The effect of pentadecapeptide BPC 157, H2-blockers, omeprazole and sucralfate on new vessels and new granulation tissue formation

A clear protection of the gastrointestinal tract and an evident anti-inflammatory effect were shown for a novel stomach pentadecapeptide BPC 157 (i.p./i.g.) in comparison with several reference standards in various ulcer models along with a protection of endothelium and particular interaction with the NO-system. Thus, we evaluated whether this pentadecapeptide along with other gastroprotective agents could affect angiogenesis and the healing process in vivo using a procedure initially described by Szabo and co-workers. In each rat, two sterile sponges (1 x 1 x 0.25 cm; V = 0.25 mL) with the same quantities of BPC 157 (10 ng x mL(-1), 10 microg x mL(-1), 50 microg x kg(-1)) or reference agents (cimetidine: 10, 100, 500 mg x mL(-1); ranitidine: 2.5, 25, 250 mg x mL(-1); famotidine: 10, 50, 100 mg x mL(-1); omeprazole: 10, 50, 100 mg x mL(-1); sucralfate: 1, 5, 10 mg x mL(-1) were implanted subcutaneously in the lumbar region. The sponges were removed after 3 or 7 d, fixed in formalin, and processed for histologic and histochemical evaluation and morphometry assessment. Compared with the control values, the number of newly formed endothelial spaces inside newly formed granulation tissue was markedly increased in all animals treated with BPC 157, cimetidine, ranitidine, famotidine, sucralfate and omeprazole, a consistent finding noted after either 3 or 7 d. Compared with control values, markedly more granulation tissue was noted in the rats in the groups of animals treated with BPC 157 (50 microg) and in the rats treated with sucralfate in all dosages used, euthanized after 3 d. In all groups treated with H2-blockers however, similar values to those of controls were noted. Thus, it could be concluded that an evident angiogenic property was consistently noted for the novel pentadecapeptide BPC 157, H2-blockers (cimetidine, famotidine and ranitidine) and omeprazole, besides the well known angiogenic effect of sucralfate. Furthermore, unlike H2-blockers and omeprazole, BPC 157 stimulates the formation of granulation tissue, suggesting a particular activity, similar to that previously noted for sucralfate.     

Calpain activity is essential in skin wound healing and contributes to scar formation

Wound healing is a multistep phenomenon that relies on complex interactions between various cell types. Calpains are ubiquitously expressed proteases regulating several processes including cellular adhesion and motility as well as inflammation and angiogenesis. Calpains can be targeted by inhibitors, and their inhibition was shown to reduce organ damage in various disease models. We aimed to assess the role of calpains in skin healing and the potential benefit of calpain inhibition on scar formation. We used a pertinent model where calpain activity is inhibited only in lesional organs, namely transgenic mice overexpressing calpastatin (CPST), a specific natural calpain inhibitor. CPST mice showed a striking delay in wound healing particularly in the initial steps compared to wild types (WT). CPST wounds displayed reduced proliferation in the epidermis and delayed re-epithelization. Granulation tissue formation was impaired in CPST mice, with a reduction in CD45+ leukocyte infiltrate and in CD31+ blood vessel density. Interestingly, wounds on WT skin grafted on CPST mice (WT/CPST) showed a similar delayed healing with reduced angiogenesis and inflammation compared to wounds on WT/WT mice demonstrating the implication of calpain activity in distant extra-cutaneous cells during wound healing. CPST wounds showed a reduction in alpha-smooth muscle actin (αSMA) expressing myofibroblasts as well as αSMA RNA expression suggesting a defect in granulation tissue contraction. At later stages of skin healing, calpain inhibition proved beneficial by reducing collagen production and wound fibrosis. In vitro, human fibroblasts exposed to calpeptin, a pan-calpain inhibitor, showed reduced collagen synthesis, impaired TGFβ-induced differentiation into αSMA-expressing myofibroblasts, and were less efficient in a collagen gel contraction assay. In conclusion, calpains are major players in granulation tissue formation. In view of their specific effects on fibroblasts a late inhibition of calpains should be considered for scar reduction.     

