid re-epithelialization of deep- and full-thickness wounds. MSCs/PET implants constitute a potential clinical therapy for treating cutaneous wounds.

Novel strategies for designing regenerative skin products for accelerated wound healing

Healthy skin protects from pathogens, water loss, ultraviolet rays, and also maintains homeostasis conditions along with sensory perceptions in normal circumstances. Skin wound healing mechanism is a multi-phased biodynamic process that ultimately triggers intercellular and intracellular mechanisms. Failure to implement the normal and effective healing process may result in chronic injuries and aberrant scarring. Chronic wounds lead to substantial rising healthcare expenditure, and innovative methods to diagnose and control severe consequences are urgently needed. Skin tissue engineering (STE) has achieved several therapeutic accomplishments during the last few decades, demonstrating tremendous development. The engineered skin substitutes provide instant coverage for extensive wounds and facilitate the prevention of microbial infections and fluid loss; furthermore, they help in fighting inflammation and allow rapid neo-tissue formation. The current review primarily focused on the wound recovery and restoration process and the current conditions of STE with various advancements and complexities associated with different strategies such as cell sources, biopolymers, innovative fabrication techniques, and growth factors delivery systems.

Urine-Derived Stem Cells for Epithelial Tissues Reconstruction and Wound Healing

Epithelial tissue injury can occur on any surface site of the body, particularly in the skin or urethral mucosa tissue, due to trauma, infection, inflammation, and toxic compounds. Both internal and external body epithelial tissue injuries can significantly affect patients’ quality of life, increase healthcare spending, and increase the global economic burden. Transplantation of epithelial tissue grafts is an effective treatment strategy in clinical settings. Autologous bio-engineered epithelia are common clinical skin substitutes that have the specific advantages of avoiding tissue rejection, obviating ethical concerns, reducing the risk of infection, and decreasing scarring compared to donor grafts. However, epithelial cells are often obtained from the individual’s skin and mucosa through invasive methods, which cause further injury or damage. Urine-derived stem cells (USC) of kidney origin, obtained via non-invasive acquisition, possess high stemness properties, self-renewal ability, trophic effects, multipotent differentiation potential, and immunomodulatory ability. These cells show versatile potential for tissue regeneration, with extensive evidence supporting their use in the repair of epidermal and urothelial injuries. We discuss the collection, isolation, culture, characterization, and differentiation of USC. We also discuss the use of USC for cellular therapies as well as the administration of USC-derived paracrine factors for epidermal and urothelial tissue repair. Specifically, we will discuss 3D constructions involving multiple types of USC-loaded hydrogels and USC-seeded scaffolds for use in cosmetic production testing, drug development, and disease modeling. In conclusion, urine-derived stem cells are a readily accessible autologous stem cell source well-suited for developing personalized medical treatments in epithelial tissue regeneration and drug testing.

Stem Cell-Based Tissue Engineering for the Treatment of Burn Wounds: A Systematic Review of Preclinical Studies

Burn wounds are a devastating type of skin injury leading to severe impacts on both patients and the healthcare system. Current treatment methods are far from ideal, driving the need for tissue engineered solutions. Among various approaches, stem cell-based strategies are promising candidates for improving the treatment of burn wounds. A thorough search of the Embase, Medline, Scopus, and Web of Science databases was conducted to retrieve original research studies on stem cell-based tissue engineering treatments tested in preclinical models of burn wounds, published between January 2009 and June 2021. Of the 347 articles retrieved from the initial database search, 33 were eligible for inclusion in this review. The majority of studies used murine models with a xenogeneic graft, while a few used the porcine model. Thermal burn was the most commonly induced injury type, followed by surgical wound, and less commonly radiation burn. Most studies applied stem cell treatment immediately post-burn, with final endpoints ranging from 7 to 90 days. Mesenchymal stromal cells (MSCs) were the most common stem cell type used in the included studies. Stem cells from a variety of sources were used, most commonly from adipose tissue, bone marrow or umbilical cord, in conjunction with an extensive range of biomaterial scaffolds to treat the skin wounds. Overall, the studies showed favourable results of skin wound repair in animal models when stem cell-based tissue engineering treatments were applied, suggesting that such strategies hold promise as an improved therapy for burn wounds.

Enhancing Stem Cell-Based Therapeutic Potential by Combining Various Bioengineering Technologies

Stem cell-based therapeutics have gained tremendous attention in recent years due to their wide range of applications in various degenerative diseases, injuries, and other health-related conditions. Therapeutically effective bone marrow stem cells, cord blood- or adipose tissue-derived mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and more recently, induced pluripotent stem cells (iPSCs) have been widely reported in many preclinical and clinical studies with some promising results. However, these stem cell-only transplantation strategies are hindered by the harsh microenvironment, limited cell viability, and poor retention of transplanted cells at the sites of injury. In fact, a number of studies have reported that less than 5% of the transplanted cells are retained at the site of injury on the first day after transplantation, suggesting extremely low (<1%) viability of transplanted cells. In this context, 3D porous or fibrous national polymers (collagen, fibrin, hyaluronic acid, and chitosan)-based scaffold with appropriate mechanical features and biocompatibility can be used to overcome various limitations of stem cell-only transplantation by supporting their adhesion, survival, proliferation, and differentiation as well as providing elegant 3-dimensional (3D) tissue microenvironment. Therefore, stem cell-based tissue engineering using natural or synthetic biomimetics provides novel clinical and therapeutic opportunities for a number of degenerative diseases or tissue injury. Here, we summarized recent studies involving various types of stem cell-based tissue-engineering strategies for different degenerative diseases. We also reviewed recent studies for preclinical and clinical use of stem cell-based scaffolds and various optimization strategies.

Integra Dermal Regeneration Template in reconstructive surgery for cutaneous tumours: a two-year retrospective review

OBJECTIVE

Integra Dermal Regeneration Template (IDRT) (Integra LifeSciences, US) is a bioengineered dermal matrix that has been widely used in burn reconstruction since its first description. However, little is reported on its use in oncologic dermatological defects. Our objective was to evaluate reconstruction using IDRT on cutaneous tumour defects.

