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Biomedical subjects

I K Cohen

Publications and source records attributed to I K Cohen.

At least 19 recordsLinked to original sources
PubMed1999

MMP-8 is the predominant collagenase in healing wounds and nonhealing ulcers.

BACKGROUND: The initial cleavage of collagen by collagenase represents the rate-limiting step in the degradation of this central extracellular matrix protein. Chronic nonhealing ulcers, especially pressure ulcers, typically contain elevated levels of collagenolytic activity. However, there have been no detailed attempts to identify the source of these collagenases and their activity either in normal healing wounds or in chronic nonhealing ulcers. MATERIALS AND METHODS: Levels of the matrix metalloproteinases, MMP-1 and MMP-8, and the tissue inhibitor of matrix metalloproteinases, TIMP-1, were measured in fluids and tissues of healing human wounds and nonhealing ulcers by ELISA. Relative MMP-1 and MMP-8 levels were also analyzed by substrate preference in a functional assay. RESULTS: The patterns of the collagenases MMP-1 and MMP-8 in healing wounds were distinct, with MMP-8 appearing in significantly greater amounts than MMP-1. Chronic nonhealing ulcers were characterized by significantly higher levels of MMP-1 and MMP-8, and lower levels of TIMP-1, than in healing wounds. Levels of both MMP-1 and MMP-8 varied greatly in chronic ulcers, although MMP-8 was always the predominant collagenase present in these wounds. Interestingly, these collagenases were present almost exclusively in their inactive forms in healing wounds, whereas nonhealing ulcers possessed significant levels of the active forms of these enzymes. CONCLUSIONS: These results clearly demonstrate that the neutrophil-derived MMP-8 is the predominant collagenase present in normal healing wounds and suggest that overexpression and activation of this collagenase may be involved in the pathogenesis of nonhealing chronic ulcers. In addition, excessive collagenolytic activity in chronic ulcers is made possible, partly because of the reduced levels of the inhibitor, TIMP-1.

Adult↗
PubMed1998

Endoscopic otoplasty in the rabbit model: effect of mechanical abrasion on ear cartilage deformation.

The purpose of this study was (1) to introduce an endoscopic technique for performing otoplasty; (2) to compare the durability of folding with scoring, sutures, or abrasion; and (3) to study the histologic changes associated with three techniques. Thirteen adult New Zealand White rabbits (26 ears) were divided into three otoplasty groups: bent cartilage (nine ears), cut cartilage (nine ears), or endoscopic abrasion of cartilage (eight ears). In all three groups, the ears were folded using external mattress sutures, with a transverse 180-degree fold. Sutures were removed at 1 to 6 weeks, and the ears followed for 4 weeks postoperatively. Ear-folding angles were followed weekly from suture removal to 4 weeks postoperatively. After sacrifice, the ear cartilage was harvested for histologic analysis. The ears were maintained in a 180-degree ventral fold by splinting sutures, which were removed at various times. Four weeks after suture removal, the mean ear angles were 13 degrees in the bent (control) group, 84 degrees in the cut group, and 132 degrees in the abraded group. The differences between the abraded and cut versus bent groups were significant (p = 0.0001 and 0.0073, respectively). There was no significant difference between the abraded versus cut groups. Histologic analysis showed perichondrial thickening on the convex surface in all of the groups. Fibrocartilage was produced in the cut and abraded groups. Based on histologic observation, the repair cartilage in the cut group was more fibrous, whereas that in the endoscopic group was more abundant with marked degenerative changes in the central zone. A new method of percutaneous endoscopic otoplasty in the rabbit model is described. This study showed that endoscopic otoplasty produced folding that was well maintained during the study period.

Animals↗
PubMed1998

Physiology of the chronic wound.

