Adipose-Derived Stem Cell-Seeded Hydrogels Increase Endogenous Progenitor Cell Recruitment and Neovascularization in Wounds

Nitric oxide-based treatments improve wound healing associated with diabetes mellitus

Non-healing wounds are long-term complications of diabetes mellitus (DM) that increase mortality risk and amputation-related disability and decrease the quality of life. Nitric oxide (NO·)-based treatments (i.e., use of both systemic and topical NO· donors, NO· precursors, and NO· inducers) have received more attention as complementary approaches in treatments of DM wounds. Here, we aimed to highlight the potential benefits of NO·-based treatments on DM wounds through a literature review of experimental and clinical evidence. Various topical NO·-based treatments have been used. In rodents, topical NO·-based therapy facilitates wound healing, manifested as an increased healing rate and a decreased half-closure time. The wound healing effect of NO·-based treatments is attributed to increasing local blood flow, angiogenesis induction, collagen synthesis and deposition, re-epithelization, anti-inflammatory and anti-oxidative properties, and potent broad-spectrum antibacterial effects. The existing literature lacks human clinical evidence on the safety and efficacy of NO·-based treatments for DM wounds. Translating experimental favors of NO·-based treatments of DM wounds into human clinical practice needs conducting clinical trials with well-predefined effect sizes, i.e., wound reduction area, rate of wound healing, and hospital length of stay.

MSC Exosomes Containing Valproic Acid Promote Wound Healing by Modulating Inflammation and Angiogenesis

PURPOSE

Chronic wounds that are difficult to heal pose a major challenge for clinicians and researchers. Currently, common treatment methods focus on isolating the wound from the outside world, relying on the tissue at the wound site to grow and heal unaided. Umbilical cord mesenchymal stem cell (MSC) exosomes can promote wound healing by enhancing new blood vessel growth at the wound site. Valproic acid (VPA) reduces the inflammatory response and acts on macrophages to accelerate wound closure. In this study, VPA was loaded into umbilical cord MSC exosomes to form a drug carrier exosome (VPA-EXO) with the aim of investigating the effect of VPA-EXO on wound healing.

METHODS

This study first isolated and obtained umbilical cord MSC exosomes, then added VPA to the exosomes and explored the ability of VPA-EXO to promote the proliferation and migration of human skin fibroblasts (HSFs) and human umbilical vein endothelial cells (HUVECs), as well as the ability to promote the angiogenesis of HUVECs, by using scratch, Transwell, and angiogenesis assays. An in vitro cell model was established and treated with VPA-EXO, and the expression levels of inflammation and pro-angiogenesis-related proteins and genes were examined using Western blot and qRT-PCR. The therapeutic effect of VPA-EXO on promoting wound healing in a whole skin wound model was investigated using image analysis of the wound site, H&E staining, and immunohistochemical staining experiments in a mouse wound model.

RESULTS

The in vitro model showed that VPA-EXO effectively promoted the proliferation and migration of human skin fibroblast cells and human umbilical vein endothelial cells; significantly inhibited the expression of MMP-9, IL-1β, IL-8, TNF-α, and PG-E2; and promoted the expression of vascular endothelial growth factors. In the mouse wound model, VPA-EXO reduced inflammation at the wound site, accelerated wound healing, and significantly increased the collagen content of tissue at the wound site.

CONCLUSIONS

As a complex with dual efficacy in simultaneously promoting tissue regeneration and inhibiting inflammation, VPA-EXO has potential applications in tissue wound healing and vascular regeneration. In future studies, we will further investigate the mechanism of action and application scenarios of drug-loaded exosome complexes in different types of wound healing and vascular regeneration.

Bioactive Materials That Promote the Homing of Endogenous Mesenchymal Stem Cells to Improve Wound Healing

Endogenous stem cell homing refers to the transport of endogenous mesenchymal stem cells (MSCs) to damaged tissue. The paradigm of using well-designed biomaterials to induce resident stem cells to home in to the injured site while coordinating their behavior and function to promote tissue regeneration is known as endogenous regenerative medicine (ERM). ERM is a promising new avenue in regenerative therapy research, and it involves the mobilizing of endogenous stem cells for homing as the principal means through which to achieve it. Comprehending how mesenchymal stem cells home in and grasp the influencing factors of mesenchymal stem cell homing is essential for the understanding and design of tissue engineering. This review summarizes the process of MSC homing, the factors influencing the homing process, analyses endogenous stem cell homing studies of interest in the field of skin tissue repair, explores the integration of endogenous homing promotion strategies with cellular therapies and details tissue engineering strategies that can be used to modulate endogenous homing of stem cells. In addition to providing more systematic theories and ideas for improved materials for endogenous tissue repair, this review provides new perspectives to explore the complex process of tissue remodeling to enhance the rational design of biomaterial scaffolds and guide tissue regeneration strategies.

Platelet-Rich Plasma in Dermatology: New Insights on the Cellular Mechanism of Skin Repair and Regeneration

The skin's recognised functions may undergo physiological alterations due to ageing, manifesting as varying degrees of facial wrinkles, diminished tautness, density, and volume. Additionally, these functions can be disrupted (patho)physiologically through various physical and chemical injuries, including surgical trauma, accidents, or chronic conditions like ulcers associated with diabetes mellitus, venous insufficiency, or obesity. Advancements in therapeutic interventions that boost the skin's innate regenerative abilities could significantly enhance patient care protocols. The application of Platelet-Rich Plasma (PRP) is widely recognized for its aesthetic and functional benefits to the skin. Yet, the endorsement of PRP's advantages often borders on the dogmatic, with its efficacy commonly ascribed solely to the activation of fibroblasts by the factors contained within platelet granules. PRP therapy is a cornerstone of regenerative medicine which involves the autologous delivery of conditioned plasma enriched by platelets. This is achieved by centrifugation, removing erythrocytes while retaining platelets and their granules. Despite its widespread use, the precise sequences of cellular activation, the specific cellular players, and the molecular machinery that drive PRP-facilitated healing are still enigmatic. There is still a paucity of definitive and robust studies elucidating these mechanisms. In recent years, telocytes (TCs)-a unique dermal cell population-have shown promising potential for tissue regeneration in various organs, including the dermis. TCs' participation in neo-angiogenesis, akin to that attributed to PRP, and their role in tissue remodelling and repair processes within the interstitia of several organs (including the dermis), offer intriguing insights. Their potential to contribute to, or possibly orchestrate, the skin regeneration process following PRP treatment has elicited considerable interest. Therefore, pursuing a comprehensive understanding of the cellular and molecular mechanisms at work, particularly those involving TCs, their temporal involvement in structural recovery following injury, and the interconnected biological events in skin wound healing and regeneration represents a compelling field of study.

Acceleration of a delayed healing wound repair model in diabetic rats by additive impacts of photobiomodulation plus conditioned medium of adipose-derived stem cells

Purpose

This study aimed to investigate the effects of photobiomodulation (PBM) and conditioned medium (CM) derived from human adipose-derived stem cells (h-ASCs), both individually and in combination, on the maturation stage of an ischemic infected delayed healing wound model (IIDHWM) in type I diabetic (TIDM) rats.

Methods

The study involved the extraction of h-ASCs from donated fat, assessment of their immunophenotypic markers, cell culture, and extraction and concentration of CM from cultured 1 × 10^6 h-ASCs. TIDM was induced in 24 male adult rats, divided into four groups: control, CM group, PBM group (80 Hz, 0.2 J/cm2, 890 nm), and rats receiving both CM and PBM. Clinical and laboratory evaluations were conducted on days 4, 8, and 16, and euthanasia was performed using CO2 on day 16. Tensiometrical and stereological examinations were carried out using two wound samples from each rat.

