Inhibition Of Wound Contraction Research Articles

Comparison of Wound Healing Effect of Skin Micrograft Impregnated into Two Kinds of Artificial Dermis in a Murine Wound Model.

Skin MG was prepared from the skin of C57BL/6JJcl mice using Rigeneracons and administered onto Pelnac Gplus and Integra sheets. The amount of MG suspension impregnated in Pelnac Gplus and Integra was evaluated. Pelnac Gplus and Integra sheets combined with MG were applied to murine defects, and wound area, neoepithelium length, granulation tissue formation, and newly formed capillaries were compared with the control groups on days 7 and 14. The weight percentage of the MG absorbed by Pelnac Gplus and Integra was 88.8% ± 3.5% and 28.2% ± 7.0%, respectively (P < 0.05). In the in vivo experiment, the area of newly formed granulation tissue and both the number and area of newly formed capillaries in the PelnacG + MG group were significantly larger than those in the control group at 14 days after implantation (P < 0.05). Skin MG was successfully impregnated into Pelnac Gplus by simple administration but not into Integra. Administration of skin MG into the Pelnac Gplus promoted granulation formation and angiogenesis. Pelnac Gplus was more suitable than Integra in the combination therapy.

Design and biofabrication of dermal regeneration scaffolds: role of oligomeric collagen fibril density and architecture.

Aim: To evaluate dermal regeneration scaffolds custom-fabricated from fibril-forming oligomeric collagen where the total content and spatial gradient of collagenfibrils was specified. Materials & methods: Microstructural and mechanical features were verified by electron microscopy and tensile testing. The ability of dermal scaffolds to induce regeneration of rat full-thickness skin wounds was determined and compared with no fill control, autograft skin and a commercial collagen dressing. Results: Increasing fibril content of oligomer scaffolds inhibited wound contraction and decreased myofibroblast marker expression. Cellular and vascular infiltration of scaffolds over the 14-day period varied with the graded density and orientation of fibrils. Conclusion: Fibril content, spatial gradient and orientation are important collagen scaffold design considerations for promoting vascularization and dermal regeneration while reducing wound contraction.

Inhibition of Skin Wound Contraction by Nanofibrillar Cellulose Hydrogel.

Although wound contraction is an essential part of healing, excessive contraction can compromise healing through induction of scarring and fibrosis. This in turn leads to development of wound contractures that limit elasticity and function. Major research efforts have focused on development of novel therapeutic approaches to gain inhibitory control over wound contraction. Despite these efforts, the need for cost-effective, clinically feasible, and effective agents to inhibit wound contraction remains. In this study, the authors investigated the effect of nanofibrillar cellulose hydrogel on wound contraction both in vitro and in vivo. Two different porcine full-thickness wounds (8-mm punch-biopsy wounds and 4 × 4-cm wounds covered with a 1:3-meshed split-thickness skin graft) were treated with or without nanofibrillar cellulose or carboxymethylcellulose (Purilon hydrogel), which was used as a reference treatment. Wound contraction was observed macroscopically, and histologic sections were taken at 14-day follow-up. Nanofibrillar cellulose hydrogel inhibited 70 percent of punch-biopsy wound contraction, whereas the carboxymethylcellulose hydrogel was ineffective. Importantly, application of nanofibrillar cellulose on split-thickness skin grafts did not inhibit epithelialization of the interstices or cell migration from the graft. The authors' results, although preliminary, indicate a potential for nanofibrillar cellulose hydrogel as a novel material for controlling excessive wound contraction.

Titanium wound chambers for wound healing research.