The promoting effect of pentadecapeptide BPC 157 on tendon healing involves tendon outgrowth, cell survival, and cell migration

Pentadecapeptide BPC 157, composed of 15 amino acids, is a partial sequence of body protection compound (BPC) that is discovered in and isolated from human gastric juice. Experimentally it has been demonstrated to accelerate the healing of many different wounds, including transected rat Achilles tendon. This study was designed to investigate the potential mechanism of BPC 157 to enhance healing of injured tendon. The outgrowth of tendon fibroblasts from tendon explants cultured with or without BPC 157 was examined. Results showed that BPC 157 significantly accelerated the outgrowth of tendon explants. Cell proliferation of cultured tendon fibroblasts derived from rat Achilles tendon was not directly affected by BPC 157 as evaluated by MTT assay. However, the survival of BPC 157-treated cells was significantly increased under the H(2)O(2) stress. BPC 157 markedly increased the in vitro migration of tendon fibroblasts in a dose-dependent manner as revealed by transwell filter migration assay. BPC 157 also dose dependently accelerated the spreading of tendon fibroblasts on culture dishes. The F-actin formation as detected by FITC-phalloidin staining was induced in BPC 157-treated fibroblasts. The protein expression and activation of FAK and paxillin were determined by Western blot analysis, and the phosphorylation levels of both FAK and paxillin were dose dependently increased by BPC 157 while the total amounts of protein was unaltered. In conclusion, BPC 157 promotes the ex vivo outgrowth of tendon fibroblasts from tendon explants, cell survival under stress, and the in vitro migration of tendon fibroblasts, which is likely mediated by the activation of the FAK-paxillin pathway.     

Physicochemical properties of extracellular matrix proteins in post-burn human granulation tissue

Wound healing is a finely controlled biological process involving a series of complex cellular interactions. Following inflammation, the wound bed matrix is gradually replaced by granulation tissue followed by the long slow process where collagen accumulates and restores tensile strength. The studies revealed that human granulation tissue varied in many aspects in comparison with normal skin. In granulation tissue the molecular organization of collagen showed an increased amount of type III collagen resembling embryonic tissue. The presence of type V collagen with three distinct chains was the characteristic feature of granulation tissue. The physicochemical properties of collagen extracted from granulation tissue showed the influence of proteoglycans during collagen aggregation and these proteoglycans from the major non-collagenous proteins during the proliferative phase of healing.     

Sustained-release adrenomedullin ointment accelerates wound healing of pressure ulcers

Pressure ulcers are one of the most common complications in elderly, incontinent or paralyzed patients. For the healing of pressure ulcers, the development of granulation tissue and reepithelialization is required. Adrenomedullin (AM), an endogenous vasodilator peptide, is reported to stimulate the proliferation and migration of various cells including endothelial cells, fibroblasts and keratinocytes. Therefore, we hypothesized that AM might accelerate the healing process of pressure ulcers in which these cells were involved. We developed a sustained-release ointment containing human recombinant AM, and applied it in a mouse model of pressure ulcer twice a day for 14 days. Human AM was efficiently absorbed in wound area, but its blood concentration was negligible. AM ointment significantly reduced the wound area on day 5 to 7 after injury. In addition, AM ointment accelerated the formation of granulation tissue and angiogenesis as well as lymphangiogenesis after 7 days of treatment. Immunological analysis revealed that Ki-67-positive proliferating cells in granulation tissue expressed AM receptors. In summary, sustained-release AM significantly improved wound healing of pressure ulcers through acceleration of granulation and induction of angiogenesis and lymphangiogenesis. Therefore, sustained-release AM ointment may be a novel therapeutic agent for pressure ulcers.     