There is as yet no unified mechanism that explains the pathophysiology of every nonhealing wound. This is largely because many of the basic biological investigations in this area have only been undertaken seriously in the past few years and many phenomena remain unexplained. As new data become available, these theoretical models undoubtedly will continue to evolve. However, a clear understanding of the facts presently available should provide the clinician with a good scientific basis for rational clinical interventions. There is an urgent need to bridge the gap that often exists between laboratory research and clinical practice. A number of wound care practices, which have been shown to be ineffective or harmful, are still widely used. This includes the application of toxic wound cleansing agents, inappropriate use of topical antibiotics, and the practice of wet-to-dry dressings. The past 2 decades have witnessed an unprecedented proliferation of wound care products, few of which have be proven to be consistently superior to simpler and more cost-effective measures. For the foreseeable future, the search for the magic wound 'portions and lotions' probably will continue to revolve around topical growth factor and antiprotease therapy. However, such efforts will only come to fruition when we truly understand the pathophysiologic basis for abnormal wound healing.

Chronic Disease↗
PubMed1998

Interleukin-1alpha and collagenase activity are elevated in chronic wounds.

Interleukin-1-alpha (IL-1alpha) is a member of a family of proinflammatory polypeptide mediators that has been shown in vitro to stimulate collagenase production. Collagenase is a proteolytic enzyme classified as one of the matrix metalloproteinases (MMP-1) that specifically recognizes and cleaves collagen. Therefore, the objective of this study was to compare the levels of these two proteins in chronic wounds as possible factors in the pathogenesis of chronic wounds. Fluids from 10 chronic wounds were collected before and after a 1-week treatment with a hydroactive dressing (Cutinova cavity). In addition, fluids were collected from 20 acute wounds for comparison. IL-1alpha and MMP-1 levels were quantified using sandwich ELISA. Collagenase activity was measured using a radiolabeled collagen as substrate. Clinically, the chronic wounds showed decreased area (-21.0 cm2) and reduced volume (-134.5 cm3) by 4 weeks after treatment with the hydroactive dressing. There were no significant differences in the protein concentrations between acute wound fluids (21.0 +/- 3.0 mg/ml) and chronic wound fluids before and after treatment with the hydroactive dressing (18.3 +/- 5.5 and 25.2 +/- 7.6 mg/ml, respectively). Levels of IL-1alpha in the acute wound fluids were low (0.019 pg/mg), whereas in the chronic wound fluid before treatment they had been significantly elevated (44.9 + 21.8 pg/mg). Following treatment with the hydroactive dressing, the IL-1alpha levels dropped to 10.3 + 3.3 pg/mg (p < 0.05). Collagenase activity was not detectable in acute wound fluid, elevated in pretreatment chronic wounds (12.9 + 3.4 units), and decreased in chronic wounds after treatment (11.4 + 3.3 units). This study correlated clinical healing of chronic wounds with biochemical changes in the ulcer microenvironment. As the chronic wounds began to heal, there was a significant decrease in the IL-1alpha levels and collagenase activity, thus suggesting that these two proteins may contribute to the lack of healing characteristic of chronic wounds.

Chronic Disease↗
PubMed1997

Hyaluronic acid inhibits fetal platelet function: implications in scarless healing.

