Lysophosphatidic acid enhances healing of acute cutaneous wounds in the mouse.

Lysophosphatidic acid is a phospholipid growth factor and intercellular signaling molecule released by activated platelets and injured fibroblasts that affects keratinocytes, fibroblasts, neutrophils,and monocytes. We therefore hypothesized that lysophosphatidic acid could influence the inflammation and reepithelialization phases of wound healing. Lysophosphatidic acid (100 microM) was applied daily for 5 days to 2 mm-diameter excisional mouse ear skin wounds and re-epithelialization was measured. We also evaluated whether the bioactivity of lysophosphatidic acid could be increased by zinc (Zn2+, 1 mM). Inflammatory cells were counted in wound sections after 1, 3, or 5 days of healing. Reepithelialization was accelerated significantly by either lysophosphatidic acid or lysophosphatidic acid + Zn2+ (p < 0.01 and p < 0.0001, respectively). Both lysophosphatidic acid solutions significantly increased the amount of new epithelium in the wounds on days 1, 2, and 3 (p < 0.05). Little wound area remained on day 4, and all wounds were fully reepithelialized by day 5. Lysophosphatidic acid did not affect the number of neutrophils or macrophages present in the wound area. Our findings show that lysophosphatidic acid increased the amount of reepithelialization in the early stages of cutaneous wound healing in excisional ear wounds, without affecting inflammatory function.     

Healing of full-thickness wounds treated with lyophilized cultured keratinocyte cell lysate in genetically diabetic mice

The effect of a lyophilized cell lysate prepared from cultured human keratinocytes on the healing of full-thickness wounds was evaluated in an impaired healing model. Full-thickness wounds (8 mm in diameter) were made on the dorsal areas of female genetically diabetic mice C57 BL/KsJ (db/db) and their normal (db/+) littermates. Wounds were covered with an occlusive polyurethane film dressing and were treated for 5 days either with the lyophilized cell lysate from cultured human keratinocytes prepared in phosphate-buffered saline solution or with phosphate-buffered saline solution. In normal (db/+) mice, all wounds were closed 16 days after wounding, and more than 90% of the wound closure was due to wound contraction. Wound contraction accounted for a similar extent of wound closure in both lyophilized cell lysate-treated and phosphate-buffered saline solution-treated wounds. In contrast, in the diabetic (db/db) mice, after histologic examination of the wounds 32 days after wounding, four of ten lyophilized cell lysate-treated wounds and four of seven phosphate-buffered saline-treated wounds were found to be closed. Moreover, applications of lyophilized cell lysate from cultured human keratinocytes to full-thickness wounds in diabetic db/db mice significantly decreased the contribution of contraction to wound closure. Day 32 after wounding, contraction contribution to wound closure amounted to 57.7%+/- 4.7% and 80.4%+/- 3.2% (mean +/- standard error of the mean, p < 0.005) of the initial wound areas, respectively, for lyophilized cell lysate-treated and phosphate-buffered saline solution-treated wounds. At this time of wound healing, the thickness of the dermis was increased 1.7-fold by the keratinocyte cell lysate treatment, but neither epithelial migration from the wound edges nor the thickness of the regenerated epithelium were significantly affected. In conclusion, in diabetic (db/db) mice the application of lyophilized cell lysate from cultured human keratinocytes influenced the healing of the dermis and wound contraction, but had no effect on reepithelialization.     

Lentiviral gene transfer of SDF-1alpha to wounds improves diabetic wound healing

BACKGROUND: Chronic wounds continue to be a major clinical problem and novel therapeutic approaches are needed. We have previously demonstrated that treatment of diabetic mouse wounds with local application of stromal progenitor cells results in improved healing and increased production of stromal-derived growth factor-1alpha (SDF-1alpha). We hypothesized that lentiviral-mediated increased production of SDF-1alpha in the wound environment could also improve diabetic wound healing. MATERIALS AND METHODS: Full-thickness excisional wounds were created in Db-/Db- mice and immediately treated with 10(6), 10(8), or 10(9) plaque-forming units of a lentiviral construct containing GFP-SDF-1alpha or GFP alone. At 7 and 14 days post wounding, wounds were harvested for histological and molecular analysis. RESULTS: At 7 days, Db-/Db- wounds treated with lenti GFP-SDF-1alpha exhibited a decrease in wound surface area for all doses tested. Morphologically, SDF-treated wounds were more cellular with increased granulation tissue volume compared to controls (P < 0.05). GFP expression was maintained in treated tissue at 7 days post wounding, but little expression was observed at 14 days. While we did not observe a difference in the gross wound surface area at 14 days, histological analysis revealed that SDF-treated wounds were fully epithelialized (n = 6) compared to only one of six controls. CONCLUSIONS: Lentiviral-mediated overproduction of SDF-1alpha is sufficient to correct the pathophysiologic abnormalities in diabetic wound healing resulting in complete epithelialization at 2 weeks. SDF-1alpha-mediated improvement in diabetic wound healing has significant implications for the development of novel therapeutic strategies to facilitate wound closure which target progenitor cell mobilization and recruitment.     

