Bone marrow-derived mesenchymal stromal cells accelerate wound healing in the rat

Bone marrow-derived mesenchymal stromal cells (BMSCs) are multipotential stem cells capable of differentiation into numerous cell types, including fibroblasts, cartilage, bone, muscle, and brain cells. BMSCs also secrete a large number of growth factors and cytokines that are critical to the repair of injured tissues. Because of the extraordinary plasticity and the ability of syngeneic or allogeneic BMSCs to secrete tissue-repair factors, we investigated the therapeutic efficacy of BMSCs for healing of fascial and cutaneous incisional wounds in Sprague-Dawley rats. Systemic administration of syngeneic BMSCs (2 x 10(6)) once daily for 4 days or a single treatment with 5 x 10(6) BMSCs 24 hours after wounding significantly increased the wound bursting strength of fascial and cutaneous wounds on days 7 and 14 postwounding. Wound healing was also significantly improved following injection of BMSCs locally at the wound site. Furthermore, allogeneic BMSCs were as efficient as syngeneic BMSCs in promoting wound healing. Administration of BMSCs labeled with iron oxides/1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate fluorescent dye revealed that systemically administered BMSCs engraft to the wound. The increase in the tensile strength of wounds treated with BMSCs was associated with increased production of collagen in the wound. In addition, BMSC treatment caused more rapid histologic maturation of wounds compared with untreated wounds. These data suggest that cell therapy with BMSCs has the potential to augment healing of surgical and cutaneous wounds.     

Wound repair by bone marrow stromal cells through growth factor production

We have previously shown that treatment with bone marrow stromal cells (BMSCs) augments the healing of fascial wounds in the rat. However, the biochemical mechanism by which BMSCs improve wound healing was not investigated. Growth factors have been shown to play a key role in repairing damaged tissue. In this study, we investigated whether BMSCs are capable of producing growth factors that play a critical role in healing of the damaged tissue. Growth factor expression in BMSCs stimulated with pro-inflammatory cytokines or wound superfusate was measured by RT-PCR and growth factor-specific quantitative sandwich enzyme-linked immunosorbent assay (ELISA). RT-PCR analysis demonstrated that BMSCs are capable of expressing transforming growth factor beta-1 (TGF-beta1), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) platelet-derived growth factor (PDGF), keratinocyte growth factor (KGF), fibroblast growth factor (FGF), and hepatocyte growth factor (HGF) constitutively or upon stimulation with LPS, IL-1alpha, or TNF-alpha. Quantitative analysis of growth factor production by ELISA showed that BMSCs do not secrete TGF-beta1, EGF or VEGF in response to uninjured fascia tissue superfusate; however, production of these growth factors is significantly increased when cells were stimulated with wound tissue superfusate. The ability of wound to stimulate growth factor production in BMSCs could be detected as early as day 1 and lasted through day 7 after wounding. Thus, growth factor production by BMSCs in response to wound microenvionment suggests that BMSCs might augment wound healing through the responsive secretion of growth factors that enhance angiogenesis and promote wound repair.     

Effects of plasma fibronectin on the healing of full-thickness skin wounds in streptozotocin-induced diabetic rats

BACKGROUND: Fibronectin has been shown to assist in wound healing. Impaired wound healing in diabetes mellitus is characterized by a reduction in plasma fibronectin (pFn) at the wound site. This study investigated whether topical application of pFn could improve the impaired wound healing in diabetic rats. MATERIALS AND METHODS: Full-thickness skin wounds were created on the backs of streptozotocin (STZ)-induced diabetic rats. Immediately, human pFn was introduced into the wound bed, while wounds receiving human serum albumin or normal saline were used as controls. Wound closure was monitored using well-recognized wound-healing parameters: epithelialization, vascularization, collagen deposition, and migration of fibroblasts were examined histologically. Transforming growth factor (TGF)-beta1 was measured by immunochemistry. Hydroxyproline levels also were assessed in the wound skin. RESULTS: Wound closure was significantly accelerated by local application of pFn. Furthermore, pFn-treated wounds showed increased fibroblast vascularization, collagen regeneration, and epithelialization. The numbers of infiltrating fibroblasts expressing TGF-beta1 and hydroxyproline levels in pFn-treated wounds were significantly higher than those in the controls. CONCLUSIONS: pFn can improve the impaired healing of diabetic wounds and this effect might involve an increase in the activity of fibroblasts and increased release of TGF-beta1.     