METHOD

We conducted a two-year retrospective review of patients with skin tumours who had an excision surgery, followed by reconstruction with IDRT, as a mid-step towards a final autograft procedure: a split-thickness skin graft. The records of all patients at a single academic institution were queried from the electronic medical record using data obtained from the operating surgeon.

RESULTS

We identified 13 patients with different tumour types and locations. The mean defect size was 105.92cm². The matrix take rate was 92.3% and average postoperative day for definite autograft was 20 days. Patients were followed for a period of up to 12 months. Of the patients, one had exposed bone without periosteum; another patient showed recurrence six months after matrix placement, requiring a new second two-stage IDRT-autograft procedure before radiation therapy. Patients reported complete satisfaction with the cosmetic, functional and oncological results. No cases of infection were encountered.

CONCLUSION

IDRT is a valid option for the reconstruction of oncologic surgical defects of the skin and can be used in different anatomical locations. Specifically, it is an alternative to the reconstructive ladder when grafts and local flaps are not possible in those patients, and an option for patients who will eventually need adjuvant radiotherapy.

The application of mesenchymal stromal cells (MSCs) and their derivative exosome in skin wound healing: a comprehensive review

Recently, mesenchymal stromal cells (MSCs) and also their exosome has become a game-changing tool in the context of tissue engineering and regenerative medicine. MSCs due to their competencies to establish skin cells, such as fibroblast and keratinocyte, and also their unique attribute to suppress inflammation in wound site has attracted increasing attention among scholars. In addition, MSC's other capabilities to induce angiogenesis as a result of secretion of pro-angiogenic factors accompanied with marked anti-fibrotic activities, which mainly mediated by the releases matrix metalloproteinase (MMPs), make them a rational and effective strategy to accelerate wound healing with a small scar. Since the chief healing properties of the MSCs depend on their paracrine effects, it appears that MSCs-derived exosomes also can be an alternative option to support wound healing and skin regeneration as an innovative cell-free approach. Such exosomes convey functional cargos (e.g., growth factor, cytokine, miRNA, etc.) from MSCs to target cells, thereby affecting the recipient skin cells' biological events, such as migration, proliferation, and also secretion of ECM components (e.g., collagen). The main superiorities of exosome therapy over parental MSCs are the diminished risk of tumor formation and also lower immunogenicity. Herein, we deliver an overview of recent in vivo reports rendering the therapeutic benefits of the MSCs-based therapies to ease skin wound healing, and so improving quality of life among patients suffering from such conditions.

MSCs and their exosomes: a rapidly evolving approach in the context of cutaneous wounds therapy

Currently, mesenchymal stem/stromal stem cell (MSC) therapy has become a promising option for accelerating cutaneous wound healing. In vivo reports have outlined the robust competences of MSCs to offer a solid milieu by inhibition of inflammatory reactions, which in turn, enables skin regeneration. Further, due to their great potential to stimulate angiogenesis and also facilitate matrix remodeling, MSCs hold substantial potential as future therapeutic strategies in this context. The MSCs-induced wound healing is thought to mainly rely on the secretion of a myriad of paracrine factors in addition to their direct differentiation to skin-resident cells. Besides, MSCs-derived exosomes as nanoscale and closed membrane vesicles have recently been suggested as an effective and cell-free approach to support skin regeneration, circumventing the concerns respecting direct application of MSCs. The MSCs-derived exosomes comprise molecular components including lipid, proteins, DNA, microRNA, and also mRNA, which target molecular pathways and also biological activities in recipient cells (e.g., endothelial cell, keratinocyte, and fibroblast). The secreted exosome modifies macrophage activation, stimulates angiogenesis, and instigates keratinocytes and dermal fibroblast proliferations as well as migrations concurrently regulate inherent potential of myofibroblast for adjustment of turnover of the ECM. In the present review, we will focus on the recent findings concerning the application of MSCs and their derivative exosome to support wound healing and skin regeneration, with special focus on last decade in vivo reports.

The Role of MSC in Wound Healing, Scarring and Regeneration

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.

Evaluating the Effect of Integra Seeded with Adipose Tissue-Derived Stem Cells or Fibroblasts in Wound Healing

BACKGROUND

Extensive loss of skin in burn patients can have devastating consequences, both physically and mentally. Adipose-Derived Stem Cells (ADSCs) and fibroblasts are known to play significant roles in the process of wound healing. Recently, bioengineered skin has been considered for wound healing purposes.

METHODS

Investigate the effect of Integra seeded with ADSCs, fibroblasts, or both on wound healing.

RESULTS

We found that when Integra is seeded with ADSCs and fibroblasts, both types of cells incorporate and proliferate, the phenomenon becoming more robust when the cells are co-cultured on Integra, both in vitro; and in vivo;. In addition, when these cells are seeded on Integra, they stimulate epithelization with no signs of inflammation and skin necrosis being observed when transplanted on animals for 7 days.

CONCLUSION

ADSCs and fibroblasts seeded on Integra could decrease the number of α-SMA positive myofibroblasts, leading to scarless wound healing. The evidence from this study is strongly supportive that Integra seeded with ADSCs and fibroblasts is an appropriate and effective bioengineered skin for wound healing.

Human Spheroids from Adipose-Derived Stem Cells Induce Calvarial Bone Production in a Xenogeneic Rabbit Model

ABSTRACT

Calvarial defects can result from several causes. Tissue engineering hold the potential to restore native form and protective function. We have recently shown that stemness and differentiation ability of spheroids from adipose-derived stem cells (S-ASCs) promotes osteoblasts growth within Integra in a small vertebral lesion. In our study, we aimed to test osteogenic potential of S-ASCs in aiding regeneration of a calvarial defect. Groups containing Integra showed increased bone regeneration at the calvarial defect-Integra interface compared with the control group. In particular, S-ASC-derived osteoblasts group showed a superior calvarial remodeling than undifferentiated S-ASCs group. Clusters of ossification were observed in these both groups with enhanced microvasculature density and fibrosis. In conclusion, seeding of S-ASCs in dermal regeneration templates enhanced bone healing in a rabbit calvarial defect model. These findings could prompt the elective use of S-ASCs with enhanced multilineage differentiation potential for tissue engineering purposes.

