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

Self-Healing Guar Gum-Based Nanocomposite Hydrogel Promotes Infected Wound Healing through Photothermal Antibacterial Therapy

Preventing bacterial infections is a crucial aspect of wound healing. There is an urgent need for multifunctional biomaterials without antibiotics to promote wound healing. In this study, we fabricated a guar gum (GG)-based nanocomposite hydrogel, termed GBTF, which exhibited photothermal antibacterial therapy for infected wound healing. The GBTF hydrogel formed a cross-linked network through dynamic borate/diol interactions between GG and borax, thereby exhibiting simultaneously self-healing, adaptable, and injectable properties. Additionally, tannic acid (TA)/Fe3+ nanocomplexes (NCs) were incorporated into the hydrogel to confer photothermal antibacterial properties. Under the irradiation of an 808 nm near-infrared laser, the TA/Fe3+ NCs in the hydrogel could rapidly generate heat, leading to the disruption of bacterial cell membranes and subsequent bacterial eradication. Furthermore, the hydrogels exhibited good cytocompatibility and hemocompatibility, making them a precandidate for preclinical and clinical applications. Finally, they could significantly promote bacteria-infected wound healing by reducing bacterial viability, accelerating collagen deposition, and promoting epithelial remodeling. Therefore, the multifunctional GBTF hydrogel, which was composed entirely of natural substances including guar gum, borax, and polyphenol/ferric ion NCs, showed great potential for regenerating infected skin wounds in clinical applications.

A multifunctional silk-hyaluronic acid self-healing hydrogel laden with alternatively activated macrophage-derived exosomes reshape microenvironment of diabetic wound and accelerate healing

The impairment of phenotype switching of pro-inflammatory M1 to pro-healing M2 macrophage induced by hyperglycemic microenvironment often elevates oxidative stress, impairs angiogenesis, and leads to chronic non-healing wounds in diabetic patients. Administration of M2 macrophage-derived exosomes (M2Exo) at wound site is known to polarize M1 to M2 macrophage and can accelerate wound healing by enhancing collagen deposition, angiogenesis, and re-epithelialization. In the present study, M2Exo were conjugated with oxidized hyaluronic acid and mixed with PEGylated silk fibroin to develop self-healing Exo-gel to achieve an efficient therapy for diabetic wounds. Exo-gel depicted porous networked morphology with self-healing and excellent water retention behaviour. Fibroblast cells treated with Exo-gel showed significant uptake of M2Exo that increased their proliferation and migration in vitro. Interestingly, in a diabetic wound model of wistar rats, Exo-gel treatment induced 75 % wound closure within 7 days with complete epithelial layer regeneration by modulating cytokine levels, stimulating fibroblast-keratinocyte interaction and migration, angiogenesis, and organized collagen deposition. Taken together, this study suggests that Exo-gel depict properties of an excellent wound healing matrix and can be used as a therapeutic alternative to treat chronic non-healing diabetic wounds.

Highly Active Frozen Nanovesicles Microneedles for Senile Wound Healing via Antibacteria, Immunotherapy, and Skin Regeneration

Senile wound healing risks a variety of health complications and makes both economic and psychological burdens on patients greatly. Poor activity of aged dermal fibroblasts (A-FBs) and local disordered immunoreaction in the deep dermis contribute to delayed wound healing. Therefore, the locally complex microenvironment in deep requires additional processing. Herein, a novel double-layer hyaluronic acid methacrylate (HAMA)/polyvinyl alcohol (PVA) microneedle patch (MNP) coated by young fibroblast-derived exosomes (Y-EXOs) (Y-EXOs@HAMA/PVA MNP) is presented for deep drug delivery, aged wound healing and immunoregulation. A spraying and freeze-drying method is applied for keeping the bioactivity of the nanovesicles. An ideal loading of Y-EXOs and enhanced strength for penetration have realized after circulation for times. The Y-EXOs@HAMA/PVA MNP shows an excellent influence on delayed wound healing of aged skin with active A-FBs, more deposition of collagen and less production of IL-17A compared with application of aged fibroblast-derived exosomes (A-EXOs). Moreover, the content microRNAs in Y-EXOs and A-EXOs are sequenced for further study. This study initiatively demonstrates that Y-EXOs have effective function on both anti-aging and anti-inflammation and Y-EXOs@HAMA/PVA MNP is expected as a novel strategy for deep drug delivery for promoting hard wound healing in aged skin in future clinical application.

Cell sheet formation enhances the therapeutic effects of adipose-derived stromal vascular fraction on urethral stricture

Urethral stricture (US) is a common disease in urology, lacking effective treatment options. Although injecting a stem cells suspension into the affected area has shown therapeutic benefits, challenges such as low retention rate and limited efficacy hinder the clinical application of stem cells. This study evaluates the therapeutic impact and the mechanism of adipose-derived vascular fraction (SVF) combined with cell sheet engineering technique on urethral fibrosis in a rat model of US. The results showed that SVF-cell sheets exhibit positive expression of α-SMA, CD31, CD34, Stro-1, and eNOS. In vivo study showed less collagen deposition, low urethral fibrosis, and minimal tissue alteration in the group receiving cell sheet transplantation. Furthermore, the formation of a three-dimensional (3D) tissue-like structure by the cell sheets enhances the paracrine effect of SVF, facilitates the infiltration of M2 macrophages, and suppresses the TGF-β/Smad2 pathway through HGF secretion, thereby exerting antifibrotic effects. Small animal in vivo imaging demonstrates improved retention of SVF cells at the damaged urethra site with cell sheet application. Our results suggest that SVF combined with cell sheet technology more efficiently inhibits the early stages of urethral fibrosis.

