Wound healing in normal and analbuminemic (NAR) rats

It has been suggested by several investigators that hypoalbuminemia results in impaired wound healing. In most studies, however, hypoalbuminemia is a manifestation of malnutrition or underlying liver disease. In this study, we examined the effect of isolated hypoalbuminemia on wound healing. Analbuminemic (NAR) rats which are Sprague-Dawley mutants with trace levels of plasma albumin due to a defect in albumin synthesis were studied. Adult NAR and Sprague-Dawley rats (n = 10 each) underwent a 7 cm dorsal skin incision and implantation of a polyvinyl alcohol sponge subcutaneously under pentobarbital anesthesia. Seven days postoperatively all rats were killed with ether, the wounds were excised, and breaking strength was measured. Sponge hydroxyproline content was determined colorimetrically. There were no significant differences in wound breaking strength (fresh or formalin fixed) or sponge collagen content between the Sprague-Dawley and analbuminemic rats. We conclude that isolated hypoalbuminemia has no detrimental effect on would healing in rats.     

Regulation of nitric oxide synthesis in wounds by IFN-gamma depends on TNF-alpha.

Macrophage-derived nitric oxide is a critical mediator in wound healing. Its regulation in vivo, however, remains unclear. We hypothesized that interferon (IFN)-gamma plays an important role in the regulation of nitric oxide in wounds. Groups of 12 male IFN-gamma -knockout mice and wild-type controls underwent dorsal skin incision and polyvinyl alcohol sponges were inserted subcutaneously. Mice were sacrificed 10 days later to determine wound breaking strength and reparative collagen deposition. Synthesis of nitric oxide (NO), tumor necrosis factor (TNF)-alpha, and IFN-gamma was measured in the wound. Wound-derived macrophages were tested for NO synthesis in the presence or absence of IFN-gamma, TNF-alpha, and anti-TNF-alpha antibody. In a separate experiment, IFN-gamma -knockout mice and wild-type controls were treated with molsidomine, a nitric oxide donor. It was found that wound collagen deposition and wound breaking strength were impaired in IFN-gamma-knockout mice (p < .05). Impaired healing was reflected in diminished synthesis of TNF-alpha and NO in wounds (p < .05). In vivo treatment with molsidomine reversed impaired healing in IFN-gamma-deficient mice. Ex vivo, addition of IFN-gamma stimulated the synthesis of TNF-alpha and NO in wound-derived macrophages. IFN-gamma -induced NO synthesis by wound-derived macrophages was abolished by anti-TNF-alpha-antibody-treatment, which could be fully reversed by exogenous TNF-alpha. Thus we conclude that IFN-gamma-deficiency impairs wound healing and diminishes NO synthesis in wound-derived macrophages. The stimulatory effect of IFN-gamma on macrophage NO production depends on endogenous TNF-alpha synthesis.     

Intravenous hyperalimentation with high arginine levels improves wound healing and immune function

The purpose of this study was to evaluate the effect of increased arginine levels in intravenous hyperalimentation (IVH) therapy on wound healing and thymic immune function. Groups of SD rats, 275-325 g, underwent placement of internal jugular catheter, 7-cm dorsal skin wounding, insertion of polyvinyl alcohol sponges subcutaneously, and closure of wounds with stainless-steel sutures. Twenty-four hours later, rats were started on IVH at a rate of 0.8-1 ml/100 g body wt/hr. All IVH solutions contained 20% dextrose, adequate amounts of minerals and vitamins, and two different amino acid mixtures: (A) Fre III (4.05 g ARG/liter) (n = 13); (B) experimental (7.50 g ARG/liter) (n = 11). Solutions were isonitrogenous, and contained similar amounts of essential amino acids. After 7 days of IVH, weight gain did not differ between the two groups; however, cumulative N balance was superior in group A. Wound healing was improved in group B as assessed by fresh wound strip breaking strength, fixed breaking strength, and the amount of reparative collagen deposition as assessed by the hydroxyproline content of the implanted sponges. Group B animals also had improved thymic function as assessed by thymic weight, the total number of thymic lymphocytes/gland and mitogenic reactivity of thymic lymphocytes to PHA and Con A. The experiments indicate that high arginine levels in IVH solutions improve wound healing and thymic immune function following injury.     