The Use of Umbilical Cord-derived Mesenchymal Stem Cells Seeded Fibrin Matrix in the Treatment of Stage IV Acute Graft-Versus-Host Disease Skin Lesions in Pediatric Hematopoietic Stem Cell Transplant Patients

Mesenchymal stem cells (MSCs) have been used systemically or locally in many chronic and nonhealing skin lesions in recent years. In this study, umbilical cord-derived MSCs (UC-MSCs)-seeded fibrin matrix was used as a wound dressing in pediatric patients with stage 4 acute graft-versus-host disease (aGVHD)-induced desquamated skin lesions. This is the first study in which the UC-MSCs-seeded fibrin matrix was used as a wound dressing in aGVHD. A total of 14 times the MSCs-seeded fibrin matrix were applied to 9 patients as a wound dressing. On the seventh day, epithelialization and clinical response were evaluated. According to the size of the skin defect min: 1, max: 6 pieces were applied at a time. After 48 to 72 hours, it was observed that all of the MSCs-seeded fibrin matrixes adhered to the skin and the crustation started in 6 (43%) applications, whereas liquefaction was detected under all of them in 7 (50%) applications. Complete response was obtained in 6 applications (43%), partial response in 1 (7%), and no response in 7 applications (50%). This study showed that the MSCs-seeded fibrin matrix can be used effectively and safely in the matrix in the local treatment of aGVHD-induced skin wounds in pediatric patients.

Efficacy of topical and systemic transplantation of mesenchymal stem cells in a rat model of diabetic ischemic wounds

BACKGROUND

Mesenchymal stem cells (MSCs) exert positive effects in chronic wounds. However, critical parameters, such as the most effective administration routes, remain unclear. Accordingly, the purpose of this study was to compare the effects of topical and systemic transplantation MSCs on diabetic ischemic wound healing and explored the underlying mechanisms.

METHOD

A diabetic ischemic wound model was created on the dorsal foot of type 2 diabetes mellitus (T2DM) rat. Bone marrow-derived mesenchymal stem cells (BM-MSCs) were administered via two routes: topical injection and intravenous (IV) infusion. Wound healing outcomes and blood glucose level were assessed dynamically. Meanwhile, blood flow recovery was evaluated in ischemic gastrocnemius muscles. The homing and transdifferentiation of mKate2-labeled BM-MSCs were assessed by fluorescence imaging and immunohistochemistry (IHC) analysis.

RESULT

Both topical and systemic treatments had a positive effect on the diabetic ischemic wound showing a significant reduction in wound area at day 14. Histological results showed an increase in the length of epithelial edges, collagen content, microvessel density in the wound bed, and a higher expression of vascular endothelial growth factor (VEGF). Meanwhile, systemic administration can ameliorate hyperglycemia and improve the blood perfusion of the ischemic hindlimb. BM-MSCs administered systemically were found distributed in wounded tissue and transdifferentiated into endothelial cells. Furthermore, BM-MSCs stimulated angiogenesis at wound sites by downregulating phosphatase and tensin homolog (PTEN) and activation of AKT signaling pathway.

CONCLUSIONS

The results demonstrated that both transplantation delivery method (topical and systemic) of BM-MSCs accelerated wound healing remarkably under pathological conditions. Nevertheless, systemic administration has the potential to ameliorate hyperglycemia and repair the damaged tissue.

Skin regeneration is accelerated by a lower dose of multipotent mesenchymal stromal/stem cells-a paradigm change

Background

Multipotent mesenchymal stromal/stem cell (MSC) therapy is under investigation in promising (pre-)clinical trials for wound healing, which is crucial for survival; however, the optimal cell dosage remains unknown. The aim was to investigate the efficacy of different low-to-high MSC dosages incorporated in a biodegradable collagen-based dermal regeneration template (DRT) Integra®.

Methods

We conducted a porcine study (N = 8 Yorkshire pigs) and seeded between 200 and 2,000,000 cells/cm² of umbilical cord mesenchymal stromal/stem cells on the DRT and grafted it onto full-thickness burn excised wounds. On day 28, comparisons were made between the different low-to-high cell dose groups, the acellular control, a burn wound, and healthy skin.

Result

We found that the low dose range between 200 and 40,000 cells/cm² regenerates the full-thickness burn excised wounds most efficaciously, followed by the middle dose range of 200,000–400,000 cells/cm² and a high dose of 2,000,000 cells/cm². The low dose of 40,000 cells/cm² accelerated reepithelialization, reduced scarring, regenerated epidermal thickness superiorly, enhanced neovascularization, reduced fibrosis, and reduced type 1 and type 2 macrophages compared to other cell dosages and the acellular control.

Conclusion

This regenerative cell therapy study using MSCs shows efficacy toward a low dose, which changes the paradigm that more cells lead to better wound healing outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02131-6.

The application of bone marrow mesenchymal stem cells and biomaterials in skeletal muscle regeneration

Skeletal muscle injuries have bothered doctors and caused great burdens to the public medical insurance system for a long time. Once injured, skeletal muscles usually go through the processes of inflammation, repairing and remodeling. If repairing and remodeling stages are out of balance, scars will be formed to replace injured skeletal muscles. At present, clinicians usually use conventional methods to restore the injured skeletal muscles, such as flap transplantation. However, flap transplantation sometimes needs to sacrifice healthy autologous tissues and will bring extra harm to patients. In recent years, stem cells-based tissue engineering provides us new treatment ideas for skeletal muscle injuries. Stem cells are cells with multiple differentiation potential and have ability to differentiate into adult cells under special condition. Skeletal muscle tissues also have stem cells, called satellite cells, but they are in small amount and new muscle fibers that derived from them may not be enough to replace injured fibers. Bone marrow mesenchymal stem cells (BM-MSCs) could promote musculoskeletal tissue regeneration and activate the myogenic differentiation of satellite cells. Biomaterial is another important factor to promote tissue regeneration and greatly enhance physiological activities of stem cells in vivo. The combined use of stem cells and biomaterials will gradually become a mainstream to restore injured skeletal muscles in the future. This review article mainly focuses on the review of research about the application of BM-MSCs and several major biomaterials in skeletal muscle regeneration over the past decades.

