Spreading, proliferation, and differentiation of the epidermis after wounding a cichlid fish, Hemichromis bimaculatus. (17/7861)

A large superficial wound has been experimentally provoked in the cichlid fish Hemichromis bimaculatus to study the interactions between the epidermal cells and the substrate on which they spread, on the one hand, and the restoration of the subepidermal tissues and the epithelial-mesenchymal interactions preceding scale regeneration, on the other hand. The re-epithelialization process, e.g., migration, spreading, differentiation, and proliferation of the epidermal cells, has been followed step by step, using light, scanning and transmission electron microscopy, and tritiated thymidine incorporation, until complete reorganization of the healing epidermis. Wound healing is fast (500 microm/hr) and proceeds centripetally from the wound margins. The epidermal cells spread on a wound surface which is composed of two different matrices: the remains of basement membrane materials covering the scale-pockets, and collagen fibrils of cut dermal strips. Even though both matrices favour cell spreading and attachment, migrating cells show a different behaviour. The re-epithelialization of the wound follows an orderly sequence similar to amphibian and mammalian wound healing, i.e., a "leap frog" mechanism of cell locomotion involving three epidermal layers. The basal layer cells, which spread on the substrate, and the superficial layer cells which protect the epidermis, differentiate first. Whatever the type of substrate over which the epithelium spreads (basement membrane material or collagen fibrils), the epidermal basal layer cells differentiate as soon as they become attached. The incorporation of tritiated thymidine has revealed that there is no proliferation in the healing epidermis until after complete closure of the wound, but that the rapid re-epithelialization of the large surface requires the recruitment of epidermal cells at the wound margins. The present study offers new data on the dynamics of re-epithelialisation and on the resistance of cichlid skin to such wounds. It is also clearly shown that the epidermal basal layer cells differentiate rapidly, a step which is interpreted as the first stage of epithelial-mesenchymal interactions that will lead to scale regeneration.  (+info)

Keratinocyte collagenase-1 expression requires an epidermal growth factor receptor autocrine mechanism. (18/7861)

In response to cutaneous injury, expression of collagenase-1 is induced in keratinocytes via alpha2beta1 contact with native type I collagen, and enzyme activity is essential for cell migration over this substratum. However, the cellular mechanism(s) mediating integrin signaling remain poorly understood. We demonstrate here that treatment of keratinocytes cultured on type I collagen with epidermal growth factor receptor (EGFR) blocking antibodies or a specific receptor antagonist inhibited cell migration across type I collagen and the matrix-directed stimulation of collagenase-1 production. Additionally, stimulation of collagenase-1 expression by hepatocyte growth factor, transforming growth factor-beta1, and interferon-gamma was blocked by EGFR inhibitors, suggesting a required EGFR autocrine signaling step for enzyme expression. Collagenase-1 mRNA was not detectable in keratinocytes isolated immediately from normal skin, but increased progressively following 2 h of contact with collagen. In contrast, EGFR mRNA was expressed at high steady-state levels in keratinocytes isolated immediately from intact skin but was absent following 2 h cell contact with collagen, suggesting down-regulation following receptor activation. Indeed, tyrosine phosphorylation of the EGFR was evident as early as 10 min following cell contact with collagen. Treatment of keratinocytes cultured on collagen with EGFR antagonist or heparin-binding (HB)-EGF neutralizing antibodies dramatically inhibited the sustained expression (6-24 h) of collagenase-1 mRNA, whereas initial induction by collagen alone (2 h) was unaffected. Finally, expression of collagenase-1 in ex vivo wounded skin and re-epithelialization of partial thickness porcine burn wounds was blocked following treatment with EGFR inhibitors. These results demonstrate that keratinocyte contact with type I collagen is sufficient to induce collagenase-1 expression, whereas sustained enzyme production requires autocrine EGFR activation by HB-EGF as an obligatory intermediate step, thereby maintaining collagenase-1-dependent migration during the re-epithelialization of epidermal wounds.  (+info)