Regulation of Nitric Oxide Synthesis in Wounds by IFN-γ Depends on TNF-α

Macrophage-derived nitric oxide is a critical mediator in wound healing. Its regulation in vivo, however, remains unclear. We hypothesized that interferon (IFN)-γ plays an important role in the regulation of nitric oxide in wounds. Groups of 12 male IFN-γ -knockout mice and wild-type controls underwent dorsal skin incision and polyvinyl alcohol sponges were inserted subcutaneously. Mice were sacrificed 10 days later to determine wound breaking strength and reparative collagen deposition. Synthesis of nitric oxide (NO), tumor necrosis factor (TNF)-α, and IFN-γ was measured in the wound. Wound-derived macrophages were tested for NO synthesis in the presence or absence of IFN-γ, TNF-α, and anti-TNF-α antibody. In a separate experiment, IFN-γ -knockout mice and wild-type controls were treated with molsidomine, a nitric oxide donor. It was found that wound collagen deposition and wound breaking strength were impaired in IFN-γ-knockout mice (p <. 05). Impaired healing was reflected in diminished synthesis of TNF-α and NO in wounds (p <. 05). In vivo treatment with molsidomine reversed impaired healing in IFN-γ-deficient mice. Ex vivo, addition of IFN-γ stimulated the synthesis of TNF-α and NO in wound-derived macrophages. IFN-γ -induced NO synthesis by wound-derived macrophages was abolished by anti-TNF-α-antibody-treatment, which could be fully reversed by exogenous TNF-α. Thus we conclude that IFN-γ-deficiency impairs wound healing and diminishes NO synthesis in wound-derived macrophages. The stimulatory effect of IFN-γ on macrophage NO production depends on endogenous TNF-α synthesis.     

Effect of enhanced macrophage function on early wound healing

Although the macrophage is important to wound healing, research has focused on its relationship to fibroblast and collagen synthesis. This study was designed to assess effects of enhanced macrophage function on early wound healing, before established collagen synthesis. Sprague-Dawley rats had dorsal incisions after one of three treatment regimens: (1) saline solution, 0.5 ml administered intravenously, (2) intravenous glucan, a macrophage stimulant, 20 mg; (3) topical glucan, 20 mg. Intravenous therapy was administered 24 hours before and after incision. Breaking strength was significantly increased (p less than 0.01) by both intravenous glucan (49.8 +/- 5.5 gm) and topical glucan (59.7 +/- 5.6 gm) on the fourth day after incision, compared with controls (22.0 +/- 2.6 gm). Similar results occurred on the seventh day after incision. Although formalin fixation significantly enhanced breaking strength in fresh control wounds (22.0 +/- 2.6 vs 39.5 +/- 2.2 gm), no increase occurred in wounds treated with intravenous glucan (49.8 +/- 5.0 vs 55.3 +/- 6.4 gm), indicating maximal cross-linking of collagen. Collagen synthesis, reflected by tritiated proline uptake, was no different in control versus glucan groups. Supernatants from control or glucan-activated macrophages were injected intraperitoneally or applied topically in the rat model. Activated supernatant, both intraperitoneal and topical, resulted in increased breaking strength on the fourth day after incision. Formalin fixation did not increase breaking strength in the activated supernatant groups. We conclude that enhanced macrophage function increases early wound breaking strength. This effect appears unrelated to collagen synthesis but may be related to increased cross-linking of collagen. Similar effects are seen with activated macrophage secretory products administered intraperitoneally or topically.     