Platelets are important for the initiation of inflammation in adults, but the role of fetal platelets in fetal wound healing is unclear because fetal dermal wounds heal with a minimal inflammatory response and lack of excessive scarring. Because fetal tissue is abundant in glycosaminoglycans (GAGs), predominantly hyaluronic acid (HA), this study was designed to test the hypothesis that HA inhibits the reactivity of platelets and thus contributes to the minimal scarring characteristic of fetal tissue repair. Platelets were isolated from 10 fetal pigs at day 80 of gestation (term, 115 days) and exposed to 0.5 mg/mL of arachidonic acid, an agent shown in prior studies to evoke maximal aggregation and degranulation of fetal platelets. The ability of HA at 0.1 and 0.5 mg/mL to inhibit this response was determined. The presence of HA resulted in a dose-dependent reduction in platelet aggregation at 180 seconds (control, 99.7 +/- 0.3%; HA [0.1 mg/mL] 91.7 +/- 3.8%; and HA [0.5 mg/mL] 48.5 +/- 9.0%; P < .005 v control). The onset of aggregation was also significantly delayed by 0.5 mg/mL of HA (13.5 +/- 2.5 seconds) compared to control (2.9 +/- 0.7 seconds), P < .05. No significant diminution of platelet aggregation could be achieved by the addition of other GAGs at similar concentrations. HA also significantly impaired the release of platelet-derived growth factor (PDGF)-AB from fetal platelets. The authors conclude that HA, the predominant GAG in fetal dermal matrix, inhibits platelet aggregation and cytokine release. This inhibition of platelet aggregation and resultant inflammatory response may explain, in part, the minimal inflammation and scarless healing characteristic of fetal dermal repair.

Analysis of Variance↗
PubMed1997

Collagen induces cytokine release by fetal platelets: implications in scarless healing.

In previous studies the authors demonstrated that unlike adult platelets, fetal platelets respond poorly to collagen. When platelets make contact with the exposed collagen at the site of injury, the result is activation, aggregation, and degranulation with the release of cytokines and growth factors. This sequence of events is well characterized in adult wounds, which heal with an acute inflammatory response and dense scar formation. In sharp contrast, fetal dermal wounds heal without an acute inflammatory response and minimal scar formation. Therefore, the aim of this study was to test the hypothesis that collagen, abundant at the site of dermal injury, is a poor inducer of cytokine release by fetal platelets. This could explain, in part, the minimal inflammation accompanying fetal dermal wound healing. Platelet suspensions from six fetal Yorkshire swine at day 80 of gestation (term, 114 days) were exposed to either arachidonic acid, 0.5 mg/mL, collagen, 0.19 mg/mL, or saline. The release into plasma of transforming growth factor-beta (TGF-beta 1), and platelet-derived growth factor (PDGF)-AB effected by these agents was determined by enzyme-linked immunosorbent assays. Transmission electron microscopy (TEM) was used to correlate the biochemical findings with ultrastructural changes and showed that arachidonate-treated platelets were aggregated and devoid of granules. In contrast, collagen-treated platelets had undergone conformational changes but showed only a moderate change in the quantity and homogeneity of their secretory granules compared with saline-treated controls. There was a significant increase in TGF-beta 1 release into plasma after treatment with collagen (6.64 +/- 0.36 ng/mL) and arachidonate (7.64 +/- 0.77 ng/mL) compared with saline (4.74 +/- 0.36 ng/mL), P < .05. Likewise, PDGF-AB release was significantly higher after collagen (0.22 +/- 0.02 ng/mL) and arachidonate treatment (0.44 +/- 0.04 ng/mL) compared with saline (0.09 +/- 0.02 ng/ mL), P < .05. The authors conclude that fetal platelets actually do release cytokines in response to contact with collagen despite poor aggregation. Therefore, impaired aggregation to collagen cannot solely explain the minimal inflammation after fetal wounding.

Animals↗
PubMed1996

Pneumothorax and wound dehiscence related to collagenase deregulation: treatment with diphenylhydantoin.

BACKGROUND: Wound dehiscence is an uncommon complication of operation, usually related to a recognized risk factor. A clinical dilemma arises when dehiscence has no identifiable cause or treatment. METHODS: We describe the case of a previously healthy 45-year-old man in whom recurrent spontaneous pneumothoraces developed followed by multiple dehiscences of thoracotomy, diaphragmatic, and abdominal wounds. Analysis over several years of laboratory investigation of cultured tissue from test incisions was initially unsuccessful. The patient was supported symptomatically until a remarkable laboratory finding enabled us to develop an effective treatment plan. RESULTS: Cultured patient fibroblasts were ultimately found to express abnormally elevated levels of collagenase, which could be inhibited by diphenylhydantoin (phenytoin) in vitro. Treatment of the patient with a course of diphenylhydantoin allowed adequate healing of test incisions and subsequent definitive surgical treatment with successful wound healing. CONCLUSIONS: This report of the rigorous application of the scientific method to the investigation and treatment of an enigmatic case of wound dehiscence might serve as a guide to surgeons faced with similar healing problems.