Revolutionizing Wound Healing: Exploring Scarless Solutions through Drug Delivery Innovations

Human skin is the largest organ and outermost surface of the human body, and due to the continuous exposure to various challenges, it is prone to develop injuries, customarily known as wounds. Although various tissue engineering strategies and bioactive wound matrices have been employed to speed up wound healing, scarring remains a significant challenge. The wound environment is harsh due to the presence of degradative enzymes and elevated pH levels, and the physiological processes involved in tissue regeneration operate on distinct time scales. Therefore, there is a need for effective drug delivery systems (DDSs) to address these issues. The objective of this review is to provide a comprehensive exposition of the mechanisms underlying the skin healing process, the factors and materials used in engineering DDSs, and the different DDSs used in wound care. Furthermore, this investigation will delve into the examination of emergent technologies and potential avenues for enhancing the efficacy of wound care devices.

Dissolvable Immunomodulatory Microneedles for Treatment of Skin Wounds

Sustained inflammation can halt or delay wound healing, and macrophages play a central role in wound healing. Inflammatory macrophages are responsible for the removal of pathogens, debris, and neutrophils, while anti-inflammatory macrophages stimulate various regenerative processes. Recombinant human Proteoglycan 4 (rhPRG4) is shown to modulate macrophage polarization and to prevent fibrosis and scarring in ear wound healing. Here, dissolvable microneedle arrays (MNAs) carrying rhPRG4 are engineered for the treatment of skin wounds. The in vitro experiments suggest that rhPRG4 modulates the inflammatory function of bone marrow-derived macrophages. Degradable and detachable microneedles are developed from gelatin methacryloyl (GelMA) attach to a dissolvable gelatin backing. The developed MNAs are able to deliver a high dose of rhPRG4 through the dissolution of the gelatin backing post-injury, while the GelMA microneedles sustain rhPRG4 bioavailability over the course of treatment. In vivo results in a murine model of full-thickness wounds with impaired healing confirm a decrease in inflammatory biomarkers such as TNF-α and IL-6, and an increase in angiogenesis and collagen deposition. Collectively, these results demonstrate rhPRG4-incorporating MNA is a promising platform in skin wound healing applications.

Evaluation of secretomes derived from human dermal and adipose tissue mesenchymal stem/stromal cells for skin wound healing: not as effective as cells

BACKGROUND

Although the paracrine effects of mesenchymal stem/stromal cells (MSCs) have been recognized as crucial mediators of their regenerative effects on tissue repair, the potential of MSC secretomes as effective substitutes for cellular therapies remains underexplored.

METHODS

In this study, we compared MSCs from the human dermis (DSCs) and adipose tissue (ASCs) with their secretomes regarding their efficacy for skin wound healing using a translationally relevant murine model.

RESULTS

Proteomic analysis revealed that while there was a substantial overlap in protein composition between DSC and ASC secretomes, specific proteins associated with wound healing and angiogenesis were differentially expressed. Despite a similar angiogenic potential in vivo, DSC and ASC secretomes were found to be less effective than cells in accelerating wound closure and promoting tissue remodeling.

CONCLUSIONS

Overall, secretome-treated groups showed intermediary results between cells- and control-treated (empty scaffold) groups. These findings highlight that although secretomes possess therapeutic potential, their efficacy might be limited compared to cellular therapies. This study contributes to the growing understanding of MSC secretomes, emphasizes the need for further protocol optimization, and offers insights into their potential applications in regenerative medicine.

Thou shall not heal: Overcoming the non-healing behaviour of diabetic foot ulcers by engineering the inflammatory microenvironment

Diabetic foot ulcers (DFUs) are a devastating complication for diabetic patients that have debilitating effects and can ultimately lead to limb amputation. Healthy wounds progress through the phases of healing leading to tissue regeneration and restoration of the barrier function of the skin. In contrast, in diabetic patients dysregulation of these phases leads to chronic, non-healing wounds. In particular, unresolved inflammation in the DFU microenvironment has been identified as a key facet of chronic wounds in hyperglyceamic patients, as DFUs fail to progress beyond the inflammatory phase and towards resolution. Thus, control over and modulation of the inflammatory response is a promising therapeutic avenue for DFU treatment. This review discusses the current state-of-the art regarding control of the inflammatory response in the DFU microenvironment, with a specific focus on the development of biomaterials-based delivery strategies and their cargos to direct tissue regeneration in the DFU microenvironment.

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.

Multiple Injections of Adipose-Derived Stem Cells Improve Graft Survival in Human-to-Rat Skin Xenotransplantation through Immune Modulation

BACKGROUND

Adipose-derived stem cells (ADSCs) exert immunomodulatory effects in the treatment of transplant rejection. This study aimed to evaluate the effects of ADSCs on the skin graft survival in a human-to-rat xenograft transplantation model and to compare single and multiple injections of ADSCs.

METHODS

Full-thickness human skin xenografts were transplanted into the backs of Sprague-Dawley rats. The rats were injected subcutaneously on postoperative days 0, 3, and 5. The injections were as follows: triple injections of phosphate-buffered saline (PBS group), a single injection of ADSCs and double injections of PBS (ADSC × 1 group), and triple injections of ADSCs (ADSC × 3 group). The immunomodulatory effects of ADSCs on human skin xenografts were assessed.

RESULTS

Triple injections of ADSCs considerably delayed cell-mediated xenograft rejection compared with the PBS and ADSC × 1 groups. The vascularization and collagen type 1-3 ratios in the ADSC × 3 group were significantly higher than those in the other groups. In addition, intragraft infiltration of CD3-, CD4-, CD8-, and CD68-positive cells was reduced in the ADSC × 3 group. Furthermore, in the ADSC × 3 group, the expression levels of proinflammatory cytokine interferon-gamma (IFN-γ) were decreased and immunosuppressive prostaglandin E synthase (PGES) was increased in the xenograft and lymph node samples.

CONCLUSION

This study presented that triple injections of ADSCs appeared to be superior to a single injection in suppressing cell-mediated xenograft rejection. The immunomodulatory effects of ADSCs are associated with the downregulation of IFN-γ and upregulation of PGES in skin xenografts and lymph nodes.