MHC-class-II-deficiency impairs wound healing

BACKGROUND: MHC-class-II-deficient mice lack T helper cell dependent immune reactions. T cell related immune functions are critical for normal wound healing. We hypothesized that MHC-II-deficiency compromises wound repair by affecting the normal wound immune response. MATERIAL AND METHODS: Groups of 10 male MHC-class II-knockout mice and wild-type controls underwent dorsal skin incision. Polyvinyl alcohol sponges were then inserted subcutaneously. The mice were sacrificed 10 days later to determine wound breaking strength and reparative collagen deposition. Activity of T cells and macrophages isolated from the spleens and from the healing wounds was investigated. Fibroblasts derived from the wounds were tested ex vivo for proliferative activity and collagen synthesis. RESULTS: Wound collagen deposition and wound breaking strength were impaired in MHC-class-II-knockout mice (P < 0.05). Impaired healing was reflected in diminished mitogen-reactivity of splenic T-cells (P < 0.01), and decreased CD4 expression in wounds. In addition, basal and LPS + IFN-gamma-induced synthesis of TNF-alpha and nitric oxide by wound-derived macrophages was impaired. Exvivo, fibroblast proliferation and fibroblast collagen production from MHC-II-deficient mice was decreased. CONCLUSION: MHC-II-deficiency compromises wound healing. This may be a reflection of impaired wound immune cell function and decreased activity of wound fibroblasts.     

Recombinant basic fibroblast growth factor accelerates wound healing

Basic fibroblast growth factor (bFGF) stimulates extracellular matrix metabolism, growth, and movement of mesodermally derived cells. We have previously shown that collagen content in polyvinyl alcohol sponges increased after bFGF treatment. We hypothesized that bFGF-treated incisional wounds would heal more rapidly. After intraperitoneal pentobarbital anesthesia, male, 200- to 250-g, Sprague-Dawley rats (n = 27) each underwent two sets of paired, transverse, dorsal incisions closed with steel sutures. On Day 3 postwounding, 0.4 ml of bFGF (recombinant, 400 ng. Synergen) or normal saline was injected into one of each paired incisions. Animals were killed with ether on postwounding Days 5, 6, and 7 and their dorsal pelts were excised. Fresh or formalin-fixed wound strips were subjected to tensile strength measurements using a tensiometer. Breaking energy was calculated. Wound collagen content (hydroxyproline) was measured in wound-edge samples following hydrolysis using high-performance liquid chromatography. There was an overall significant increase in fresh wound tensile strength (13.7 +/- 1.06 vs 19.1 +/- 1.99 g/mm, P less than 0.01) and wound breaking energy (476 +/- 47 vs 747 +/- 76 mm2, P less than 0.001) in bFGF-treated incisions. There was an increase in wound collagen content which was not statistically significant and there was no difference in fixed incisional tensile strength. Histologic examination showed better organization and maturation in bFGF wounds. Recombinant bFGF accelerates normal rat wound healing. This may be due to earlier accumulation of collagen and fibroblasts and/or to greater collagen crosslinking in bFGF-treated wounds.     

Thymic inhibition of wound healing: Abrogation by adult thymectomy

It has been previously observed that the thymus and wound respond in a similar manner, i.e., agents that enhance thymic function increase wound healing, while factors which decrease thymic function impair healing. In order to elucidate if the thymus has a direct influence on wounds, we have studied wound healing in adult rats who have undergone thymectomy at 4–8 weeks of age. In three separate experiments we found that thymectomized rats had fresh wound breaking strengths significantly greater than sham-thymectomized rats. There were no differences noted in the amount of reparative collagen accumulated in subcutaneously implanted polyvinyl alcohol sponges or in the breaking strength of wound strips fixed in 10% formalin, which maximally cross-links the collagen present; the ratios of fixed to fresh wound breaking strengths were significantly greater in sham-thymectomized rats. Rats who had undergone thymectomy with immediate intraperitoneal placement of Millipore chambers containing autologous thymic fragments had wound breaking strengths similar to sham-thymectomized or intact animals. We conclude that thymectomy at 4–8 weeks of age increases wound maturation and collagen cross-linking. This suggests that the thymus normally has an inhibitory effect on wound healing and a role of T-suppressor cells on this process is postulated.     

