Persistent Ischemia Impairs Myofibroblast Development in Wound Granulation Tissue a New Model of Delayed Wound Healing

Skin substitutes are slowly finding a position in the treatment of burns, scar reconstructions and chronic wounds. Some of the substitutes consist of extracellular matrix replacement material only, such as Integra and Alloderm; some include allogeneic cells (Dermagraft, Appligraf). The ideal skin substitute has not been developed yet, since none of the presently available products can ultimately prevent scar formation.
Study of the role of autologous fibroblasts in the healing process might give further insight into the scarring process and eventually lead to improved skin substitutes.
We compared wound reepithelialization of experimental wounds treated with proliferating keratinocytes and a dermal substitute with either dermal fibroblasts, adipose tissue derived fibroblasts or no fibroblasts. We also investigated the rate of keratinocyte migration of human skin equivalents cultured in vitro in the presence of dermal or adipose tissue derived fibroblasts.
We reached successful wound closure in 8 days with transfer of proliferating keratinocytes on a dermal substitute seeded with dermal fibroblasts. However, the wounds treated with substitutes which contained adipose tissue derived fibroblasts or no fibroblasts at all were not closed even after 21 days.
Keratinocytes seeded onto collagen lattices populated with either dermal or fat‐derived fibroblasts showed similar findings: a retarded migration and/or proliferation of keratinocytes on the collagen lattices with fat‐derived fibroblasts. The collagen lattices populated with fat‐derived fibroblasts also showed a marked contraction, up till 50% of the original area.
In both models, more alpha‐smooth muscle actin positive cells were found in the fibroblast population from adipose origin.
We conclude that epidermal regeneration is negatively influenced by the presence of fat‐derived fibroblasts in a dermal matrix; possibly, myofibroblasts play a role in this.     

Differential cutaneous wound healing in thermally injured MRL/MPJ mice

Adult wound repair occurs with an initial inflammatory response, reepithelialization, and the formation of a permanent scar. MRL/MpJ mice following ear‐hole punch biopsies display accelerated healing and tissue regeneration. In this study, we characterized the healing responses in both MRL/MpJ and BALB/c mice following a 15% total body surface area full‐thickness cutaneous burn injury. Macroscopic and histological observations show that delayed wound closure in MRL/MpJ mice is accompanied by an increase in edema, reduced neutrophil infiltration, and more prominent eschar. In vivo bromodeoxyuridine labeling showed no defect in keratinocyte proliferation and migration (reepithelialization). In comparison with BALB/c mice, MRL/MpJ wounds had greater collagen deposition, less granulation tissue formation, and contained fewer α‐smooth muscle actin‐positive myofibroblasts. An observed reduction in dermal neutrophil infiltration and myofibroblast development correlated with enhanced angiogenesis. Overall, BALB/c wounds contracted sooner and to a larger degree, resulting in a significant decrease in scar formation. Interestingly, MRL/MpJ mice showed overt abnormalities in hair follicle proliferation, morphogenesis, and subsequent hair regrowth postburn injury. No substantial evidence of tissue regeneration was observed in either BALB/c or MRL/MpJ wounds. Our results convincingly demonstrate that MRL/MpJ skin burn wounds heal with scar formation with delays in two critical wound healing events: wound closure, and myofibroblast development.     

Curcumin accelerates cutaneous wound healing via multiple biological actions: The involvement of TNF‐α, MMP‐9, α‐SMA,and collagen

Curcumin, a constituent of the turmeric plant, has antitumor, anti‐inflammatory, and antioxidative effects, but its effects on wound healing are unclear. We created back wounds in 72 mice and treated them with or without topical curcumin (0.2 mg/mL) in Pluronic F127 gel (20%) daily for 3, 5, 7, 9, and 12 days. Healing in wounds was evaluated from gross appearance, microscopically by haematoxylin and eosin staining, by immunohistochemistry for tumour necrosis factor alpha and alpha smooth muscle actin, and by polymerase chain reaction amplification of mRNA expression levels. Treatment caused fast wound closure with well‐formed granulation tissue dominated by collagen deposition and regenerating epithelium. Curcumin increased the levels of tumour necrosis factor alpha mRNA and protein in the early phase of healing, which then decreased significantly. However, these levels remained high in controls. Levels of collagen were significantly higher in curcumin‐treated wounds. Immunohistochemical staining for alpha smooth muscle actin was increased in curcumin‐treated mice on days 7 and 12. Curcumin treatment significantly suppressed matrix metallopeptidase‐9 and stimulated alpha smooth muscle levels in tumour necrosis factor alpha‐treated fibroblasts via nuclear factor kappa B signalling. Thus, topical curcumin accelerated wound healing in mice by regulating the levels of various cytokines.     