十五肽BPC-157对人脐静脉内皮细胞功能的影响

目的:观察十五肽BPC-157对人脐静脉内皮细胞株HUVEC增殖、周期、迁移及小管形成的影响。方法:用不同浓度(0、1、5、10、50、100μg/mL)的BPC-157作用于HUVEC细胞株,采用MTT法检测药物对内皮细胞增殖的影响,通过流式细胞仪观察细胞周期的变化,经细胞划痕和Transwell实验检测药物对内皮细胞迁移的影响,并且通过小管形成实验观察BPC-157对内皮细胞小管形成能力的影响。结果:HUVEC细胞株经BPC-157刺激48 h后,细胞增殖率和各时期细胞比例没有明显变化;而在刺激12 h时,BPC-157显著性促进细胞伤口愈合及穿膜细胞数的增加(P0.01);刺激8 h时,给药组细胞开始聚合,形成复杂的管状网络结构,特别是5μg/mL剂量组。结论:十五肽BPC-157对人脐静脉内皮细胞株HUVEC增殖及细胞周期的改变基本没有影响,但对内皮细胞的迁移及小管形成能力具有明显的促进作用。     

Nacre-driven water-soluble factors promote wound healing of the deep burn porcine skin by recovering angiogenesis and fibroblast function

To assess the recovery effect of water-soluble components of nacre on wound healing of burns, water-soluble nacre (WSN) was obtained from powdered nacre. Alterations to WSN-mediated wound healing characteristics were examined in porcine skin with deep second-degree burns; porcine skin was used as a proxy for human. When WSN was applied to a burned area, the burn-induced granulation sites were rapidly filled with collagen, and the damaged dermis and epidermis were restored to the appearance of normal skin. WSN enhanced wound healing recovery properties for burn-induced apoptotic and necrotic cellular damage and spurred angiogenesis. Additionally, WSN-treated murine fibroblast NIH3T3 cells showed increased proliferation and collagen synthesis. Collectively, the findings indicate that WSN improves the process of wound healing in burns by expeditiously restoring angiogenesis and fibroblast activity. WSN may be useful as a therapeutic agent, with superior biocompatibility to powdered nacre, and evoking less discomfort when applied to a wounded area.     

Nitrooxyethylation reverses the healing-suppressant effect of Ibuprofen

Nonsteroidal antiinflammatory drugs like ibuprofen impede tissue repair by virtue of retarding inflammation. The present study was undertaken to explore if linking of nitrooxyethyl ester to ibuprofen reverses its healing-depressant propensity. Nitrooxyethyl ester of ibuprofen (NOE-Ibu) was synthesized in our laboratory through a well-established synthetic pathway. NOE-Ibu was screened for its influence on collagenation, wound contraction and epithelialization phases of healing, and scar size of healed wound in three wound models, namely, incision, dead space, and excision wounds. Besides, its influence on the oxidative stress (levels of GSH and TBARS) was also determined in 10-day-old granulation tissue. NOE-Ibu was further screened for its antiinflammatory activity in rat paw edema model. NOE-Ibu promoted collagenation (increase in breaking strength, granulation weight, and collagen content), wound contraction and epithelialization phases of healing. NOE-Ibu also showed a significant antioxidant effect in 10-day-old granulation tissue as compared to ibuprofen. Results vindicate that the esterification of ibuprofen with nitrooxyethyl group reverses the healing-suppressant effect of ibuprofen. The compound also showed equipotent antiinflammatory activity as ibuprofen.     

Effect of cyclic guanidine monophosphate on experimental wound healing

Studies on the effect of cGMP on the proliferation of granulation tissue and collagenogenesis in experimental wound healing have shown that cGMP promoted more rapid formation and differentiation of fibroblasts rose thereby promoting an accelerated formation of collagen. Histological and biochemical findings correlated with wound planimetry data. In the course of stimulation the wound healing surfaces diminished more quickly as compared to the control.     