In vivo characterization of interleukin-4 as a potential wound healing agent

Interleukin-4 increases the synthesis of extracellular matrix proteins, including types I and III collagen and fibronectin, by both human and rat fibroblasts. Because fibroblasts are the final common effector cells of most phases of tissue repair, this study set out to investigate the effects of interleukin-4 on the healing of three different types of wounds. Acute excisional and chronic granulating wounds inoculated with Escherichia coli and incisional wounds in streptozotocin-induced diabetic Sprague-Dawley rats were used. Recombinant murine or human interleukin-4 was applied topically to the open wounds at doses of 0.1, 1.0, or 10.0 microg/cm(2)/wound for 5 or 10 days. Incisional wounds received the same doses once-at the time of wounding. The time taken to achieve wound closure or wound breaking strength measurements of wounds was recorded and compared with relevant untreated control groups. Wound contraction was impaired in the presence of bacteria, and this was reversed by all doses of recombinant murine interleukin-4. Recombinant murine interleukin-4 had no effect on the wound closure of noncontaminated wounds; it reduced wound breaking strength in acute excisional wounds, except in a contaminated setting when wounds were treated with 1.0 pg/cm(2)/wound. Recombinant interleukin-4 (1.0 microg) improved breaking strength of both diabetic and normal incisional wounds. The apparent pleiotropic effect of interleukin-4 on wound breaking strength under different wound conditions may be related not only to the activity of the fibroblast but also the ratio of cross-linked collagen/total collagen content of wounds. This study suggests that interleukin-4 may be a useful agent for accelerating closure of wounds, particularly where healing is impaired.     

Significance of T-lymphocytes in wound healing

To determine the importance of T-lymphocytes in wound healing, we examined the effect of T-lymphocyte depletion on the healing of surgical wounds. Thirty Balb/c mice were injected intraperitoneally with 1 mg of rat anti-mouse (IgG2b) cytotoxic monoclonal antibody (30H12) against the Thy1.2 (all T) determinant. Twenty-four hours later animals showed a greater than 95% depletion of Thy1.2 cells in peripheral blood and spleen. Thirty control mice received nonspecific rat immunoglobulin (1 mg). Twenty-four hours after treatment mice underwent a 2.5 cm dorsal skin incision with subcutaneous placement of polyvinyl alcohol sponges. Injections were repeated at weekly intervals. Wound healing was assessed at 2, 3, and 4 weeks by the breaking strength of wound strips and by the hydroxyproline content of sponge granulomas (an index of wound reparative collagen deposition). Thy1.2 depletion at death was 95% to 57% in peripheral blood and 86% to 68% in the spleen. Both groups gained weight equally. We found that T cell depletion significantly impairs wound breaking strength and wound collagen deposition at all times studied. The data strongly suggest that T-lymphocytes modulate fibroblast activity during normal wound healing.     

The effect of in vivo T helper and T suppressor lymphocyte depletion on wound healing.

The role of T lymphocytes in wound healing is still not well-defined. Because it had been previously shown that in vivo depletion of T cells leads to impaired wound healing, the effect of depleting T cell subsets on subsequent fibroplasia was studied. T helper/effector cells were depleted by the use of the monoclonal antibody GK1.5, reactive against the L3T4 antigen (CD4). T suppressor/cytotoxic lymphocytes were depleted by using the 2.43 monoclonal antibody reactive against the Lyt 2 antigen (CD8). In the first experiment, Balb/c mice were treated with the antibodies starting at 24 hours before wounding was performed, and weekly thereafter. Depletion of the T helper/effector cells had no effect on wound-breaking strength or hydroxyproline deposition in sponge granulomas, whereas depletion of T suppressor/cytotoxic cells significantly enhanced both of these healing parameters. In a second experiment, T cell subset depletion was started on Days 0, 3, 7, 10, and 14 postwounding, and treatments were continued weekly thereafter. Once again, depletion of T helper/effector cells had no effect on wound healing, whereas depletion of T suppressor/cytotoxic cells markedly increased both wound-breaking strength and collagen synthesis. In conclusion, the data show that T suppressor/cytotoxic cells have a counter-regulatory role in wound healing, whereas the T cell subset responsible for up-regulating wound healing remains to be identified.     