Proapoptotic effect of control‐released basic fibroblast growth factor on skin wound healing in a diabetic mouse model

The ability of basic fibroblast growth factor (bFGF) to improve wound healing is attenuated by its short half‐life in free form. This study aimed to enhance skin wound healing in a diabetes mouse model while concomitantly decreasing scar formation using control‐released bFGF together with acidic gelatin hydrogel microspheres (AGHMs). Bilateral full‐thickness wounds (10 mm in diameter) were made on the backs of db/db mice. Forty‐five mice were divided into three groups, and the base of the wound under the panniculus carnosus and the wound periphery were injected with phosphate‐buffered saline (300 μL) containing (1) control‐released bFGF (50 μg), (2) control‐released bFGF (20 μg), or (3) AGHMs alone. The size of the wound area was recorded on each postoperative day (POD). Mice were sacrificed on postoperative day 4, 7, 10, 14, and 28, and skin wound specimens were obtained to assess the endothelium/angiogenesis index via cluster of differentiation 31 immunohistochemistry, the proliferation index via Ki‐67 immunohistochemistry, and the myofibroblast and fibroblast apoptosis indices by terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling and alpha‐smooth muscle actin or vimentin staining, respectively. Epithelialization rates and indices of proliferation and myofibroblast/fibroblast apoptosis were higher in the bFGF groups than in the AGHM group, mainly within 2 weeks of injury. No dose‐effect relationship was found for control‐released bFGF, although the actions of 50 μg bFGF seemed to last longer than those of 20 μg bFGF. Therefore, control‐released bFGF may accelerate diabetic skin wound healing and induce myofibroblast/fibroblast apoptosis, thereby reducing scar formation.     

Extracellular matrix/stromal vascular fraction gel conditioned medium accelerates wound healing in a murine model

Conditioned medium (CM) is a new treatment modality in regenerative medicine and has shown a successful outcome in wound healing. We recently introduced extracellular matrix/stromal vascular fraction gel (ECM/SVF‐gel), an adipose‐derived stem cell and adipose native extracellular matrix‐enriched product for cytotherapy. This study aimed to evaluate the effect of CM from ECM/SVF‐gel (Gel‐CM) on wound healing compared with the conventional CM from adipose tissue (Adi‐CM) and stem cell (SVF‐CM). In vitro wound healing effect of three CMs on keratinocytes and fibroblasts was evaluated in terms of proliferation property, migratory property, and extracellular matrix production. In vivo, two full‐thickness wounds were created on the back of each mice. The wounds were randomly divided to receive Gel‐CM, Adi‐CM, SVF‐CM, and PBS injection. Histologic observations and collagen content of wound skin were made. Growth factors concentration in three CMs was further quantified. In vitro, Gel‐CM promoted the proliferation and migration of keratinocytes and fibroblasts and enhanced collagen I synthesis in fibroblasts compared to Adi‐CM and SVF‐CM. In vivo, wound closure was faster, and dermal and epidermal regeneration was improved in the Gel‐CM‐treated mice compared to that in Adi‐CM and SVF‐CM‐treated mice. Moreover, The growth factors concentration (i.e., vascular endothelial growth factor, basic fibroblast growth factor, hepatocyte growth factor, and transforming growth factor‐β) in Gel‐CM were significantly higher than those in Adi‐CM and SVF‐CM. Gel‐CM generated under serum free conditions significantly enhanced wound healing effect compared to Adi‐CM and SVF‐CM by accelerating cell proliferation, migration, and production of ECM. This improved trophic effect may be attributed to the higher growth factors concentration in Gel‐CM. Gel‐CM shows potential as a novel and promising alternative to skin wound healing treatment. But limitations include the safety and immunogenicity studies of Gel‐CM still remain to be clearly clarified and more data on mechanism study are needed.     