Results

Across all evaluated factors, including wound closure ratio, microbiological, tensiometrical, and stereological parameters, similar patterns were observed. The outcomes of CM + PBM, PBM, and CM treatments were significantly superior in all evaluated parameters compared to the control group (p = 0.000 for all). Both PBM and CM + PBM treatments showed better tensiometrical and stereological results than CM alone (almost all, p = 0.000), and CM + PBM outperformed PBM alone in almost all aspects (p = 0.000). Microbiologically, both CM + PBM and PBM exhibited fewer colony-forming units (CFU) than CM alone (both, p = 0.000).

Conclusion

PBM, CM, and CM + PBM interventions substantially enhanced the maturation stage of the wound healing process in IIDHWM of TIDM rats by mitigating the inflammatory response and reducing CFU count. Moreover, these treatments promoted new tissue formation in the wound bed and improved wound strength. Notably, the combined effects of CM + PBM surpassed the individual effects of CM and PBM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01285-3.

Promising improvement in infected Wound Healing in Type two Diabetic rats by Combined effects of conditioned medium of human adipose-derived stem cells plus Photobiomodulation

BACKGROUND

We aimed to examine the accompanying and solo impacts of conditioned medium of human adipose-derived stem cells (h-ASC-COM) and photobiomodulation (PBM) on the maturation stage of an ischemic infected delayed-healing wound model (IIDHWM) of rats with type 2 diabetes (TIIDM).

RESULTS

Outcomes of the wound closure ratio (WCR) results, tensiometrical microbiological, and stereological assessment followed almost identical patterns. While the outcomes of h-ASC-COM + PBM, PBM only, and h-ASC-COM only regimes were significantly better for all evaluated methods than those of group 1(all, p < 0.001), PBM alone and h-ASC-COM + PBM therapy achieved superior results than h-ASC-COM only (ranged from p = 0.05 to p < 0.001). In terms of tensiometrical and stereological examinations, the results of h-ASC-COM + PBM experienced better results than the PBM only (all, p < 0.001).

CONCLUSIONS

h-ASC-COM + PBM, PBM, and h-ASC-COM cures expressively accelerated the maturation stage in the wound healing process of IIDHWM with MRSA in TIIDM rats by diminishing the inflammatory reaction, and the microbial flora of MRSA; and increasing wound strength, WCR, number of fibroblasts, and new blood vessels. While the h-ASC-COM + PBM and PBM were more suitable than the effect of h-ASC-COM, the results of h-ASC-COM + PBM were superior to PBM only.

Mechanisms regulating wound healing: Functional changes in biology mediated by lactate and histone lactylation

The high incidence, low healing rate and huge economic burden of wounds (especially chronic wounds) worldwide remain a great challenge for clinical staff and patients. The various stages of wound healing are regulated by paracrine or autocrine cytokines and growth factors, and the study of their intrinsic mechanisms is a prerequisite for better wound treatment. Lactate, the end product of glycolysis, plays a role in all stages of wound healing, and recent studies have identified lactate as an epigenetic regulator that regulates gene expression through histone lysine lactylation and stimulates posttranslational modifications to regulate related gene expression, thereby causing a series of biological functional changes. This article reviews the progress of research on lactate and lactylation during wound healing or in related diseases, including its involvement in immune regulation, inflammation control, and proliferative remodeling, and finally describes the prospects for lactate therapy regarding wound healing.

Healing Effect of a Nano-Functionalized Medical-Grade Honey for the Treatment of Infected Wounds

Based on the qualities of Ulmo honey (Eucryphia cordifolia), a medical-grade honey (Ulmoplus®) has been developed. Relevant to this, the use of copper represents an emerging therapy for the treatment of wounds. Therefore, the aim of this study was to see how this medical-grade honey with copper nanoparticles (CuNPs) helped to heal infected or non-infected wounds. Twenty-four guinea pigs (Cavia porcellus) were divided into four groups for phase 1 (without and with infection, U + F1 and U + F2), and two groups for phase 2 (selected formulation, without and with infection, U + F2NI and U + F2I). Bacteriological and histopathological studies, collagen fibers content evaluation, and stereological analysis were performed. The selected formulation displayed the same antibacterial potency as Ulmoplus®, indicating that this medical-grade honey by itself can be used as an antibacterial agent. However, the evaluation of collagen content demonstrated a significant increase in fibroblast and type III collagen fibers for infected and uninfected groups, which correlated with the histopathological study. Therefore, it is correct to affirm that adding CuNPs to Ulmoplus® improved the maturation of collagen fibers. Finally, polymorphonuclear cells presented similar values between experimental groups, which would indicate that the formulation under study was able to regulate the inflammatory process despite their infectious condition.

Healing Effect of a Nano-Functionalized Medical-Grade Honey for the Treatment of Infected Wounds

Based on the qualities of Ulmo honey (Eucryphia cordifolia), a medical-grade honey (Ulmoplus®) has been developed. Relevant to this, the use of copper represents an emerging therapy for the treatment of wounds. Therefore, the aim of this study was to see how this medical-grade honey with copper nanoparticles (CuNPs) helped to heal infected or non-infected wounds. Twenty-four guinea pigs (Cavia porcellus) were divided into four groups for phase 1 (without and with infection, U + F1 and U + F2), and two groups for phase 2 (selected formulation, without and with infection, U + F2NI and U + F2I). Bacteriological and histopathological studies, collagen fibers content evaluation, and stereological analysis were performed. The selected formulation displayed the same antibacterial potency as Ulmoplus®, indicating that this medical-grade honey by itself can be used as an antibacterial agent. However, the evaluation of collagen content demonstrated a significant increase in fibroblast and type III collagen fibers for infected and uninfected groups, which correlated with the histopathological study. Therefore, it is correct to affirm that adding CuNPs to Ulmoplus® improved the maturation of collagen fibers. Finally, polymorphonuclear cells presented similar values between experimental groups, which would indicate that the formulation under study was able to regulate the inflammatory process despite their infectious condition.

Functional carbohydrate-based hydrogels for diabetic wound therapy

Diabetes wound are grave and universal complications of diabetes. Owing to poor treatment course, high amputation rate and mortality, diabetes wound treatment and care have become a global challenge. Wound dressings have received much attention due to their ease of use, good therapeutic effect, and low costs. Among them, carbohydrate-based hydrogels with excellent biocompatibility are considered to be the best candidates for wound dressings. Based on this, we first systematically summarized the problems and healing mechanism of diabetes wounds. Next, common treatment methods and wound dressings were discussed, and the application of various carbohydrate-based hydrogels and their corresponding functionalization (antibacterial, antioxidant, autoxidation and bioactive substance delivery) in the treatment of diabetes wounds were emphatically introduced. Ultimately, the future development of carbohydrate-based hydrogel dressings was proposed. This review aims to provide a deeper understanding of wound treatment and theoretical support for the design of hydrogel dressings.

Cellular Therapeutics for Chronic Wound Healing: Future for Regenerative Medicine

Chronic wounds are associated with significant morbidity and mortality, which demand long-term effective treatment and represent a tremendous financial strain on the global healthcare systems. Regenerative medicines using stem cells have recently become apparent as a promising approach and are an active zone of investigation. They hold the potential to differentiate into specific types of cells and thus possess self-renewable, regenerative, and immune-modulatory effects. Furthermore, with the rise of technology, various cell therapies and cell types such as Bone Marrow and Adipose-derived Mesenchymal Cell (ADMSC), Endothelial Progenitor Cells (EPCs), Embryonic Stem Cells (ESCs), Mesenchymal Stem Cell (MSCs), and Pluripotent Stem Cells (PSCs) are studied for their therapeutic impact on reparative processes and tissue regeneration. Cell therapy has proven to have substantial control over enhancing the quality and rate of skin regeneration and wound restoration. The literature review brings to light the mechanics of wound healing, abnormalities resulting in chronic wounds, and the obstacles wound care researchers face, thus exploring the multitude of opportunities for potential improvement. Also, the review is focused on providing particulars on the possible cell-derived therapeutic choices and their associated challenges in healing, in the context of clinical trials, as solutions to these challenges will provide fresh and better future opportunities for improved study design and therefore yield a substantial amount of data for the development of more specialized treatments.

