Autologous bone marrow‐derived cells with placental extract for healing excisional cutaneous wounds in animal model

Topical wound‐healing potential of autologous bone marrow‐derived nucleated cells along with placental extract was evaluated in comparison with buffy coat of autologous blood on full‐thickness cutaneous wounds in the thoracolumbar region of 15 clinically healthy New Zealand rabbits. Three wounds of 2 × 2 cm, one on the right side of the body and two on the left side of the midline were created on the dorsal lumbar region of each rabbit under xylazine–ketamine anaesthesia. The wounds of each animal were randomly assigned to one of the three treatments: topical application of autologous bone marrow‐derived cells with placental extract (group I), application of buffy coat in the autologous plasma with placental extract (group II) and autologous plasma with placental extract as control (group III). Wounds were observed for 30 days macroscopically and for granulation tissue formation, histomorphological and histochemical evaluation. Time of appearance of granulation tissues and filling of wound beds were faster in group I followed by group II and group III animals, respectively. Histomorphological findings exhibited an earlier disappearance of inflammatory reaction, better epithelialisation, significantly maximum neovascularisation, fibroplasias and collagenation in group I followed by group II and group III animals, respectively. Histochemical findings also depicted maximum number of robust, thick, interwoven type of collagen fibres, stout, highly tortuous and interwoven network of elastin fibres and numerous mesh war form of reticulin fibres within the dermal component were present in group I when compared with group II and III animals. Experiment conclude that single application of autologous bone marrow‐nucleated cells with placental extract topically could be a novel option for faster healing in complicated non healing wounds both in human beings and animals.     

Mobilised bone marrow‐derived cells accelerate wound healing

Massive skin defects caused by severe burn and trauma are a clinical challenge to surgeons. Timely and effective wound closure is often hindered by the lack of skin donor site. Bone marrow‐derived cells (BMDCs) have been shown to ‘differentiate’ into multiple tissue cells. In this study we focused on the direct manipulation of endogenous BMDCs, avoiding the immunocompatibility issues and complicated cell isolation, purification, identification and amplification procedures in vitro on wound repair. We found that mobilisation of the BMDCs into the circulation significantly increased the amount of BMDCs at the injury site which in turn accelerated healing of large open wound. We used a chimeric green fluorescent protein (GFP) mouse model to track BMDCs and to investigate their role in full‐thickness skin excisional wounds. We have shown that bone marrow mobilisation by granulocyte colony stimulating factor (G‐CSF) exerted multiple beneficial effects on skin repair, both by increasing the engraftment of BMDCs into the skin to differentiate into multiple skin cell types and by upregulating essential cytokine mRNAs critical to wound repair. The potential trophic effects of G‐CSF on bone marrow stem cells to accelerate wound healing could have a significant clinical impact.     

Evaluation of autologous bone marrow in wound healing in animal model: a possible application of autologous stem cells

A study was conducted to evaluate the potential of autologous bone marrow-derived cells in comparison with buffy coat of autologous blood for rapid cutaneous wound healing in rabbit model. Three square full-thickness skin excisional wounds were created in 15 selected experimental animals (rabbit) divided randomly into three groups. The wound was treated with autologous bone marrow cells in plasma (group 1), buffy coat of blood in plasma (group 2) and autologous plasma as control (group 3). Wounds were observed for 30 days for granulation tissue formation, biochemical, histomorphological and histochemical evaluation. In this study, granulation tissue appeared significantly lesser in wounds of group 3 animals followed by group 2 and 1 animals. Neovascularisation, granulation tissue formation, denser, thicker and better arranged collagen fibres, reticulin fibres and elastin fibres formation was more in group 1 as compared with other groups. It was concluded that the application of bone marrow-derived nucleated cells into the wound margins resulted in early and significantly faster rate of complete healing as compared with buffy coat of autologous blood and autologous plasma (control). This approach may be beneficial in various surface wounds that heal at a slower rate and recommended for healing of various complicated wound in future.     