Combined Treatment With CCR1-Overexpressing Mesenchymal Stem Cells and CCL7 Enhances Engraftment and Promotes the Recovery of Simulated Birth Injury-Induced Stress Urinary Incontinence in Rats

Objective: To observe whether urethral injection of chemokine (c-c motif) ligand 7 (CCL7) and overexpressing CC receptor 1 (CCR1) in mesenchymal stem cells (MSCs) can promote their homing and engraftment to the injured tissue, and improve the recovery of simulated birth injury-induced stress urinary incontinence (SUI) in rats.

Methods: Female rats underwent a dual injury consisting of vaginal distension (VD) and pudendal nerve crush (PNC) to induce SUI. Bone marrow-derived MSCs were transduced with lentivirus carrying CCR1 (MSC-CCR1) and green fluorescent protein (GFP). Forty virgin Sprague–Dawley rats were evenly distributed into four groups: sham SUI + MSC-CCR1+CCL7, SUI + MSCs, SUI + MSC-CCR1, and SUI + MSC-CCR1+CCL7 group. The engrafted MSCs in urethra were quantified. Another three groups of rats, including sham SUI + sham MSC-CCR1+CCL7 treatment, SUI + sham MSC-CCR1+CCL7 treatment, and SUI + MSC-CCR1+CCL7 treatment group, were used to evaluate the functional recovery by testing external urethral sphincter electromyography (EUS EMG), pudendal nerve motor branch potentials (PNMBP), and leak point pressure (LPP) 1 week after injury and injection. Urethra and vagina were harvested for histological examination.

Results: The SUI + MSC-CCR1+CCL7 group received intravenous injection of CCR1-overexpressing MSCs and local injection of CCL7 after simulated birth injury had the most engraftment of MSCs to the injured tissues and best functional recovery from SUI compared to other groups. Histological examination showed a partial repair in the SUI + MSC-CCR1+CCL7 group.

Conclusions: Our study demonstrated combined treatment with CCR1-overexpressing MSCs and CCL7 can increase engraftment of MSCs and promote the functional recovery of simulated birth trauma-induced SUI in rats, which could be a new therapeutic strategy for SUI.

Mesenchymal Stem Cells for Chronic Wound Healing: Current Status of Preclinical and Clinical Studies

Healing skin wounds with anatomic and functional integrity, especially under chronic pathological conditions, remain an enormous challenge. Due to their outstanding regenerative potential, mesenchymal stem cells (MSCs) have been explored in many studies to determine the healing ability for difficult-to-treat diseases. In this article, we review current animal studies and clinical trials of MSC-based therapy for chronic wounds, and discuss major challenges that confront future clinical applications. We found that a wealth of animal studies have revealed the versatile roles and the benefits of MSCs for chronic wound healing. MSC treatment results in enhanced angiogenesis, facilitated reepithelialization, improved granulation, and accelerated wound closure. There are some evidences of the transdifferentiation of MSCs into skin cells. However, the healing effect of MSCs depends primarily on their paracrine actions, which alleviate the harsh microenvironment of chronic wounds and regulate local cellular responses. Consistent with the findings of preclinical studies, some clinical trials have shown improved wound healing after transplantation of MSCs in chronic wounds, mainly lower extremity ulcers, pressure sores, and radiation burns. However, there are some limitations in these clinical trials, especially a small number of patients and imperfect methodology. Therefore, to better define the safety and efficiency of MSC-based wound therapy, large-scale controlled multicenter trials are needed in the future. In addition, to build a robust pool of clinical evidence, standardized protocols, especially the cultivation and quality control of MSCs, are recommended. Altogether, based on current data, MSC-based therapy represents a promising treatment option for chronic wounds. Impact statement Chronic wounds persist as a significant health care problem, particularly with increasing number of patients and the lack of efficient treatments. The main goal of this article is to provide an overview of current status of mesenchymal stem cell (MSC)-based therapy for chronic wounds. The roles of MSCs in skin wound healing, as revealed in a large number of animal studies, are detailed. A critical view is made on the clinical application of MSCs for lower extremity ulcers, pressure sores, and radiation burns. Main challenges that confront future clinical applications are discussed, which hopefully contribute to innovations in MSC-based wound treatment.

Macrophages promote network formation and maturation of transplanted adipose tissue-derived microvascular fragments

Adipose tissue–derived microvascular fragments rapidly reassemble into microvascular networks within implanted scaffolds. Herein, we analyzed the contribution of macrophages to this process. C57BL/6 mice received clodronate (clo)-containing liposomes for macrophage depletion, whereas animals treated with phosphate-buffered-saline-containing liposomes served as controls. Microvascular fragments were isolated from clo- and phosphate-buffered-saline-treated donor mice and seeded onto collagen–glycosaminoglycan matrices, which were implanted into dorsal skinfold chambers of clo- and phosphate-buffered-saline-treated recipient mice. The implants’ vascularization and incorporation were analyzed by stereomicroscopy, intravital fluorescence microscopy, histology, and immunohistochemistry. Compared to controls, matrices within clo-treated animals exhibited a significantly reduced functional microvessel density. Moreover, they contained a lower fraction of microvessels with an α-smooth muscle actin (SMA)⁺ cell layer, indicating impaired vessel maturation. This was associated with a deteriorated implant incorporation. These findings demonstrate that macrophages not only promote the reassembly of microvascular fragments into microvascular networks, but also improve their maturation during this process.