Advances in mesenchymal stem/stromal cell-based therapy and their extracellular vesicles for skin wound healing

Wound healing is a dynamic and complicated process containing overlapping phases. Presently, definitive therapy is not available, and the investigation into optimal wound care is influenced by the efficacy and cost-effectiveness of developing therapies. Accumulating evidence demonstrated the potential role of mesenchymal stem/stromal cell (MSC) therapy in several tissue injuries and diseases due to their high proliferation and differentiation abilities along with an easy collection procedure, low tumorigenesis, and immuno-privileged status. MSCs have also accelerated wound repair in all phases through their advantageous properties, such as accelerating wound closure, improving re-epithelialization, elevating angiogenesis, suppressing inflammation, and modulating extracellular matrix (ECM) remodeling. In addition, the beneficial therapeutic impacts of MSCs are largely associated with their paracrine functions, including extracellular vesicles (EVs). Exosomes and microvesicles are the two main subgroups of EVs. These vesicles are heterogeneous bilayer membrane structures that contain several proteins, lipids, and nucleic acids. EVs have emerged as a promising alternative to stem cell-based therapies because of their lower immunogenicity, tumorigenicity, and ease of management. MSCs from various sources have been widely investigated in skin wound healing and regeneration. Considering these features, in this review, we highlighted recent studies that the investigated therapeutic potential of various MSCs and MSC-EVs in skin damages and wounds.

Single-stage transplantation combined with epidermal stem cells promotes the survival of tissue-engineered skin by inducing early angiogenesis

BACKGROUND

The composite transplantation of a split-thickness skin graft (STSG) combined with an acellular dermal matrix (ADM) is a promising repair method for full-thickness skin defects. Due to delayed vascularization of the ADM, no currently available engineered skin tissue is able to permanently cover full-thickness skin defects via a single-stage procedure. Epidermal stem cells (EpSCs) have been found to promote angiogenesis in the wound bed. Whether EpSCs can induce early angiogenesis of dermal substitutes and promote the survival of single-stage tissue-engineered skin transplantation needs to be further studied.

METHODS

In vitro, rat vascular endothelial cells (RVECs) were treated with the supernatant of EpSCs cultured in ADM and stimulated for 48 h. RVECs were analysed by RNA sequencing and tube formation assays. For the in vivo experiment, 75 rats were randomly divided into five groups: ADM, ADM + EpSCs (AE), STSG, ADM + STSG (AS), and ADM + STSG + EpSCs (ASE) groups. The quality of wound healing was estimated by general observation and H&E and Masson staining. The blood perfusion volume was evaluated using the LDPI system, and the expression of vascular markers was determined by immunohistochemistry (IHC).

RESULTS

The active substances secreted by EpSCs cultured in ADM promoted angiogenesis, as shown by tube formation experiments and RNA-seq. EpSCs promoted epithelialization of the ADM and vascularization of the ADM implant. The ASE group showed significantly increased skin graft survival, reduced skin contraction, and an improved cosmetic appearance compared with the AS group and the STSG control group.

CONCLUSIONS

In summary, our findings suggest that EpSCs promote the formation of new blood vessels in dermal substitutes and support one-step transplantation of tissue-engineered skin, and thereby provide new ideas for clinical application.

Optical coherence tomography for in vivo longitudinal monitoring of artificial dermal scaffold

OBJECTIVES

Artificial dermal scaffold (ADS) has undergone rapid development and been increasingly used for treating skin wound in clinics due to its good biocompatibility, controllable degradation, and low risk of disease infection. To obtain good treatment efficacy, ADS needs to be monitored longitudinally during the treatment process. For example, scaffold-tissue fit, cell in-growth, vascular regeneration, and scaffold degradation are the key properties to be inspected. However, to date, there are no effective, real-time, and noninvasive techniques to meet the requirement of the scaffold monitoring above.

MATERIALS AND METHODS

In this study, we propose to use optical coherence tomography (OCT) to monitor ADS in vivo through three-dimensional imaging. A swept source OCT system with a handheld probe was developed for in vivo skin imaging. Moreover, a cell in-growth, vascular regeneration, and scaffold degradation rate (IRDR) was defined with the volume reduction rate of the scaffold's collagen sponge layer. To measure the IRDR, a semiautomatic image segmentation algorithm was designed based on U-Net to segment the collagen sponge layer of the scaffold from OCT images.

RESULTS

The results show that the scaffold-tissue fit can be clearly visualized under OCT imaging. The IRDR can be computed based on the volume of the segmented collagen sponge layer. It is observed that the IRDR appeared to a linear function of the time and in addition, the IRDR varied among different skin parts.

CONCLUSION

Overall, it can be concluded that OCT has a good potential to monitor ADS in vivo. This can help guide the clinicians to control the treatment with ADS to improve the therapy.

Modulation of Macrophage Function by Bioactive Wound Dressings with an Emphasis on Extracellular Matrix-Based Scaffolds and Nanofibrous Composites

Bioactive wound dressings that are capable of regulating the local wound microenvironment have attracted a very large interest in the field of regenerative medicine. Macrophages have many critical roles in normal wound healing, and the dysfunction of macrophages significantly contributes to impaired or non-healing skin wounds. Regulation of macrophage polarization towards an M2 phenotype provides a feasible strategy to enhance chronic wound healing, mainly by promoting the transition of chronic inflammation to the proliferation phase of wound healing, upregulating the level of anti-inflammatory cytokines around the wound area, and stimulating wound angiogenesis and re-epithelialization. Based on this, modulation of macrophage functions by the rational design of bioactive scaffolds has emerged as a promising way to accelerate delayed wound healing. This review outlines current strategies to regulate the response of macrophages using bioactive materials, with an emphasis on extracellular matrix-based scaffolds and nanofibrous composites.