Midgestational excisional fetal lamb wounds contract in utero

Clinical observations and experimental data suggest that fetal wound healing is very different from adult wound healing. An understanding of the biology of scarless fetal wound healing has tremendous clinical potential for modulating postnatal wound problems. In this study, the fetal lamb model was used to assess excisional fetal skin wound contraction in utero. Full-thickness 9-mm punch biopsy wounds were created on fetal lambs at 100 days' gestation (term, 145 days). Half of the wounds remained exposed to amniotic fluid, whereas the other half were covered by a silastic patch to exclude amniotic fluid. Wounds were harvested 3, 7, or 14 days later and wound areas were calculated. Exposure to amniotic fluid retarded wound contraction significantly at 3 days, but by 14 days all wounds had completely contracted and reepithelialized. Myofibroblasts are an important cellular element of wound contraction. The presence of wound myofibroblasts was documented by both transmission electronmicroscopy and immunocytochemistry with antimuscle actin antibody. It is concluded that fetal lamb wounds contract in utero and exposure to amniotic fluid appears to retard fetal skin wound contraction only during the early healing process.     

Sympathetic denervation accelerates wound contraction but delays reepithelialization in rats

Participation of the peripheral nervous system in wound healing is not well understood. The aim of this study was to investigate the effects of sympathetic denervation on rat excisional cutaneous wound healing. Male rats were chemically denervated with intraperitoneal administration of 6-hydroxydopamine (6-OHDA) in 1% ascorbic acid. 6-OHDA or vehicle was administered twice a week until euthanasia, beginning 7 days before wounding. A full-thickness excisional lesion was performed and the lesion area measured to evaluate wound contraction. After euthanasia, the lesion and adjacent normal skin were formalin-fixed and paraffin-embedded. Sections were stained with hematoxylin and eosin or toluidine blue, or immunostained for alpha-smooth muscle actin. Animals treated with 6-OHDA showed acceleration in wound contraction, increase in myofibroblastic differentiation, reduction in mast cell migration, and a delay in reepithelialization. To investigate the effects of neurogenic inflammation, a group of animals was treated with 6-OHDA only after the acute inflammatory phase, and these animals showed delayed wound contraction 3 and 7 days after wounding when compared to those treated before the lesion. In conclusion, the present study shows that sympathetic denervation affects cutaneous wound healing, probably by a decrease in neurogenic inflammation during the initial phase of healing and the absence of catecholamines throughout the final phase.     

Alterations of Angiotensin II Receptor Levels in Sutured Wounds in Rat Skin

Angiotensin II receptor levels have been shown to vary with postoperative time in tissue harvested from full-thickness dermal excisional wounds on adult rats. This study examined the expression of AII receptors in a sutured wound model. Two full-thickness incisionul wounds were made in the dorsal skin of adult Sprague-Dawley rats and sutured immediately under general anesthesia. The wound tissues were harvested at 0, 0.5, 1, 2, 4, 24 h and on days 2, 3, 4. 5, 7, and 10 after the wounding. The levels of ¹²⁵I-Sar¹.lle⁸-AII bound to membrane preparations of the wound tissues decreased at early time points (from 0.5 to 4 h), increased from day 1 to day 7, and returned to nonsurgical levels by day 10. Competitive binding studies showed that the receptors were predominantly of the ATI receptor subtype. These results suggest that an immediate and transient reduction in AII receptor expression occurred after wounding, followed by an increase in the number of AII receptors that was maintained for 5 to 7 days postoperatively. Because these data are consistent with those observed after excisional wounding, temporal changes in AII receptor expression may be integral to the process of wound healing     

Healing of partial thickness porcine skin wounds in a liquid environment.