Serum amyloid P inhibits dermal wound healing

The repair of open wounds depends on granulation tissue formation and contraction, which is primarily mediated by myofibroblasts. A subset of myofibroblasts originates from bone‐marrow‐derived monocytes which differentiate into fibroblast‐like cells called fibrocytes. Serum amyloid P (SAP) inhibits differentiation of monocytes into fibrocytes. Thus, we hypothesized that the addition of exogenous SAP would hinder the normal wound healing process. Excisional murine dorsal wounds were either injected with SAP (intradermal group) or the mice were treated with systemic SAP (intraperitoneal group) and compared with animals treated with vehicle. Grossly, SAP‐treated wounds closed slower than respective controls in both groups. Histologically, the contraction rate was slower in SAP‐treated wounds in both groups and the reepithelialization rate was slower in the intraperitoneal group. Furthermore, significantly less myofibroblasts expressing α‐smooth muscle actin were noted in the intraperitoneal group wounds compared with controls. These data suggest that SAP delays normal murine dermal wound healing, probably due to increased inhibition of fibrocyte differentiation, and ultimately a decreased wound myofibroblast population. SAP may provide a potential therapeutic target to prevent or limit excessive fibrosis associated with keloid or hypertrophic scar formation. Furthermore, SAP removal from wound fluid could potentially accelerate the healing of chronic, nonhealing wounds.     

Effect of interferon-α2b on guinea pig wound closure and the expression of cytoskeletal proteins in vivo

Scar contraction following the healing of deep partial-thickness or full-thickness dermal injury is a leading cause of functional and cosmetic morbidity. The therapeutic use of interferon for the treatment of fibroproliferative disorders associated with scar contraction, including hypertrophic scar, has been suggested because of its antifibrotic properties. Treatment of fibroblasts with interferon has been shown to reduce the rate and extent of contraction using the in vitro fibroblast-populated collagen lattice model. In order to establish the effect of interferon-α2b on full-thickness wound contraction in vivo, osmotic pumps loaded with interferon or sterile saline were implanted intraperitoneally in guinea pigs. Seven days following implantation, six full-thickness punch biopsy wounds were created and were monitored by daily assessment of the wound. There was a significant reduction in the rate of wound contraction in the interferon-treated animals after day 3 (p < 0.01). Western blot analysis was used to quantitate selected cytoskeletal proteins in the normal skin and tissue biopsied from the wound at days 7, 14, and 21 postinjury. The amount of vimentin in the contracted wound increased following injury as compared with the amount present in normal skin (p < 0.0001); however, the relative amounts of the myofibroblast-associated cytoskeletal proteins α-smooth muscle actin and smooth muscle myosin were less than those found in normal, uninjured skin. By using vimentin to adjust the levels of cytoskeletal proteins for the increase in cellularity in the wounds, both α-smooth muscle actin and smooth muscle myosin significantly increased after closure of the wounds on day 14, as compared with the open-wound stage (day 7), before further reductions occurred with remodeling on day 21. Measurement of apoptotic cells using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay revealed an increase in apoptosis in the interferon-α2b-treated animals at 21 days following wounding (p < 0.001), which did not colocalize with α-smooth muscle actin staining. Taken together, these findings suggest that interferon-α2b inhibits wound contraction in vivo, not through an appreciable alteration in myofibroblast number or cytoskeletal protein expression, but possibly through a reduction in fibroblast cellularity by the induction of apoptosis.     