Standardized and reproducible animal models are crucial in medical research. Rodents are commonly used in wound healing studies since, they are easily available, affordable and simple to handle and house. However, the most significant limitation of rodent models is that the wounds heal by contraction while in humans the primary mechanisms of healing are reepithelialization and granulation tissue formation. The robust contraction results in faster wound closure that complicates the reproducibility of rodent studies in clinical trials. We have developed a titanium wound chamber for rodent wound healing research. The chamber is engineered from two pieces of titanium and is placed transcutaneously on the dorsum of a rodent. The chamber inhibits wound contraction and provides a means for controlled monitoring and sampling of the wound environment in vivo with minimal foreign body reaction. This technical report introduces two modalities utilizing the titanium chambers in rats: (1) Wound in a skin island model and, (2) Wound without skin model. Here, we demonstrate in rats how the "wound in a skin island model" slows down wound contraction and how the "wound without skin" model completely prevents the closure. The titanium wound chamber provides a reproducible standardized models for wound healing research in rodents.

ILK–PI3K/AKT pathway participates in cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblast

The interactions between fibroblasts and the extracellular matrix in wound contraction are mainly mediated via integrin signaling. Integrin-linked kinase (ILK) is a key mediator in integrin signal transduction. We investigated the role of ILK in cutaneous wound contraction. We found that ILK was involved in cutaneous wound healing in rats, and ILK and PI3K/AKT inhibitors inhibited wound contraction and re-epithelialization, consequently delaying wound healing in vivo. Further, using in vitro studies, we demonstrated that ILK and PI3K/AKT inhibitors suppressed the contraction of fibroblast-populated collagen lattices, inhibited fibroblast migration, and interrupted the effect of TGF-β1 on promoting alpha smooth muscle actin (α-SMA) expression in fibroblasts. When ILK expression was directly blocked by ILK small interfering RNA transfection, the migration and α-SMA expression of normal dermal fibroblasts were significantly suppressed as well. The data suggest that the ILK–PI3K/AKT signaling pathway mediates cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblasts.

Down-regulation of Smad3 Accelerates Palatal Wound Repair

Smad3-deficient mice exhibit accelerated re-epithelialization and tissue remodeling during palatal wound repair. In addition, transforming growth factor beta 1 (TGF-β1) and other inflammatory factors are down-regulated compared with those in wild-type mice. The aim of this study was to examine whether targeting of Smad3 with small interfering RNA (siRNA) accelerates wound-healing and inhibits wound contraction in palatal mucoperiosteal wounds. An initial histological examination of wound closure in mouse palates treated with Smad3-targeted siRNA vs. a scrambled siRNA found that wound-healing was accelerated when levels of Smad3 were decreased. Furthermore, with real-time PCR, mRNA levels of Smad3, TGF-β1, monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) were found to be significantly down-regulated in palatal tissue treated with Smad3–targeted siRNA vs. a control siRNA. Protein and mRNA levels of α-smooth-muscle actin (α-SMA), type I collagen, and fibronectin were also lower in palates treated with Smad3-targeted siRNA vs. control siRNA. Taken together, these results indicate that down-regulation of Smad3 expression by siRNA can accelerate wound-healing and may inhibit wound contraction. Therefore, siRNA-targeted inhibition of Smad3 may represent a valuable therapeutic tool for palatal mucoperiosteal wound-healing.

The roles of knitted mesh-reinforced collagen–chitosan hybrid scaffold in the one-step repair of full-thickness skin defects in rats