Therapeutic potential of adipose tissue-derivatives in modern dermatology

Stem cell-mediated therapies in combination with biomaterial and growth factor-based approaches in regenerative medicine are rapidly evolving with increasing application beyond the dermatologic field. Adipose-derived stem cells (ADSCs) are the more frequently used adult stem cells due to their abundance and easy access. In the case of volumetric defects, adipose tissue can take the shape of defects, restoring the volume and enhancing the regeneration of receiving tissue. When regenerative purposes prevail on volume restoration, the stromal vascular fraction (SVF) rich in staminal cells, purified mesenchymal stem cells (MSCs) or their cell-free derivatives grafting are favoured. The therapeutic efficacy of acellular approaches is explained by the fact that a significant part of the natural propensity of stem cells to repair damaged tissue is ascribable to their secretory activity that combines mitogenic factors, cytokines, chemokines and extracellular matrix components. Therefore, the secretome's ability to modulate multiple targets simultaneously demonstrated preclinical and clinical efficacy in reversing pathological mechanisms of complex conditions such atopic dermatitis (AD), vitiligo, psoriasis, acne and Lichen sclerosus (LS), non-resolving wounds and alopecia. This review analysing both in vivo and in vitro models gives an overview of the clinical relevance of adipose tissue-derivatives such as autologous fat graft, stromal vascular fraction, purified stem cells and secretome for skin disorders application. Finally, we highlighted the major disease-specific limitations and the future perspective in this field.

Update on the application of mesenchymal stem cell-derived exosomes in the treatment of Parkinson's disease: A systematic review

Parkinson's disease (PD) has become the second largest neurodegenerative disease after Alzheimer's disease, and its incidence is increasing year by year. Traditional dopamine replacement therapy and deep brain stimulation can only alleviate the clinical symptoms of patients with PD but cannot cure the disease. In recent years, stem cell therapy has been used to treat neurodegenerative diseases. Many studies have shown that stem cell transplantation has a therapeutic effect on PD. Here, we review recent studies indicating that exosomes derived from mesenchymal stem cells also have the potential to treat PD in animal models, but the exact mechanism remains unclear. This article reviews the mechanisms through which exosomes are involved in intercellular information exchange, promote neuroprotection and freely cross the blood-brain barrier in the treatment of PD. The increase in the incidence of PD and the decline in the quality of life of patients with advanced PD have placed a heavy burden on patients, families and society. Therefore, innovative therapies for PD are urgently needed. Herein, we discuss the mechanisms underlying the effects of exosomes in PD, to provide new insights into the treatment of PD. The main purpose of this article is to explore the therapeutic potential of exosomes derived from mesenchymal stem cells and future research directions for this degenerative disease.

The Immunomodulatory Effect of Adipose-Derived Stem Cells in Xenograft Transplantation Model

Adipose-derived stem cells (ASCs) have demonstrated immunomodulatory and anti-inflammatory effects in preclinical studies. The purpose of this study was to evaluate the effects of ASCs on the survival of xenogeneic full-thickness skin grafts and compare intravenous and subcutaneous injections of ASCs. We divided 30 male C57BL/6 mice into control, intravenous (IV), and subcutaneous (SC) injection groups. In one group of 10 mice, mouse ASCs were intravenously injected after human full-thickness skin grafting (IV group). In another group of 10 mice, ASCs were directly injected into the subcutaneous plane under the xenogeneic grafts (SC group). An additional group of 10 mice received no treatment and served as controls. Bioluminescent imaging showed that ASCs were concentrated at the grafts during the study period in both IV and SC groups. We performed graft survival assessment, histologic examination, and immunohistochemistry analysis. ASCs significantly prolonged xenograft survival at postoperative week 2 in the SC group compared with the control group (P < .05). Histologic evaluation revealed fewer inflammatory reactions in the SC group than in the control group at 1 week posttransplantation. In addition, we observed relative reduction in CD4- and CD8-positive cells in the SC group compared with the control group. Intravenous injection of ASCs led to increased graft survival and decreased inflammatory reactions, but these differences were not statistically significant. The results of this study indicate that subcutaneous injection of ASCs promoted the survival of xenogeneic full-thickness skin grafts in mice. The underlying mechanisms of the immunosuppressive effects of ASCs should be further investigated.

Pharmaceutical Prophylaxis of Scarring with Emphasis on Burns: A Review of Preclinical and Clinical Studies

Significance: The worldwide estimate of burns requiring medical attention each year is 11 million. Each year in the United States, ∼486,000 burn injuries receive medical attention, including 40,000 hospitalizations. Scars resulting from burns can be disfiguring and impair functions. The development of prophylactic drugs for cutaneous scarring could improve the outcomes for burns, traumatic lacerations (>6 million/year treated in U.S. emergency rooms), and surgical incisions (∼250 million/year worldwide). Antiscar pharmaceuticals have been estimated to have a market of $12 billion. Recent Advances: Many small molecules, cells, proteins/polypeptides, and nucleic acids have mitigated scarring in animal studies and clinical trials, but none have received Food and Drug Administration (FDA) approval yet. Critical Issues: The development of antiscar pharmaceuticals involves the identification of the proper dose, frequency of application, and window of administration postwounding for the indicated wound. Risks of infection and impaired healing must be considered. Scar outcome needs to be evaluated after scars have matured. Future Directions: Once treatments have demonstrated safety and efficacy in rodent and/or rabbit and porcine wound models, human testing can begin, such as on artificially created wounds on healthy subjects and on bilateral-surgical wounds, comparing treatments versus vehicle controls on intrapatient-matched wounds, before testing on separate cohorts of patients. Given the progress made in the past 20 years, FDA-approved drugs for improving scar outcomes may be expected.

Cell-based dressings: A journey through chronic wound management

The field of regenerative medicine has undergone a paradigm shift in recent decades thanks to the emergence of novel therapies based on the use of living organisms. The development of cell-based strategies has become a trend for the treatment of different conditions and pathologies. In this sense, the need for more adequate, biomimetic and well-planned treatments for chronic wounds has found different and innovative strategies, based on the combination of cells with dressings, which seek to revolutionize the wound healing management. Therefore, the objective of this review is to analyze the current state and the latest advances in the research of cell-based dressings for chronic wounds, ranging from traditional and "second generation" bioengineered living skin equivalents to mesenchymal stem cell dressings; the latter include biopolymeric porous scaffolds, electrospun nanofiber meshes, hydrogels and 3D printed bio-printed dressings. Finally, this review updates the completed and ongoing clinical trials in this field and encourages researchers to rethink these new approaches, manufacturing processes and mechanisms of action, as well as their administration strategies and timings.