Collagen deposition in the subcutaneous tissue during wound healing in humans: a model evaluation

Wound healing encompasses coagulation, inflammation, angiogenesis, fibroplasia, contraction, epithelialisation and remodeling. A granulation tissue is produced following incision of tissue such as skin, abdominal wall or the gastrointestinal tract, and the strength of the wound is determined primarily by the collagen content early in the healing course. Few models are available to study wound healing in man. The percutaneous insertion of expanded poly-tetrafluoroethylene tubes (ePTFE) into the subcutaneous tissue has been an established model for 20 years. The procedure is performed using a local anesthesia. The model has a diameter of 2.5 mm, a length of 5-10 cm and a pore size of 90-120 microns which is substantially more than that of vascular grafts. The polymer accumulates granulation tissue, the architecture of which resembles that of a normal surgical wound. Previous studies on the use of the ePTFE model in wound healing research are summarized in detail. Histological and immunohistochemical analyses of the granulation tissue deposited in the model were undertaken. The content of amino acids following hydrolysis of the granulation tissue was determined applying spectrophotometric or HPLC assays. Collagen amounts accumulated in the model are expressed as hydroxyproline per length of ePTFE or per total protein. Following a study in rats we examined 85 healthy volunteers and 158 surgical patients in the studies. Higher contents of hydroxyproline were found 10 days after implantation as compared to 5 days with considerable inter-person variation. Regarding median values there was a 25% difference between two measurements performed on two distinct ePTFE tubes from the same person, and a 12% difference between values obtained from two different pieces of the same ePTFE. Higher accumulation levels of hydroxyproline did not result in higher variability. Deposition of proline in the model correlated closely to total protein content. The ePTFE and a modified PVA model were compared in surgical patients. No reproducible measurements of hydroxyproline deposition were obtained with the PVA model as opposed to the ePTFE model. It is concluded that the modified PVA model is inadequate for determination of collagen deposition in subcutaneous granulation tissue. We found no correlation between collagen deposition levels obtained with placement of the ePTFE model in the subcutaneous tissue of the arm and in an uncomplicated surgical wound of the groin in the same patient, respectively. Significantly higher collagen deposition levels in the model were found in the surgical wound. Conversely, there was a significant correlation between protein deposition levels obtained at the two sites. Patients undergoing minor surgery (groin hernia repair) did not differ from healthy non-traumatized volunteers as regards deposition of collagen in subcutaneous tissue of the arm, whereas patients subjected to major general surgery demonstrated a significant decline during the postoperative phase compared to a preoperative evaluation. This decline was enhanced in patients who had infectious complications. Non-smoking volunteers were found to specifically accumulate more collagen (median value 82%) than smokers matched for age and gender. Irrespective of the smoking status women accumulated significantly more collagen in the model than men. These findings were re-tested in a prospective series leading to the same conclusion. Matrix metalloproteinases (MMP-2 and MMP-9) were determined in wound fluid obtained from the subcutaneous cavities of herniotomy wounds 24 and 48 h after operation. A significant and inverse correlation was demonstrated between MMP-9 after 24 h and accumulation levels of collagen in the ePTFE tube 10 days after implantation in the wound. Finally, it was demonstrated that local application of granulocyte-macrophage colony-stimulating factor into the ePTFE model during implantation specifically and dose-dependently reduced the number of fibroblasts and deposition of collagen. The doses chosen for the experiments resulted in both a local and a systemic effect. It is concluded that the minimally invasive ePTFE model, despite a certain level of variability, presently provides one of the best possibilities of evaluation of the wound healing potential in both volunteers and patients under various conditions. We found the model convenient for the assessment of both matrix deposition during wound healing and the influence of several factors including demographic characteristics, trauma, tobacco smoking, drugs and tissue degrading components of the wound.     

Roles of lactoferrin on skin wound healing

Skin wound healing is a complex biological process that requires the regulation of different cell types, including immune cells, keratinocytes, fibroblasts, and endothelial cells. It consists of 5 stages: hemostasis, inflammation, granulation tissue formation, re-epithelialization, and wound remodeling. While inflammation is essential for successful wound healing, prolonged or excess inflammation can result in nonhealing chronic wounds. Lactoferrin, an iron-binding glycoprotein secreted from glandular epithelial cells into body fluids, promotes skin wound healing by enhancing the initial inflammatory phase. Lactoferrin also exhibits anti-inflammatory activity that neutralizes overabundant immune response. Accumulating evidence suggests that lactoferrin directly promotes both the formation of granulation tissue and re-epithelialization. Lactoferrin stimulates the proliferation and migration of fibroblasts and keratinocytes and enhances the synthesis of extracellular matrix components, such as collagen and hyaluronan. In an in vitro model of wound contraction, lactoferrin promoted fibroblast-mediated collagen gel contraction. These observations indicate that lactoferrin supports multiple biological processes involved in wound healing.     