Effect of piracetam and nimodipine on full‐thickness skin burns in rabbits

The potential of several drugs for full‐thickness skin burns has been investigated, but the treatment of such burns remains a challenge in plastic surgery. The present study was designed to determine the effect of systemic and topical administration of piracetam and nimodipine on full‐thickness skin burn wound healing. A total of 36 New Zealand male rabbits were divided into six groups. Full‐thickness skin burns were produced in all the groups, except the control group. Piracetam was administered systemically (piracetam‐IV) and topically (piracetam‐C) for 14 days, and nimodipine was administered systemically (nimodipine‐IV) and topically (nimodipine‐C) over the burn wounds for 14 days. The sham group underwent burn injury but was not administered any drug. After 21 days, gross examination and histopathological analysis were performed and the results were compared statistically. Nimodipine‐C and nimodipine‐IV had no effect on burn wound healing. However, both piracetam‐IV and piracetam‐C significantly enhanced the healing of the full‐thickness skin burn wounds, although the latter was more effective, useful and practical in burn wound healing. The histopathological features of the wounds in the piracetam‐C group were closer to those of the control group than those of the other groups. Piracetam‐C rather than piracetam‐IV may promote full‐thickness burn wound healing in rabbits.     

Wound healing in Mac‐1 deficient mice

Mac‐1 (CD11b/CD18) is a macrophage receptor that plays several critical roles in macrophage recruitment and activation. Because macrophages are essential for proper wound healing, the impact of Mac‐1 deficiency on wound healing is of significant interest. Prior studies have shown that Mac‐1^?/? mice exhibit deficits in healing, including delayed wound closure in scalp and ear wounds. This study examined whether Mac‐1 deficiency influences wound healing in small excisional and incisional skin wounds. Three millimeter diameter full thickness excisional wounds and incisional wounds were prepared on the dorsal skin of Mac‐1 deficient (Mac‐1^?/?) and wild type (WT) mice, and wound healing outcomes were examined. Mac‐1 deficient mice exhibited a normal rate of wound closure, generally normal levels of total collagen, and nearly normal synthesis and distribution of collagens I and III. In incisional wounds, wound breaking strength was similar for Mac‐1^?/? and WT mice. Wounds of Mac‐1 deficient mice displayed normal total macrophage content, although macrophage phenotype markers were skewed as compared to WT. Interestingly, amounts of TGF‐β1 and its downstream signaling molecules, SMAD2 and SMAD3, were significantly decreased in the wounds of Mac‐1 deficient mice compared to WT. The results suggest that Mac‐1 deficiency has little impact on the healing of small excisional and incisional wounds. Moreover, the findings demonstrate that the effect of single genetic deficiencies on wound healing may markedly differ among wound models. These conclusions have implications for the interpretation of the many prior studies that utilize a single model system to examine wound healing outcomes in genetically deficient mice.     

A Dermal Equivalent Engineered with TGF‐β3 Expressing Bone Marrow Stromal Cells and Amniotic Membrane: Cosmetic Healing of Full‐Thickness Skin Wounds in Rats

Transforming growth factor beta‐3 (TGF‐β3) has been shown to decrease scar formation after scheduled topical applications to the cutaneous wounds. This study aimed to continuously deliver TGF‐β3, during the early phase of wound healing, by engineering a dermal equivalent (DE) using TGF‐β3 expressing bone marrow stromal cells (BM‐SCs) and human dehydrated amniotic membrane (hDAM). To engineer a DE, rat BM‐SCs were seeded on the hDAM and TGF‐β3 was transiently transfected into the BM‐SCs using a plasmid vector. Pieces of the dermal equivalent were transplanted onto the full‐thickness excisional skin wounds in rats. The process of wound healing was assessed by image analysis, Manchester Scar Scale (MSS), and histopathological studies 7, 14, 21, and 85 days after the excision. The results confirmed accurate construction of recombinant pcDNA3.1‐TGF‐β3 expression system and showed that the transfected BM‐SCs seeded on hDAM expressed TGF‐β3 mRNA and protein from day 3 through day 7 after transfection. After implantation of the DE, contraction of the wounds was measured from day 7 through 21 and analyzed by linear regression, which revealed that the rate of wound contraction in all experimental groups was similar. Histologic evaluation demonstrated that transfected BM‐SCs decreased retention and recruitment of the cells during the early stage of wound healing, decreased the formation of vascular structures and led to formation of uniformly parallel collagen bundles. MSS scores showed that TGF‐β3 secreting cells significantly improved the cosmetic appearance of the healed skin and decreased the scar formation. From these results, it could be concluded that transient secretion of TGF‐β3, during the early phase of healing, by BM‐SCs seeded on hDAM can improve the cosmetic appearance of the scar in cutaneous wounds without negatively affecting the process of wound repair.     