Bioactive Materials Promote Wound Healing through Modulation of Cell Behaviors

Skin wound repair is a multistage process involving multiple cellular and molecular interactions, which modulate the cell behaviors and dynamic remodeling of extracellular matrices to maximize regeneration and repair. Consequently, abnormalities in cell functions or pathways inevitably give rise to side effects, such as dysregulated inflammation, hyperplasia of nonmigratory epithelial cells, and lack of response to growth factors, which impedes angiogenesis and fibrosis. These issues may cause delayed wound healing or even non-healing states. Current clinical therapeutic approaches are predominantly dedicated to preventing infections and alleviating topical symptoms rather than addressing the modulation of wound microenvironments to achieve targeted outcomes. Bioactive materials, relying on their chemical, physical, and biological properties or as carriers of bioactive substances, can affect wound microenvironments and promote wound healing at the molecular level. By addressing the mechanisms of wound healing from the perspective of cell behaviors, this review discusses how bioactive materials modulate the microenvironments and cell behaviors within the wounds during the stages of hemostasis, anti-inflammation, tissue regeneration and deposition, and matrix remodeling. A deeper understanding of cell behaviors during wound healing is bound to promote the development of more targeted and efficient bioactive materials for clinical applications.

Effect of uncultured adipose-derived stromal vascular fraction on preventing urethral stricture formation in rats

Urethral stricture (US) remains a challenging disease without effective treatment options due to the high recurrence rate. This study aims to evaluate the preventive effect of uncultured adipose derived stromal vascular fraction (SVF) on urethral fibrosis in a rat model of US. Results demonstrated that US rats displayed hyperechogenic urethral wall with a narrowed lumen compared with sham rats, while SVF rats exhibited less extensive urethral changes. By histology, US rats showed obvious submucosal fibrosis in the urethral specimens, while SVF rats exhibited mild submucosal fibrosis with less extensive tissue changes. Furthermore, US rats showed increased gene and protein expression of collagen I (2.0 ± 0.2, 2.2 ± 0.2, all were normalized against GAPDH, including the following), collagen III (2.5 ± 0.3, 1.2 ± 0.1), and TGFβ1R (2.8 ± 0.3, 1.9 ± 0.2), while SVF cells administration contributed to decreased gene and protein expression of collagen I (1.6 ± 0.2, 1.6 ± 0.2), collagen III (1.8 ± 0.4, 0.9 ± 0.1), and TGFβ1R (1.8 ± 0.3, 1.3 ± 0.2), in parallel with the improvement of vascularization and increased expression of VEGF (1.7 ± 0.1) and bFGF (3.1 ± 0.3). Additionally, SVF served anti-inflammatory effect through regulation of inflammatory cytokines and cells, accompanied with conversion of the macrophage phenotype. Our findings suggested that uncultured SVF presented an inhibitory effect on stricture formation at an early stage of urethral fibrosis.

Research update of adipose tissue-based therapies in regenerative dermatology

Mesenchymal stromal/stem cells (MSCs) have a spontaneous propensity to support tissue homeostasis and regeneration. Among the several sources of MSCs, adipose-derived tissue stem cells (ADSCs) have received major interest due to the higher mesenchymal stem cells concentration, ease, and safety of access. However, since a significant part of the natural capacity of ADSCs to repair damaged tissue is ascribable to their secretory activity that combines mitogenic factors, cytokines, chemokines, lipids, and extracellular matrix components, several studies focused on cell-free strategies. Furthermore, adipose cell-free derivatives are becoming more attractive especially for non-volumizing purposes, such as most dermatological conditions. However, when keratinocytes, fibroblasts, melanocytes, adipocytes, and hair follicle cells might not be locally sourced, graft of materials containing concentrated ADSCs is preferred. The usage of extracellular elements of adipose tissue aims to promote a self-autonomous regenerative microenvironment in the receiving area restoring physiological homeostasis. Hence, ADSCs or their paracrine activity are currently being studied in several dermatological settings including wound healing, skin fibrosis, burn, and aging.The present work analyzing both preclinical and clinical experiences gives an overview of the efficacy of adipose tissue-derivatives like autologous fat, the stromal vascular fraction (SVF), purified ADSCs, secretome and extracellular matrix graft in the field of regenerative medicine for the skin.

A Mg2+/polydopamine composite hydrogel for the acceleration of infected wound healing

Bacterial infection is a vital factor to delay the wound healing process. The antibiotics abuse leads to drug resistance of some pathogenic bacteria. Non-antibiotic-dependent multifunctional biomaterials with accelerated wound healing performance are urgently desired. Herein, we reported a composite antibacterial hydrogel PDA-PAM/Mg²⁺ that shows excellent self-healing and tissue adhesive property, and photothermal antibacterial functions for accelerating wound healing. The gel was composed of polyacrylamide (PAM), polydopamine (PDA), and magnesium (Mg²⁺) and prepared via a two-step procedure: an alkali-induced dopamine pre-polymerization and followed radical polymerization process. The composite gel shows excellent tissue adhesiveness and Mg²⁺-synergized photothermal antibacterial activity, inducing a survival rate of 5.29% for S. aureus and 7.06% for E. coli after near infrared light irradiation. The composite hydrogel further demonstrated efficient bacteria inhibition, enhanced wound healing and collagen deposition in a full-thickness skin defect rat model. Together, the PDA-PAM/Mg²⁺ hydrogel presents an excellent wound dressing with excellent tissue adhesion, wound healing, and antibacterial functions.

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A self-healing multifunctional hydrogel with photothermal antibacterial properties was developed and applied in wound healing.