Multifunctional 3D platforms for rapid hemostasis and wound healing: Structural and functional prospects at biointerfaces

354Fabrication of multifunctional hemostats is indispensable against chronic blood loss and accelerated wound healing. Various hemostatic materials that aid wound repair or rapid tissue regeneration has been developed in the last 5 years. This review provides an overview of the three-dimensional (3D) hemostatic platforms designed through the latest technologies like electrospinning, 3D printing, and lithography, solely or in combination, for application in rapid wound healing. We critically discuss the pivotal role of micro/nano-3D topography and biomaterial properties in mediating rapid blood clots and healing at the hemostat-biointerface. We also highlight the advantages and limitations of the designed 3D hemostats. We anticipate that this review will guide the fabrication of smart hemostats of the future for tissue engineering applications.

Topographical and Compositional Gradient Tubular Scaffold for Bone to Tendon Interface Regeneration

The enthesis is an extremely specific region, localized at the tendon–bone interface (TBI) and made of a hybrid connection of fibrocartilage with minerals. The direct type of enthesis tissue is commonly subjected to full laceration, due to the stiffness gradient between the soft tissues and hard bone, and this often reoccurs after surgical reconstruction. For this purpose, the present work aimed to design and develop a tubular scaffold based on pullulan (PU) and chitosan (CH) and intended to enhance enthesis repair. The scaffold was designed with a topographical gradient of nanofibers, from random to aligned, and hydroxyapatite (HAP) nanoparticles along the tubular length. In particular, one part of the tubular scaffold was characterized by a structure similar to bone hard tissue, with a random mineralized fiber arrangement; while the other part was characterized by aligned fibers, without HAP doping. The tubular shape of the scaffold was also designed to be extemporarily loaded with chondroitin sulfate (CS), a glycosaminoglycan effective in wound healing, before the surgery. Micro CT analysis revealed that the scaffold was characterized by a continuous gradient, without interruptions from one end to the other. The gradient of the fiber arrangement was observed using SEM analysis, and it was still possible to observe the gradient when the scaffold had been hydrated for 6 days. In vitro studies demonstrated that human adipose stem cells (hASC) were able to grow and differentiate onto the scaffold, expressing the typical ECM production for tendon in the aligned zone, or bone tissue in the random mineralized part. CS resulted in a synergistic effect, favoring cell adhesion/proliferation on the scaffold surface. These results suggest that this tubular scaffold loaded with CS could be a powerful tool to support enthesis repair upon surgery.

Evaluating polymeric biomaterials to improve next generation wound dressing design

Wound healing is a dynamic series of interconnected events with the ultimate goal of promoting neotissue formation and restoration of anatomical function. Yet, the complexity of wound healing can often result in development of complex, chronic wounds, which currently results in a significant strain and burden to our healthcare system. The advancement of new and effective wound care therapies remains a critical issue, with the current therapeutic modalities often remaining inadequate. Notably, the field of tissue engineering has grown significantly in the last several years, in part, due to the diverse properties and applications of polymeric biomaterials. The interdisciplinary cohesion of the chemical, biological, physical, and material sciences is pertinent to advancing our current understanding of biomaterials and generating new wound care modalities. However, there is still room for closing the gap between the clinical and material science realms in order to more effectively develop novel wound care therapies that aid in the treatment of complex wounds. Thus, in this review, we discuss key material science principles in the context of polymeric biomaterials, provide a clinical breadth to discuss how these properties affect wound dressing design, and the role of polymeric biomaterials in the innovation and design of the next generation of wound dressings.

Matrix Metalloproteases from Adipose Tissue-Derived Stromal Cells Are Spatiotemporally Regulated by Hydrogel Mechanics in a 3D Microenvironment

Adipose tissue-derived stromal cells (ASCs) are of interest in tissue engineering and regenerative medicine (TERM) due to their easy acquisition, multipotency, and secretion of a host of factors that promote regeneration. Retention of ASCs in or around lesions is poor following direct administration. Therefore, for TERM applications, ASCs can be ‘immobilized’ via their incorporation into hydrogels such as gelatine methacryloyl (GelMA). Tweaking GelMA concentration is a common approach to approximate the mechanical properties found in organs or tissues that need repair. Distinct hydrogel mechanics influence the ability of a cell to spread, migrate, proliferate, and secrete trophic factors. Mesenchymal cells such as ASCs are potent remodellers of the extracellular matrix (ECM). Not only do ASCs deposit components, they also secrete matrix metalloproteases (MMPs) which degrade ECM. In this work, we investigated if GelMA polymer concentration influenced the expression of active MMPs by ASCs. In addition, MMPs’ presence was interrogated with regard to ASCs morphology and changes in hydrogel ultrastructure. For this, immortalised ASCs were embedded in 5%, 10%, and 15% (w/v) GelMA hydrogels, photopolymerised and cultured for 14 d. Zymography in situ indicated that MMPs had a variable, hydrogel concentration-dependent influence on ASCs-secreted MMPs. In 5% GelMA, ASCs showed a high and sustained expression of MMPs, while, in 10% and 15% GelMA, such expression was almost null. ASCs morphology based on F-actin staining showed that increasing GelMA concentrations inhibit their spreading. Scanning electron microscopy (SEM) showed that hydrogel ultrastructure in terms of pore density, pore size, and percentage porosity were not consistently influenced by cells. Interestingly, changes in ultrastructural parameters were detected also in cell-free materials, albeit without a clear trend. We conclude that hydrogel concentration and its underlying mechanics influenced MMP expression by ASCs. The exact MMPs that respond to these mechanical cues should be defined in follow-up experiments.

Role of copper nanoparticles in wound healing for chronic wounds: literature review

Chronic wounds are defined as wounds that fail to proceed through the normal phases of wound healing in an orderly and timely manner. The most common and inevitable impairment to wound healing is the installation of an infection, usually in the case of chronic wounds. Therefore, the objective of the present review was to identify the importance of copper nanoparticles in dressings for wound healing. Nanoparticles such as silver, gold and copper combat infectious processes through the inhibition of protein synthesis, peroxidation of the cell membrane and destroying the nucleic acids of bacteria and viruses. Among bioactive nanoparticles, copper plays a complex role in various cells, it modulates several cytokines and growth factor mechanisms of action and is essentially involved in all stages of the wound healing process. More importantly, copper plays a key role in skin regeneration and angiogenesis and accelerates the healing process through induction of vascular endothelial growth factor (VEGF) and angiogenesis by hypoxia-induced factor-1-alpha (HIF-1α) action where copper enhances HIF-1α expression and HIF-1α binding to the critical motifs in the promoter and putative enhancer regions of HIF-1-regulated genes.