Paracrine anti‐fibrotic effects of neonatal cells and living cell constructs on young and senescent human dermal fibroblasts

Senescent cells observed in the area of chronic wounds have been proposed to affect wound healing. Therapeutic approaches against chronic wounds include, among others, the local application of living cell constructs (LCCs), containing fibroblasts and/or keratinocytes. Accordingly, the aim of the present work was to examine the effects of factors secreted by early passage neonatal fibroblasts and LCCs—in the form of a conditioned medium (CM)—on senescent adult dermal fibroblasts regarding functions related to the healing process, i.e., cell proliferation, alpha‐smooth muscle actin and metalloproteinase expression, and collagen synthesis. Target cells were fibroblasts senescent either due to subsequent divisions (replicative senescence) or due to an exogenous stress (stress‐induced premature senescence). No effect on the proliferation of senescent fibroblasts was observed, as expected. All CMs were found to inhibit overall collagen synthesis both in early passage and in senescent fibroblasts. The LCC‐derived CM was found to be more potent than fibroblast‐derived CMs and, furthermore, to inhibit alpha‐smooth muscle actin expression. In conclusion, these results may indicate anti‐contractile and anti‐fibrotic activities of factor(s) secreted by neonatal skin fibroblasts, and more intensely by LCCs on adult donor‐derived fibroblasts. These activities seem to persist during senescence of the target cells.     

Regeneration of injured skin and peripheral nerves requires control of wound contraction,not scar formation

We review the mounting evidence that regeneration is induced in wounds in skin and peripheral nerves by a simple modification of the wound healing process. Here, the process of induced regeneration is compared to the other two well‐known processes by which wounds close, i.e., contraction and scar formation. Direct evidence supports the hypothesis that the mechanical force of contraction (planar in skin wounds, circumferential in nerve wounds) is the driver guiding the orientation of assemblies of myofibroblasts (MFB) and collagen fibers during scar formation in untreated wounds. We conclude that scar formation depends critically on wound contraction and is, therefore, a healing process secondary to contraction. Wound contraction and regeneration did not coincide during healing in a number of experimental models of spontaneous (untreated) regeneration described in the literature. Furthermore, in other studies in which an efficient contraction‐blocker, a collagen scaffold named dermis regeneration template (DRT), and variants of it, were grafted on skin wounds or peripheral nerve wounds, regeneration was systematically observed in the absence of contraction. We conclude that contraction and regeneration are mutually antagonistic processes. A dramatic change in the phenotype of MFB was observed when the contraction‐blocking scaffold DRT was used to treat wounds in skin and peripheral nerves. The phenotype change was directly observed as drastic reduction in MFB density, dispersion of MFB assemblies and loss of alignment of the long MFB axes. These observations were explained by the evidence of a surface‐biological interaction of MFB with the scaffold, specifically involving binding of MFB integrins α₁β₁ and α₂β₁ to ligands GFOGER and GLOGER naturally present on the surface of the collagen scaffold. In summary, we show that regeneration of wounded skin and peripheral nerves in the adult mammal can be induced simply by appropriate control of wound contraction, rather than of scar formation.     

真皮生物模板对成纤维细胞生物学行为的影响

目的　研究真皮生物模板的应用对皮肤组织创伤修复过程中成纤维细胞 (fibroblast,FB)生物学行为的影响 ,探讨其在影响组织修复及减轻瘢痕形成中的作用机制。　方法　 SD大鼠 12 0只 ,在背部造成 2 .5 cm× 2 .5 cm的全层皮肤组织缺损创面 ,随机分为 4个处理组 ,即开放创面组、全厚皮移植组、刃厚皮移植组、复合移植组 (无细胞真皮基质 +刃厚皮移植 ) ,分别于术后 1、2、4、6及 12周取材。通过免疫组织化学及图像分析技术检测组织标本中肌成纤维细胞 (myofibroblast,MFB)的标志蛋白—— α平滑肌肌动蛋白 (α smooth muscle actin,α- SMA)的表达以及纤维连接蛋白(fibronectin,FN)、整合素 α2 、β1 及转化生长因子 β1 (transforming growth factorβ1 ,TGF- β1 ) )的表达量。　结果　复合移植组 α- SMA在术后 1～ 12周低于开放创面组 ,术后 1、4、6周低于刃厚皮移植组 ,术后 2、12周高于全厚皮移植组(P<0 .0 5 ) ;复合移植组 FN在术后 1～ 12周低于开放创面组和刃厚皮移植组 ,术后 1～ 4周高于全厚皮移植组 (P<0 .0 5 ) ;复合移植组整合素 α2 在术后 1～ 12周低于开放创面移植组 ,术后 1～ 4周低于刃厚皮移植组 ,术后 1、2周高于全厚皮移植组 (P<0 .0 5 ) ;复合移植组整合素 β1 在术后 1～ 12周低     

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.     