Soft tissue cover for the exposed knee prosthesis. (19/7861)

This study assess the use of muscle flaps to cover exposed knee prostheses and emphasises the need for early plastic surgery consultation. In five of the six patients studied the wound was successfully covered and the knee prosthesis salvaged with a reasonable functional outcome.  (+info)

Proliferation and mitogenic response to PDGF-BB of fibroblasts isolated from chronic venous leg ulcers is ulcer-age dependent. (20/7861)

Several pathophysiologic mechanisms have been proposed to explain slow-healing leg ulcers, but little is known about the growth behavior of cells in these wounds. Platelet-derived growth factor-BB applied topically to chronic wounds has shown beneficial effects, although the effects have been less pronounced than would have been expected based on studies on acute wounds. The objective of this study was to compare fibroblasts in culture obtained from chronic wounds (non-healing chronic venous leg ulcers), acute wounds and normal dermis regarding growth, mitogenic response to platelet-derived growth factor-BB and levels ofplatelet-derived growth factor alpha-receptor and beta-receptor. Fibroblasts were obtained by an explant technique and expanded in vitro using fibroblast growth medium supplemented with 10% fetal bovine serum and used for the assays at their third passage. Growth of chronic wound fibroblasts (n = 8) was significantly (p < 0.05) decreased compared with those from acute wounds (n = 10) and normal dermis (n = 5). Fibroblasts from ulcers older than 3 y grew significantly (p < 0.01) slower than those from ulcers that had been present for less than 3 y. Morphology and size of fibroblasts from the oldest chronic wounds deviated substantially from those of acute wounds and normal dermis, and resembled in vitro aged or senescent fibroblasts. Mitogenic response of chronic wound fibroblasts to human recombinant platelet-derived growth factor-BB was also reduced with ulcer age. No significant differences were found in the amount of either platelet-derived growth factor alpha-receptor or beta-receptor among the three groups. The features decreased growth related to ulcer age, altered morphology, and reduced response to platelet-derived growth factor, indicating that fibroblasts in some chronic wounds have approached or even reached the end of their lifespan (phase III). This might provide one explanation for the non-healing state and therapy resistance to topical platelet-derived growth factor-BB of some venous leg ulcers.  (+info)

Bovine colostrum is a health food supplement which prevents NSAID induced gut damage. (21/7861)

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) are effective for arthritis but cause gastrointestinal injury. Bovine colostrum is a rich source of growth factors and is marketed as a health food supplement. AIMS: To examine whether spray dried, defatted colostrum or milk preparations could reduce gastrointestinal injury caused by indomethacin. METHODS: Effects of test solutions, administered orally, were examined using an indomethacin restraint rat model of gastric damage and an indomethacin mouse model of small intestinal injury. Effects on migration of the human colonic carcinoma cell line HT-29 and rat small intestinal cell line RIE-1 were assessed using a wounded monolayer assay system (used as an in vitro model of wound repair) and effects on proliferation determined using [3H]thymidine incorporation. RESULTS: Pretreatment with 0.5 or 1 ml colostral preparation reduced gastric injury by 30% and 60% respectively in rats. A milk preparation was much less efficacious. Recombinant transforming growth factor beta added at a dose similar to that found in the colostrum preparation (12.5 ng/rat), reduced injury by about 60%. Addition of colostrum to drinking water (10% vol/vol) prevented villus shortening in the mouse model of small intestinal injury. Addition of milk preparation was ineffective. Colostrum increased proliferation and cell migration of RIE-1 and HT-29 cells. These effects were mainly due to constituents of the colostrum with molecular weights greater than 30 kDa. CONCLUSIONS: Bovine colostrum could provide a novel, inexpensive approach for the prevention and treatment of the injurious effects of NSAIDs on the gut and may also be of value for the treatment of other ulcerative conditions of the bowel.  (+info)