Wound healing and T-lymphocytes

T-cell depletion leads to impaired wound healing. We studied the effect of combined T-helper and T-suppressor lymphocyte depletion on wound healing and compared it with the effect of all T-cell depletion. Groups of 10 male balb/c mice, 8 weeks old, underwent a 2.5-cm skin incision and subcutaneous implantation of polyvinyl alcohol sponges. Twenty-four hours prior to wounding one group was treated with 3OH12, a rat anti-mouse monoclonal antibody against the Thy-1.2 antigen present on all T-cells (1 mg); another group received 1 mg each of GK1.5 (anti-L3T4, CD4; anti-helper/effector subset) and 2.43 (anti-Lyt 2.1, CD8; anti-suppressor/cytotoxic subset). All monoclonal antibodies are cytotoxic in vivo. Controls received 1 mg of nonspecific rat IgG. Treatments were repeated weekly. Animals were sacrificed at 2 and 4 weeks postwounding. Equal depletion of all T- and Th- and Ts-subsets in peripheral blood and spleens was noted in the two experimental groups at sacrifice. Depleting Thy-1.2 cells (all T-cells) impaired wound healing as assessed by wound breaking strength and collagen synthesis. Combined anti-T-helper/effector and T-suppressor/cytotoxic depletion resulted in improved wound-healing parameters. This suggests that there is a Thy-1.2+, L3T4-, Lyt2- subpopulation of T lymphocytes which normally stimulates wound healing.     

Supplemental L-arginine enhances wound healing in diabetic rats

L-arginine has been shown to enhance wound strength and collagen deposition in rodents and humans. Diabetes mellitus, which impairs wound healing, is accompanied by a reduction in nitric oxide at the wound site. The amino acid L-arginine is the only substrate for nitric oxide synthesis. We sought to determine whether supplemental L-arginine can restore the impaired wound healing of diabetic rats. Fifty-six male Lewis rats were used in this study, of which twenty-nine rats were rendered diabetic 7 days prior to surgery with intraperitoneal streptozotocin. Twenty-seven untreated rats served as controls. Animals underwent a dorsal skin incision with implantation of polyvinyl-alcohol sponges. Sixteen diabetic and 14 normal rats received 1 g/kg/day of L-arginine by injection, while the remainder received saline injections only. Animals were euthanized 10 days postwounding, and their wounds were analyzed for breaking strength. The wound sponges were assayed for total hydroxyproline and nitrite/nitrate content. Plasma and wound fluid concentrations of L-arginine, ornithine, and citrulline were determined. Wound sponge RNA was extracted and subjected to Northern blot analysis for procollagen I and III. Diabetic wounds had greatly decreased breaking strengths compared with controls. L-arginine significantly enhanced wound breaking strengths in both control (+23%) and diabetic animals (+44%), and also increased wound hydroxyproline levels in both diabetic (+40%) and control animals (+24%) as compared to their saline-treated counterparts. mRNA for procollagen I and III were elevated by L-arginine treatment in both diabetic rats and controls. Treatment with L-arginine significantly increased wound fluid nitrite/nitrate levels in diabetic animals. The data show that the impaired healing of diabetic wounds can be partially corrected by L-arginine supplementation, and that this effect is accompanied by enhanced wound nitric oxide synthesis.     

Organ preservation I. kidney and pancreas

The present study was performed to determine the effect of cortisosteroid hormones on the mechanical properties and collagen content of healing wounds in rat stomach and duodenum. Long-term cortisol (hydrocortisone) treatment was started 4 weeks before wounding and continued until sacrifice. Wounds were made in the nonglandular part (rumen) and in the glandular oxyntic part (corpus) of the stomach and in duodenum. The wounds were tested 7 and 20 days after operation. Cortisol treatment decreased the mechanical strength of healing wounds in stomach and duodenum. A reduction was found for breaking strength as well as breaking energy. The inhibition was most pronounced early after (7 days) operation, while an apparently normal increase of wound strength was found between 7 and 20 days of healing. A relation between mechanical strength and total collagen content was shown. These findings indicate that the increase of mechanical strength and collagen content in wounds from stomach and duodenum is impaired by systemic long-term corticosteroid treatment. The effect is a delay of the healing process rather than a real inhibition.     