MSCs seeded on bioengineered scaffolds improve skin wound healing in rats

Growing evidence has shown the promise of mesenchymal stromal cells (MSCs) for the treatment of cutaneous wound healing. We have previously demonstrated that MSCs seeded on an artificial dermal matrix, Integra (Integra Lifesciences Corp., Plainsboro, NJ) enriched with platelet‐rich plasma (Ematrix) have enhanced proliferative potential in vitro as compared with those cultured on the scaffold alone. In this study, we extended the experimentation by evaluating the efficacy of the MSCs seeded scaffolds in the healing of skin wounds in an animal model in vivo. It was found that the presence of MSCs within the scaffolds greatly ameliorated the quality of regenerated skin, reduced collagen deposition, enhanced reepithelization, increased neo‐angiogenesis, and promoted a greater return of hair follicles and sebaceous glands. The mechanisms involved in these beneficial effects were likely related to the ability of MSCs to release paracrine factors modulating the wound healing response. MSC‐seeded scaffolds, in fact, up‐regulated matrix metalloproteinase 9 expression in the extracellular matrix and enhanced the recruitment of endogenous progenitors during tissue repair. In conclusion, the results of this study provide evidence that the treatment with MSC‐seeded scaffolds of cutaneous wounds contributes to the recreation of a suitable microenvironment for promoting tissue repair/regeneration at the implantation sites.     

Modulatory effect of a complex fraction derived from colostrum on fibroblast contractibility and consequences on repair tissue

A complex compound (immune ('IM') fraction) from colostrum-derived whey was investigated for its potential wound healing properties. One of its most intriguing in vitro abilities was to significantly inhibit the contraction of collagen gel while fibroblast density remained as in control gels. This antagonist effect was dose dependent and fibroblasts in these gels did not exhibit any stress fibres. Subsequently, in vivo studies have been conducted in two wound models in guinea pigs. Daily application on full-thickness wounds of a liquid formulation of the IM fraction (first model) significantly delayed wound closure by contraction compared to what normally occurred in control wounds. In another wound model, a gel formulation of the IM fraction was applied on scar tissues, which resulted in a minimised residual scar on 5/8 wounds compared to corresponding wound areas seen prior to treatment. Conversely, most control wounds exhibited scar tissue from which 3/8 resembled hypertrophic scar tissue. Wound tissue treated with IM fraction covered a significantly larger area than in the control wounds, whereas the collagen deposition was unchanged as in the presence of α-smooth muscle actin. Thus, IM fraction may act by modulating the contraction rate and wound remodelling.     

Impaired wound contraction in stromelysin-1-deficient mice.

OBJECTIVE: To determine whether the deletion of stromelysin-1, a single metalloproteinase gene product, will alter the time course and quality of dermal wound repair in mice. SUMMARY BACKGROUND DATA: After dermal injury, a highly coordinated program of events is initiated by formation of a fibrin clot, followed by migration of keratinocytes, contraction of the dermis, recruitment of inflammatory macrophages, formation of granulation tissue with angiogenesis, and finally tissue remodeling. Matrix metalloproteinases are rapidly induced in the dermis and granulation tissue and at the leading edge of the epidermis in the healing wounds. METHODS: Incisional and circular full-thickness wounds 2 to 10 mm were made in the dermis of stromelysin-1-deficient and wild-type mice. The wounds were analyzed for rate of cellular migration and epithelialization. The wound contraction was examined by immunohistochemical staining for alpha-smooth muscle actin and fluorescent staining for fibrillar actin. RESULTS: Independent of the age of the animal, excisional wounds in stromelysin-1-deficient mice failed to contract and healed more slowly than those in wild-type mice. Cellular migration and epithelialization were unaffected in the stromelysin-1-deficient animals. The functional defect in these mice is failure of contraction during the first phase of healing because of inadequate organization of actin-rich stromal fibroblasts. CONCLUSIONS: Excisional dermal wound healing is impaired in mice with a targeted deletion in the stromelysin-1 gene. Incisional wound healing is not affected. These data implicate stromelysin-1 proteolysis during early wound contraction and indicate that stromelysin-1 is crucial for the organization of a multicellular actin network.     