Full-thickness skin defects represent a significant and urgent clinical problem. Dermal substitutes serving as a regenerative template to induce dermal reconstruction provide a promising method to treat serious skin defects. Although collagen–chitosan dermal scaffolds display good biocompatibility and a suitable porous structure for angiogenesis and tissue regeneration, their poor mechanical properties compromise their application. To develop a well-supported dermal substitute, a poly(l-lactide-co-glycolide) (PLGA) knitted mesh was fabricated and integrated with collagen–chitosan scaffold (CCS) to obtain a PLGA knitted mesh-reinforced CCS (PLGAm/CCS). The morphology of this PLGAm/CCS was investigated in vitro. To characterize the tissue response, specifically angiogenesis and tissue regeneration, the PLGAm/CCS was transplanted in combination with thin split-thickness autografts to repair full-thickness skin wounds using a one-step surgical procedure in Sprague–Dawley rats. These results were then compared with CCSs. At weeks 2, 4 and 8 after the operation, the healing wounds were imaged to analyse wound changes, and tissue specimens were harvested for histology, immunohistochemistry, real-time quantitative polymerase chain reaction and Western blot analysis. The results demonstrated that collagen–chitosan sponge in the PLGAm/CCS remained porous, interconnected and occupied the openings of PLGA mesh, and the incorporation of the PLGA knitted mesh into CCS improved the mechanical strength with little influence on its mean pore size and porosity. Following transplantation, PLGAm/CCS inhibited wound contraction, and effectively promoted neotissue formation and blood vessel ingrowth. In conclusion, the mechanical strength of the scaffolds plays an important role in the process of tissue regeneration and vascularization. The ability of PLGAm/CCS to promote angiogenesis and induce in situ tissue regeneration demonstrates its potential in skin tissue engineering.

Emerging rules for inducing organ regeneration

We review the available evidence for regeneration of adult organs of very diverse nature and examine the applicability of simple rules that can be used to summarize these treatments. In the field of regenerative medicine no widely accepted paradigm is currently available that can guide formulation of new theories on the mechanism of regeneration in adults and open new directions for improved regeneration outcomes. The four rules have emerged from multiyear quantitative studies with skin and peripheral nerve regeneration using scaffold libraries based on a simple, well-defined collagen scaffold. These largely quantitative rules distinguish sharply between spontaneously regenerative and nonregenerative tissues, select the two reactants that are required for regeneration, recognize the essential modification of the wound healing process that must be realized prior to regeneration, and identify three structural features of scaffolds that are required for regenerative activity. The combined evidence points at certain requirements for the structure of a collagen scaffold with regenerative activity. An active scaffold emerges as a temporarily insoluble collagen surface, equipped with sufficient ligands for integrins of contractile cells, that inhibits wound contraction while also serving as a topographic template for new stroma synthesis. The four rules, based on studies with just two organs (skin and peripheral nerves), are now viewed in the context of ongoing studies using scaffolds based on decellularized matrices, which are mostly based on collagen. Decellularized matrices have been used during the past few years to regenerate, in whole or in part, the urethra, the abdominal wall, the Achilles tendon, the bladder, the trachea and other organs in several animal models and occasionally in humans. Although these acellular matrices are distinctly different from simple collagen scaffolds, and the methods used by the investigators are still evolving, the results obtained are shown to be broadly consistent with the predictions of the four rules. Future use or adaptations of these largely quantitative rules could account more satisfactorily for problems, such as imperfect function of regenerated organs, that are currently encountered by researchers. It could also further the explanation of the mechanism of regeneration at the cellular and molecular level.

Wound Contraction Is Attenuated by Fasudil Inhibition of Rho-Associated Kinase

Dermal scarring and scar contracture result in restriction of movement. There are no effective drugs to prevent scarring. RhoA and Rho-associated kinase have emerged as regulators of fibrosis and contracture. Fasudil, a Rho-associated kinase inhibitor, has been demonstrated to have antifibrotic effects in models of liver, renal, and cardiac fibrosis. The role of fasudil in preventing dermal scarring and contractures has not been studied. The authors used a rat model of dermal wound healing to assess the effects of fasudil with regard to the prevention of scarring. Human scar tissue and surrounding normal skin were immunostained for RhoA and Rho-associated kinase. Full-thickness wounds were created on Wistar-Han rats, and fasudil (30 mg/kg/day) or saline was continuously delivered subcutaneously. Wound contraction was measured by gravitational planimetry. After 21 days, tissue was harvested for Masson's trichrome, hematoxylin and eosin, Ki-67, and CD31 staining. Fibroblast-populated collagen lattices were used to assess the mechanistic effects of fasudil on contractility. Myofibroblast formation was assessed in the presence of fasudil. Human scar tissue in the remodeling phase of repair showed increased expression of RhoA and Rho-associated kinase in scar tissue compared with surrounding normal tissue. Fasudil inhibited wound contraction as compared with controls. Hematoxylin and eosin and Masson's trichrome were similar between groups. Fasudil did not alter angiogenesis or proliferation. Fasudil inhibited fibroblast contractility and myofibroblast formation in vitro. There is growing evidence that the RhoA/Rho-associated kinase pathway plays an important role in wound healing and scar contracture. The authors present data showing that inhibition of Rho-associated kinase hinders fibroblast contractility and may be beneficial in preventing scar contracture.