Different wound healing properties of dermis,adipose, and gingiva mesenchymal stromal cells

Oral wounds heal faster and with better scar quality than skin wounds. Deep skin wounds where adipose tissue is exposed, have a greater risk of forming hypertrophic scars. Differences in wound healing and final scar quality might be related to differences in mesenchymal stromal cells (MSC) and their ability to respond to intrinsic (autocrine) and extrinsic signals, such as human salivary histatin, epidermal growth factor, and transforming growth factor beta1. Dermis‐, adipose‐, and gingiva‐derived MSC were compared for their regenerative potential with regards to proliferation, migration, and matrix contraction. Proliferation was assessed by cell counting and migration using a scratch wound assay. Matrix contraction and alpha smooth muscle actin was assessed in MSC populated collagen gels, and also in skin and gingival full thickness tissue engineered equivalents (reconstructed epithelium on MSC populated matrix). Compared to skin‐derived MSC, gingiva MSC showed greater proliferation and migration capacity, and less matrix contraction in full thickness tissue equivalents, which may partly explain the superior oral wound healing. Epidermal keratinocytes were required for enhanced adipose MSC matrix contraction and alpha smooth muscle actin expression, and may therefore contribute to adverse scarring in deep cutaneous wounds. Histatin enhanced migration without influencing proliferation or matrix contraction in all three MSC, indicating that salivary peptides may have a beneficial effect on wound closure in general. Transforming growth factor beta1 enhanced contraction and alpha smooth muscle actin expression in all three MSC types when incorporated into collagen gels. Understanding the mechanisms responsible for the superior oral wound healing will aid us to develop advanced strategies for optimal skin regeneration, wound healing and scar formation.     

Acceleration of cutaneous wound healing by brassinosteroids

Brassinosteroids are plant growth hormones involved in cell growth, division, and differentiation. Their effects in animals are largely unknown, although recent studies showed that the anabolic properties of brassinosteroids are possibly mediated through the phosphoinositide 3‐kinase/protein kinase B signaling pathway. Here, we examined biological activity of homobrassinolide (HB) and its synthetic analogues in in vitro proliferation and migration assays in murine fibroblast and primary keratinocyte cell culture. HB stimulated fibroblast proliferation and migration and weakly induced keratinocyte proliferation in vitro. The effects of topical HB administration on progression of wound closure were further tested in the mouse model of cutaneous wound healing. C57BL/6J mice were given a full‐thickness dermal wound, and the rate of wound closure was assessed daily for 10 days, with adenosine receptor agonist CGS‐21680 as a positive control. Topical application of brassinosteroid significantly reduced wound size and accelerated wound healing in treated animals. mRNA levels of transforming growth factor beta and intercellular adhesion molecule 1 were significantly lower, while tumor necrosis factor alpha was nearly suppressed in the wounds from treated mice. Our data suggest that topical application of brassinosteroids accelerates wound healing by positively modulating inflammatory and reepithelialization phases of the wound repair process, in part by enhancing Akt signaling in the skin at the edges of the wound and enhancing migration of fibroblasts in the wounded area. Targeting this signaling pathway with brassinosteroids may represent a promising approach to the therapy of delayed wound healing.     