Full‐thickness splinted skin wound healing models in db/db and heterozygous mice: Implications for wound healing impairment

The excisional dorsal full‐thickness skin wound model with or without splinting is widely utilized in wound healing studies using diabetic or normal mice. However, the effects of splinting on dermal wound healing have not been fully characterized, and there are limited data on the direct comparison of wound parameters in the splinted model between diabetic and normal mice. We compared full‐thickness excisional dermal wound healing in db/db and heterozygous mice by investigating the effects of splinting, semi‐occlusive dressing, and poly(ethylene glycol) treatment. Two 8‐mm full‐thickness wounds were made with or without splinting in db/db and heterozygous mice. Body weights, splint maintenance, wound contraction, wound closure, and histopathological parameters including reepithelialization, wound bed collagen deposition, and inflammation were compared between groups. Our results show that silicone splint application effectively reduced wound contraction in heterozygous and db/db mice. Splinted wounds, as opposed to nonsplinted wounds, exhibited no significant differences in wound closure between heterozygous and db/db mice. Finally, polyethylene glycol and the noncontact dressing had no significant effect on wound healing in heterozygous or db/db mice. We believe these findings will help investigators in selection of the appropriate wound model and data interpretation with fully defined parameters.     

Combination of stromal cell‐derived factor‐1 and collagen–glycosaminoglycan scaffold delays contraction and accelerates reepithelialization of dermal wounds in wild‐type mice

While dermal substitutes can mitigate scarring and wound contraction, a significant drawback of current dermal replacement technologies is the apparent delay in vascular ingrowth compared with conventional skin grafts. Herein, we examined the effect of the chemokine stromal cell‐derived factor‐1 (SDF‐1) on the performance of a porous collagen–glycosaminoglycan dermal analog in excisional wounds in mice. C57BL/6 mice with 1 cm × 1 cm dorsal full‐thickness wounds were covered with a collagen–glycosaminoglycan scaffold, followed by four daily topical applications of 1 μg SDF‐1 or phosphate‐buffered saline vehicle. Some animals were also pretreated with five daily doses of 300 mg/kg granulocyte colony‐stimulating factor. Animals treated with SDF‐1 and no granulocyte colony‐stimulating factor reepithelialized 36% faster than vehicle controls (16 vs. 25 days), and exhibited less wound contraction on postwounding day 18 (～35% greater wound area) plus three‐fold longer neoepidermis formed than controls. Conversely, granulocyte colony‐stimulating factor promoted contraction and no epidermal regeneration. Early (postwounding Day 3) inflammatory cell infiltration in the SDF‐1‐treated group was 86% less, while the fraction of proliferating cells (positive Ki67 staining) was 32% more, when compared with controls. These results suggest that SDF‐1 simultaneously delays contraction and promotes reepithelialization and may improve the wound‐healing performance of skin substitutes.     