Bringing hydrogel-based craniofacial therapies to the clinic

This review explores the evolution of the use of hydrogels for craniofacial soft tissue engineering, ranging in complexity from acellular injectable fillers to fabricated, cell-laden constructs with complex compositions and architectures. Addressing both in situ and ex vivo approaches, tissue restoration secondary to trauma or tumor resection is discussed. Beginning with relatively simple epithelia of oral mucosa and gingiva, then moving to more functional units like vocal cords or soft tissues with multilayer branched structures, such as salivary glands, various approaches are presented toward the design of function-driven architectures, inspired by native tissue organization. Multiple tissue replacement paradigms are presented here, including the application of hydrogels as structural materials and as delivery platforms for cells and/or therapeutics. A practical hierarchy is proposed for hydrogel systems in craniofacial applications, based on their material and cellular complexity, spatial order, and biological cargo(s). This hierarchy reflects the regulatory complexity dictated by the Food and Drug Administration (FDA) in the United States prior to commercialization of these systems for use in humans. The wide array of available biofabrication methods, ranging from simple syringe extrusion of a biomaterial to light-based spatial patterning for complex architectures, is considered within the history of FDA-approved commercial therapies. Lastly, the review assesses the impact of these regulatory pathways on the translational potential of promising pre-clinical technologies for craniofacial applications. STATEMENT OF SIGNIFICANCE: While many commercially available hydrogel-based products are in use for the craniofacial region, most are simple formulations that either are applied topically or injected into tissue for aesthetic purposes. The academic literature previews many exciting applications that harness the versatility of hydrogels for craniofacial soft tissue engineering. One of the most exciting developments in the field is the emergence of advanced biofabrication methods to design complex hydrogel systems that can promote the functional or structural repair of tissues. To date, no clinically available hydrogel-based therapy takes full advantage of current pre-clinical advances. This review surveys the increasing complexity of the current landscape of available clinical therapies and presents a framework for future expanded use of hydrogels with an eye toward translatability and U.S. regulatory approval for craniofacial applications.

Self-adhesive hydrogels for tissue engineering

Hydrogels consisting of a three-dimensional hydrophilic network of biocompatible polymers have been widely used in tissue engineering. Owing to their tunable mechanical properties, hydrogels have been applied in both hard and soft tissues. However, most hydrogels lack self-adhesive properties that enable integration with surrounding tissues, which may result in suture or low repair efficacy. Self-adhesive hydrogels (SAHs), an emerging class of hydrogels based on a combination of three-dimensional hydrophilic networks and self-adhesive properties, continue to garner increased attention in recent years. SAHs exhibit reliable and suitable adherence to tissues, and easily integrate into tissues to promote repair efficiency. SAHs are designed either by mimicking the adhesion mechanism of natural organisms, such as mussels and sandcastle worms, or by using supramolecular strategies. This review summarizes the design and processing strategies of SAHs, clarifies underlying adhesive mechanisms, and discusses their applications in tissue engineering, as well as future challenges.

Biomimetic Hydrogels to Promote Wound Healing

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

Curcumin preconditioning enhances the efficacy of adipose-derived mesenchymal stem cells to accelerate healing of burn wounds

Background

Following recent findings from our group that curcumin preconditioning augments the therapeutic efficacy of adipose-derived stem cells in the healing of diabetic wounds in rats, we aimed to investigate the regenerative effects of curcumin preconditioned adipose-derived mesenchymal stem cells (ASCs) for better recovery of acid inflicted burns in this study.

Methods

ASCs were preconditioned with 5 μM curcumin for 24 hours and assessed for proliferation, migration, paracrine release potential and gene expression comparative to naïve ASCs. Subsequently, the healing capacity of curcumin preconditioned ASCs (Cur-ASCs) versus naïve ASCs was examined using acidic wounds in rats. For this, acid inflicted burns of 20 mm in diameter were made on the back of male Wistar rats. Then, 2 × 10⁶ cells of Cur-ASCs and naïve ASCs were intradermally injected in the wound periphery (n = 6) for comparison with an untreated saline control. Post-transplantation, wounds were macroscopically analysed and photographed to evaluate the percentage of wound closure and period of re-epithelization. Healed wound biopsies were excised and used for histological evaluation and expression analysis of wound healing markers at molecular level by quantitative PCR and western blotting.

Results

We found that Cur-ASCs exhibited greater proliferation, migration and paracrine potential in vitro. Further, Cur-ASCs showed more effective recovery than naïve ASCs as exhibited by gross morphology, faster wound closure and earlier re-epithelialization. Masson’s trichrome and hematoxylin and eosin staining demonstrated the improved architecture of the healing burns, as evidenced by reduced infiltration of inflammatory cells, compact collagen and marked granulation in Cur-ASC treated rats. Corroborating these findings, molecular assessment showed significantly reduced expressions of pro-inflammatory factors (interleukin-1 beta, interleukin-6, tumor necrosis factor alpha) a with striking upsurge of an oxidative marker (superoxide dismutase 1), pro-angiogenic factors (vascular endothelial growth factor, hepatocyte growth factor, hypoxia-inducible factor-1 alpha) and collagen markers (transforming growth factor beta 1, fibroblast growth factor-2, collagen type 1 alpha 1), verifying that Cur-ASCs modulate the regulation of pro-inflammatory and healing markers at burn sites.

Conclusions

Treatment with Cur-ASCs resulted in faster re-epithelization of acid inflicted burns compared to the treatment with naïve ASCs. Based on observed findings, we suggest the transplantation of Cur-ASCs is a valuable therapy for the potent clinical management of acidic burns.

Wound healing applications of creams and "smart" hydrogels

Although superficial wounds are often easy to treat for healthy individuals, there are some more severe types of wounds (burns, ulcers, diabetic wounds, etc.) that are a challenge for clinicians. A good therapeutic result is based on the delivery of a treatment at the right time, for the right patient. Our goal was to sum up useful knowledge regarding wound healing and wound treatments, based on creams and hydrogels with various active ingredients. We concluded that both preparations have application in preventing infections and promoting healing, but their efficacy is clearly conditioned by the type, depth, severity of the wound and patient profile. However, due to their superior versatility and capability of maintaining the integrity and functionality of the active ingredient, as well as it is controlled release at site, hydrogels are more suited for incorporating different active ingredients. New wound healing devices can combine smart hydrogel dressings with physical therapies to deliver a more efficient treatment to patients if the indications are appropriate.

Hydrogel Scaffolds to Deliver Cell Therapies for Wound Healing

Cutaneous wounds are a growing global health burden as a result of an aging population coupled with increasing incidence of diabetes, obesity, and cancer. Cell-based approaches have been used to treat wounds due to their secretory, immunomodulatory, and regenerative effects, and recent studies have highlighted that delivery of stem cells may provide the most benefits. Delivering these cells to wounds with direct injection has been associated with low viability, transient retention, and overall poor efficacy. The use of bioactive scaffolds provides a promising method to improve cell therapy delivery. Specifically, hydrogels provide a physiologic microenvironment for transplanted cells, including mechanical support and protection from native immune cells, and cell-hydrogel interactions may be tailored based on specific tissue properties. In this review, we describe the current and future directions of various cell therapies and usage of hydrogels to deliver these cells for wound healing applications.

Multiplex Analysis of Adipose-Derived Stem Cell (ASC) Immunophenotype Adaption to In Vitro Expansion

In order to enhance the therapeutic potential, it is important that sufficient knowledge regarding the dynamic changes of adipose-derived stem cell (ASC) immunophenotypical and biological properties during in vitro growth is available. Consequently, we embarked on a study to follow the evolution of highly defined cell subsets from three unrelated donors in the course of eight passages on tissue culture polystyrene. The co-expression patterns were defined by panels encompassing seven and five cell surface markers, including CD34, CD146, CD166, CD200, CD248, CD271, and CD274 and CD29, CD31, CD36, CD201, and Stro-1, respectively. The analysis was performed using multichromatic flow cytometry. We observed a major paradigm shift, where the CD166-CD34⁺ combination which was found across all cell subsets early in the culture was replaced by the CD166⁺ phenotype as the population homogeneity increased with time. At all analysis points, the cultures were dominated by a few major clones that were highly prevalent in most of the donors. The selection process resulted in two predominant clones in the larger panel (CD166⁺CD34^-CD146^-CD271^- CD274^-CD248^-CD200^- and CD166⁺CD34⁺ CD146^-CD271^-CD274^-CD248^-CD200^-) and one clone in the smaller panel (CD29⁺CD201⁺CD36^- Stro-1^- CD31^-). The minor subsets, including CD166⁺CD34^-CD146^-CD271⁺CD274^-CD248^-CD200^- and CD166⁺CD34⁺CD146⁺CD271^-CD274^-CD248^-CD200^-, and CD29⁺CD201^-CD36^-Stro-1^-CD31^-, CD29⁺CD201⁺CD36^-Stro-1⁺CD31^-, and CD29⁺CD201⁺CD36⁺Stro-1^-CD31^-, in the seven and five marker panels, respectively, were, on the other, hand highly fluctuating and donor-dependent. The results demonstrate that only a limited number of phenotypical repertoires are possible in ASC cultures. Marked differences in their relative occurrence between distinct individuals underscore the need for potency standardization of different ASC preparation to improve the clinical outcome.