Mesenchymal stromal cells from dermal and adipose tissues induce macrophage polarization to a pro-repair phenotype and improve skin wound healing

The process of wound healing restores skin homeostasis but not full functionality; thus, novel therapeutic strategies are needed to accelerate wound closure and improve the quality of healing. In this context, tissue engineering and cellular therapies are promising approaches. Although sharing essential characteristics, mesenchymal stromal cells (MSCs) isolated from different tissues might have distinct properties. Therefore, the aim of this study was to comparatively investigate, by a mouse model in vivo assay, the potential use of dermal-derived MSCs (DSCs) and adipose tissue-derived MSCs (ASCs) in improving skin wound healing. Human DSCs and ASCs were delivered to full-thickness mouse wounds by a collagen-based scaffold (Integra Matrix). We found that the association of both DSCs and ASCs with the Integra accelerated wound closure in mice compared with the biomaterial only (control). Both types of MSCs stimulated angiogenesis and extracellular matrix remodeling, leading to better quality scars. However, the DSCs showed smaller scar size,superior extracellular matrix deposition, and greater number of cutaneous appendages. Besides, DSCs and ASCs reduced inflammation by induction of macrophage polarization from a pro-inflammatory (M1) to a pro-repair (M2) phenotype. In conclusion, both DSCs and ASCs were able to accelerate the healing of mice skin wounds and promote repair with scars of better quality and more similar to healthy skin than the empty scaffold. DSCs associated with Integra induced superior overall results than the Integra alone, whereas scaffolds with ASCs showed an intermediate effect, often not significantly better than the empty biomaterial.

A 3-Dimensional Bioprinted Scaffold With Human Umbilical Cord Blood-Mesenchymal Stem Cells Improves Regeneration of Chronic Full-Thickness Rotator Cuff Tear in a Rabbit Model

BACKGROUND

Chronic full-thickness rotator cuff tears (FTRCTs) represent a major clinical concern because they show highly compromised healing capacity.

PURPOSE

To evaluate the efficacy of using a 3-dimensional (3D) bioprinted scaffold with human umbilical cord blood (hUCB)-mesenchymal stem cells (MSCs) for regeneration of chronic FTRCTs in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 rabbits were randomly assigned to 4 treatment groups (n = 8 per group) at 6 weeks after a 5-mm FTRCT was created on the supraspinatus tendon. Group 1 (G1-SAL) was transplanted with normal saline. Group 2 (G2-MSC) was transplanted with hUCB-MSCs (0.2 mL, 1 × 10⁶) into FTRCTs. Group 3 (G3-3D) was transplanted with a 3D bioprinted construct without MSCs, and group 4 (G4-3D+MSC) was transplanted with a 3D bioprinted construct containing hUCB-MSCs (0.2 mL, 1 × 10⁶ cells) into FTRCTs. All 32 rabbits were euthanized at 4 weeks after treatment. Examination of gross morphologic changes and histologic results was performed on all rabbits after sacrifice. Motion analysis was also performed before and after treatment.

RESULTS

In G4-3D+MSC, newly regenerated collagen type 1 fibers, walking distance, fast walking time, and mean walking speed were greater than those in G2-MSC based on histochemical and motion analyses. In addition, when compared with G3-3D, G4-3D+MSC showed more prominent regenerated tendon fibers and better parameters of motion analysis. However, there was no significant difference in gross tear size among G2-MSC, G3-3D, and G4-3D+MSC, although these groups showed significant decreases in tear size as compared with the control group (G1-SAL).

CONCLUSION

Findings of this study show that a tissue engineering strategy based on a 3D bioprinted scaffold filled with hUCB-MSCs can improve the microenvironment for regenerative processes of FTRCT without any surgical repair.

CLINICAL RELEVANCE

In the case of rotator cuff tear, the cell loss of the external MSCs can be increased by exposure to synovial fluid. Therefore, a 3D bioprinted scaffold in combination with MSCs without surgical repair may be effective in increasing cell retention in FTRCT.

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.

Ultrasmall CuS@BSA nanoparticles with mild photothermal conversion synergistically induce MSCs-differentiated fibroblast and improve skin regeneration

Mesenchymal stem cell (MSC)-based therapies have been used in skin regeneration due to their ability to differentiate into many cells, promote cytokine secretion and participate in collagen deposition. In this study, we concluded that a CuS@BSA nanoparticles exhibited similar potential in inducing MSCs differentiation to fibroblasts as Cu ions for wound healing.

Methods: First, we verified the photothermal efficiency of CuS@BSA in vivo and vitro and had no cytotoxicity for MSCs when the temperature was controlled at 42 °C by adjusting the power of irradiation at 980 nm. And then we detected the expression of vimentin in MSCs, which further directed the MSCs to fibroblasts through Western blotting and Immunofluorescence when treated with CuS@BSA or pre-heat at 42 °C. In addition, we implanted MSCs into the Matrigel or electrospun PLA nanofiber membrane in vitro to evaluating the effect of heating or CuS@BSA on the morphological change of MSCs by SEM. Finally, we evaluated improving skin regeneration by the combination of preheated-MSCs and CuS@BSA nanoparticles that were encapsulated in Matrigel.

Results: The CuS@BSA nanoparticles have good photothermal conversion efficiency. Not only CuS nanoparticles itself or after irradiation at 980 nm stimulated the expressioin of vimentin in MSCs. Besides, the CuS@BSA can promote cell proliferation as Cu ion through the expression of ERK. The combination of the CuS@BSA nanoparticles and thermal treatment synergistically improved the closure of an injured wound in an injured wound model.

Conclusions: MSCs combined with CuS@BSA are a promising wound dressing for the reconstruction of full-thickness skin injuries.