The Rho Kinase Inhibitor, Fasudil, Inhibits Wound Contraction

Introduction: Scar contracture affects approximately 40 million people worldwide. There are currently no effective preventative treatments. Scar contracture is caused by fibroblast and myofibroblast contractility. Cellular contractility is stimulated by calcium independent activation of the small GTP-ases, Rho A and Rho C, which phosphorylate and activate the downstream kinase Rho-associated coiled coil-containing protein kinase (ROCK). ROCK has recently been found to cause renal, pulmonary, and cardiovascular fibrosis in vivo. This study evaluates the expression profile of RhoA and ROCK in human scar tissue and determines the effects of ROCK inhibition on rodent wound contraction. Methods: Human scar tissue and surrounding normal skin in the same specimen was immunostained for RhoA and ROCK. Full-thickness wounds (2×2cm) were created on the backs of age-matched Wistar-han rats (n=10). Fasudil (30mg/kg/d) or vehicle alone were continuously delivered systemically by subcutaneous implanted osmotic pumps for 21d. Wound contraction was measured by gravitational planimetry and rodents were assessed for signs of toxicity by measuring weight changes and observing behavior. On day 21, rodents were euthanized and wounds were harvested for Mason's trichrome, hematoxylin and eosin (H&E), and picosirius red staining, and immunohistochemistry performed for α-SMA (myofibroblasts), Ki-67 (proliferation) and CD31 (angiogenesis). Results: Human scar tissue showed significantly increased expression of RhoA and ROCK in dermal fibroblasts compared to surrounding normal tissue. Fasudil significantly inhibited wound contraction as compared to controls. Fasudil was non-toxic. H&E, Masson's, and Sirius Red staining was similar between groups. Fasudil did not alter angiogenesis nor proliferation (p>0.05). Conclusion: The increased expression of RhoA and ROCK in human scar tissue suggests an association between protein presence and scar contracture. Fasudil significantly inhibited rodent wound contraction without adversely affecting healing. Fasudil may be a potential drug to prevent scar contractures. Future work will involve a dose response curve of fasudil in rodents and application of Fasudil to the red duroc pig scar model.

Specific interactions between human fibroblasts and particular chondroitin sulfate molecules for wound healing

The chondroitin sulfates (CSs) constitute an important group of biomacromolecules in the extracellular matrix. However, limited information is available about their specific biological functions. This study aimed to define the interactions between cells and various types of CS. The effects of CSs on cellular activities and the cell cycle were evaluated using cell culture, RNA interference, real-time polymerase chain reaction, flow cytometry, wound healing and contraction models. The results showed that C-6-S promoted both cell proliferation and adhesion, while C-4-S promoted proliferation but inhibited adhesion. Moreover, knockdown of chondroitin inhibited cell proliferation and migration, as well as arresting cells in the G 2/M phase. Also, both C-4-S and C-6-S promoted wound closure in a two-dimensional wound model, whereas only C-6-S inhibited wound contraction in a three-dimensional wound model. This study illustrates that the interaction between cells and different CSs are specific and sulfate-group-dependent. These findings provide useful information for better applications of CSs for wound healing.