Landscape of transcription and expression regulated by DNA methylation related to age of donor and cell passage in adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (ADSCs) are pluripotent stromal cells that can differentiate into a variety of cell types, including skin cells. High-throughput sequencing was performed on cells of different ages and cell passage, obtaining their methylation, mRNA expression, and protein profile data. The stemness of each sample was then calculated using the TCGAbiolinks package in R. Co-expression modules were identified using WGCNA, and a crosstalk analysis was performed on the corresponding modules. The ClusterProfile package was used for the functional annotation of module genes. Finally, the regulatory network diagram was visualized using the Cytoscape software. First, a total of 16 modules were identified, where 3 modules were screened that were most relevant to the phenotype. 29 genes were screened in combination of the RNA seq, DNA methylation seq and protein iTRAQ. Finally, a comprehensive landscape comprised of RNA expression, DNA methylation and protein profiles of age relevant ADSCs was constructed. Overall, the different omics of ADSCs were comprehensively analyzed in order to reveal mechanisms pertaining to their growth and development. The effects of age, cell passage, and stemness on the therapeutic effect of ADSCs were explored. Additionally, a theoretical basis for selecting appropriate ADSC donors for regenerative medicine was provided.

Analysis of Cell-seeded, Collagen-rich Hydrogel for Wound Healing

Our laboratory has previously developed a novel collagen-rich hydrogel (cHG), which significantly increases the speed of wound healing in diabetic rats.

Methods

In this study, we examine the in vitro survival and migration of fibroblasts, endothelial cells, and adipose-derived stem cells in a novel cHG. Furthermore, we test the ability of adipose-derived stem cell-seeded cHG to support cell survival and accelerate healing in vivo.

Results

In vitro, cell survival within the cHG was retained for 25 days. We were unable to detect cellular migration into, out of, or through cHG. In the in vivo model, bioluminescence of stem cells seeded within the cHG in diabetic rat wounds was detected until day 10. Rate of wound closure was higher for cHG plus adipose-derived stem cells versus control from day 2 until day 16 and significant on days 6, 8, and 12 (P < 0.05). This significant difference was also observed on day 16 by histology (P ≤ 0.05).

Conclusions

We conclude that cHG is a good candidate for delivering adipose-derived stem cells, endothelial cells, and fibroblasts to wounds. Future studies will determine whether the delivery of combinations of different cell lines in cHG further enhances wound healing.

Adipose tissue and the vascularization of biomaterials: Stem cells, microvascular fragments and nanofat-a review

Tissue defects in the human body after trauma and injury require precise reconstruction to regain function. Hence, there is a great demand for clinically translatable approaches with materials that are both biocompatible and biodegradable. They should also be able to adequately integrate within the tissue through sufficient vascularization. Adipose tissue is abundant and easily accessible. It is a valuable tissue source in regenerative medicine and tissue engineering, especially with regard to its angiogenic potential. Derivatives of adipose tissue, such as microfat, nanofat, microvascular fragments, stromal vascular fraction and stem cells, are commonly used in research, but also clinically to enhance the vascularization of implants and grafts at defect sites. In plastic surgery, adipose tissue is harvested via liposuction and can be manipulated in three ways (macro-, micro- and nanofat) in the operating room, depending on its ultimate use. Whereas macro- and microfat are used as a filling material for soft tissue injuries, nanofat is an injectable viscous extract that primarily induces tissue remodeling because it is rich in growth factors and stem cells. In contrast to microfat that adds volume to a defect site, nanofat has the potential to be easily combined with scaffold materials due to its liquid and homogenous consistency and is particularly attractive for blood vessel formation. The same is true for microvascular fragments that are easily isolated from adipose tissue through collagenase digestion. In preclinical animal models, it has been convincingly shown that these vascular fragments inosculate with host vessels and subsequently accelerate scaffold perfusion and host tissue integration. Adipose tissue is also an ideal source of stem cells. It yields larger quantities of cells than any other source and is easier to access for both the patient and doctor compared with other sources such as bone marrow. They are often used for tissue regeneration in combination with biomaterials. Adipose-derived stem cells can be applied unmodified or as single cell suspensions. However, certain pretreatments, such as cultivation under hypoxic conditions or three-dimensional spheroids production, may provide substantial benefit with regard to subsequent vascularization in vivo due to induced growth factor production. In this narrative review, derivatives of adipose tissue and the vascularization of biomaterials are addressed in a comprehensive approach, including several sizes of derivatives, such as whole fat flaps for soft tissue engineering, nanofat or stem cells, their secretome and exosomes. Taken together, it can be concluded that adipose tissue and its fractions down to the molecular level promote, enhance and support vascularization of biomaterials. Therefore, there is a high potential of the individual fat component to be used in regenerative medicine.

Co-transplantation with adipose-derived cells to improve parathyroid transplantation in a mice model

Background

Accidentally removed parathyroid glands are still challenging in neck surgery, leading to hypoparathyroidism characterized with abnormally low levels of parathyroid hormone. Parathyroid auto-transplantation is usually applied in compensation. To improve the efficiency of parathyroid transplantation, we introduced a method by co-transplanting with adipose-derived cells, including stromal vascular fractions (SVFs) and adipose-derived stem cells (ADSCs), and investigated the underlying molecular mechanisms involved in parathyroid transplantation survival.

Methods

Rat and human parathyroid tissues were transplanted into nude mice as parathyroid transplantation model to examine the effects of SVFs and ADSCs on grafts angiogenesis and survival rates, including blood vessel assembly and parathyroid hormone levels. Several angiogenic factors, such as vascular endothelial growth factor (VEGF)-A and fibroblast growth factor (FGF) 2, were assessed in parathyroid grafts. The effects of hypoxia were investigated on ADSCs. The modulatory roles of the eyes absent homolog 1 (EYA1), which is vital in parathyroid development, was also investigated on angiogenic factor production and secretion by ADSCs. All experimental data were statistically processed. Student’s t test was used to assess significant differences between 2 groups. For multiple comparisons with additional interventions, two-way ANOVA followed by Tukey’s post hoc test was performed. P < 0.05 was considered as significant.

Results

SVFs improve rat parathyroid transplantation survival and blood vessel assembly, as well as FGF2 and VEGF-A expression levels in parathyroid transplantation mice. Functional human parathyroid grafts have higher microvessel density and increased VEGF-A expression. The supernatant of ADSCs induced tubule formation and migration of human endothelial cells in vitro. Hypoxia had no effect on proliferation and apoptosis of human ADSCs but induced higher angiogenic factor levels of VEGF-A and FGF2, modulated by EYA1, which was confirmed by parathyroid glands transplantation in mice.