Mesenchymal stem cells: Cell therapy and regeneration potential

Rapid advances in the isolation of multipotent progenitor cells, routinely called mesenchymal stromal/stem cells (MSCs), from various human tissues and organs have provided impetus to the field of cell therapy and regenerative medicine. The most widely studied sources of MSCs include bone marrow, adipose, muscle, peripheral blood, umbilical cord, placenta, fetal tissue, and amniotic fluid. According to the standard definition of MSCs, these clonal cells adhere to plastic, express cluster of differentiation (CD) markers such as CD73, CD90, and CD105 markers, and can differentiate into adipogenic, chondrogenic, and osteogenic lineages in vitro. However, isolated MSCs have been reported to vary in their potency and self-renewal potential. As a result, the MSCs used for clinical applications often lead to variable or even conflicting results. The lack of uniform characterization methods both in vitro and in vivo also contributes to this confusion. Therefore, the name "MSCs" itself has been increasingly questioned lately. As the use of MSCs is expanding rapidly, there is an increasing need to understand the potential sources and specific potencies of MSCs. This review discusses and compares the characteristics of MSCs and suggests that the variations in their distinctive features are dependent on the source and method of isolation as well as epigenetic changes during maintenance and growth. We also discuss the potential opportunities and challenges of MSC research with the hope to stimulate their use for therapeutic and regenerative medicine.

Platelet-Rich Plasma and Bone Marrow-Derived Mesenchymal Stromal Cells Prevent TGF-β1-Induced Myofibroblast Generation but Are Not Synergistic when Combined: Morphological in vitro Analysis

The persistence of activated myofibroblasts is a hallmark of fibrosis of many organs. Thus, the modulation of the generation/functionality of these cells may represent a strategical anti-fibrotic therapeutic option. Bone marrow-derived mesenchymal stromal cell (MSC)-based therapy has shown promising clues, but some criticisms still limit the clinical use of these cells, including the need to avoid xenogeneic compound contamination for ex vivo cell amplification and the identification of appropriate growth factors acting as a pre-conditioning agent and/or cell delivery vehicle during transplantation, thus enabling the improvement of cell survival in the host tissue microenvironment. Many studies have demonstrated the ability of platelet-rich plasma (PRP), a source of many biologically active molecules, to positively influence MSC proliferation, survival, and functionality, as well as its anti-fibrotic potential. Here we investigated the effects of PRP, murine and human bone marrow-derived MSCs, and of the combined treatment PRP/MSCs on in vitro differentiation of murine NIH/3T3 and human HDFα fibroblasts to myofibroblasts induced by transforming growth factor (TGF)-β1, a well-known pro-fibrotic agent. The myofibroblastic phenotype was evaluated morphologically (cell shape and actin cytoskeleton assembly) and immunocytochemically (vinculin-rich focal adhesion clustering, α-smooth muscle actin and type-1 collagen expression). We found that PRP and MSCs, both as single treatments and in combination, were able to prevent the TGF-β1-induced fibroblast-myofibroblast transition. Unexpectedly, the combination PRP/MSCs had no synergistic effects. In conclusion, within the limitations related to an in vitro experimentation, our study may contribute to providing an experimental background for supporting the anti-fibrotic potential of the combination PRP/MSCs which, once translated "from bench to bedside," could potentially offer advantages over the single treatments.

A review on different methods to increase the efficiency of mesenchymal stem cell-based wound therapy

Mesenchymal stem cells (MSCs) accelerate wound healing but the harsh environment of wound site limits the engraftment, retention, and survival rate of transplanted cells. There are multiple approaches that amplify the therapeutic potential of MSCs. The MSCs derived from medical waste material, provide comparable regenerative abilities compared to traditional sources. The application of different scaffolds increases MSC delivery and migration into the wound. The spheroid culture of MSC increases the paracrine effects of the entrapped cells and the secretion of pro-angiogenic and anti-inflammatory cytokines. The MSC pretreating and preconditioning enhances the cell migration, proliferation, and survival rate, which lead to higher angiogenesis, re-epithelialization, wound closure, and granulation tissue formation. Moreover, genetic modification has been performed in order to increase MSC angiogenesis, differentiation potential, as well as the cell life span. Herein, we review the results of aforementioned approaches and provide information accommodating to the continued development of MSC-based wound therapy in the future.

Hydrogen sulfide: a gaseous signaling molecule modulates tissue homeostasis: implications in ophthalmic diseases

Hydrogen sulfide (H2S) serves as a gasotransmitter in the regulation of organ development and maintenance of homeostasis in tissues. Its abnormal levels are associated with multiple human diseases, such as neurodegenerative disease, myocardial injury, and ophthalmic diseases. Excessive exposure to H2S could lead to cellular toxicity, orchestrate pathological process, and increase the risk of various diseases. Interestingly, under physiological status, H2S plays a critical role in maintaining cellular physiology and limiting damages to tissues. In mammalian species, the generation of H2S is catalyzed by cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CSE), 3-mercapto-methylthio pyruvate aminotransferase (3MST) and cysteine aminotransferase (CAT). These enzymes are found inside the mammalian eyeballs at different locations. Their aberrant expression and the accumulation of substrates and intermediates can change the level of H2S by orders of magnitude, causing abnormal structures or functions in the eyes. Detailed investigations have demonstrated that H2S donors' administration could regulate intraocular pressure, protect retinal cells, inhibit oxidative stress and alleviate inflammation by modulating the function of intra or extracellular proteins in ocular tissues. Thus, several slow-releasing H2S donors have been shown to be promising drugs for treating multiple diseases. In this review, we discuss the biological function of H2S metabolism and its application in ophthalmic diseases.