Effect of supplemental ornithine on wound healing

BACKGROUND: Supplemental arginine has been shown to enhance wound healing, in particular collagen synthesis. Ornithine is the main metabolite of arginine in the urea cycle and shares many of the biopharmacologic effects of arginine. The present study examines the effect of ornithine supplementation on wound healing and attempts to describe its possible mechanism. METHODS: Wild type (WT) and iNOS knockout (KO) mice were randomized to receive either normal chow and tap water or chow and water each supplemented with 0.5% ornithine (w/w). All animals underwent a midline dorsal skin incision with implantation of polyvinyl alcohol sponges into subcutaneous pockets. On postoperative day 14 the animals were sacrificed. The dorsal wound was harvested for breaking strength determination while the wound sponges were assayed for hydroxyproline content, total wound fluid amino acid, and nitrite/nitrate (NOx) concentration. RESULTS: Dietary ornithine supplementation enhanced wound breaking strength and collagen deposition in both WT and KO mice. This was accompanied by increased wound fluid proline and ornithine levels but not arginine, citrulline, or NOx levels. CONCLUSIONS: The results from this study demonstrate that ornithine supplementation enhances wound healing in both WT and KO mice. This suggests that ornithine's effect on wound healing is independent of the iNOS pathway.     

Fascial incisions heal faster than skin: a new model of abdominal wall repair

BACKGROUND: Optimal healing of the fascial layer is a necessary component of complete abdominal wall repair. The majority of acute wound healing studies have focused on the dermis. We designed a model of abdominal wall repair that, to our knowledge, for the first time simultaneously characterizes differences in the wound healing trajectories of the fascia and skin. METHODS: Full-thickness dermal flaps were raised on the ventral abdominal walls of rats, and midline fascial celiotomies were completed. The dimensions of the flap were developed so as to have no detrimental effect on skin healing. The dermal flaps were replaced so that the fascial incisions would heal separately from the overlying skin incisions. Animals were killed 7, 14, and 21 days after operation and fascial and dermal wounds were harvested and tested for breaking strength. Fascial and dermal wounds were also compared histologically for inflammatory response, fibroplasia, and collagen staining. RESULTS: Fascial wound breaking strength exceeded dermal wound breaking strength at all time points (9.16 +/- 2.17 vs 3.51 +/- 0.49 N at 7 days, P <.05). Fascial wounds also developed greater fibroblast cellularity and greater collagen staining 7 days after the incision. There was no difference in wound inflammatory response. CONCLUSIONS: Fascial incisions regain breaking strength faster than simultaneous dermal incisions. The mechanism for this appears to involve increased fascial fibroplasia and collagen production after acute injury.     

Nitric oxide enhances experimental wound healing in diabetes

BACKGROUND: Diabetes is characterized by a nitric oxide deficiency at the wound site. This study investigated whether exogenous nitric oxide supplementation with the nitric oxide donor molsidomine (N-ethoxycarbomyl-3-morpholinyl-sidnonimine) could reverse the impaired healing in diabetes. METHODS: Wound healing was studied by creating a dorsal skin incision with subcutaneous polyvinyl alcohol sponge implantation in diabetic and non-diabetic rats. Half of each group was treated with molsidomine. Collagen metabolism was assessed by wound breaking strength, hydroxyproline (OHP) content, RNA expression for collagen type I and III, and matrix metalloproteinase (MMP) 2 activity in wound sponges. Wound fluid, plasma and urinary nitric oxide metabolite levels, and the number of inflammatory cells were assessed. RESULTS: OHP content and wound breaking strength were significantly increased by molsidomine. MMP-2 activity in wound fluid was decreased in diabetes and upregulated by nitric oxide donors. The impaired inflammatory reaction in diabetes was unaffected by nitric oxide donor treatment and ex vivo nitric oxide synthesis was no different between wound macrophages from control and diabetic animals, suggesting that the nitric oxide deficiency in the wound is due to a smaller inflammatory reaction in diabetes. CONCLUSION: The nitric oxide donor molsidomine can at least partially reverse impaired healing associated with diabetes.     

Recombinant basic fibroblast growth factor in red blood cell ghosts accelerates incisional wound healing.