Use of microparticulate systems to accelerate skin wound healing

Rapid and proper healing is important in the treatment of skin wounds. The dressing achieves the functions of the natural skin by protecting the wound area from the bulk loss of tissue and creating an effective barrier to outside contaminants without increasing the bacterial load on the wound surface. There are many wound dressings available on the market which can be used in the healing process. Different dressings have been used according to the condition of the wound and the phases of wound healing. Biodegradable polymers are being widely used in drug delivery and also in wound healing. These polymers that are applicable as a wound dressing protect the wound site against unwanted external effects, inhibit wound contraction, and, if possible, stimulate the healing process. Micro- and nanoparticulates are currently being evaluated as a potential drug delivery in clinical applications. Growth factors also play a vital role in wound healing. Polymers used in wound healing act as sustained release vehicles for growth factors. Controlled release of growth factors from microspheres has provided a higher degree of healing in the wound areas. This review is intended to provide information regarding the various formulations and microparticulate systems used in wound healing.

Retardation of wound healing by silver sulfadiazine is reversed by Aloe vera and nystatin

Inhibition of wound contraction by topical anti microbial agents has been described. The purpose of this study was to further investigate that phenomenon and to explore the effect that other agents such as Aloe vera might have on this process. Full-thickness excised wounds were created on the dorsum of Sprague-Dawley rats under anaesthesia. The wounds were treated with topical agents three times daily for fourteen days, then observed until healed. Groups were: saline control, placebo (aqueous cream) control, silver sulphadiazine (SSD) cream 1%, SSD 0.5%, SSD 1% with Aloe vera, SSD 1% with nystatin, nystatin. Wound surface areas were measured each three days. Time to 50% and 90% healing was compared using ANOVA. Wound half-life and healing times were shortest in the SSD/ Aloe vera and nystatin groups ( P<0.05) and longest in the 1% SSD and saline control groups. The placebo group (aqueous cream) healed in a significantly shorter time ( P<0.05) than the control (saline) group. Wound contraction was delayed by saline and SSD. Nystatin and Aloe vera, when added to SSD, reversed that effect. These data suggest that a dry wound (saline) heals slowly. Infection control without delay of wound healing is most appealing and clinical trials are planned.

Effectiveness and Safety of the PEGT/PBT Copolymer Scaffold as Dermal Substitute in Scar Reconstruction Wounds (Feasibility Trial).

Skin defects left after excision of hypertrophic scars were treated with a dermal substitute and split-thickness skin grafts transplanted after vascularisation of the substitute. The used substitute was a synthetic porous scaffold made from the biodegradable copolymer polyethyleneglycol-terephtalate and polybuthylene-terephtalate. The study was designed to assess the rate of granulation tissue formation, graft take, and after 3 and 12 months the quality of life (pain, comfort of treatment, cosmetic or functional nuisance), scar formation and wound contraction. In addition, scaffold biodegradation and scar tissue formation were evaluated histologically.Seven patients with different causes of burn injury were enrolled, of which 5 completed the study. In the first 4 patients the time between scaffold application and split-thickness skin overgrafting was in between 17 and 24 days. The time point of overgrafting was significantly reduced to 10-12 days by meshing of the dermal scaffold as evidenced in the last 3 patients. Histological evaluation at 3 months revealed normal generation of dermal tissue, however, the collagen bundles were parallel organized like in scar tissue. In the deeper layers of the neodermis, fragments of the dermal substitute were present, causing a mild inflammatory response. One year post-treatment, some fragments of the copolymer were still observed. The extent of wound contraction after successful overgrafting ranged from 30% to 57% after 1 year. All 5 patients showed an improvement in the total Vancouver Scar Score compared to the value before scar removal being similar to what can be expected when treated with split-thickness skin grafts alone. No unanticipated adverse effects due to application of the substitute were observed.We conclude that although this synthetic dermal substitute can be safely used in humans, the presence of 3D dermal template in a full-thickness skin defect will not automatically improve the skin tissue regeneration process or inhibit wound contraction.