Novel non-angiogenic role for mesenchymal stem cell-derived vascular endothelial growth factor on keratinocytes during wound healing

With chronic wounds remaining a substantial healthcare issue, new therapies are sought to improve patient outcomes. Various studies have explored the benefits of promoting angiogenesis in wounds by targeting proangiogenic factors such as Vascular Endothelial Growth Factor (VEGF) family members to improve wound healing. Along similar lines, Mesenchymal Stem Cell (MSC) secretions, usually containing VEGF, have been used to improve angiogenesis in wound healing via a paracrine mechanism. Recent evidence for keratinocyte VEGF receptor expression, as well as proliferative and chemotactic responses by keratinocytes to exogenous VEGFA in vitro implies distinct non-angiogenic actions for VEGF during wound healing. In this review, we discuss the expression of VEGF family members and their receptors in keratinocytes in relation to the potential for wound healing treatments. We also explore recent findings of MSC secreted paracrine wound healing activity on keratinocytes. We report here the concept of keratinocyte wound healing responses driven by MSC-derived VEGF that is supported in the literature, providing a new mechanism for cell-free therapy of chronic wounds.

Platelet-Rich Plasma Prevents In Vitro Transforming Growth Factor-β1-Induced Fibroblast to Myofibroblast Transition: Involvement of Vascular Endothelial Growth Factor (VEGF)-A/VEGF Receptor-1-Mediated Signaling †

The antifibrotic potential of platelet-rich plasma (PRP) is controversial. This study examined the effects of PRP on in vitro transforming growth factor (TGF)-β1-induced differentiation of fibroblasts into myofibroblasts, the main drivers of fibrosis, and the involvement of vascular endothelial growth factor (VEGF)-A in mediating PRP-induced responses. The impact of PRP alone on fibroblast differentiation was also assessed. Myofibroblastic phenotype was evaluated by confocal fluorescence microscopy and western blotting analyses of α-smooth muscle actin (sma) and type-1 collagen expression, vinculin-rich focal adhesion clustering, and stress fiber assembly. Notch-1, connexin 43, and VEGF-A expression were also analyzed by RT-PCR. PRP negatively regulated fibroblast-myofibroblast transition via VEGF-A/VEGF receptor (VEGFR)-1-mediated inhibition of TGF-β1/Smad3 signaling. Indeed TGF-β1/PRP co-treated fibroblasts showed a robust attenuation of the myofibroblastic phenotype concomitant with a decrease of Smad3 expression levels. The VEGFR-1 inhibition by KRN633 or blocking antibodies, or VEGF-A neutralization in these cells prevented the PRP-promoted effects. Moreover PRP abrogated the TGF-β1-induced reduction of VEGF-A and VEGFR-1 cell expression. The role of VEGF-A signaling in counteracting myofibroblast generation was confirmed by cell treatment with soluble VEGF-A. PRP as single treatment did not induce fibroblast myodifferentiation. This study provides new insights into cellular and molecular mechanisms underpinning PRP antifibrotic action.

Allogeneic mesenchymal stem cells improve the wound healing process of sheep skin

BACKGROUND

Skin wound healing includes a system of biological processes, collectively restoring the integrity of the skin after injury. Healing by second intention refers to repair of large and deep wounds where the tissue edges cannot be approximated and substantial scarring is often observed. The objective of this study was to evaluate the effects of mesenchymal stem cells (MSCs) in second intention healing using a surgical wound model in sheep. MSCs are known to contribute to the inflammatory, proliferative, and remodeling phases of the skin regeneration process in rodent models, but data are lacking for large animal models. This study used three different approaches (clinical, histopathological, and molecular analysis) to assess the putative action of allogeneic MSCs at 15 and 42 days after lesion creation.

RESULTS

At 15 days post-lesion, the wounds treated with MSCs showed a higher degree of wound closure, a higher percentage of re-epithelialization, proliferation, neovascularization and increased contraction in comparison to a control group. At 42 days, the wounds treated with MSCs had more mature and denser cutaneous adnexa compared to the control group. The MSCs-treated group showed an absence of inflammation and expression of CD3+ and CD20+. Moreover, the mRNA expression of hair-keratine (hKER) was observed in the MSCs-treated group 15 days after wound creation and had increased significantly by 42 days post-wound creation. Collagen1 gene (Col1α1) expression was also greater in the MSCs-treated group compared to the control group at both days 15 and 42.

CONCLUSION

Peripheral blood-derived MSCs may improve the quality of wound healing both for superficial injuries and deep lesions. MSCs did not induce an inflammatory response and accelerated the appearance of granulation tissue, neovascularization, structural proteins, and skin adnexa.

Sphingosine 1-Phosphate Receptor 1 Is Required for MMP-2 Function in Bone Marrow Mesenchymal Stromal Cells: Implications for Cytoskeleton Assembly and Proliferation

Bone marrow-derived mesenchymal stromal cell- (BM-MSC-) based therapy is a promising option for regenerative medicine. An important role in the control of the processes influencing the BM-MSC therapeutic efficacy, namely, extracellular matrix remodelling and proliferation and secretion ability, is played by matrix metalloproteinase- (MMP-) 2. Therefore, the identification of paracrine/autocrine regulators of MMP-2 function may be of great relevance for improving BM-MSC therapeutic potential. We recently reported that BM-MSCs release the bioactive lipid sphingosine 1-phosphate (S1P) and, here, we demonstrated an impairment of MMP-2 expression/release when the S1P receptor subtype S1PR1 is blocked. Notably, active S1PR1/MMP-2 signalling is required for F-actin structure assembly (lamellipodia, microspikes, and stress fibers) and, in turn, cell proliferation. Moreover, in experimental conditions resembling the damaged/regenerating tissue microenvironment (hypoxia), S1P/S1PR1 system is also required for HIF-1α expression and vinculin reduction. Our findings demonstrate for the first time the trophic role of S1P/S1PR1 signalling in maintaining BM-MSCs' ability to modulate MMP-2 function, necessary for cytoskeleton reorganization and cell proliferation in both normoxia and hypoxia. Altogether, these data provide new perspectives for considering S1P/S1PR1 signalling a pharmacological target to preserve BM-MSC properties and to potentiate their beneficial potential in tissue repair.