Fascial fibroblast kinetic activity is increased during abdominal wall repair compared to dermal fibroblasts

Abdominal wall fascial wound healing failure is a common clinical problem for general surgeons, manifesting in early postoperative fascial dehiscence as well as delayed development of incisional hernias. We previously reported that abdominal wall fascial incisions normally recover breaking strength faster than simultaneous dermal incisions in a rodent model. The accelerated fascial repair was associated with greater fibroblast cellularity within fascial wounds and increased wound collagen deposition. The current study was designed to determine whether accelerated fascial healing is the result of increased fascial fibroblast kinetic activity as measured by a more efficient fibroblast phenotype for binding to and remodeling a collagen matrix. Using a new model of abdominal wall repair, fibroblast cell cultures were developed from uninjured and wounded fascia and compared to dermal fibroblasts in order to define the fibroproliferative kinetic properties of abdominal wall fibroblasts. Fascial wound fibroblasts produced a more efficient and greater overall collagen lattice compaction compared to dermal fibroblasts. Acute fascial wound fibroblasts also showed enhanced cell proliferation compared to dermal fibroblasts but no significant differences in collagen production when normalized to cell number. These results suggest that fascial fibroblasts express distinct acute repair phenotypes and therefore a specific mechanism for fascial repair following injury.     

Exogenous calreticulin improves diabetic wound healing

A serious consequence of diabetes mellitus is impaired wound healing, which largely resists treatment. We previously reported that topical application of calreticulin (CRT), an endoplasmic reticulum chaperone protein, markedly enhanced the rate and quality of wound healing in an experimental porcine model of cutaneous repair. Consistent with these in vivo effects, in vitro CRT induced the migration and proliferation of normal human cells critical to the wound healing process. These functions are particularly deficient in poor healing diabetic wounds. Using a genetically engineered diabetic mouse (db/db) in a full‐thickness excisional wound healing model, we now show that topical application of CRT induces a statistically significant decrease in the time to complete wound closure compared with untreated wounds by 5.6 days (17.6 vs. 23.2). Quantitative analysis of the wounds shows that CRT increases the rate of reepithelialization at days 7 and 10 and increases the amount of granulation tissue at day 7 persisting to day 14. Furthermore, CRT treatment induces the regrowth of pigmented hair follicles observed on day 28. In vitro, fibroblasts isolated from diabetic compared with wild‐type mouse skin and human fibroblasts cultured under hyperglycemic compared with normal glucose conditions proliferate and strongly migrate in response to CRT compared with untreated controls. The in vitro effects of CRT on these functions are consistent with CRT's potent effects on wound healing in the diabetic mouse. These studies implicate CRT as a potential powerful topical therapeutic agent for the treatment of diabetic and other chronic wounds.     

Increased calcium levels alter cellular and molecular events in wound healing

Surgical morbidity is dictated directly by wound healing. We have studied the effects of elevated calcium levels using cultured keratinocytes in vitro on two of the rate-limiting steps of wound healing, chemotaxis (directed migration) and adhesion. We found that the increased calcium (10 mmol/L) significantly inhibited both keratinocyte chemotaxis and adhesion (p less than 0.05). The calcium effect on adhesion could be partially reversed by pretreatment with the calcium channel blocker verapamil. Based on these data, an animal model was formulated in which topical calcium (5 mmol/L/day) was added to linear incision wounds. This resulted in significantly (p less than 0.05) delayed wound contraction characteristic of a chronic or impaired wound. Wound contraction depends on the presence of fibroblasts that synthesize collagen. The chronic wound was characterized by increased collagenase activity (p less than 0.05) but little alteration in collagen I synthesis. The addition of verapamil to these chronic wounds resulted in improved wound closure. These studies define the molecular and cellular events occurring as a result of the addition of elevated levels of calcium both in vitro and in vivo. Calcium may play a key role in the pathogenesis of chronic wounds.     