This study employs a liquid-tight vinyl chamber for the topical fluid-phase treatment of experimental wounds in pigs. Continuous treatment with normal saline significantly reduced the early progression of tissue destruction in partial thickness burns. Uncovered burns formed a deep layer of necrosis (0.49 +/- 0.004 mm, mean +/- SD) although burn wounds covered with empty chambers demonstrated less necrosis (0.14 +/- 0.01 mm), fluid-treated wounds formed no eschar, and little tissue necrosis could be detected (less than 0.005 mm). Topical treatment with hypertonic dextran increased water flux across burn wounds by 0.24 ml/cm2/24 hr (mean, n = 95) over saline-treated wounds during the first 5 days after wounding. When partial thickness burn and excisional wounds were immersed in isotonic saline until healed, the daily efflux of water, protein, electrolytes, and glucose across the wound surface declined during healing to baseline values found in controls (saline-covered unwounded skin). The declining protein permeability was used as a reproducible, noninvasive, endogenous marker for the return of epithelial barrier function. Saline-treated excisional wounds healed within 8.6 +/- 0.6 days (mean +/- SD, n = 27) and burn wounds within 12.1 +/- 1.4 days (mean +/- SD, n = 15). Healing of fluid-treated wounds occurred without tissue maceration and showed less inflammation and less scar formation than healing of air exposed wounds (no attempt was made to compare rates of healing between air- and fluid-exposed wounds). We consider the fluid-filled chamber a potentially very useful diagnostic, monitoring, and delivery system for wound-healing research and for human wound therapy.     

Administration of prednisolone phosphate–liposomes reduces wound contraction in a rat partial-thickness wound model

Macrophages play an important role in the inflammatory phase of wound healing and their activity regulates fibroblasts and keratinocytes. Modulation of macrophage function may result in improvement of the wound healing process. Prednisolone phosphate (PLP) encapsulated into liposomes was administered to partial-thickness wounds in rats. A single dose of 75 microg/kg, applied directly after wounding, resulted in up to a 30% reduction of wound contraction at 28 days after wounding. This effect could not be achieved in the group that was administered free PLP or liposomes containing phosphate-buffered saline to the wound. The number of myofibroblasts was up to 50% lower in wounds treated with the liposomal PLP at 4 days after wounding. The number of macrophages present in the wounds was not statistically different between groups. Most probably, the production of cytokines and growth factors by macrophages is altered after phagocytosing the liposomes, resulting in reduced wound contraction.     

Fetal wound healing using a genetically modified murine model: the contribution of P-selectin

Purpose

During early gestation, fetal wounds heal with paucity of inflammation and absent scar formation. P-selectin is an adhesion molecule that is important for leukocyte recruitment to injury sites. We used a murine fetal wound healing model to study the specific contribution of P-selectin to scarless wound repair.

Methods

Linear excisional wounds were created on the dorsa of E15.5 and E17.5 gestation fetuses in wild-type and P-selectin (-/-) mice (term = 19 days). Wounds were harvested at various time-points after wounding and analyzed using histology and immunohistochemistry.

Results

The E15.5 wounds in both wild-type and P-selectin (-/-) fetuses healed scarlessly and with minimal inflammation, whereas E17.5 wounds healed with fibrosis and inflammation. However, the scars of the P-selectin (-/-) wounds appeared slightly different than wild-type. There were significantly more inflammatory cells in E17.5 wild-type wounds 6 hours after injury (P < .001), but the difference was no longer significant by 24 hours. Finally, reepithelialization was slower in the E15.5 knockout wounds compared to their wild-type counterparts.

Conclusions

Absence of P-selectin delays inflammatory cell recruitment and reepithelialization of fetal wounds; however, scar formation still occurs in late gestation wounds. The contribution of specific molecules to fetal wound healing can be elucidated using murine knockout or transgenic models.     