Effects of collagen matrix containing transforming growth factor (TGF)-β 1 on wound contraction

We evaluated the effectiveness of transforming growth factor (TGF)-β 1 on wound contraction, both alone and in combination with collagen matrix, using an in vivo delayed wound healing type model. To clarify the mechanisms involved in the effectiveness of TGF-β 1, we also used a fibroblast-populated collagen gel contraction in vitro model. Although we found that TGF-β 1 significantly accelerated contraction of the fibroblast-populated collagen gel in vitro, we demonstrated that both collagen matrix alone and 1.0 μg of TGF-β 1 alone significantly inhibited wound contraction in the in vivo model. In addition, the combination of TGF-β 1 and collagen matrix was much more effective than TGF-β 1 alone, a finding which was supported by histopathological examination. Wounds treated with collagen matrix containing TGF-β 1 showed horizontal rearrangement of collagen fibers in the dermal part as well as evidence of active fibroblast proliferation, which was not observed in the scar regions of controls. These results show that the application of TGF-β 1 treated collagen matrix is effective for preventing contraction producing so called ‘neodermis’ in treating a delayed healing type model and may be highly beneficial for treating chronic wounds.

Effects of a collagen matrix containing prostaglandin E 1 on wound contraction

In this study, we evaluated the effectiveness of prostaglandin (PG) E 1 in inhibiting wound contraction, both alone and in combination with collagen matrix, using a in vivo full thickness skin defect model. To clarify the mechanisms involved in this inhibition we also used a fibroblast-populated collagen gel contraction in vitro model. We demonstrated that collagen matrix alone significantly inhibited wound contraction PG E 1 alone did not. Interestingly, their combination was much more effective than either collagen matrix or PG E 1 alone, a finding which was also supported by histopathological examination. Wounds treated with collagen matrix, but not control wounds, showed horizontal rearrangement of collagen fibers in the dermal part as well as evidence of active fibroblast proliferation which was not observed in scar regions surrounded by normal dermis. With the fibroblast-populated collagen gel contraction in vitro model, we found that PG E 1 significantly inhibited contraction at a high dose. It was concluded that collagen matrix combined with PG E 1 is effective for preventing contracture producing so called neodermis than collagen matrix alone, which remains one of the most challenging problems in treating full thickness type wounds.

Effects of a collagen matrix containing basic fibroblast growth factor on wound contraction.

We evaluated the effectiveness of basic fibroblast growth factor (bFGF) in inhibiting wound contraction, both alone and in combination with collagen matrix, using a simulated in vivo delayed healing type model. We also studied the mechanisms involved in this inhibition in in vitro experiments using fibroblast populated collagen gels. As a result, we were able to demonstrate that both collagen matrix and bFGF significantly inhibited wound contraction; especially, bFGF acted in a dose-dependent fashion. Interestingly, their combination was much more effective than either collagen matrix or bFGF alone, a finding that was supported by the histopathological data. Wounds treated with collagen matrix, but not control wounds, showed horizontal rearrangement of collagen fibers in dermis as well as evidence of fibroblast proliferation, which was not observed in scar regions surrounded by normal dermis. Using fibroblast-populated collagen gel contraction as an in vitro model, we found that bFGF significantly inhibited contraction. Taking all these results together, it was concluded that collagen matrix is useful not only as a carrier of cytokines such as bFGF, but also for the quick closure of chronic wounds, thereby preventing contracture, which remains one of the most challenging problems in treating this type of wound. Application of bFGF-treated collagen matrix to chronic wounds such as decubitus, and diabetic and leg ulcers may prove to be highly beneficial in clinical practice.

Effect of a collagen matrix containing epidermal growth factor on wound contraction.