In vitro migration and adhesion of fibroblasts from different phases of palatal wound healing

Cleft palate patients often show mid-facial growth impairment after surgical closure of the defect. This is a consequence of palatal wound healing, and more specifically of wound contraction and scar tissue formation. Cells of the fibroblast lineage are responsible for these processes and they display different phenotypes in the course of the wound healing process. The aim of this study was to analyze the in vitro adhesion and migration of wound fibroblasts, isolated during the palatal wound healing process in the rat. Additionally, we analyzed the expression of beta1 integrins and vinculin, the key players in adhesion and migration. Palatal fibroblasts from age-matched controls were analyzed to measure the effects of normal aging. Palatal fibroblasts from unwounded tissue showed a low migratory behavior (<25 microm), a strong capability to adhere (>80%) and a low expression of beta1 integrins and vinculin. In contrast, fibroblasts obtained from healing palatal wounds were highly migratory (>200 microm) coupled to a weak capability to adhere (<65%) and a high expression of vinculin and beta1 integrins. These data show that the palatal wound healing process induces a change in fibroblast phenotype from "quiescent" to "activated," which persists in vitro.     

Treatment with bone marrow-derived stromal cells accelerates wound healing in diabetic rats

Bone marrow stem cells participate in tissue repair processes and may have a role in wound healing. Diabetes is characterised by delayed and poor wound healing. We investigated the potential of bone marrow-derived mesenchymal stromal cells (BMSCs) to promote healing of fascial wounds in diabetic rats. After manifestation of streptozotocin (STZ)-induced diabetic state for 5 weeks in male adult Sprague-Dawley rats, healing of fascial wounds was severely compromised. Compromised wound healing in diabetic rats was characterised by excessive polymorphonuclear cell infiltration, lack of granulation tissue formation, deficit of collagen and growth factor [transforming growth factor (TGF-beta), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), platelet-derived growth factor PDGF-BB and keratinocyte growth factor (KGF)] expression in the wound tissue and significant decrease in biomechanical strength of wounds. Treatment with BMSC systemically or locally at the wound site improved the wound-breaking strength (WBS) of fascial wounds. The improvement in WBS was associated with an immediate and significant increase in collagen levels (types I-V) in the wound bed. In addition, treatment with BMSCs increased the expression of growth factors critical to proper repair and regeneration of the damaged tissue moderately (TGF-beta, KGF) to markedly (EGF, VEGF, PDGF-BB). These data suggest that cell therapy with BMSCs has the potential to augment healing of the diabetic wounds.     

Vitamin A and retinoic acid: induced fibroblast differentiation in vitro

The role of vitamin A in wound healing and fibroplasia has been studied extensively in vivo but the mechanism(s) of its action has not been established. In this study the effect of vitamin A and retinoic acid on fibroblast growth and collagen accumulation in vitro was examined. Vitamin A and retinoic acid added to Balb 3T3 mouse fibroblasts in tissue culture resulted in induction of cell differentiation as manifested by a decrease in cell growth rate, enhanced collagen accumulation, and morphologic differentiation. The results of this in vitro study suggest that the stimulatory in vivo effect of vitamin A and retinoic acid on collagen accumulation and fibroplasia in healing wounds is due in a major way to fibroblast differentiation and enhanced collagen synthesis.     

Enhanced adenoviral-vector mediated gene transfer using human albumin solder

BACKGROUND AND OBJECTIVE: Laser tissue welding with human albumin solder (HAS) has been used as an alternative method of wound closure. Adenoviral vectors have been used to introduce various cytokine genes into wounds to accelerate wound closure. In the present study, we were interested in the effect of HAS on adenoviral vector transfer of the beta-galactosidase (beta-gal) gene in vitro and in vivo. STUDY DESIGN/MATERIALS AND METHODS: 3T3 fibroblasts were used to study the effect of HAS on beta-gal gene transfer in vitro. The presence of beta-gal was determined by Western blot, and its activity by a colorimetric assay. A punch biopsy model of wound healing in pigs was used for in vivo experiments. RESULTS: HAS increased the efficiency of adenoviral-mediated beta-gal transduction and stabilized the adenovirus at room temperature. HAS protected adenovirus from inactivation by laser, both in vitro and in vivo. CONCLUSIONS: HAS may stabilize adenoviral vectors to deliver cytokine genes in future wound healing experiments.     

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.     