Adipose tissue extract enhances skin wound healing

The main function of adipose tissue has been considered as storage of triglycerides. Adipose tissue was considered harmful for healing extensive and deep burns because of poor circulation and easy liquefaction in wound beds, which offer an excellent culture medium for bacteria. However, these traditional concepts have been challenged with the discovery of the endocrine function of adipose tissue. To investigate the effects of adipose tissue extract on wound healing, we created four 3.0 x 2.5 cm full-thickness wounds on each side of the back of male Wu Zhi Shan minipigs (n=6), for eight wounds in each animal. The wounds were randomly divided to receive normal saline (0.5 mL; controls), adipose tissue extract (1.5 g), basic fibroblast growth factor (50 U/cm(2)), and epidermal growth factor (50 U/cm(2)). Reduction in wound area and wound volume was accelerated with adipose tissue treatment as compared with growth factor or control treatment. The thickness of the regenerated epidermis and the number of new vascular nets were markedly increased in adipose tissue-treated wounds. Biopsy of adipose tissue-treated wounds showed enhanced expression of proliferation cell nuclear antigen (PCNA) and Factor VIII-related antigen, which indicated active cell differentiation and proliferation. In vitro study in rat tissue showed adipose tissue extracts stimulating skin growth. Bacteriology results showed no significant differences in amount or type of bacteria, whatever the treatment. These results may challenge the traditional concept that adipose tissue plays a negative role in wound healing and may offer direct evidence for encouraging the retention of adipose tissue in autologous skin grafting for skin wounds.     

CXCR4 antagonist delivery on decellularized skin scaffold facilitates impaired wound healing in diabetic mice by increasing expression of SDF‐1 and enhancing migration of CXCR4‐positive cells

C‐X‐C chemokine receptor type 4 (CXCR4) is an alpha‐chemokine receptor specific for stromal cell‐derived factor 1 (SDF‐1 also called CXCL12). The antagonist of CXCR4 can mobilize CD34+ cells and hematopoietic stem cells from bone marrow within several hours, and it has an efficacy on diabetes ulcer through acting on the SDF‐1/CXCR4 axis. In this study, we investigated for the first time whether the antagonist of CXCR4 (Plerixafor/AMD3100) delivered on acellular dermal matrix (ADM) may accelerate diabetes‐impaired wound healing. ADM scaffolds were fabricated from nondiabetic mouse skin through decellularization processing and incorporated with AMD3100 to construct ADM‐AMD3100 scaffold. Full‐thickness cutaneous wound in streptozotocin (STZ)‐induced diabetic mice were treated with ADM, AMD3100, or ADM‐AMD3100. 21 days after treatment, wound closure in ADM‐AMD3100‐treated mice was more complete than ADM group and AMD3100 group, and it was accompanied by thicker collagen formation. Correspondingly, diabetic mice treated with ADM‐AMD3100 demonstrated prominent neovascularization (higher capillary density and vascular smooth muscle actin), which were accompanied by up‐regulated mRNA levels of SDF‐1 and enhanced migration of CXCR4 in the granulation tissue. Our results demonstrate that ADM scaffold provide perfect niche for loading AMD3100 and ADM‐AMD3100 is a promising method for diabetic wound healing mainly by increasing expression of SDF‐1 and enhancing migration of CXCR4‐positive cells.     