The therapeutic potential of a C‐X‐C chemokine receptor type 4 (CXCR‐4) antagonist on hypertrophic scarring in vivo

Effective prevention and treatment of hypertrophic scars (HTSs), a dermal form of fibrosis that frequently occurs following thermal injury to deep dermis, are unsolved significant clinical problems. Previously, we have found that stromal cell‐derived factor 1/CXCR4 signaling is up‐regulated during wound healing in burn patients and HTS tissue after thermal injury. We hypothesize that blood‐borne mononuclear cells are recruited into wound sites after burn injury through the chemokine pathway of stromal cell‐derived factor 1 and its receptor CXCR4. Deep dermal injuries to the skin are often accompanied by prolonged inflammation, which leads to chemotaxis of mononuclear cells into the wounds by chemokine signaling where fibroblast activation occurs and ultimately HTS are formed. Blocking mononuclear cell recruitment and fibroblast activation, CXCR4 antagonism is expected to reduce or minimize scar formation. In this study, the inhibitory effect of CXCR4 antagonist CTCE‐9908 on dermal fibrosis was determined in vivo using a human HTS‐like nude mouse model, in which split‐thickness human skin is transplanted into full‐thickness dorsal excisional wounds in athymic mice, where these wounds subsequently develop fibrotic scars that resemble human HTS as previously described. CTCE‐9908 significantly attenuated scar formation and contraction, reduced the accumulation of macrophages and myofibroblasts, enhanced the remodeling of collagen fibers, and down‐regulated the gene and protein expression of fibrotic growth factors in the human skin tissues. These findings support the potential therapeutic value of CXCR4 antagonist in dermal fibrosis and possibly other fibroproliferative disorders.     

Repair of large full‐thickness articular cartilage defects by transplantation of autologous uncultured bone‐marrow‐derived mononuclear cells

The objective of this study was to investigate the feasibility of autologous uncultured bone marrow‐derived mononuclear cell transplantation in large full‐thickness cartilage regeneration. After fixing with a hinged external fixator, the entire surface of the left tibial plateau was resected and large full‐thickness cartilage defects were formed in 48 rabbits. Animals were divided into four groups: autologous uncultured bone marrow‐derived mononuclear cells with fibrin gel (BMC), autologous uncultured peripheral blood‐derived mononuclear cells with fibrin gel (PBC), fibrin gel alone (GEL), or nothing (CON) transplanted to the articular cavity 7 days after the operation. The rabbits were killed 8 or 12 weeks after the operation. The repair of defects was investigated histologically and scored using a histological and histochemical grading scale that was modified from the International Cartilage Repair Society Visual Histological Assessment Scale. To evaluate the regenerated cartilage, we also morphometrically measured the staining area positive for Safranin‐O or type II collagen and calculated the percentages of the positive staining areas with respect to the regenerated soft tissue area. Histological findings showed that the BMC group had superior cartilage repair compared with the other groups, and that the PBC and CON group showed better cartilage repair than did the GEL group. Histological scores and morphometrical measurements also showed the same results quantitively. The transplantation of autologous uncultured bone marrow‐derived mononuclear cells contributes to articular cartilage repair. The easy and safe method used in this study is potentially viable for clinical application. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:18–26, 2008     

The recruitment of bone marrow‐derived cells to skin wounds is independent of wound size

Wounded skin recruits progenitor cells, which repair the tissue defect. These cells are derived from stem cells in several niches in the skin. In addition, bone marrow‐derived cells (BMDCs) are recruited and contribute to wound repair. We hypothesized that larger wounds recruit more cells from the bone marrow. Wild‐type rats were lethally irradiated and transplanted with bone marrow cells from green fluorescent protein (GFP)‐transgenic rats. Seven weeks later, 4, 10, and 20 mm wounds were created. The wound tissue was harvested after 14 days. The density of GFP‐positive cells in the wounds and the adjacent tissues was determined, as well as in normal skin from the flank. Bone marrow‐derived myofibroblasts, activated fibroblasts, and macrophages were also quantified. After correction for cell density, the recruitment of BMDCs (23±11%) was found to be independent of wound size. Similar fractions of GFP‐positive cells were also detected in nonwounded adjacent tissue (29±11%), and in normal skin (26±19%). The data indicate that BMDCs are not preferentially recruited to skin wounds. Furthermore, wound size does not seem to affect the recruitment of BMDCs.     