Stem Cells and Engineered Scaffolds for Regenerative Wound Healing

The normal wound healing process involves a well-organized cascade of biological pathways and any failure in this process leads to wounds becoming chronic. Non-healing wounds are a burden on healthcare systems and set to increase with aging population and growing incidences of obesity and diabetes. Stem cell-based therapies have the potential to heal chronic wounds but have so far seen little success in the clinic. Current research has been focused on using polymeric biomaterial systems that can act as a niche for these stem cells to improve their survival and paracrine activity that would eventually promote wound healing. Furthermore, different modification strategies have been developed to improve stem cell survival and differentiation, ultimately promoting regenerative wound healing. This review focuses on advanced polymeric scaffolds that have been used to deliver stem cells and have been tested for their efficiency in preclinical animal models of wounds.

Therapeutic Application of Human Wharton Jelly Mesenchymal Stem Cells in Skin Injury of SCID

Mesenchymal stem cells (MSCs) are blossoming as a credible source for regenerative medical applications. The use of fetal MSCs is gaining momentum for therapeutic use. The ease of isolation, enhanced characteristics, and immunomodulation properties renders the utilization of fetal MSCs for numerous clinical applications. In this article, we will demonstrate a step-by-step protocol for isolation of Wharton's jelly MSCs (WJMSCs) from the human umbilical cord matrix, preparation of human platelet lysate, fabricating amniotic membrane scaffold and mice model to study skin regeneration using a combination of MSCs and decellularized amniotic membrane scaffold.

Combined use of bone marrow-derived mesenchymal stromal cells (BM-MSCs) and platelet rich plasma (PRP) stimulates proliferation and differentiation of myoblasts in vitro: new therapeutic perspectives for skeletal muscle repair/regeneration

Satellite cell-mediated skeletal muscle repair/regeneration is compromised in cases of extended damage. Bone marrow mesenchymal stromal cells (BM-MSCs) hold promise for muscle healing but some criticisms hamper their clinical application, including the need to avoid animal serum contamination for expansion and the scarce survival after transplant. In this context, platelet-rich plasma (PRP) could offer advantages. Here, we compare the effects of PRP or standard culture media on C2C12 myoblast, satellite cell and BM-MSC viability, survival, proliferation and myogenic differentiation and evaluate PRP/BM-MSC combination effects in promoting myogenic differentiation. PRP induced an increase of mitochondrial activity and Ki67 expression comparable or even greater than that elicited by standard media and promoted AKT signaling activation in myoblasts and BM-MSCs and Notch-1 pathway activation in BM-MSCs. It stimulated MyoD, myogenin, α-sarcomeric actin and MMP-2 expression in myoblasts and satellite cell activation. Notably, PRP/BM-MSC combination was more effective than PRP alone. We found that BM-MSCs influenced myoblast responses through a paracrine activation of AKT signaling, contributing to shed light on BM-MSC action mechanisms. Our results suggest that PRP represents a good serum substitute for BM-MSC manipulation in vitro and could be beneficial towards transplanted cells in vivo. Moreover, it might influence muscle resident progenitors' fate, thus favoring the endogenous repair/regeneration mechanisms. Finally, within the limitations of an in vitro experimentation, this study provides an experimental background for considering the PRP/BM-MSC combination as a potential therapeutic tool for skeletal muscle damage, combining the beneficial effects of BM-MSCs and PRP on muscle tissue, while potentiating BM-MSC functionality.

Transplanted adipose-derived stem cells can be short-lived yet accelerate healing of acid-burn skin wounds: a multimodal imaging study

The incidence of accidental and intentional acid skin burns is rising. Current treatment strategies are mostly inadequate, leaving victims disfigured and without treatment options. Here, we have shown that transplantation of adipose-derived stem cells (ASCs) accelerates the process of acid burn wound-healing. Pre-conditioning of ASCs using ascorbic acid (AA) or hypoxic conditions provided additional benefit. While the wounds were ultimately healed in all mice, histological analysis revealed that, in non-transplanted animals, the number of hair follicles was reduced. Bioluminescent imaging (BLI) of transplanted ASCs revealed a gradual loss of transplanted cells, with a similar rate of cell death for each treatment group. The signal of fluorinated cells detected by a clinically applicable ¹⁹F MRI method correlated with the BLI findings, which points to ¹⁹F MRI as a reliable method with which to track ASCs after transplantation to skin wounds. No difference in therapeutic effect or cell survival was observed between labeled and non-labeled cells. We conclude that, despite being short-lived, transplanted ASCs can accelerate wound-healing and reduce hair loss in acid-burn skin injury. The fluorine nanoemulsion is a clinically applicable cell label capable of reporting on the survival of transplanted cells.

Immunomodulatory oligonucleotide IMT504: Effects on mesenchymal stem cells as a first-in-class immunoprotective/immunoregenerative therapy

The immune responses of humans and animals to insults (i.e., infections, traumas, tumoral transformation and radiation) are based on an intricate network of cells and chemical messengers. Abnormally high inflammation immediately after insult or abnormally prolonged pro-inflammatory stimuli bringing about chronic inflammation can lead to life-threatening or severely debilitating diseases. Mesenchymal stem cell (MSC) transplant has proved to be an effective therapy in preclinical studies which evaluated a vast diversity of inflammatory conditions. MSCs lead to resolution of inflammation, preparation for regeneration and actual regeneration, and then ultimate return to normal baseline or homeostasis. However, in clinical trials of transplanted MSCs, the expectations of great medical benefit have not yet been fulfilled. As a practical alternative to MSC transplant, a synthetic drug with the capacity to boost endogenous MSC expansion and/or activation may also be effective. Regarding this, IMT504, the prototype of a major class of immunomodulatory oligonucleotides, induces in vivo expansion of MSCs, resulting in a marked improvement in preclinical models of neuropathic pain, osteoporosis, diabetes and sepsis. IMT504 is easily manufactured and has an excellent preclinical safety record. In the small number of patients studied thus far, IMT504 has been well-tolerated, even at very high dosage. Further clinical investigation is necessary to demonstrate the utility of IMT504 for resolution of inflammation and regeneration in a broad array of human diseases that would likely benefit from an immunoprotective/immunoregenerative therapy.