The pharmacological manipulation of wound healing with locally applied growth factors is now a practical possibility. The effect of topical applications of recombinant basic fibroblast growth factor (bFGF) on the strength and cellularity of healing incisional rat skin wounds was investigated. Applications of bFGF in a simple vector (either a collagen suspension or saline) were not associated with any positive effects on wound breaking load at 7 days after injury in comparison with vector-treated control wounds; at the highest dose of 50 micrograms per wound, breaking loads were significantly decreased from a mean(s.e.m.) of 287(22) g/cm2 in controls to 201(23) g/cm2 (P < 0.005). Increasing doses of applied peptide were paralleled by increasing wound cellularity. Delay of bFGF release at the site of application was achieved by encapsulation into red blood cell ghosts. Wounds treated with bFGF in such ghosts were 50 per cent stronger than paired control wounds (388(27) versus 256(28) g/cm2, P < 0.002) 7 days after injury. Treated wounds were significantly more cellular at 4 days than paired control wounds. Topical applications of bFGF applied at the time of injury exert a positive effect on incisional wound strength only when a vector that delays release is used.     

L-arginine improves wound healing after trauma-hemorrhage by increasing collagen synthesis

BACKGROUND: Several studies indicate impaired wound healing after trauma and shock. Wound immune cell dysfunction seems to be responsible for altered wound healing after trauma-hemorrhage (T-H). In this respect, administration of the amino acid L-arginine normalized wound immune cell function under those conditions. It remains unknown, however, whether L-arginine improves impaired wound healing after T-H. METHODS: To study this, male C3H/HeN mice were subjected to a midline laparotomy (i.e., soft tissue trauma induced), and polyvinyl sponges were implanted subcutaneously at the wound site before hemorrhage (35 +/- 5 mm Hg for 90 minutes) or were subjected to sham operation. During resuscitation, mice received 300 mg/kg body weight L-arginine or saline (vehicle). Seven days thereafter, hydroxyproline (OHP), a metabolite of collagen synthesis, was measured in the wound fluid using high-performance liquid chromatography. Collagen types I and III were determined in the wound by Western blot analysis. In addition, wound breaking strength was measured 10 days after T-H or sham operation. RESULTS: The results indicate that OHP was significantly decreased in T-H mice. L-arginine, however, restored depressed OHP in the wound fluid in the T-H animals. Similarly, L-arginine treatment prevented a significant depression of collagen I synthesis after T-H. Collagen III was not significantly affected by T-H or L-arginine. Most important, L-arginine increased maximal wound breaking strength after severe blood loss. Therefore, L-arginine improves wound healing after T-H by increasing collagen synthesis. CONCLUSION: Because L-arginine improves wound healing, the results suggest that L-arginine might represent a novel and useful adjunct to fluid resuscitation for decreasing wound complications after trauma and severe blood loss.     

血小板源性伤口愈合因子促糖尿病大鼠伤口愈合与成纤维细 …

OBJECTIVE: The effect of platelet-derived wound healing factor (PDWHF) on wound healing in diabetic rats was studied. METHODS: Forty-four male SD rats were randomly divided into 2 groups. Thirty-two rats of experimental group accepted intraperitoneal injection of alloxan (1.5 mg/10 g body weight). Within one or two days after injection, while the blood sugar of the rats was higher than 180 mg/dl, the animal model of diabetic rat should have been established. Then a dorsal incision was given to every rat. After the addition of PDWHF (the experimental group) or bovine albumin (the control group), the incision was sutured up. Seven, ten and fourteen days after operation, the breaking strength of the wound was measured. On another hand, specimen from the wound was taken for the culture of fibroblasts. When the cultured fibroblasts have been incubated with 10% PDWHF for 4, 8 and 12 hours, the procollagen I (alpha 1) mRNA levels were examined respectively, and compared with those of control. RESULTS: Significant difference in wound breaking strength had been observed between PDWHF-treated incisions and the control on 7, 10 and 14 days after wounding (P < 0.01). Experiment in vitro demonstrated that the procollagen I (alpha 1) mRNA levels in wound fibroblasts incubated with 10% PDWHF for 4, 8 and 12 hours were 0.9, 3.7 and 2.2 folds higher than those in fibroblasts in control. CONCLUSION: It was suggested that direct stimulation of procollagen I (alpha 1) gene expression was one of the ways that PDWHF played its role in accelerating wound healing.