Organic light emitting diode improves diabetic cutaneous wound healing in rats

A major complication for diabetic patients is chronic wounds due to impaired wound healing. It is well documented that visible red wavelengths can accelerate wound healing in diabetic animal models and patients. In vitro and in vivo diabetic models were used to investigate the effects of organic light emitting diode (OLED) irradiation on cellular function and cutaneous wound healing. Human dermal fibroblasts were cultured in hyperglycemic medium (glucose concentration 180 mM) and irradiated with an OLED (623 nm wavelength peak, range from 560 to 770 nm, power density 7 or 10 mW/cm² at 0.2, 1, or 5 J/cm²). The OLED significantly increased total adenosine triphosphate concentration, metabolic activity, and cell proliferation compared with untreated controls in most parameters tested. For the in vivo experiment, OLED and laser (635 ± 5 nm wavelength) treatments (10 mW/cm², 5 J/cm² daily for a total of seven consecutive days) for cutaneous wound healing were compared using a genetic, diabetic rat model. Both treatments had significantly higher percentage of wound closure on day 6 postinjury and higher total histological scores on day 13 postinjury compared with control. No statistical difference was found between the two treatments. OLED irradiation significantly increased fibroblast growth factor‐2 expression at 36‐hour postinjury and enhanced macrophage activation during initial stages of wound healing. In conclusion, the OLED and laser had comparative effects on enhancing diabetic wound healing.     

Wound chronicity and fibroblast senescence--implications for treatment

A proportion of chronic wounds fail to heal in response to standard therapy. For venous leg ulcers, a correlation exists between longer duration before treatment initiation and poor healing response to compression therapy. Differences identified between the healing wound microenvironment and that of the non healing chronic wound suggests that many potential mechanisms exist to impair healing. One contributory mechanism may be inhibition of fibroblast proliferation and induction of a stress-induced premature senescence phenotype by the continuing inflammation found in chronic wounds. Senescent fibroblasts exhibit an extracellular matrix degradative phenotype that contributes to wound chronicity. Accumulation of greater than 15% senescent fibroblasts has been described as a threshold beyond which wounds become hard to heal. The ratio of senescent : non senescent cells is therefore critical to determining response to treatment, and adjunctive therapies that modulate this ratio in favour of non senescent cells are likely to enhance therapeutic healing rates. A number of tissue-engineered dermal replacements contain non senescent fibroblasts and can donate cells to the wound environment additional to releasing growth factors and reversing the antiproliferative activity of chronic wound exudate. Recognition of the role of fibroblast senescence in wound chronicity may allow for identification of those wounds that will respond positively to these products.     

MicroRNA signature in diabetic wound healing: promotive role of miR-21 in fibroblast migration

A major complication of diabetes mellitus is the disruption of normal wound repair process, characterised by insufficient production of growth factors. A molecular genetic approach wherein resident cells synthesise and deliver the growth factors to the wound site would be a powerful therapeutic strategy to treat diabetic wounds. One such molecular approach could be the application of microRNAs (miRNAs). This study reports differential expression of miRNAs related to cell development and differentiation, during wound healing in diabetic mice. Comparison of skin tissue from normal and diabetic mice showed that 14 miRNAs were differentially expressed in diabetic skin; miR-146b and miR-21 were the most noteworthy. Expression pattern of these miRNAs was also altered during healing of diabetic wounds. A subset of miRNAs (miR-20b, miR-10a, miR-10b, miR-96, miR-128, miR-452 and miR-541) exhibited similar basal levels in normal and diabetic skins, but displayed dysregulation during healing of diabetic wounds. Amongst the miRNAs studied, miR-21 showed a distinct signature with increased expression in diabetic skin but decreased expression during diabetic wound healing. We analysed the role of miR-21 in fibroblast migration, because migration of fibroblasts into the wound area is an important landmark facilitating secretion of growth factors and migration of other cell types into the wound, thus enhancing the healing process. Using gain-of and loss-of function approaches, we show that miR-21 is involved in fibroblast migration. Our preliminary studies implicate an important role for miRNAs in the pathogenesis of diabetic wounds.     

