Search

Purpose: Neoadjuvant radiation therapy has been used increasingly to downstage rectal cancer and decrease local recurrence. Despite its efficacy, preoperative radiation therapy may inhibit healing and contribute to wound complications. This study was designed to evaluate perineal wound complications after abdominoperineal resection., Methods: The clinical records of a consecutive series of patients who underwent abdominoperineal resection for rectal carcinoma between 1988 and 2002 were reviewed. Demographic data, disease stage, and use of preoperative radiation therapy were recorded. Major wound complications included delayed wound healing (>1 month), wound infection requiring drainage/debridement, or reoperation., Results: A total of 160 patients underwent abdominoperineal resection with primary closure of the perineal wound (mean age, 63 +/- 12 years); 117 (73 percent) patients received preoperative radiation therapy; 114 received radiation therapy for rectal cancer (radiation therapy + chemotherapy = 107, radiation therapy alone = 7); 3 received radiation therapy for other pelvic malignancies. Median radiation dose was 5,040 (range, 900-5,400) cGY. Overall wound complication rate was 41 percent. Major wound complication rate was 35 percent. Delayed healing was the most common complication (24 percent), followed by infection (10 percent). Radiation therapy increased the risk of any wound complication (47 vs. 23 percent; P = 0.005), risk of a major wound complication (41 vs. 19 percent; P = 0.021), and risk of infection (14 vs. 0 percent; P = 0.015). Risk of wound complications did not correlate with age, gender, disease stage, smoking, or diabetes., Conclusions: Wound complications are frequent after abdominoperineal resection and primary closure of the perineum. Preoperative radiation therapy doubles the rate of total and major perineal wound complications. Alternatives to primary perineal closure should be considered, particularly after radiation therapy.

The early-gestation fetus heals dermal wounds rapidly and scarlessly. This phenomenon appears to be intrinsic to fetal skin and independent of the intrauterine environment. Unique properties of fetal cells, extracellular matrix, cytokine profile, and gene expression contribute to scarless repair. An intensive research effort has focused on unraveling the mechanisms that underlie scarless fetal wound healing in an attempt to improve the quality of healing in both children and adults.

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

Targeted disruption of the stromelysin-1 gene in mice causes a delay in excisional wound healing due to a failure in wound contraction. Therefore, we postulated that stromelysin-1 activity is responsible for initiating contraction. To test this hypothesis, we compared the contractile capacity of fibroblasts from stromelysin-1 knockout mice (strom-1 KO) with that of normal fibroblasts using a collagen gel contraction model. Fibroblast cultures were established from explants of skin and lung parenchyma from strom-1 KO and wild-type mice, then transferred to the surface of collagen gels. The extent of contraction was determined by measuring greatest gel diameter. Results demonstrated that (1) all fibroblasts contracted collagen gels in a uniform concentric fashion, (2) skin fibroblasts from both sets of mice exhibited greater gel contraction than did lung fibroblasts, and (3) strom-1 KO fibroblasts demonstrated significantly less contraction (21-23%) than wild-type fibroblasts. These data support the hypothesis that absence of stromelysin-1 results in defective fibroblast contraction that may contribute to delayed wound healing., (Copyright 1999 Academic Press.)

Background/purpose: The fetus heals skin wounds rapidly and scarlessly. The mechanisms that mediate the rapid reepithelialization that is seen in this process are unknown. Integrins are a family of cell surface receptors that bind fibronectin, tenascin, collagen, and other extracellular matrix proteins that are deposited rapidly in fetal wounds. The authors hypothesized that epidermal integrin receptors specific for fibronectin and other wound matrix proteins are upregulated rapidly during human fetal repair., Methods: To investigate the spatial and temporal expression of integrins in scarless fetal repair, fetal skin from six human abortuses (16 to 23 weeks' gestation) was transplanted subcutaneously into severe combined immunodeficient mice. After graft take, full-thickness incisional wounds were made in the grafts, and grafts were harvested at various time-points from 4 hours to 28 days after wounding. Integrin receptor protein expression was analyzed at each time-point using immunohistochemistry with monoclonal antibodies specific for the receptors that bind fibronectin, tenascin, collagen, and laminin (alpha5, alpha(v), beta6, alpha2, alpha3, alpha6, and beta4)., Results: In this model, wounded human fetal skin grafts reepithelialized rapidly (within 24 to 36 hours) and healed scarlessly. Within 4 hours of wounding, the grafts showed increased, suprabasal expression (alpha2, alpha3, alpha6, beta4) or neoexpression (alpha5, alpha(b), beta6) of integrins at the epidermal wound edge. This increased expression persisted until reepithelialization was complete., Conclusions: Early upregulation of integrins in fetal wounds may permit rapid keratinocyte migration and reepithelialization, and may be important in limiting the induction of inflammatory mediators and scar.