Excessive wound contraction is known to lead to pathological wound contracture. Using a rabbit model, we applied a bovine type I collagen matrix sponge as a dermal substitute and human epidermal growth factor to full-thickness excisional wounds. Wound contraction was assessed 14 and 28 days after wounding. It was found that both collagen matrix and epidermal growth factor significantly inhibited wound contraction (p < 0.001) in all wounds treated with collagen matrix alone or treated with 0.1 and 1 microg of epidermal growth factor 28 days after wounding. Interestingly, the combination of collagen matrix with epidermal growth factor strongly inhibited wound contraction over matrix alone (p < 0.01 on day 28). Histological analyses showed a regular horizontal arrangement of collagen fibers in the dermis under wounds treated with these substances but not under untreated wounds. Furthermore, using a fibroblast-populated collagen gel, the direct inhibitory effect of epidermal growth factor on gel contraction by fibroblasts was also observed. Collagen gels without stimulation contracted to 29.5 +/- 0. 6% of their original size, as determined 6 days after culturing. At 3 days or more, epidermal growth factor inhibited collagen gel contraction by fibroblasts (after 6 days: 34.2 +/- 1.8%, p > 0.05; 36.5 +/- 2.8%, p < 0.05; and 39.8 +/- 2.1%, p < 0.001 at 1, 10, and 100 ng/ml of epidermal growth factor, respectively). In conclusion, collagen matrix and epidermal growth factor, particularly in combination, may be useful in the prevention of wound contracture.

Effect of interferon-alpha2b 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-alpha2b 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 alpha-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 alpha-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-alpha2b-treated animals at 21 days following wounding (p < 0.001), which did not colocalize with alpha-smooth muscle actin staining. Taken together, these findings suggest that interferon-alpha2b 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.

Wound healing: A paradigm for lumen narrowing after arterial reconstruction

Purpose: The intimal hyperplasia hypothesis that equates lumen narrowing after arterial injury with intimal mass has recently been challenged. Evidence has emerged to suggest that lumen narrowing is caused in large part by changes in artery wall geometry rather than intimal mass per se. We have begun to explore this hypothesis in a unique nonhuman primate model of atherosclerosis. Methods: Monkeys who were fed an atherogenic diet for 3 to 5 years underwent experimental angioplasty of the left iliac artery. The contralateral iliac artery served as an intraanimal control. Arteries were removed 2, 4, 7, 14, 28, or 112 days later for analysis (6 or 13 per time point). Angioplasty dilated arteries by fracturing atheroma and stretching or tearing the media. Cross-sections of injured arteries were analyzed for expression of extracellular matrix components and cell surface integrins that are important in wound healing. Antibodies, riboprobes, or histochemical stains specific for fibrin, hyaluronan, versican (chondroitin sulfate–containing proteoglycan), procollagen-I, elastin, and the α 2β 1 and α Vβ 3 integrins were used. Results: A thin mural thrombus was seen at sites of denudation and plaque fracture (days 2 to 7). This provisional matrix was invaded by leukocytes (days 2 to 4) and α-actin–positive smooth muscle cells (SMCs; days 4 to 7). Thrombus was replaced by SMCs expressing hyaluronan and the associated versican proteoglycans (day 14). Versican was expressed throughout the neointima as it enlarged (day 28), but expression later subsided (day 112). Procollagen-I expression initially increased in the adventitia (day 4) and then in the forming neointima (day 14). Procollagen-I expression was found to persist within the adventitia and in the neointima in SMCs nearest the lumen (days 28 to 112). Elastin staining was prominent within the mature neointima (day 112) but not at earlier time points. Integrin expression also increased within the injured artery wall. α Vβ 3 staining (fibrin[ogen] receptor) increased in the injured media (days 2 to 7) and was then seen throughout the early neointima (day 7). Low level expression of α Vβ 3 subsequently persisted within the forming neointima (day 28). α 2β 1 (collagen receptor) expression increased in the neointima in SMCs nearest the lumen (day 28). Conclusions: Lumen narrowing after angioplasty in this model of atherosclerosis is caused largely by decreased artery wall diameter. The pattern of matrix and integrin expression within the injured artery wall is in many ways analogous to that of healing wounds. These observations suggest that tissue contraction may play a role in lumen narrowing at sites of arterial reconstruction. Strategies to inhibit wound contraction may prove effective in preventing restenosis. (J Vasc Surg 1998;27:96-108.)