Abdomen↗
PubMed1996

Lower cytokine release by fetal porcine platelets: a possible explanation for reduced inflammation after fetal wounding.

Fetal dermal wound healing is unique because of its rapidity, minimal inflammation, and lack of scarring. Cytokines such as transforming growth factor beta (TGF-beta) and platelet-derived growth factor (PDGF) evoke an inflammatory response and scarring when applied to fetal wounds. Because adult and fetal platelet counts are comparable, the aim of this study was to test the hypothesis that the minimal inflammatory response seen in the fetus is attributable to differences in the serum content of cytokines released by fetal platelets. Using Yorkshire swine, blood was collected from 10 adults and 10 fetuses at day 60 of gestation (fullterm, 114 days). Platelets were isolated from anticoagulated blood and examined by transmission electron microscopy. Serum was analyzed for PDGF-AB and TGF-beta 2 by enzyme-linked immunosorbent assay (ELISA), and TGF-beta 1 by 125I radioimmunoassay. TGF-beta samples were assayed with and without prior acid activation to determine the total TGF-beta and the biologically active form of the cytokine. Electron microscopy of adult and fetal platelets showed no gross structural differences. Alpha granules, which contain cytokines as well as procoagulant factors, were present in similar quantities and with the same degree of homogeneity. The cytokines analyzed were present in all the adult and fetal sera tested. However, PDGF-AB was present in significantly lower concentrations in the fetus (383 +/- 72 pg/mL v 972 +/- 185 pg/mL in the adult; P<.05). In addition, the fetal samples contained lower amounts of TGF-beta 1 (13,895 +/- 1,770 v 29,864 +/- 5,050 pg/mL; P < .05) and TGF-beta 2 (6,758 +/- 734 v 13,407 +/- 1,395 pg/mL; P < .05). The majority of TGF-beta was in latent form; the adult sera contained significantly more active TGF-beta 1 and active TGF-beta 2 than the fetal sera. The ratios of active TGF-beta 1 to active TGF-beta 2 were similar for the adult (22.3) and fetus (18.5). However the ratio of total TGF-beta 1 to total TGF-beta 2 was significantly lower for the fetus (2.26 v 7.69). The authors conclude that although no gross differences in platelet ultrastructure were noted, fetal porcine platelets release lower quantities of cytokines into serum. This lower serum cytokine content and the relative concentrations of TGF-beta 1 of TGF-beta 2 may explain, in part, the minimal inflammation and sparse fibrosis characteristic of fetal wounds. These observations provide further insight into the unique fetal response to wounding and may offer alternative avenues to modulate the postnatal wound healing response.

Animals↗
PubMed1996

The effect of TGF-beta on keloid fibroblast proliferation and collagen synthesis.

Keloids are characterized by an overabundant deposition of collagen, and they recur frequently following excision. Fibroblasts isolated from keloid tissue and maintained in cell culture continue to express an increased capacity to produce collagen. In an effort to define the mechanisms responsible for keloid formation, the potential of exogenous transforming growth factor beta 1 (TGF-beta 1) to differentially affect DNA synthesis and collagen expression in cultured human fibroblasts derived from keloid or normal dermis was investigated. In this study, TGF-beta 1 at a concentration of 5.0 ng/ml was found to stimulate DNA synthesis of keloid-derived fibroblasts to a greater extent than fibroblasts derived from normal dermis. With a microassay to measure levels of collagenase-digestible radiolabeled proteins, TGF-beta 1 was found to elicit a greater increase in absolute collagen synthesis in keloid-derived fibroblasts compared with fibroblasts derived from normal dermis. Examination of tRNA(pro) pool-specific activities indicated that these observed differences in rates of collagen synthesis were not the result of unequal rates of proline transport or pool size. Likewise, TGF-beta 1 did not alter the uptake of vitamin C, an essential cofactor and mediator needed for maximal collagen expression. The increase in collagen synthesis by keloid-derived fibroblasts treated with TGF-beta 1 was accompanied by a corresponding increase in procollagen type I mRNA levels, indicating that the differential response of keloid and normal dermal fibroblasts to this growth factor is occurring primarily at a pretranslational level. These results suggest a unique sensitivity of keloid fibroblasts to TGF-beta 1 and thus a possible role for this mediator in keloid pathogenesis.