Topical vanadate improves tensile strength and alters collagen organisation of excisional wounds in a mouse model

Wound dehiscence, oftentimes a result of the poor tensile strength of early healing wounds, is a significant threat to the post-operative patient, potentially causing life-threatening complications. Vanadate, a protein tyrosine phosphatase inhibitor, has been shown to alter the organisation of deposited collagen in healing wounds and significantly improve the tensile strength of incisional wounds in rats. In this study, we sought to explore the effects of locally administered vanadate on tensile strength and collagen organisation in both the early and remodelling phases of excisional wound healing in a murine model. Wild-type mice underwent stented excisional wounding on their dorsal skin and were divided equally into three treatment conditions: vanadate injection, saline injection control and an untreated control. Tensile strength testing, in vivo suction Cutometer analysis, gross wound measurements and histologic analysis were performed during healing, immediately upon wound closure, and after 4 weeks of remodelling. We found that vanadate treatment significantly increased the tensile strength of wounds and their stiffness relative to control wounds, both immediately upon healing and into the remodelling phase. Histologic analysis revealed that these biomechanical changes were likely the result of increased collagen deposition and an altered collagen organisation composed of thicker and distinctly organised collagen bundles. Given the risk that dehiscence poses to all operative patients, vanadate presents an interesting therapeutic avenue to improve the strength of post-operative wounds and unstable chronic wounds to reduce the risk of dehiscence.     

Neutral endopeptidase inhibition in diabetic wound repair

In response to cutaneous injury, sensory nerves release substance P, a proinflammatory neuropeptide. Substance P stimulates mitogenesis and migration of keratinocytes, fibroblasts, and endothelial cells. Neutral endopeptidase (NEP), a cell surface metallopeptidase, degrades substance P. Chronic nonhealing wounds and skin from patients with diabetes mellitus show increased NEP localization and activity. We hypothesized that increased NEP may retard wound healing and that NEP inhibition would improve closure kinetics in an excisional murine wound model. NEP enzyme activity was measured in skin samples from mutant diabetic mice (db/db) and nondiabetic (db/-) littermates by degradation of glutaryl-ala-ala-phe-4-methoxy-2-naphthylamine. Full-thickness 6-mm dorsal excisional wounds treated with normal saline or the NEP inhibitor thiorphan (10 microM or 25 microM) for 7 days were followed until closure. Histological examination and NEP activity were evaluated in a subset of wounds. NEP activity in unwounded db/db skin (20.6 pmol MNA/hr/ microg) significantly exceeded activity in db/-skin (7.9 pmol MNA/hr/ microg; p = 0.02). In db/db mice, 25 microM thiorphan shortened time to closure (18.0 days; p < 0.05) compared to normal saline (23.5 days). NEP inhibition did not alter closure kinetics in db/-mice. While the inflammatory response appeared enhanced in early wounds treated with thiorphan, blinded histological scoring of healed wounds using a semiquantitative scale showed no difference in inflammation. Unwounded skin from diabetic mice shows increased NEP activity and NEP inhibition improved wound closure kinetics without affecting contraction, suggesting that its principal effect was to augment epithelialization.     

Live imaging of Smad2/3 signaling in mouse skin wound healing

Biophotonics and real-time imaging are novel technologies that can greatly enhance the study of complex biological processes. We applied this technology in a transgenic mouse with a luciferase reporter gene fused to a transforming growth factor-beta (TGF-beta) responsive Smad2/3-binding element to study bioluminescence after skin wounding. Two dorsal midline excisional skin wounds were made using a biopsy punch. One wound was randomized to suture closure and the other allowed to heal by secondary intention (n=8 each wound). Bioluminescence was measured at fixed time points following surgery. Phospho-Smad2/3 immunohistochemistry was performed to localize expression in skin wound samples. In vivo bioluminescence increased following skin wounding. Peak activity occurred on day 17 and was fourfold that of baseline (p<0.05). Subgroup analysis of primary and secondary healing showed that primarily sutured wounds had peak activities earlier than those with secondary healing, although this did not reach statistical significance. Intense phospho-Smad2/3 staining was found in the hair follicles. In vivo bioluminescence tracks Smad2/3-dependent TGF-beta signaling in the in vivo wound healing process. Our findings suggest that signaling increases after wound healing, which contrasts with other studies that show raised TGF-beta signaling in the initial days following wounding.     