血管紧张素Ⅱ对创伤愈合中成纤维细胞增殖影响的研究

目的：探讨血管紧张素Ⅱ（angiotensinⅡ,AngⅡ）对创面愈合中成纤维细胞增殖的影响及不同浓度AngⅡ对创面作用的差异。方法：采用不同浓度AngⅡ作用于小鼠新鲜创面,应用流式细胞仪检测相同面积创面中S（DNA合成期）期成纤维细胞所占的比例。结果：与对照组相比,AngⅡ可有效促进创面中成纤维细胞的增殖,从而促进创面肉芽组织生长,使创面愈合加快。结论：AngⅡ可促使局部创面成纤维细胞增殖,从而加快创面愈合,且呈浓度依赖性。     

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.     

Cellular events and biomarkers of wound healing

Researchers have identified several of the cellular events associated with wound healing. Platelets, neutrophils, macrophages, and fibroblasts primarily contribute to the process. They release cytokines including interleukins (ILs) and TNF-α, and growth factors, of which platelet-derived growth factor (PDGF) is perhaps the most important. The cytokines and growth factors manipulate the inflammatory phase of healing. Cytokines are chemotactic for white cells and fibroblasts, while the growth factors initiate fibroblast and keratinocyte proliferation. Inflammation is followed by the proliferation of fibroblasts, which lay down the extracellular matrix. Simultaneously, various white cells and other connective tissue cells release both the matrix metalloproteinases (MMPs) and the tissue inhibitors of these metalloproteinases (TIMPs). MMPs remove damaged structural proteins such as collagen, while the fibroblasts lay down fresh extracellular matrix proteins. Fluid collected from acute, healing wounds contains growth factors, and stimulates fibroblast proliferation, but fluid collected from chronic, nonhealing wounds does not. Fibroblasts from chronic wounds do not respond to chronic wound fluid, probably because the fibroblasts of these wounds have lost the receptors that respond to cytokines and growth factors. Nonhealing wounds contain high levels of IL1, IL6, and MMPs, and an abnormally high MMP/TIMP ratio. Clinical examination of wounds inconsistently predicts which wounds will heal when procedures like secondary closure are planned. Surgeons therefore hope that these chemicals can be used as biomarkers of wounds which have impaired ability to heal. There is also evidence that the application of growth factors like PDGF will help the healing of chronic, nonhealing wounds.KEY WORDS: Cytokines, growth factors, matrix metalloproteinases, platelet-derived growth factor, wound healingIn the last 30 or so years, researchers have identified several of the cellular and biochemical events associated with wound healing. The process is becoming clearer, with the understanding of the cells and chemicals that help wounds to heal, and of those that inhibit healing. Investigators are trying to analyze the chemicals in chronic wounds in order to determine their condition and fitness for closure. A major advance is the clinical application of some of these chemicals to improve outcomes in wound healing.In this paper we look at the biology of normal and abnormal healing, see if wounds analysis can predict poor healing, and review some literature on the clinical applications of this knowledge.     

The effects of platelet gel–released supernatant on human fibroblasts

In recent years, interest in the topical use of platelet gel (PG) to stimulate wound healing has rapidly extended into various clinical applications and specialized fields. Many recent in vitro and in vivo studies have attempted to explain the biological mechanisms involved in PG‐induced tissue regeneration/reparation. However, it remains unclear which parameters should be used in clinical applications to obtain satisfactory results in the healing of wounds. Toward this end, the present study focused on understanding the relationship between platelet concentrations and the cellular parameters of the cell types, i.e., fibroblasts, involved in wound healing. Normal human dermal fibroblasts were treated with PG‐released supernatant at various concentrations in different assays (proliferation, migration, invasion, and in vitro scratch wound closure) to identify the most effective concentration to promote the fibroblasts' activities. Different concentrations of platelets per microliter in PG have different levels of efficacy in inducing fibroblast activity. The most effective concentration was obtained from PG at a concentration of approximately 0.5–1.5 × 10⁶ plt/μL; higher concentrations were less effective. This study shows that excessively high concentrations of platelets per microliter have an inhibitory effect on the wound healing processes and are, therefore, counterproductive.