The angiogenesis inhibitor endostatin impairs blood vessel maturation during wound healing.

Endostatin is a cleavage product of collagen XVIII that strongly inhibits tumor angiogenesis. To determine if endostatin affects other angiogenic processes, we generated full-thickness excisional wounds on the back of mice that were systemically treated with recombinant murine endostatin. No macroscopic abnormalities of the wound healing process were observed. Histological analysis revealed normal wound contraction and re-epithelialization, but a slight reduction in granulation tissue formation and reduced matrix deposition at the wound edge. The blood vessel density in the wounds of endostatin-treated mice was not affected. However, ultrastructural analysis demonstrated severe abnormalities in blood vessel maturation. The wound vessels in the endostatin-treated mice were narrowed or closed with an irregular luminal surface, resulting in a severe reduction in the number of functional vessels and extravasation of erythrocytes. Endostatin treatment did not affect the expression level and localization of collagen XVIII mRNA and protein. Furthermore, the angiogenesis regulators vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 were normally expressed in the wounds of endostatin-treated mice. However, expression of the major wound matrix proteins fibronectin and collagens I and III was significantly reduced. This reduction is likely to explain the reduced density of the wound matrix. Our results demonstrate that endostatin treatment reduces the number of functional blood vessels and the matrix density in the granulation tissue, but does not significantly affect the overall wound healing process.     

The beneficial effect of BPC 157, a 15 amino acid peptide BPC fragment,on gastric and duodenal lesions induced by restraint stress,cysteamine and 96% ethanol in rats. A comparative study with H2 receptor antagonists,dopamine promotors and gut peptides

The protection of stomach and duodenum in conjecture with anti-inflammatory effect was demonstrated for a novel 15 amino acid peptide, coded BPC 157, a fragment of the recently discovered gastric juice peptide BPC. BPC 157 (i.p./i.g.) was investigated in rats in comparison with several reference standards in three experimental ulcer models (48 h-restriant stress, subcutaneous cysteamine, intragastrical 96% ethanol ulcer tests) (pre-/co-/post-treatment). Only BPC 157 regimes were consistently effective in all of the tested models. On the other hand, bromocriptine, amantadine, famotidine, cimetidine and somatostatin were in effective (restraint stress). A dose-dependent protection (cysteamine) and/or partial positive effect (related to treatment conditions) (ethanol), was obtained with glucagon, NPY and secretin whereas CCK/26– 30/ was not effective. Based on Monastral blue studies BPC 157 beneficial effect appears to be related to a strong endothelial protection.     

Epidermal growth factor increases collagen production in granulation tissue by stimulation of fibroblast proliferation and not by activation of procollagen genes.

The effects of epidermal growth factor (EGF) on granulation-tissue formation and collagen-gene expression were studied in experimental sponge-induced granulomas in rats. After daily administration of 5 micrograms of EGF into the sponge, total RNA was extracted from the ingrown granulation tissue at days 4 and 7 and analysed by Northern hybridization for the contents of mRNAs for types I and III procollagens. EGF treatment increased procollagen mRNA, particularly at day 4. To determine whether this elevation was due to increased proliferation of collagen-producing fibroblasts or to activation of collagen-gene expression in these cells, fibroblast cultures were started from granulation tissue and treated with EGF. These experiments confirmed that EGF is a potent mitogen for granuloma fibroblasts in a dose-dependent manner. The effect of EGF treatment on radioactive hydroxyproline production in cultured cells was inhibitory. The decreased rate of collagen synthesis was also indicated by decreased amounts of procollagen mRNAs. The results suggest that the stimulation of wound healing and collagen production by EGF is due to increased fibroblast proliferation, and not to increased expression of type I and III procollagen genes.     