Conclusions

Adipose-derived cells, including ADSCs and SVFs, improve parathyroid transplantation survival via promoting angiogenesis through EYA1-regulating angiogenetic factors in vitro and in vivo. Our studies proved an effective method to improve the parathyroid autotransplantation, which is promising for clinical patients with hypoparathyroidism when parathyroid glands were accidentally injured, removed, or devascularized.

Design Considerations for Hydrogel Wound Dressings: Strategic and Molecular Advances

Wound dressings are traditionally used to protect a wound and to facilitate healing. Currently, their function is expanding. There is an urgent need for new smart products that not only act as a protective barrier but also actively support the wound healing process. Hydrogel dressings are an example of such innovative products and typically facilitate wound healing by providing a hospitable and moist environment in which cells can thrive, while the wound can still breathe and exudate can be drained. These dressings also tend to be less painful or have a soothing effect and allow for additional drug delivery. In this review, various strategic and molecular design considerations are discussed that are relevant for developing a hydrogel into a wound dressing product. These considerations vary from material choice to ease of use and determine the dressing's final properties, application potential, and benefits for the patient. The focus of this review lies on identifying and explaining key aspects of hydrogel wound dressings and their relevance in the different phases of wound repair. Molecular targets of wound healing are discussed that are relevant when tailoring hydrogels toward specific wound healing scenarios. In addition, the potential of hydrogels is reviewed as medicine advances from a repair-based wound healing approach toward a regenerative-based one. Hydrogels can play a key role in the transition toward personal wound care and facilitating regenerative medicine strategies by acting as a scaffold for (stem) cells and carrier/source of bioactive molecules and/or drugs. Impact statement Improved wound healing will lead to a better quality of life around the globe. It can be expected that this coincides with a reduction in health care spending, as the duration of treatment decreases. To achieve this, new and modern wound care products are desired that both facilitate healing and improve comfort and outcome for the patient. It is proposed that hydrogel wound dressings can play a pivotal role in improving wound care, and to that end, this review aims to summarize the various design considerations that can be made to optimize hydrogels for the purpose of a wound dressing.

Tunable hydrogels for mesenchymal stem cell delivery: Integrin-induced transcriptome alterations and hydrogel optimization for human wound healing

Therapeutic applications for mesenchymal stem/stromal cells (MSCs) are growing; however, the successful implementation of these therapies requires the development of appropriate MSC delivery systems. Hydrogels are ideally suited to cultivate MSCs but tuning hydrogel properties to match their specific in vivo applications remains a challenge. Thus, further characterization of how hydrogel-based delivery vehicles broadly influence MSC function and fate will help lead to the next generation of more intelligently designed delivery vehicles. To date, few attempts have been made to comprehensively characterize hydrogel impact on the MSC transcriptome. Herein, we have synthesized cell-degradable hydrogels based on bio-inert poly(ethylene glycol) tethered with specific integrin-binding small molecules and have characterized their resulting effect on the MSC transcriptome when compared with 2D cultured and untethered 3D hydrogel cultured MSCs. The 3D culture systems resulted in alterations in the MSC transcriptome, as is evident by the differential expression of genes related to extracellular matrix production, glycosylation, metabolism, signal transduction, gene epigenetic regulation, and development. For example, genes important for osteogenic differentiation were upregulated in 3D hydrogel cultures, and the expression of these genes could be partially suppressed by tethering an integrin-binding RGD peptide within the hydrogel. Highlighting the utility of tunable hydrogels, when applied to ex vivo human wounds the RGD-tethered hydrogel was able to support wound re-epithelialization, possibly due to its ability to increase PDGF expression and decrease IL-6 expression. These results will aid in future hydrogel design for a broad range of applications.

Tissue-Engineered Soft-Tissue Reconstruction Using Noninvasive Mechanical Preconditioning and a Shelf-Ready Allograft Adipose Matrix

BACKGROUND

Adipose tissue defects leading to severe functional (disability) and morphologic (disfigurement) morbidity are often treated in plastic surgery with fat grafting, which can be limited by resorption, necrosis, and cyst formation. This study aimed to assess whether adipose scaffolds could provide an environment for in situ autologous fat grafting, and to study whether adipose cell migration and proliferation (adipogenesis) within scaffolds could be enhanced by preliminarily increasing the vascularity (preconditioning) of the surrounding tissue receiving the scaffolds.

METHODS

Using an established rodent model of subcutaneous tissue/scaffold grafting, the authors tested the potential of a human-derived, shelf-ready, injectable, decellularized allograft adipose matrix to reconstruct soft-tissue defects when used in combination with noninvasive mechanical (suction-induced) skin preconditioning.

RESULTS

Combined use of the allograft adipose matrix and noninvasive skin preconditioning significantly improved long-term volume retention (50 to 80 percent higher at a 12-week follow-up) and histologic quality of reconstructed tissues compared with standard of care (autologous adipose grafts). The components of the allograft adipose matrix supported adipogenesis and angiogenesis. Combining the allograft adipose matrix with living adipose grafts mitigated negative outcomes (lower long-term volume retention, higher presence of cystic-like areas).

CONCLUSIONS

This study suggests that the synergistic use of the allograft adipose matrix and noninvasive tissue preconditioning provides an effective solution for improving fat grafting. These strategies can easily be tested in clinical trials and could establish the basis for a novel therapeutic paradigm in reconstructive surgery.

Hydrogel-Based Strategies to Advance Therapies for Chronic Skin Wounds

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

Matrix-assisted cell transplantation for tissue vascularization

Cell therapy offers much promise for the treatment of ischemic diseases by augmenting tissue vasculogenesis. Matrix-assisted cell transplantation (MACT) has been proposed as a solution to enhance cell survival and integration with host tissue following transplantation. By designing semi synthetic matrices (sECM) with the correct physical and biochemical signals, encapsulated cells are directed towards a more angiogenic phenotype. In this review, we describe the choice of cells suitable for pro-angiogenic therapies, the properties that should be considered when designing sECM for transplantation and their relative importance. Pre-clinical models where MACT has been successfully applied to promote angiogenesis are reviewed to show the great potential of this strategy to treat ischemic conditions.

Therapeutic strategies for enhancing angiogenesis in wound healing

The enhancement of wound healing has been a goal of medical practitioners for thousands of years. The development of chronic, non-healing wounds is a persistent medical problem that drives patient morbidity and increases healthcare costs. A key aspect of many non-healing wounds is the reduced presence of vessel growth through the process of angiogenesis. This review surveys the creation of new treatments for healing cutaneous wounds through therapeutic angiogenesis. In particular, we discuss the challenges and advancement that have been made in delivering biologic, pharmaceutical and cell-based therapies as enhancers of wound vascularity and healing.

Adipose-derived stem cells promote survival, growth, and maturation of early-stage murine follicles

BACKGROUND

Premature ovarian insufficiency is a common complication of anticancer treatments in young women and girls. The ovary is a complex, highly regulated reproductive organ, whose proper function is contingent upon the bidirectional endocrine, paracrine, and autocrine signaling. These factors facilitate the development of the follicles, the functional units of the ovary, to progress from the gonadotropin-independent, paracrine-controlled early stage to the gonadotropin-dependent, endocrine-controlled later stage. We hypothesized that the low survival rate of individually cultured early-stage follicles could be improved with co-culture of adipose-derived stem cells (ADSCs) that secrete survival- and growth-promoting factors.

MATERIALS AND METHODS

Ovarian follicles ranging from 85 to 115 μm in diameter, from 10- to 12-day-old B6CBAF1 mice were mechanically isolated and co-encapsulated with ADSCs within alginate-based 3D culture system. The follicles were cultured for 14 days, imaged using light microscopy every 2 days, and matured at the end. Follicle media were changed every 2 days and collected for hormone measurements. Follicle diameter, morphology, number of transzonal projections, and survival and maturation rates were recorded. Statistical analyses using one- and two-way ANOVA were performed to compare hormone levels, survival of the follicles and ADSCs, oocyte maturation rates, and follicle growth.