Cell Division↗
PubMed1996

Wound fluids from human pressure ulcers contain elevated matrix metalloproteinase levels and activity compared to surgical wound fluids.

Fluid from acute surgical wounds and from nonhealing pressure ulcers was examined for the presence of several matrix metalloproteinases. Gelatin zymography demonstrated the presence of two major gelatinases with apparent molecular masses of 72 kDa and 92 kDa and two minor gelatinases with apparent mobilities of 68 kDa and 125 kDa. Antigen-specific sera identified the 72-kDa protein as matrix melloproteinase-2. The same sera also reacted with the 68-kDa protein, which is consistent with it being an activated form of matrix metalloproteinase-2. Antigen-specific sera identified the 92-kDa and 125-kDa proteins as matrix metalloproteinase-9. Levels of matrix metalloproteinase-2 and matrix metalloproteinase-9 were elevated more than 10-fold and 25-fold, respectively, in fluids from pressure ulcers compared with fluids from healing wounds. Examination of total potential and actual collagenolytic activity revealed that fluid from pressure ulcers contained significantly greater levels of both total and active collagenase compared with that of acute surgical wounds. In addition, an enzyme-linked immunosorbent assay demonstrated that fluids from pressure ulcers contained significantly more collagenase complexed with the inhibitor, tissue inhibitor of metalloproteinases. Together, these observations suggest that an imbalance exists between levels of matrix metalloproteinases and their inhibitors in the fluids of pressure ulcers and that this is primarily the result of elevated levels of the matrix metalloproteinases. The presence of excessive levels of activated forms of matrix-degrading enzymes at the wound surface of pressure ulcers may impede the healing of these wounds and may be relevant to the development of new rationales for treatment.

Animals↗
PubMed1995

Hyaluronic acid metabolism in keloid fibroblasts.

Hyaluronic acid (HA), an important component of the tissue extracellular matrix, is a ubiquitous glycosaminoglycan (GAG) that forms a pericellular coat on the surface of cells. It has been speculated that this pericellular HA boundary may localize cytokines, such as transforming growth factor-beta 1, which is known to stimulate collagen production. The purpose of this study was to examine the role of HA and its cell surface receptor (CD44), an active participant in HA degradation, as they relate to keloid formation. Dermal excisions from both normal patients (n = 13) and keloid patients (n = 13) were analyzed for HA content using an alcian blue staining technique. Fibroblast cell cultures were used to quantitate HA synthesis and CD44 receptor density. Histological analyses showed a greater HA content in keloid tissue compared with normal dermal tissue. In agreement with this observation, keloid fibroblasts were found to synthesize significantly more HA than normal dermal fibroblasts (2469 +/- 483 cpm versus 1122 +/- 256 cpm, P = .02). Treatment of keloid fibroblasts with triamcinolone acetonide reduced the level of HA synthesis to that of normal fibroblasts (1560 +/- 477 cpm versus 1293 +/- 264 cpm, P = .6). However, there was no significant difference in HA receptor density on keloid cells compared with normal skin fibroblasts. Therefore, the increased HA deposits found in keloids are attributable to increased synthesis rather than to decreased degradation mediated by the CD44 receptor.