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The hydrogel exhibited enhanced self-healing and adhesion properties.

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The hydrogel exhibited excellent photothermal effect and photothermal stability and repeatability.

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The hydrogel could accelerate wound healing by promoting cell proliferation and collagen deposition.

Stem cells part of the innate and adaptive immune systems as a therapeutic for Covid-19

Some stem cell types not only release molecules that reduce viral replication, but also reduce the hypercytokinemia and inflammation induced by the immune system, and have been found to be part of the innate and adaptive immune systems. An important component of the stem cell's ability to ameliorate viral diseases, especially the complications post-clearance of the pathogen, is the ability of adult stem cells to reset the innate and adaptive immune systems from an inflammatory state to a repair state. Thus, the molecules released from certain stem cell types found to be safe and efficacious, may be an important new means for therapeutic development in Covid-19, especially for late-stage inflammation and tissue damage once the virus has cleared, particularly in the aged population.

Asiaticoside-laden silk nanofiber hydrogels to regulate inflammation and angiogenesis for scarless skin regeneration

Scarless skin regeneration remains a challenge due to the complicated microenvironment involved in wound healing. Here, the hydrophobic drug, asiaticoside (AC), was loaded inside silk nanofiber hydrogels to achieve bioactive and injectable matrices for skin regeneration. AC was dispersed in aqueous silk nanofiber hydrogels with retention of biological functions that regulated inflammatory reactions and vascularization in vitro. After implantation in full-thickness wound defects, these AC-laden hydrogel matrices achieved scarless wound repair. Inflammatory reactions and angiogenesis were regulated during inflammation and remodeling, which was responsible for wound regeneration similar to normal skin. Both in vitro and in vivo studies demonstrated promising applications of these AC-laden silk hydrogels towards scarless tissue regeneration.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

Human adipose-derived mesenchymal stromal cells from face and abdomen undergo replicative senescence and loss of genetic integrity after long-term culture

Body fat depots are heterogeneous concerning their embryonic origin, structure, exposure to environmental stressors, and availability. Thus, investigating adipose-derived mesenchymal stromal cells (ASCs) from different sources is essential to standardization for future therapies. In vitro amplification is also critical because it may predispose cell senescence and mutations, reducing regenerative properties and safety. Here, we evaluated long-term culture of human facial ASCs (fASCs) and abdominal ASCs (aASCs) and showed that both met the criteria for MSCs characterization but presented differences in their immunophenotypic profile, and differentiation and clonogenic potentials. The abdominal tissue yielded more ASCs, and these had higher proliferative potential, but facial cells displayed fewer mitotic errors at higher passages. However, both cell types reduced clonal efficiency over time and entered replicative senescence around P12, as evaluated by progressive morphological alterations, reduced proliferative capacity, and SA-β-galactosidase expression. Loss of genetic integrity was detected by a higher proportion of cells showing nuclear alterations and γ-H2AX expression. Our findings indicate that the source of ASCs can substantially influence their phenotype and therefore should be carefully considered in future cell therapies, avoiding, however, long-term culture to ensure genetic stability.

Cellular human tissue-engineered skin substitutes investigated for deep and difficult to heal injuries

Wound healing is an important function of skin; however, after significant skin injury (burns) or in certain dermatological pathologies (chronic wounds), this important process can be deregulated or lost, resulting in severe complications. To avoid these, studies have focused on developing tissue-engineered skin substitutes (TESSs), which attempt to replace and regenerate the damaged skin. Autologous cultured epithelial substitutes (CESs) constituted of keratinocytes, allogeneic cultured dermal substitutes (CDSs) composed of biomaterials and fibroblasts and autologous composite skin substitutes (CSSs) comprised of biomaterials, keratinocytes and fibroblasts, have been the most studied clinical TESSs, reporting positive results for different pathological conditions. However, researchers' purpose is to develop TESSs that resemble in a better way the human skin and its wound healing process. For this reason, they have also evaluated at preclinical level the incorporation of other human cell types such as melanocytes, Merkel and Langerhans cells, skin stem cells (SSCs), induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs). Among these, MSCs have been also reported in clinical studies with hopeful results. Future perspectives in the field of human-TESSs are focused on improving in vivo animal models, incorporating immune cells, designing specific niches inside the biomaterials to increase stem cell potential and developing three-dimensional bioprinting strategies, with the final purpose of increasing patient's health care. In this review we summarize the use of different human cell populations for preclinical and clinical TESSs under research, remarking their strengths and limitations and discuss the future perspectives, which could be useful for wound healing purposes.

Human Mesenchymal Stromal Cell-Derived Exosomes Promote In Vitro Wound Healing by Modulating the Biological Properties of Skin Keratinocytes and Fibroblasts and Stimulating Angiogenesis

Bone marrow-derived mesenchymal stromal cells (MSCs) are major players in regenerative therapies for wound healing via their paracrine activity, mediated partially by exosomes. Our purpose was to test if MSC-derived exosomes could accelerate wound healing by enhancing the biological properties of the main cell types involved in the key phases of this process. Thus, the effects of exosomes on (i) macrophage activation, (ii) angiogenesis, (iii) keratinocytes and dermal fibroblasts proliferation and migration, and (iv) the capacity of myofibroblasts to regulate the turnover of the extracellular matrix were evaluated. The results showed that, although exosomes did not exhibit anti-inflammatory properties, they stimulated angiogenesis. Exposure of keratinocytes and dermal (myo)fibroblasts to exosomes enhanced their proliferation and migratory capacity. Additionally, exosomes prevented the upregulation of gene expression for type I and III collagen, α-smooth muscle actin, and MMP2 and 14, and they increased MMP13 expression during the fibroblast–myofibroblast transition. The regenerative properties of exosomes were validated using a wound healing skin organotypic model, which exhibited full re-epithelialization upon exosomes exposure. In summary, these data indicate that exosomes enhance the biological properties of keratinocytes, fibroblasts, and endothelial cells, thus providing a reliable therapeutic tool for skin regeneration.