RGTA OTR 4120, a heparan sulfate proteoglycan mimetic, increases wound breaking strength and vasodilatory capability in healing rat full-thickness excisional wounds

ReGeneraTing Agents (RGTAs), a family of polymers engineered to protect and stabilize heparin‐binding growth factors, have been shown to promote tissue repair and regeneration. In this study, the effects of one of these polymers, RGTA OTR4120, on healing of full‐thickness excisional wounds in rats were investigated. Two 1.5 cm diameter circular full‐thickness excisional wounds were created on the dorsum of a rat. After creation of the wounds, RGTA OTR4120 was applied. The progress of healing was assessed quantitatively by evaluating the wound closure rate, vasodilatory capability, and wound breaking strength. The results showed a triple increase of the local vascular response to heat provocation in the RGTA OTR4120‐treated wounds as compared with vehicle‐treated wounds. On days 14 and 79 after surgery, the wounds treated with RGTA OTR4120 gained skin strength 12% and 48% of the unwounded skin, respectively, and displayed a significantly increased gain in skin strength when compared with control animals. These results raise the possibility of efficacy of RGTA OTR4120 in accelerating surgically cutaneous wound healing by enhancing the wound breaking strength and improving the microcirculation.     

Tissue‐Engineered Skin Containing Mesenchymal Stem Cells Improves Burn Wounds

There is increasing evidence showing that adult stem cells are useful for tissue regeneration. Bone marrow mesenchymal stem cells (MSCs) are self‐renewing and are potent in differentiating into multiple cells and tissues. To investigate the practicability of repairing burn wounds with tissue‐engineered (TE) skin combined with bone MSCs, we established a burn wound model in the porcine skin. With a controlling temperature and time of the burning device to obtain different degrees of burn wounds, a deep dermal partial thickness burn was introduced to the porcine skin using a heated‐brass contact injury at 100°C for 20 s. Collagen‐GAG scaffolds were utilized as the matrix; MSCs separated from pigs were seeded on them to form the skin equivalent. When grafted to the burn wounds, the TE skin containing MSCs showed better healing and keratinization, less wound contraction, and more vascularization. Grafts proliferated well and contributed to the neo‐tissues. These data suggest that TE skin containing MSCs in a burn defect can accelerate wound healing and receive satisfactory effects.     

Accelerated epithelialization and improved wound healing metrics in porcine full‐thickness wounds transplanted with full‐thickness skin micrografts

Split‐thickness skin grafting (STSG) is the current gold standard for treatment of extensive burn and traumatic skin injuries. However, STSG is limited by donor‐site morbidity and availability, and often leads to scarring and wound contracture. Furthermore, these thin grafts lack dermal elements such as nerves and adnexa which are important in recapitulating normal skin function. Methods of fractional skin replacement either as minced STSGs or microscopic skin tissue columns have been proposed, though these techniques have not been fully characterized and lack evidence of regenerated adnexal structures. Here, we describe an alternative method of fractional skin replacement using full‐thickness skin micrografts containing deep dermal components and intact adnexa. Full‐thickness wounds measuring 3 cm in diameter and 2 cm apart were created on adult female Yorkshire swine. Full‐thickness skin tissue columns (FTSTCs) 1.5 mm in diameter with intact adnexa and subcutaneous tissue were obtained using a suction‐assisted device. Explant culture was initiated to demonstrate the capacity of FTSTCs to act as reservoirs of viable and proliferative epidermal and dermal cells. FTSTCs were applied directly to excisional wounds at three different expansion ratios (1:16, 1:40, 1:100) in fibrin sealant. Biopsies were collected at defined time points postwounding and processed for histology and immunohistochemistry. Wounds grafted with FTSTCs showed enhanced reepithelialization and epidermal differentiation over untreated control wounds in a dosage dependent manner. Adnexal structures such as hair follicles and sweat glands were only evident in FTSTC‐treated wounds. Furthermore, whereas ungrafted wounds were marked by extensive infiltration of α‐Smooth Muscle Actin⁺ (α‐SMA⁺) myofibroblasts at POD 60, α‐SMA expression was sparse and largely limited to perivascular cells in FTSTC‐treated wounds. The number of Ki67⁺ cells was also greatly reduced in FTSTC‐treated wounds. Transplantation of FTSTCs containing intact adnexa improved wound healing parameters in porcine full‐thickness wounds and may have implications for the treatment of large, traumatic wounds.     