RESULTS

The co-encapsulation of the follicles with ADSCs increased follicle survival, ranging from 42.4% for the 86-95 μm to 86.2% for the 106-115-μm follicle size group. Co-culture also improved the follicle growth, the rate of antrum formation and oocyte maturation compared to the follicles cultured alone. The levels of androstenedione, estradiol, and progesterone of co-encapsulated follicles increased progressively with time in culture.

CONCLUSIONS

To our knowledge, this is the first report of an in vitro system utilizing mouse adipose-derived stem cells to support the development of the mouse follicles. Our findings suggest that co-encapsulation of ADSCs with early-stage follicles supports follicular development, through secretion of cytokines that promote follicular survival, antrum formation, and meiotic competence. The unique 3D culture system that supports the survival of both cell types has translational implications, as ADSCs could be used as an autologous source for in vitro maturation of early-stage human follicles.

Wound Healing: A Cellular Perspective

Wound healing is one of the most complex processes in the human body. It involves the spatial and temporal synchronization of a variety of cell types with distinct roles in the phases of hemostasis, inflammation, growth, re-epithelialization, and remodeling. With the evolution of single cell technologies, it has been possible to uncover phenotypic and functional heterogeneity within several of these cell types. There have also been discoveries of rare, stem cell subsets within the skin, which are unipotent in the uninjured state, but become multipotent following skin injury. Unraveling the roles of each of these cell types and their interactions with each other is important in understanding the mechanisms of normal wound closure. Changes in the microenvironment including alterations in mechanical forces, oxygen levels, chemokines, extracellular matrix and growth factor synthesis directly impact cellular recruitment and activation, leading to impaired states of wound healing. Single cell technologies can be used to decipher these cellular alterations in diseased states such as in chronic wounds and hypertrophic scarring so that effective therapeutic solutions for healing wounds can be developed.

Fibrin Glue Enhances Adipose-Derived Stromal Cell Cytokine Secretion and Survival Conferring Accelerated Diabetic Wound Healing

Introduction

Although chronic wounds are a major personal and economic burden, treatment options are still limited. Among those options, adipose-derived stromal cell- (ASC-) based therapies rank as a promising approach but are restricted by the harsh wound environment. Here we use a commercially available fibrin glue to provide a deliverable niche for ASCs in chronic wounds.

Material and Methods

To investigate the in vitro effect of fibrin glue, cultivation experiments were performed and key cytokines for regeneration were quantified. By using an established murine chronic diabetic wound-healing model, we evaluated the influence of fibrin glue spray seeding on cell survival (In Vivo Imaging System, IVIS), wound healing (wound closure kinetics), and neovascularization of healed wounds (CD31 immunohistochemistry).

Results

Fibrin glue seeding leads to a significantly enhanced secretion of key cytokines (SDF-1, bFGF, and MMP-2) of human ASCs in vitro. IVIS imaging showed a significantly prolonged murine ASC survival in diabetic wounds and significantly accelerated complete wound closure in the fibrin glue seeded group. CD31 immunohistochemistry revealed significantly more neovascularization in healed wounds treated with ASCs spray seeded in fibrin glue vs. ASC injected into the wound bed.

Conclusion

Although several vehicles have shown to successfully act as cell carrier systems in preclinical trials, regulatory issues have prohibited clinical usage for chronic wounds. By demonstrating the ability of fibrin glue to act as a carrier vehicle for ASCs, while simultaneously enhancing cellular regenerative function and viability, this study is a proponent of clinical translation for ASC-based therapies.

Single-Cell Gene Expression Analysis and Evaluation of the Therapeutic Function of Murine Adipose-Derived Stromal Cells (ASCs) from the Subcutaneous and Visceral Compartment

Introduction

Adipose-derived stromal cells (ASCs) are a promising resource for wound healing and tissue regeneration because of their multipotent properties and cytokine secretion. ASCs are typically isolated from the subcutaneous fat compartment, but can also be obtained from visceral adipose tissue. The data on their equivalence diverges. The present study analyzes the cell-specific gene expression profiles and functional differences of ASCs derived from the subcutaneous (S-ASCs) and the visceral (V-ASCs) compartment.

Material and Methods

Subcutaneous and visceral ASCs were obtained from mouse inguinal fat and omentum. The transcriptional profiles of the ASCs were compared on single-cell level. S-ASCs and V-ASCs were then compared in a murine wound healing model to evaluate their regenerative functionality.

Results

On a single-cell level, S-ASCs and V-ASCs displayed distinct transcriptional profiles. Specifically, significant differences were detected in genes associated with neoangiogenesis and tissue remodeling (for example, Ccl2, Hif1α, Fgf7, and Igf). In addition, a different subpopulation ecology could be identified employing a cluster model. Nevertheless, both S-ASCs and V-ASCs induced accelerated healing rates and neoangiogenesis in a mouse wound healing model.

Conclusion

With similar therapeutic potential in vivo, the significantly different gene expression patterns of ASCs from the subcutaneous and visceral compartments suggest different signaling pathways underlying their efficacy. This study clearly demonstrates that review of transcriptional results in vivo is advisable to confirm the tentative effect of cell therapies.

Advancements in Regenerative Strategies Through the Continuum of Burn Care

Burns are caused by several mechanisms including flame, scald, chemical, electrical, and ionizing and non-ionizing radiation. Approximately half a million burn cases are registered annually, of which 40 thousand patients are hospitalized and receive definitive treatment. Burn care is very resource intensive as the treatment regimens and length of hospitalization are substantial. Burn wounds are classified based on depth as superficial (first degree), partial-thickness (second degree), or full-thickness (third degree), which determines the treatment necessary for successful healing. The goal of burn wound care is to fully restore the barrier function of the tissue as quickly as possible while minimizing infection, scarring, and contracture. The aim of this review is to highlight how tissue engineering and regenerative medicine strategies are being used to address the unique challenges of burn wound healing and define the current gaps in care for both partial- and full-thickness burn injuries. This review will present the current standard of care (SOC) and provide information on various treatment options that have been tested pre-clinically or are currently in clinical trials. Due to the complexity of burn wound healing compared to other skin injuries, burn specific treatment regimens must be developed. Recently, tissue engineering and regenerative medicine strategies have been developed to improve skin regeneration that can restore normal skin physiology and limit adverse outcomes, such as infection, delayed re-epithelialization, and scarring. Our emphasis will be centered on how current clinical and pre-clinical research of pharmacological agents, biomaterials, and cellular-based therapies can be applied throughout the continuum of burn care by targeting the stages of wound healing: hemostasis, inflammation, cell proliferation, and matrix remodeling.

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.

Promotion of Cell-Based Therapy: Special Focus on the Cooperation of Mesenchymal Stem Cell Therapy and Gene Therapy for Clinical Trial Studies

Regenerative medicine (RM) is a promising new field of medicine that has mobilized several new tools to repair or replace lost or damaged cells or tissues by stimulating natural regenerative mechanisms nearby cell and tissue-based therapy approaches. However, mesenchymal stem cell (MSC) based therapy has been shown to be safe and effective to a certain degree in multiple clinical trial studies (CTSs) of several diseases, in most MSC CTSs the efficacy of treatment has been reported low. Therefore, researchers have focused on efficacy enhancing of MSC to improve migratory and homing, survival, stemness, differentiation and other therapeutic applicable properties by using different approaches. Gene therapy is one of the experimental technique tools that uses genes to change cells for therapeutic and investigation purposes. In this study has been focused on genetically modified MSCs for use in RM with an emphasis on CTSs. We highlight the basic concept of genetic modifications and also discuss recent clinical studies aspects. Recently reviewed studies show that MSC therapy with assistant gene therapy can be used in cancer therapy, heart diseases, Fanconi anemia and several other diseases.