Chronic critical limb ischemia: diagnosis, treatment and prognosis. (22/7861)

Chronic critical limb ischemia is manifested by pain at rest, nonhealing wounds and gangrene. Ischemic rest pain is typically described as a burning pain in the arch or distal foot that occurs while the patient is recumbent but is relieved when the patient returns to a position in which the feet are dependent. Objective hemodynamic parameters that support the diagnosis of critical limb ischemia include an ankle-brachial index of 0.4 or less, an ankle systolic pressure of 50 mm Hg or less, or a toe systolic pressure of 30 mm Hg or less. Intervention may include conservative therapy, revascularization or amputation. Progressive gangrene, rapidly enlarging wounds or continuous ischemic rest pain can signify a threat to the limb and suggest the need for revascularization in patients without prohibitive operative risks. Bypass grafts are usually required because of the multilevel and distal nature of the arterial narrowing in critical limb ischemia. Patients with diabetes are more likely than other patients to have distal disease that is less amenable to bypass grafting. Compared with amputation, revascularization is more cost-effective and is associated with better perioperative morbidity and mortality. Limb preservation should be the goal in most patients with critical limb ischemia.  (+info)

Inverse relationship between systemic resistance of plants to microorganisms and to insect herbivory. (23/7861)

Pre-inoculation of plants with a pathogen that induces necrosis leads to the development of systemic acquired resistance (SAR) to subsequent pathogen attack [1]. The phenylpropanoid-derived compound salicylic acid (SA) is necessary for the full expression of both local resistance and SAR [2] [3]. A separate signaling pathway involving jasmonic acid (JA) is involved in systemic responses to wounding and insect herbivory [4] [5]. There is evidence both supporting and opposing the idea of cross-protection against microbial pathogens and insect herbivores [6] [7]. This is a controversial area because pharmacological experiments point to negative cross-talk between responses to systemic pathogens and responses to wounding [8] [9] [10], although this has not been demonstrated functionally in vivo. Here, we report that reducing phenylpropanoid biosynthesis by silencing the expression of phenylalanine ammonialyase (PAL) reduces SAR to tobacco mosaic virus (TMV), whereas overexpression of PAL enhances SAR. Tobacco plants with reduced SAR exhibited more effective grazing-induced systemic resistance to larvae of Heliothis virescens, but larval resistance was reduced in plants with elevated phenylpropanoid levels. Furthermore, genetic modification of components involved in phenylpropanoid synthesis revealed an inverse relationship between SA and JA levels. These results demonstrate phenylpropanoid-mediated cross-talk in vivo between microbially induced and herbivore-induced pathways of systemic resistance.  (+info)

Effects of extracellular pH on restitution and proliferation of rabbit oesophageal epithelial cells. (24/7861)

BACKGROUND AND AIMS: Exposure to luminal acid induces mucosal damage in the oesophagus. The extent and degree of interaction of acid with wound repair mechanisms of the oesophagus have not been explored. METHODS: Rabbit oesophageal cells were isolated, cultured and exposed to different extracellular pHs for several periods of time. Cell mortality was studied in both isolated and primary cultures of these cells by cell flow cytometry using fluorochrome propidium iodide and LDH release. Subconfluent cell cultures were used to study proliferative responses determined by [3H]-thymidine incorporation into DNA. Restitution was studied in confluent monolayers wounded by mechanical denudation. RESULTS: Isolated cells were resistant to acid when exposed to pH > 2 for 15 min. Cell proliferation increased with small pH decreases (7-6.5) if the period of exposure was less than 6 h, but was inhibited with lower pHs and/or longer periods of acid exposure. However, restitution was gradually inhibited with further pH decreases (6.5-3) and time of acid exposure (0.5-24 h). CONCLUSIONS: The wound repair activities of oesophageal epithelial cells are deeply affected by even small decreases in pH. These findings may help to explain the need for profound acid inhibition in acid-related reflux oesophagitis.  (+info)