Wound‐healing effect of adipose stem cell‐derived extracellular matrix sheet on full‐thickness skin defect rat model: Histological and immunohistochemical study

The potential use of extracellular matrix (ECM) as a source of wound dressing material has recently received much attention. The ECM is an intricate network of various combinations of elastin, collagens, laminin, fibronectin, and proteoglycans that play a key role in stimulating cell proliferation and differentiation. We evaluated the efficacy of an ECM sheet derived from human adipose tissue as a wound dressing material to enhance healing. We prepared a novel porous ECM sheet dressing scaffold from human adipose tissue. in vitro analysis of the ECM sheets showed efficient decellularisation; absence of immunostimulatory components; and the presence of a wide number of angiogenic and bioactive factors, including collagen, elastin, and proteoglycans. To evaluate in vivo efficacy, full‐thickness excisional wounds were created on the dorsal skin of a rat, and the ECM sheets; secondary healing foam wound dressing, Healoderm; or a conventional dressing were applied to each wound site. Photographs were taken every other day, and the degree of reepithelialisation of the wounds was determined. Application of an ECM sheet dressing enhanced the macroscopic wound‐healing rate on days 4, 7, and 10 compared with that in the control group. Microscopic analysis indicated that the reepithelialisation rate of the wound was higher in the ECM group compared with that in the control group; the reepithelialisation rate was better than that of the secondary healing foam wound dressing. Moreover, a denser and more organised granulation tissue was formed in the ECM sheet group compared with that in the secondary healing foam wound dressing and control groups. The ECM sheet also showed the highest microvessel density compared with the secondary healing foam wound dressing and control groups. Based on these data, we suggest that a bioactive ECM sheet dressing derived from human adipose can provide therapeutic proteins for wound healing.     

Diabetic wound healing in a MMP9‐/‐ mouse model

Reduced mobilization of endothelial progenitor cells (EPCs) from the bone marrow (BM) and impaired EPC recruitment into the wound represent a fundamental deficiency in the chronic ulcers. However, mechanistic understanding of the role of BM‐derived EPCs in cutaneous wound neovascularization and healing remains incomplete, which impedes development of EPC‐based wound healing therapies. The objective of this study was to determine the role of EPCs in wound neovascularization and healing both under normal conditions and using single deficiency (EPC) or double‐deficiency (EPC + diabetes) models of wound healing. MMP9 knockout (MMP9 KO) mouse model was utilized, where impaired EPC mobilization can be rescued by stem cell factor (SCF). The hypotheses were: (1) MMP9 KO mice exhibit impaired wound neovascularization and healing, which are further exacerbated with diabetes; (2) these impairments can be rescued by SCF administration. Full‐thickness excisional wounds with silicone splints to minimize contraction were created on MMP9 KO mice with/without streptozotocin‐induced diabetes in the presence or absence of tail‐vein injected SCF. Wound morphology, vascularization, inflammation, and EPC mobilization and recruitment were quantified at day 7 postwounding. Results demonstrate no difference in wound closure and granulation tissue area between any groups. MMP9 deficiency significantly impairs wound neovascularization, increases inflammation, decreases collagen deposition, and decreases peripheral blood EPC (pb‐EPC) counts when compared with wild‐type (WT). Diabetes further increases inflammation, but does not cause further impairment in vascularization, as compared with MMP9 KO group. SCF improves neovascularization and increases EPCs to WT levels (both nondiabetic and diabetic MMP9 KO groups), while exacerbating inflammation in all groups. SCF rescues EPC‐deficiency and impaired wound neovascularization in both diabetic and nondiabetic MMP9 KO mice. Overall, the results demonstrate that BM‐derived EPCs play a significant role during wound neovascularization and that the SCF‐based therapy with controlled inflammation could be a viable approach to enhance healing in chronic diabetic wounds.     