The essential involvement of cross-talk between IFN-gamma and TGF-beta in the skin wound-healing process

Several lines of in vitro evidence suggest the potential role of IFN-gamma in angiogenesis and collagen deposition, two crucial steps in the wound healing process. In this report, we examined the role of IFN-gamma in the skin wound healing process utilizing WT and IFN-gamma KO mice. In WT mice, excisional wounding induced IFN-gamma mRNA and protein expression by infiltrating macrophages and T cells, with a concomitant enhancement of IL-12 and IL-18 gene expression. Compared with WT mice, IFN-gamma KO mice exhibited an accelerated wound healing as evidenced by rapid wound closure and granulation tissue formation. Moreover, IFN-gamma KO mice exhibited enhanced angiogenesis with augmented vascular endothelial growth factor mRNA expression in wound sites, compared with WT mice, despite a reduction in the infiltrating neutrophils, macrophages, and T cells. IFN-gamma KO mice also exhibited accelerated collagen deposition with enhanced production of TGF-beta1 protein in wound sites, compared with WT mice. Furthermore, the absence of IFN-gamma augmented the TGF-beta1-mediated signaling pathway, as evidenced by increases in the levels of total and phosphorylated Smad2 and a reciprocal decrease in the levels of Smad7. These results demonstrate that there is crosstalk between the IFN-gamma/Stat1 and TGF-beta1/Smad signaling pathways in the wound healing process.     

Wound healing activity of the human antimicrobial peptide LL37

Antimicrobial peptides (AMPs) are part of the innate immune system and are generally defined as cationic, amphipathic peptides, with less than 50 amino acids, including multiple arginine and lysine residues. The human cathelicidin antimicrobial peptide LL37 can be found at different concentrations in many different cells, tissues and body fluids and has a broad spectrum of antimicrobial and immunomodulatory activities. The healing of wound is a complex process that involves different steps: hemostasis, inflammation, remodeling/granulation tissue formation and re-epithelialization. Inflammation and angiogenesis are two fundamental physiological conditions implicated in this process. We have recently developed a new method for the expression and purification of recombinant LL37. In this work, we show that the recombinant peptide P-LL37 with a N-terminus proline preserves its immunophysiological properties in vitro and in vivo. P-LL37 neutralized the activation of macrophages by lipopolysaccharide (LPS). Besides, the peptide induced proliferation, migration and tubule-like structures formation by endothelial cells. Wound healing experiments were performed in dexamethasone-treated mice to study the effect of LL37 on angiogenesis and wound regeneration. The topical application of synthetic and recombinant LL37 increased vascularization and re-epithelialization. Taken together, these results clearly demonstrate that LL37 may have a key role in wound regeneration through vascularization.     

Nod-Like Receptor Protein-3 Inflammasome Plays an Important Role during Early Stages of Wound Healing

The Nod-like receptor protein (NLRP)-3 inflammasome/IL-1β pathway is involved in the pathogenesis of various inflammatory skin diseases, but its biological role in wound healing remains to be elucidated. Since inflammation is typically thought to impede healing, we hypothesized that loss of NLRP-3 activity would result in a downregulated inflammatory response and accelerated wound healing. NLRP-3 null mice, caspase-1 null mice and C57Bl/6 wild type control mice (WT) received four 8 mm excisional cutaneous wounds; inflammation and healing were assessed during the early stage of wound healing. Consistent with our hypothesis, wounds from NLRP-3 null and caspase-1 null mice contained lower levels of the pro-inflammatory cytokines IL-1β and TNF-α compared to WT mice and had reduced neutrophil and macrophage accumulation. Contrary to our hypothesis, re-epithelialization, granulation tissue formation, and angiogenesis were delayed in NLRP-3 null mice and caspase-1 null mice compared to WT mice, indicating that NLRP-3 signaling is important for early events in wound healing. Topical treatment of excisional wounds with recombinant IL-1β partially restored granulation tissue formation in wounds of NLRP-3 null mice, confirming the importance of NLRP-3-dependent IL-1β production during early wound healing. Despite the improvement in healing, angiogenesis and levels of the pro-angiogenic growth factor VEGF were further reduced in IL-1β treated wounds, suggesting that IL-1β has a negative effect on angiogenesis and that NLRP-3 promotes angiogenesis in an IL-1β-independent manner. These findings indicate that the NLRP-3 inflammasome contributes to the early inflammatory phase following skin wounding and is important for efficient healing.     