We have developed a new in vivo model for the study of fetal wound healing. Fetal ICR mice (total gestation, 21 days) received a full-thickness incisional wound in the hind limb at gestational day 14 (N = 100). The wound was made with a 28.5-gauge needle that was passed transplacentally into the amniotic cavity. The wounds were analyzed histologically on postoperative days 0, 1, 3, and 5 by hematoxylin-eosin and Mallory's trichrome stains. Once the wounding technique was mastered, the overall mortality rate for this model was 20% by postwounding day 5. Each fetus healed their wound without scar by postwounding day 3. In 3 animals, 5 microliters of human transforming growth factor beta 1 (25 micrograms per microliter) was injected into the wound site, resulting in scar and an inflammatory cell infiltrate, indicating that the 14-day-gestation fetal mouse can be manipulated if necessary. This model offers the advantages of an in vivo system that can be studied at an early gestational age. Furthermore, it is inexpensive, easy to manipulate, and can be studied with commercially available murine probes.

Fetal dermal wounds heal without scarring. Because wound repair requires extracellular matrix turnover, the authors hypothesized that fetal skin would have increased levels of proteinases responsible for matrix degradation compared with adult skin. It was further hypothesized that transforming growth factor beta-1 (TGF-beta1) induces scarring in fetal skin by altering proteinase synthesis. A model of human fetal skin transplanted subcutaneously onto immunodeficient mice was used to study the role of matrix metalloproteinases in healing human fetal skin. In this model, transplanted second trimester fetal skin heals without scarring; addition of TGF-beta1 induces scarring. Proteinases were detected by immunohistochemistry in untransplanted fetal skin, untransplanted adult skin, TGF-beta1-treated fetal skin grafts, and sucrose-treated control grafts. In untransplanted fetal skin, interstitial collagenase, stromelysin-1, and gelatinase A were found in dermal cells and keratinocytes, and around vascular structures. Proteinases were detected in adult skin at similar locations but stained less intensely. Addition of TGF-beta1 decreased interstitial collagenase in fetal skin, but detection of gelatinase A and stromelysin-1 was unchanged. The authors conclude that matrix metalloproteinases are present in midgestation human fetal skin and that more proteinase-containing cells are found in fetal skin than in adult skin. Manipulation of fetal skin with TGF-beta1 is accompanied by a decrease in interstitial collagenase. These data suggest that the increased matrix metalloproteinases found in fetal skin contribute to scarless healing and that the fibrotic effects of TGF-beta1 on fetal skin may be mediated in part by decreasing the synthesis of interstitial collagenase.

The early-gestation fetus heals incisional skin wounds rapidly and scarlessly. The morphology with which the fetus heals excisional skin wounds remains unclear. To characterize excisional fetal wound repair, and to determine whether there is a developmentally regulated wound-size threshold beyond which fetal skin heals with scar, the authors created excisional wounds in fetal lambs of varying gestational age. Time-mated pregnant ewes carrying 22 fetuses at 60 to 90 days' gestation (term, 145 days) underwent laparotomy and hysterotomy. An incisional wound and four circular, punch biopsy wounds of 2, 4, 6, and 10 mm in diameter were placed on the back of each fetal lamb and marked with India ink. The wounds were harvested at 14 days' postwounding and examined grossly and microscopically after serial sectioning and histological staining. Morphological features of all wounds were graded. By 14 days' postwounding all fetal wounds had healed completely. for lambs at each gestational age, increasing wound size was strongly associated with an increase in the frequency of scar. Also, as gestational age increased from 60 to 90 days' gestation the frequency of scarless repair decreased. By understanding the cellular and molecular processes that mediate scar formation with increasing wound size and advancing gestational age, the authors hope to gain further insight into the mechanisms of scarless fetal wound repair.