Immunology of Acute and Chronic Wound Healing

Skin wounds greatly affect the global healthcare system, creating a substantial burden on the economy and society. Moreover, the situation is exacerbated by low healing rates, which in fact are overestimated in reports. Cutaneous wounds are generally classified into acute and chronic. The immune response plays an important role during acute wound healing. The activation of immune cells and factors initiate the inflammatory process, facilitate wound cleansing and promote subsequent tissue healing. However, dysregulation of the immune system during the wound healing process leads to persistent inflammation and delayed healing, which ultimately result in chronic wounds. The microenvironment of a chronic wound is characterized by high quantities of pro-inflammatory macrophages, overexpression of inflammatory mediators such as TNF-α and IL-1β, increased activity of matrix metalloproteinases and abundance of reactive oxygen species. Moreover, chronic wounds are frequently complicated by bacterial biofilms, which perpetuate the inflammatory phase. Continuous inflammation and microbial biofilms make it very difficult for the chronic wounds to heal. In this review, we discuss the role of innate and adaptive immunity in the pathogenesis of acute and chronic wounds. Furthermore, we review the latest immunomodulatory therapeutic strategies, including modifying macrophage phenotype, regulating miRNA expression and targeting pro- and anti-inflammatory factors to improve wound healing.

Current Advanced Therapies Based on Human Mesenchymal Stem Cells for Skin Diseases

Skin disease may be related with immunological disorders, external aggressions, or genetic conditions. Injuries or cutaneous diseases such as wounds, burns, psoriasis, and scleroderma among others are common pathologies in dermatology, and in some cases, conventional treatments are ineffective. In recent years, advanced therapies using human mesenchymal stem cells (hMSCs) from different sources has emerged as a promising strategy for the treatment of many pathologies. Due to their properties; regenerative, immunomodulatory and differentiation capacities, they could be applied for the treatment of cutaneous diseases. In this review, a total of thirteen types of hMSCs used as advanced therapy have been analyzed, considering the last 5 years (2015-2020). The most investigated types were those isolated from umbilical cord blood (hUCB-MSCs), adipose tissue (hAT-MSCs) and bone marrow (hBM-MSCs). The most studied diseases were wounds and ulcers, burns and psoriasis. At preclinical level, in vivo studies with mice and rats were the main animal models used, and a wide range of types of hMSCs were used. Clinical studies analyzed revealed that cell therapy by intravenous administration was the advanced therapy preferred except in the case of wounds and burns where tissue engineering was also reported. Although in most of the clinical trials reviewed results have not been posted yet, safety was high and only local slight adverse events (mild nausea or abdominal pain) were reported. In terms of effectiveness, it was difficult to compare the results due to the different doses administered and variables measured, but in general, percentage of wound's size reduction was higher than 80% in wounds, Psoriasis Area and Severity Index and Severity Scoring for Atopic Dermatitis were significantly reduced, for scleroderma, parameters such as Modified Rodnan skin score (MRSC) or European Scleroderma Study Group activity index reported an improvement of the disease and for hypertrophic scars, Vancouver Scar Scale (VSS) score was decreased after applying these therapies. On balance, hMSCs used for the treatment of cutaneous diseases is a promising strategy, however, the different experimental designs and endpoints stablished in each study, makes necessary more research to find the best way to treat each patient and disease.

Injectable Desferrioxamine-Laden Silk Nanofiber Hydrogels for Accelerating Diabetic Wound Healing

Dysangiogenesis and chronic inflammation are two critical reasons for diabetic foot ulcers. Desferrioxamine (DFO) was used clinically in the treatment of diabetic foot ulcers by repeated injections because of its capacity to induce vascularization. Biocompatible carriers that release DFO slowly and facilitate healing simultaneously are preferable options to accelerate the healing of diabetic wounds. Here, DFO-laden silk nanofiber hydrogels that provided a sustained release of DFO for more than 40 days were used to treat diabetic wounds. The DFO-laden hydrogels stimulated the healing of diabetic wounds. In vitro cell studies revealed that the DFO-laden hydrogels modulated the migration and gene expression of endothelial cells, and they also tuned the inflammation behavior of macrophages. These results were confirmed in an in vivo diabetic wound model. The DFO-laden hydrogels alleviated dysangiogenesis and chronic inflammation in the diabetic wounds, resulting in a more rapid wound healing and increased collagen deposition. Both in vitro and in vivo studies suggested potential clinical applications of these DFO-laden hydrogels in the treatment of diabetic ulcers.

Macrophages in Healing Wounds: Paradoxes and Paradigms

Macrophages are prominent cells in normally healing adult skin wounds, yet their exact functions and functional significance to healing outcomes remain enigmatic. Many functional attributes are ascribed to wound macrophages, including host defense and support of the proliferation of new tissue to replace that lost by injury. Indeed, the depletion of macrophages is unmistakably detrimental to normal skin healing in adult mammals. Yet in certain systems, dermal wounds seem to heal well with limited or even no functional macrophages, creating an apparent paradox regarding the function of this cell in wounds. Recent advances in our understanding of wound macrophage phenotypes, along with new information about cellular plasticity in wounds, may provide some explanation for the apparently contradictory findings and suggest new paradigms regarding macrophage function in wounds. Continued study of this remarkable cell is needed to develop effective therapeutic options to improve healing outcomes.

Adipose-Derived Stem Cells: Current Applications and Future Directions in the Regeneration of Multiple Tissues

Adipose-derived stem cells (ADSCs) can maintain self-renewal and enhanced multidifferentiation potential through the release of a variety of paracrine factors and extracellular vesicles, allowing them to repair damaged organs and tissues. Consequently, considerable attention has increasingly been paid to their application in tissue engineering and organ regeneration. Here, we provide a comprehensive overview of the current status of ADSC preparation, including harvesting, isolation, and identification. The advances in preclinical and clinical evidence-based ADSC therapy for bone, cartilage, myocardium, liver, and nervous system regeneration as well as skin wound healing are also summarized. Notably, the perspectives, potential challenges, and future directions for ADSC-related researches are discussed. We hope that this review can provide comprehensive and standardized guidelines for the safe and effective application of ADSCs to achieve predictable and desired therapeutic effects.