创伤合并海水浸泡后愈合过程的病理学观察

目的观察创伤合并海水浸泡后对伤口愈合时间的影响及愈合过程中的病理学改变。方法以大鼠为实验动物,建立背部双侧圆形创伤模型,创后随机分为对照组和实验组,每组50只,实验组创后置海水中浸泡30min。观察2组创面的愈合生长状况。观察伤口局部愈合过程中的病理学改变,应用免疫组化方法观察愈合过程中伤口修复细胞增殖指数及微血管密度变化。结果对照组平均愈合时间为（12.0±1.0）d,而实验组的平均愈合时间为（14.3±0.8）d;两组在肉芽组织形成时间上以及修复细胞增殖能力上存在差异。结论创伤合并海水浸泡可导致伤口愈合时间延迟,加重创伤局部的炎症反应、延缓肉芽组织形成时间。     

The Polyvinyl Alcohol Sponge Model Implantation

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds^1-3. Because of this complexity, wound healing studies are most comprehensive when carried out in vivo. There are many in vivo models available to study acute wound healing, including incisional, excisional, dead space, and burns. Dead space models are artificial, porous implants which are used to study tissue formation and the effects of substances on the wound. Some of the commonly used dead space models include polyvinyl alcohol (PVA) sponges, steel wire mesh cylinders, expanded polytetrafluoroethylene (ePTFE) material, and the Cellstick^1,2.Each dead space model has its own limitations based on its material''s composition and implantation methods. The steel wire mesh cylinder model has a lag phase of infiltration after implantation and requires a long amount of time before granulation tissue formation begins¹. Later stages of wound healing are best analyzed using the ePTFE model^1,4. The Cellstick is a cellulose sponge inside a silicon tube model which is typically used for studying human surgery wounds and wound fluid². The PVA sponge is limited to acute studies because with time it begins to provoke a foreign body response which causes a giant cell reaction in the animal⁵. Unlike other materials, PVA sponges are easy to insert and remove, made of inert and non-biodegradable materials and yet are soft enough to be sectioned for histological analysis^2,5.In wound healing the PVA sponge is very useful for analyzing granulation tissue formation, collagen deposition, wound fluid composition, and the effects of substances on the healing process^1,2,5. In addition to its use in studying a wide array of attributes of wound healing, the PVA sponge has also been used in many other types of studies. It has been utilized to investigate tumor angiogenesis, drug delivery and stem cell survival and engraftment^1,2,6,7. With its great alterability, prior extensive use, and reproducible results, the PVA sponge is an ideal model for many studies^1,2.Here, we will describe the preparation, implantation and retrieval of PVA sponge disks (Figure 1) in a mouse model of wound healing.     

Transgenic mice reveal novel activities of growth hormone in wound repair, angiogenesis, and myofibroblast differentiation

An increasing number of patients are being treated with growth hormone (GH) for the enhancement of body growth but also as an anti-aging strategy. However, the side effects of GH have been poorly defined. In this study we determined the effect of GH on wound repair and its mechanisms of action at the wound site. For this purpose, we performed wound healing studies in transgenic mice overexpressing GH. Full thickness incisional and excisional wounds of transgenic animals developed extensive, highly vascularized granulation tissue. However, wound bursting strength was not increased. Wound closure was strongly delayed as a result of enhanced granulation tissue formation and impaired wound contraction. The latter effect is most likely due to a significantly reduced number of myofibroblasts at the wound site. By using in vitro studies with stressed collagen lattices, we identified GH as an inhibitor of transforming growth factor beta-induced myofibroblast differentiation, resulting in a reduction in fibroblast contractile activity. These results revealed novel roles of GH in angiogenesis and myofibroblast differentiation, which are most likely not mediated via insulin-like growth factors at the wound site. Furthermore, our data suggested that systemic GH treatment is detrimental for wound healing in healthy individuals.