Adolescent↗
PubMed1995

Aggregatory characteristics and expression of the collagen adhesion receptor in fetal porcine platelets.

Fetal wound healing differs significantly from that of the adult by its rapidity, the paucity of an inflammatory response, and the lack of scarring. In the adult, activation and aggregation of platelets at the site of injury result in the release of cytokines and inflammatory mediators that stimulate wound healing by initiating an acute inflammatory response. The aim of this study was to characterize the activity of midtrimester (day 60) and third-trimester (day 95) fetal porcine platelets (full term, 114 days) compared with that of adults in an attempt to understand the lack of inflammation in fetal wounds. The aggregatory capabilities of adult and fetal platelets were analyzed after exposure to adenosine diphosphate (ADP) concentrations of 10 mumol/L and 40 mumol/L concentrations, collagen of 0.19 mg/mL, and arachidonic acid of 0.5 mg/mL. Expression of the alpha 2 subunit of the collagen receptor (alpha 2 beta 1) was evaluated by Western blot analysis. The aggregation of day-60 fetal platelets when exposed to ADP (10 mumol/L and 40mumol/L) and collagen was significantly lower than that of the adult. The aggregation of third-trimester platelets to 10 mumol/L of ADP was similar to that of the adult and significantly greater than that of midtrimester fetuses at higher concentrations (40 mumol/L). Both fetal groups responded suboptimally to collagen, and the response was significantly less than that of adults. In contrast, arachidonic acid caused rapid and complete aggregation of both fetal platelet groups, suggesting that both mid- and late-trimester fetal platelets possessed the ability to fully aggregate with the appropriate stimulus. The different aggregatory responses to collagen could not be explained by differences in collagen receptor expression, because these were found to be similar in adults and midtrimester fetuses. It is concluded that although fetal platelets have the potential to aggregate effectively, they aggregate poorly to collagen and exhibit improved aggregation to ADP with increasing maturity. There is a transition to "adultlike" platelet aggregatory activity in the third trimester, which correlates with the period of transition to adultlike wound healing in utero. Similar expression of the alpha 2 beta 1 collagen receptor in the fetus and adult cannot explain the differences observed in their responses to collagen.

Animals↗
PubMed1995

Topical application of epidermal growth factor onto partial-thickness wounds in human volunteers does not enhance reepithelialization.

Recent reports have suggested that human epidermal growth factor will accelerate the healing of corneal wounds and donor sites of burned patients undergoing split-thickness skin grafts. In one report using human epidermal growth factor in a silver sulfadiazine cream, these data were gathered from patients of various ages who had various depths of donor sites and degrees of burn. Therefore, despite the fact that these data were prospective, randomized, and double-blinded, we questioned the validity of the study. To test the hypothesis that topical application of human epidermal growth factor will enhance the healing of partial-thickness wounds, we utilized healthy volunteers (n = 17) and created bilateral split-thickness skin wounds (4 cm2) of the same depth (0.014 in) on each flank and then studied time until total epithelialization occurred. One side was treated with silver sulfadiazine as a control and the opposite side with silver sulfadiazine and human epidermal growth factor. There was no significant difference in the healing times between the human epidermal growth factor-treated sites and the silver sulfadiazine cream controls.

Administration, Topical↗
PubMed1994

Platelet-derived growth factor induces fetal wound fibrosis.