Polycaprolactone based electrospun matrices loaded with Ag/hydroxyapatite as wound dressings: Morphology, cell adhesion, and antibacterial activity

The development of a scaffold matrix that can inhibit bacterial infection and promote wound healing simultaneously is an essential demand to improve the health care system. Hydroxyapatite (HAP) doped with different concentrations of silver ions (Ag⁺) were incorporated into electrospun nanofibrous scaffolds of polycaprolactone (PCL) using the electrospinning technique. The formed phase was identified using XRD, while the morphological and roughness behavior were investigated using FESEM. It was shown that scaffolds were configured in randomly distributed nanofibers with diameters around of 0.19-0.40, 0.31-0.54, 1.36, 0.122-0.429 μm for 0.0Ag-HAP@PCL, 0.2Ag-HAP@PCL, 0.6Ag-HAP@PCL, and 0.8Ag-HAP@PCL, respectively. Moreover, the maximum roughness peak height increased significantly from 179 to 284 nm, with the lowest and highest contributions of Ag. The mechanical properties were examined and displayed that the tensile strength increased from 3.11 ± 0.21 MPa to its highest value at 3.57 ± 0.31 MPa for 0.4Ag-HAP@PCL. On the other hand, the cell viability also was enhanced with the addition of Ag and improved from 97.1 ± 4.6% to be around 102.3 ± 3.1% at the highest contribution of Ag. The antibacterial activity was determined, and the highest imbibition zones were achieved at the highest Ag dopant to be 12.5 ± 1.1 mm and 11.4 ± 1.5 mm against E. coli and S. aureus. The in vitro cell proliferation was observed through human fibroblasts cell lone (HFB4) and illustrated that cells were able to grow and spread not only on the fibers' surface but also, they were spreading and adhered through the deep pores.

Adipose Stromal Cells Enhance Decellularized Adipose Tissue Remodeling Through Multimodal Mechanisms

Decellularized adipose tissue (DAT) scaffolds represent a promising cell-instructive platform for soft tissue engineering. While recent work has highlighted that mesenchymal stromal cells, including adipose-derived stromal cells (ASCs), can be combined with decellularized scaffolds to augment tissue regeneration, the mechanisms involved require further study. The objective of this work was to probe the roles of syngeneic donor ASCs and host-derived macrophages in tissue remodeling of DAT scaffolds within an immunocompetent mouse model. Dual transgenic reporter mouse strains were employed to track and characterize the donor ASCs and host macrophages within the DAT implants. More specifically, ASCs isolated from dsRed mice were seeded on DAT scaffolds, and the seeded and unseeded control scaffolds were implanted subcutaneously into MacGreen transgenic mice for up to 8 weeks. ASC seeding was shown to augment cell infiltration into the DAT implants at 8 weeks, and this was linked to significantly enhanced angiogenesis relative to the unseeded controls. Immunohistochemical staining demonstrated long-term retention of the syngeneic donor ASCs over the duration of the 8-week study, providing evidence that the DAT scaffolds are a cell-supportive delivery platform. Notably, newly formed adipocytes within the DAT implants were not dsRed⁺, indicating that the donor ASCs supported fat formation through indirect mechanisms. Immunohistochemical tracking of host macrophages through costaining for enhanced green fluorescent protein with the macrophage marker Iba1 revealed that ASC seeding significantly increased the number of infiltrating macrophages within the DAT implants at 3 weeks, while the fraction of macrophages relative to the total cellular infiltrate was similar between the groups at 1, 3, and 8 weeks. Consistent with the tissue remodeling response that was observed, western blotting demonstrated that there was significantly augmented expression of CD163 and CD206, markers of constructive M2-like macrophages, within the ASC-seeded DAT implants. Overall, our results demonstrate that exogenous ASCs enhance tissue regeneration within DAT scaffolds indirectly through multimodal mechanisms that include host cell recruitment and immunomodulation. These data provide further evidence to support the use of decellularized scaffolds as a delivery platform for ASCs in tissue engineering.

Macrophage Activation and M2 Polarization in Wound Bed of Diabetic Patients Treated by Dermal/Epidermal Substitute Nevelia

Clinical evidences have shown good results using dermal/epidermal substitutes (DESs) to treat diabetic foot ulcers. Recent studies suggest that, in addition to their scaffold action, DESs may favor wound healing by influencing wound bed inflammatory cells. This study aims to investigate whether DES may influence the inflammatory infiltrate and macrophages polarization toward a reparative phenotype. Fifteen diabetic patients with chronic foot ulcers have been randomly enrolled: 5 treated only by standard of care, served as control group (CG), and 10 treated with DES composed of type 1 bovin collagen (Nevelia, SYMATESE) considered as test group (TG). A biopsy was taken at baseline (T0) and after 30 days (T1). From bioptic paraffin specimen histological, immunohistochemical, and immunofluorescence analysis was performed. Immunohistochemistry reactions evaluated the number of M1 macrophage (CD38⁺) and M2 macrophage (CD163⁺). TG patients displayed general macrophage activation and their greater polarization toward M2 subpopulation 30 days after DES implant, compared with CG. From T0 to T1 there was a significant decrease of CD38⁺ (230 ± 42 and 135 ± 48 mm², respectively; P < .001) and significant increase of CD163⁺ (102 ± 21 positive cells/mm² and 366 ± 42 positive cells/mm², respectively; P < .001). Confocal microscopy confirmed an increase of M2 cells as expressed by the reduced CD68⁺/CD163⁺ ratio. After 6 months of observation 6 patients (60%) of the TG completely healed, while only 1 patient (20%) healed in the CG (P < .01). The tested DES makes possible to treat diabetic foot ulcers inducing tissue reparative processes through macrophage activation and M2 reparative polarization.