Embryonic stem cell–derived M2‐like macrophages delay cutaneous wound healing

In adults, repair of deeply injured skin wounds results in the formation of scar tissue, whereas in embryos wounds heal almost scar‐free. Macrophages are important mediators of wound healing and secrete cytokines and tissue remodeling enzymes. In contrast to host defense mediated by inflammatory M1 macrophages, wound healing and tissue repair involve regulatory M2/M2‐like macrophages. Embryonic/fetal macrophages are M2‐like, and this may promote scar‐free wound healing. In the present study, we asked whether atopical application of ex vivo generated, embryonic stem cell–derived macrophages (ESDM) improve wound healing in mice. ESDM were tested side by side with bone marrow–derived macrophages (BMDM). Compared to BMDM, ESDM resembled a less inflammatory and more M2‐like macrophage subtype as indicated by their reduced responsiveness to lipopolysaccharide, reduced expression of Toll‐like receptors, and reduced bacterial phagocytosis. Despite this anti‐inflammatory phenotype in cell culture, ESDM prolonged the healing of deep skin wounds even more than BMDM. Healed wounds had more scar formation compared to wounds receiving BMDM or cell‐free treatment. Our data indicate that atopical application of ex vivo generated macrophages is not a suitable cell therapy of dermal wounds.     

Role of adipose‐derived stem cells in wound healing

Impaired wound healing remains a challenge to date and causes debilitating effects with tremendous suffering. Recent advances in tissue engineering approaches in the area of cell therapy have provided promising treatment options to meet the challenges of impaired skin wound healing such as diabetic foot ulcers. Over the last few years, stem cell therapy has emerged as a novel therapeutic approach for various diseases including wound repair and tissue regeneration. Several different types of stem cells have been studied in both preclinical and clinical settings such as bone marrow‐derived stem cells, adipose‐derived stem cells (ASCs), circulating angiogenic cells (e.g., endothelial progenitor cells), human dermal fibroblasts, and keratinocytes for wound healing. Adipose tissue is an abundant source of mesenchymal stem cells, which have shown an improved outcome in wound healing studies. ASCs are pluripotent stem cells with the ability to differentiate into different lineages and to secrete paracrine factors initiating tissue regeneration process. The abundant supply of fat tissue, ease of isolation, extensive proliferative capacities ex vivo, and their ability to secrete pro‐angiogenic growth factors make them an ideal cell type to use in therapies for the treatment of nonhealing wounds. In this review, we look at the pathogenesis of chronic wounds, role of stem cells in wound healing, and more specifically look at the role of ASCs, their mechanism of action and their safety profile in wound repair and tissue regeneration.     

Coacervate delivery of HB‐EGF accelerates healing of type 2 diabetic wounds

Chronic wounds such as diabetic ulcers pose a significant challenge as a number of underlying deficiencies prevent natural healing. In pursuit of a regenerative wound therapy, we developed a heparin‐based coacervate delivery system that provides controlled release of heparin‐binding epidermal growth factor (EGF)‐like growth factor (HB‐EGF) within the wound bed. In this study, we used a polygenic type 2 diabetic mouse model to evaluate the capacity of HB‐EGF coacervate to overcome the deficiencies of diabetic wound healing. In full‐thickness excisional wounds on NONcNZO10 diabetic mice, HB‐EGF coacervate enhanced the proliferation and migration of epidermal keratinocytes, leading to accelerated epithelialization. Furthermore, increased collagen deposition within the wound bed led to faster wound contraction and greater wound vascularization. Additionally, in vitro assays demonstrated that HB‐EGF released from the coacervate successfully increased migration of diabetic human keratinocytes. The multifunctional role of HB‐EGF in the healing process and its enhanced efficacy when delivered by the coacervate make it a promising therapy for diabetic wounds.