Black, White, and Gray: Macrophages in Skin Repair and Disease

PURPOSE OF REVIEW

Macrophages alter their responses during the temporal stages of wound healing. During the inflammatory phase macrophages perform phagocytosis. During neovascularization macrophages activate angiogenesis. In the proliferation phase of wound healing, macrophages deposit extracellular matrix and during wound resolution macrophages phagocytize excessive cellular components. This review addresses how these changing phenotypes affect skin repair and disease.

RECENT FINDINGS

Macrophages can determine the outcome of repair and can shift the normal wound healing response into fibrosis or chronic wounds. Emerging single cell technologies for the first time provide us with tools to uncover macrophage origin, heterogeneity and function.

SUMMARY

Macrophages may exist as one population where all cells alter their phenotype in response to signals from the microenvironment. Alternatively, macrophages may exist as distinct subsets that can control wound outcomes. A clarified understanding will strengthen our knowledge of skin biology and aid in the development of wound healing therapies.

The Effect of Human Adipose Tissue-Derived Mesenchymal Stem Cells in Rat's Subglottic Stenosis Model

OBJECTIVE

Subglottic stenosis remains a clinical challenge. The aim of this study was to evaluate the effect of human adipose tissue-derived mesenchymal stem cells (hAMSCs) in rat model of subglottic stenosis.

SUBJECTS AND METHODS

Ninety-six 13-week-old male rats were enrolled in this study. They were divided into 3 groups as normal control (NC) group, a subglottic injury and media injection (SM) group, and a subglottic injury and media-stem cell injection (SMSC) group. The hAMSCs were immediately injected into subglottis after injury. Histologic characteristics of subglottis; the mRNA expressions of interleukin-1β, cyclooxygenase-2, tumor growth factor-β and basic fibroblast growth factor; and hAMSCs' survival were evaluated.

RESULTS

The hAMSCs survived in the subglottis of the rat until 10 days after implantation. The NC and SMSC groups had a significantly wider subglottic lumen and thinner lamina propria than the SM group at 56 days after injury. Collagen intensity of subglottis was significantly higher in the SM group than in the NC and SMSC groups at 28 days after injury. Gene expression didn't show significant difference between the SM group and the SMSC group.

CONCLUSIONS

The hAMSCs injection was found to be helpful for preventing subglottic stenosis in a rat model.

Topical administration of cryopreserved living micronized amnion accelerates wound healing in diabetic mice by modulating local microenvironment

Approximately 25% of diabetic patients suffer from diabetic lower-extremity ulcer throughout their lives and 7%-20% of patients will eventually need an amputation despite standard care treatment. The development of new therapies to treat diabetic wounds is urgent. In this study, we used cryopreserved living micronized amnion (300-600 μm) to treat wounds in diabetic mice. Post-thaw micronized amnion retained high cell viability, as well as intact cell morphology and membrane structure. When transplanted onto the wounds of db/db mice, the cryopreserved living micronized amnion greatly promoted wound healing in diabetic mice mainly by secreting growth, inflammation, and chemotaxis-related factors that regulated macrophage migration and phenotype switch, recruited CD34⁺ progenitor cells, and increased neovascularization. In addition, the micronized amnion matrix can exist in the dermis and serve as a long-term dermal scaffold. These results demonstrated the potential of the cryopreserved living micronized amnion as a ready-to-use living dermal substitute that addresses multiple defective physiological processes of impaired wounds to treat diabetic ulcers and other chronic wounds in clinics.

Cell-mediated remodeling of biomimetic encapsulating hydrogels triggered by adipogenic differentiation of adipose stem cells

One of the most common regenerative therapies is autologous fat grafting, which frequently suffers from unexpected volume loss. One approach is to deliver adipose stem cells encapsulated in the engineered hydrogels supportive of cell survival, differentiation, and integration after transplant. We describe an encapsulating, biomimetic poly(ethylene)-glycol hydrogel, with embedded peptides for attachment and biodegradation. Poly(ethylene)-glycol hydrogels containing an Arg–Gly–Asp attachment sequence and a matrix metalloprotease 3/10 cleavage site supported adipose stem cell survival and showed remodeling initiated by adipogenic differentiation. Arg–Gly–Asp–matrix metalloprotease 3/10 cleavage site hydrogels showed an increased number and area of lacunae or holes after adipose stem cell differentiation. Image analysis of adipose stem cells in Arg–Gly–Asp–matrix metalloprotease 3/10 cleavage site hydrogels showed larger Voronoi domains, while cell density remained unchanged. The differentiated adipocytes residing within these newly remodeled spaces express proteins and messenger RNAs indicative of adipocytic differentiation. These engineered scaffolds may provide niches for stem cell differentiation and could prove useful in soft tissue regeneration.

Suction assisted liposuction does not impair the regenerative potential of adipose derived stem cells

Background

Adipose-derived stem cells (ASCs) have been identified as a population of multipotent cells with promising applications in tissue engineering and regenerative medicine. ASCs are abundant in fat tissue, which can be safely harvested through the minimally invasive procedure of liposuction. However, there exist a variety of different harvesting methods, with unclear impact on ASC regenerative potential. The aim of this study was thus to compare the functionality of ASCs derived from the common technique of suction-assisted lipoaspiration (SAL) versus resection.

Methods

Human adipose tissue was obtained from paired abdominoplasty and SAL samples from three female donors, and was processed to isolate the stromal vascular fraction. Fluorescence-activated cell sorting was used to determine ASC yield, and cell viability was assayed. Adipogenic and osteogenic differentiation capacity were assessed in vitro using phenotypic staining and quantification of gene expression. Finally, ASCs were applied in an in vivo model of tissue repair to evaluate their regenerative potential.

Results

SAL specimens provided significantly fewer ASCs when compared to excised fat tissue, however, with equivalent viability. SAL-derived ASCs demonstrated greater expression of the adipogenic markers FABP-4 and LPL, although this did not result in a difference in adipogenic differentiation. There were no differences detected in osteogenic differentiation capacity as measured by alkaline phosphatase, mineralization or osteogenic gene expression. Both SAL- and resection-derived ASCs enhanced significantly cutaneous healing and vascularization in vivo, with no significant difference between the two groups.

Conclusion

SAL provides viable ASCs with full capacity for multi-lineage differentiation and tissue regeneration, and is an effective method of obtaining ASCs for cell-based therapies.

A Comparison of Conventional Collagen Sponge and Collagen-Gelatin Sponge in Wound Healing

The objective of this study was to compare the effectiveness of the collagen-gelatin sponge (CGS) with that of the collagen sponge (CS) in dermis-like tissue regeneration. CGS, which achieves the sustained release of basic fibroblast growth factor (bFGF), is a promising material in wound healing. In the present study, we evaluated and compared CGSs and conventional CSs. We prepared 8 mm full-thickness skin defects on the backs of rats. Either CGSs or CSs were impregnated with normal saline solution (NSS) or 7 μg/cm(2) of bFGF solution and implanted into the defects. At 1 and 2 weeks after implantation, tissue specimens were obtained from the rats of each group (n = 3, total n = 24). The wound area, neoepithelial length, dermis-like tissue area, and the number and area of capillaries were evaluated at 1 and 2 weeks after implantation. There were no significant differences in the CGS without bFGF and CS groups. Significant improvements were observed in the neoepithelial length, the dermis-like tissue area, and the number of newly formed capillaries in the group of rats that received CGSs impregnated with bFGF. The effects on epithelialization, granulation, and vascularization of wound healing demonstrated that, as a scaffold, CGSs are equal or superior to conventional CSs.