Mesenchymal stem cell‐conditioned medium accelerates wound healing with fewer scars

Mesenchymal stem cells (MSCs) derived from umbilical cord s (UC‐MSCs) have been shown to enhance cutaneous wound healing by means of the paracrine activity. Fibroblasts are the primary cells involved in wound repair. The paracrine effects of UC‐MSCs on dermal fibroblasts have not been fully explored in vitro or in vivo. Dermal fibroblasts were treated with conditioned media from UC‐MSCs (UC‐MSC‐CM). In this model, UC‐MSC‐CM increased the proliferation and migration of dermal fibroblasts. Moreover, adult dermal fibroblasts transitioned into a phenotype with a low myofibroblast formation capacity, a decreased ratio of transforming growth factor‐β1,3 (TGF‐β1/3) and an increased ratio of matrix metalloproteinase/tissue inhibitor of metalloproteinases (MMP/TIMP). Additionally, UC‐MSC‐CM‐treated wounds showed accelerated healing with fewer scars compared with control groups. These observations suggest that UC‐MSC‐CM may be a feasible strategy to promote cutaneous repair and a potential means to realise scarless healing.     

Accelerated closure of skin wounds in mice deficient in the homeobox gene Msx2

Differences in cellular competence offer an explanation for the differences in the healing capacity of tissues of various ages and conditions. The homeobox family of genes plays key roles in governing cellular competence. Of these, we hypothesize that Msx2 is a strong candidate regulator of competence in skin wound healing because it is expressed in the skin during fetal development in the stage of scarless healing, affects postnatal digit regeneration, and is reexpressed transiently during postnatal skin wound repair. To address whether Msx2 affects cellular competence in injury repair, 3 mm full-thickness excisional wounds were created on the back of C.Cg- Msx2^tm1Rilm /Mmcd (Msx2 null) mice and the healing pattern was compared with that of the wild type mice. The results show that Msx2 null mice exhibited faster wound closure with accelerated reepithelialization plus earlier appearance of keratin markers for differentiation and an increased level of smooth muscle actin and tenascin in the granulation tissue. In vitro, keratinocytes of Msx2 null mice exhibit increased cell migration and the fibroblasts show stronger collagen gel contraction. Thus, our results suggest that Msx2 regulates the cellular competence of keratinocytes and fibroblasts in skin injury repair.     

更进一步提高深度烧伤创面修复质量

This article summarizes methods of repair of massive and deep wounds, elucidates how to improve wound healing quality and avoid scar deformity after deep hum. A part of denatured dermis (non-necrotic)in deep partial-thickness burn, "mixed degree" burn, even in full-thickness burn wounds before forming eschar can be preserved and covered with autolo-gous skin, thereby to avoid secondary damage to the structure of subcutaneous tissue and the junction of dermis-adipose, thus to result in good functions, appearance, and survival rate. After skin grafting, wound healing quality and appearance are im-proved, joint function and elasticity of skin are enhanced, the degree of scar contracture is relieved due to preservation of nor-mal adipose tissue after escharectomy. The study of composite artifical skin will be actively developed in the future. Tissue-en-gineering skin and stem cells can be successfully used in pa-tients with deep burns for starless healing with restoration of physiological functions in a short period.     

A novel implantable collagen gel assay for fibroblast traction and proliferation during wound healing

BACKGROUND: A novel implantable assay for studying cellular behavior in the wound environment was developed. The assay is unique in that it combines the more quantitative nature of in vitro assays with the greater physiological relevance of in vivo wound healing models. MATERIALS AND METHODS: Cells were seeded in a physiologically relevant biological matrix, a collagen gel, contained within a semipermeable tube, and then exposed to soluble factors of the wound environment at different stages of the wound healing response. Gels were harvested at prescribed time points, and cell proliferation rates and gel compaction were measured. These data were combined with our theory for cell-matrix mechanical interactions to estimate the cell traction exerted by the cells leading to gel compaction. Cell morphology and alpha-smooth muscle actin expression were also characterized. RESULTS: The proliferation of and traction exerted by fibroblasts exposed to the soluble wound environment were different from those in similar collagen gels maintained in culture in complete medium. Proliferation and traction also varied over the course of the wound healing response. Traction was higher and proliferation lower in day 1-5 wounds compared to day 7-11 wounds. Recovered cells no longer stained for alpha-smooth muscle actin, in contrast to cells maintained in culture. CONCLUSIONS: Changes in the soluble wound environment that occur as the wound healing response proceeds alter fibroblast traction and migration. We have developed a new assay that employs a physiologically relevant biological matrix and allows the effects of the dynamic soluble wound environment on cellular traction, proliferation, and other phenomena such as protein expression to be quantified.