The fetal response to cutaneous injury differs markedly from that of the adult, proceeding with only minimal inflammation, minimal fibroblast proliferation, and only essential collagen deposition. Although the sequence of events in adult wound healing is well defined and thought to be controlled in part by potent polypeptide cytokines, relatively sparse information exists regarding growth factor involvement in fetal wound repair. Thus, the authors sought to examine the effect of platelet-derived growth factor (PDGF), a putative adult wound healing regulator, on the cellular and extracellular matrix events at a fetal wound site. SILASTIC wound implants containing 0, 1.0, 5.0, or 10.0 ng of human PDGF were placed subcutaneously on the backs of 24-day-gestation fetal rabbits (full term, 31 days) and then harvested after either 1, 3, or 5 days in utero. The specimens underwent standard histological processing and were evaluated in a blinded fashion. Compared with controls, PDGF-treated implants had a marked increase in acute inflammation, fibroblast recruitment, and collagen and hyaluronic acid deposition; these differences appeared to be largely time- and PDGF dose-dependent. Thus, the fetal system is responsive to an adult wound healing mediator, and these data suggest that fetal repair proceeds in the absence of PDGF.

Animals↗
PubMed1994

Biology of fetal wound healing: hyaluronate receptor expression in fetal fibroblasts.

Fetal tissue repair is rapid, relatively scarless, and proceeds in an environment rich in hyaluronic acid. Understanding the interaction of hyaluronic acid (HA) with the reparative cells may provide important insight into the remarkable process of fetal wound healing. Therefore, the purpose of this study was to characterize the HA receptor (a member of the CD44 family of cell surface glycoproteins) and its density on the cell surface of fetal fibroblasts. HA receptor expression on both adult and fetal fibroblasts was first studied by Western blot analysis. Autoradiographs of the blots were assessed by densitometry to quantitate the relative amounts of the HA receptor. It appears that the HA receptor expressed on both adult and fetal rabbit dermal fibroblasts is a 56-kd protein. After normalizing for total protein concentration using the Bradford protein assay, the fetal HA receptor density was found to be approximately four-fold greater than that of the adult. The same adult and fetal fibroblasts were then studied by flow cytometry, using a fluorescence-activated cell sorter (FACS). Relative fluorescence was representative of HA receptor density. Corroborating the authors' earlier result with the Western blot analysis, the FACS analysis showed that the fetal fibroblasts had 2.5 times the fluorescence of the adult cells. It is concluded that, in comparison to adult fibroblasts, fetal fibroblasts have an increased density of cell-surface HA receptor.

Animals↗
PubMed1994

The role of inflammatory cytokines in wound healing: accelerated healing in endotoxin-resistant mice.

UNLABELLED: The role of cytokines in normal wound healing remains poorly defined. In vitro, tumor necrosis factor alpha (TNF-alpha) decreases collagen accumulation, perhaps by increasing collagenase activity. The current study was undertaken to test the hypothesis that cytokines impair wound healing and collagen production. Wounds in C3H/HeJ (J) mice, which are characterized by a genetic defect in macrophage production of TNF and other cytokines in response to endotoxin, were compared with wounds in normal endotoxin-sensitive C3H/HeN (N) mice. METHODS: TNF (by murine ELISA) and collagenolytic activity (CA by in vivo labelled collagen fibril degradation assay) were measured in wound fluid from silicone reservoirs on post-wounding days 1, 3, and 5 (n = 5 per group). Hydroxyproline (HOP, nmol/mg sponge) incorporation (by HPLC) in polyvinylacohol sponges and breaking strength (BS, as determined by tensiometry) in linear wounds were assessed on days 5, 7, 10, and 14 (n = 5 per group). The data demonstrate significantly increased BS at 5 and 7 days in endotoxin-resistant J mice compared with that in endotoxin-sensitive N mice. An early, significant reduction in TNF production in J mice corresponded with a significant increase in CA on day 1, increased collagen production at day 7, and increased procollagen gene transcription at early time points. Conclusion. The reduced production of inflammatory cytokines including TNF in the wound fluid of J mice corresponded with an early improvement in wound tensile strength. An accelerated accumulation of collagen in the wounds of J mice, perhaps resulting from a significant decrease in collagenolytic activity or increased collagen production, are potential mechanisms. The data suggest that cytokines produced in normal healing of clean wounds may contribute to a delay in increased tensile strength.

Animals↗