Flii neutralizing antibodies improve wound healing in porcine preclinical studies

Wound healing is an important area of widely unmet medical need, with millions of procedures carried out worldwide which could potentially benefit from a product to improve the wound repair process. Our studies investigating the actin‐remodeling protein Flightless I (Flii) show it to be an important regulator of wound healing. Flii‐deficient mice have enhanced wound healing in comparison to Flii overexpressing mice which have impaired wound healing. For the first time, we show that a Flightless I neutralizing monoclonal antibody (FnAb) therapy is effective in a large animal model of wound repair. Porcine 5 cm incisional and 6.25 cm² excisional wounds were treated with FnAb at the time of wounding and for two subsequent days. The wounds were dressed in Tegaderm dressings and left to heal by secondary intention for 7 and 35 days, respectively. At the relevant end points, the wounds were excised and processed for histological analysis. Parameters of wound area, collagen deposition, and scar appearance were analyzed. The results show that treatment with FnAb accelerates reepithelialization and improves the macroscopic appearance of early scars. FnAbs have the potential to enhance wound repair and reduce scar formation.     

Partial thickness wound: Does mechanism of injury influence healing?

Wound healing is a complex multistep process which is temporally and spatially controlled. In partial thickness wounds, regeneration is possible from the stem cells in the edges of the wound and from the remnants of the epidermal appendages (such as hair follicles and sebaceous glands). This study examines whether the mechanism of injury influences healing of wounds of similar depth. Burn and excisional wounds were created on the back of Hampshire pigs and harvested at 7, 14, 28, 44, 57 and 70 days after injury and processed for histology and immunohistochemistry. Quantitative analysis of re-epithelialisation, inflammatory response and thickness of the scar and semi-quantitative analyses of the architecture of the resultant scar were performed and subjected to statistical analysis. Results demonstrated a higher number of neutrophils, macrophages and lymphocytes present in the burn on day 7 compared to the excisional wounds. The inflammatory profile of burn wounds was higher than that of excisional wounds for the first month after injury albeit less marked than on day 7 after injury. Re-epithelialisation was markedly advanced in excisional wounds compared to burn wounds at day 7 after injury, corresponding to the higher number of hair follicles in the underlying dermis of excisional wounds at this time point. The thickness of the neo-epidermis increased with time and at day 70 after wounding, the neo-epidermis of the burn was significantly thicker than the neo-epidermis of the excisional scar. Interestingly, following partial thickness excision of skin, there was neo-dermal reformation albeit with an altered architecture, lacking the normal basket-weave pattern of collagen. The thickness of the dermis of partial thickness excisional scar was greater than that of the adjacent unwounded skin. The neo-dermis of the burn scar was even thicker, with the collagen arranged more compactly and disorganised compared to excisional scar and normal skin. This study provides evidence that the mechanism of injury does influence wound healing and the resultant scarring.     

Exercise prior to,but not concomitant with,stress reverses stress‐induced delayed skin wound healing

Stress‐induced prolonged inflammation impairs cutaneous wound healing. Exercise may inhibit this effect via an anti‐inflammatory mechanism. Our aim was to investigate the effect of moderate exercise on skin wound healing in chronically stressed mice. Mice were trained five times per week on a treadmill or received no training. Mice underwent daily rotational stress from the 6th week until euthanasia. During the 8th week, two wounds were created in the dorsum and collected 10 days later. A control group only received wounds. Exercise was performed prior to and simultaneous with stress for 2 weeks or only prior to stress. Stress increased normetanephrine levels 10 days after wounding, resulting in an increased amount of inflammatory cells and reduced expression of inflammatory cytokines as well as angiogenesis, myofibroblast differentiation and matrix deposition. Concomitant exercise and stress potentiated these effects, intensifying the delayed wound contraction. When exercise was performed only prior to stress, however, the mice showed reduced inflammatory cells in granulation tissue 10 days after wounding and improved wound healing compared with animals with exercise and concomitant stress. Moderate exercise in association with stress potentiates the stress effect; however, when exercise was performed prior to stress, wound healing was improved.     

Effect of chitosan acetate bandage on wound healing in infected and noninfected wounds in mice

HemCon^® bandage is an engineered chitosan acetate preparation designed as a hemostatic dressing, and is under investigation as a topical antimicrobial dressing. We studied its effects on healing of excisional wounds that were or were not infected with Staphylococcus aureus, in normal mice or mice previously pretreated with cyclophosphamide (CY). CY significantly suppressed wound healing in both the early and later stages, while S. aureus alone significantly stimulated wound healing in the early stages by preventing the initial wound expansion. CY plus S. aureus showed an advantage in early stages by preventing expansion, but a significant slowing of wound healing in later stages. In order to study the conflicting clamping and stimulating effects of chitosan acetate bandage on normal wounds, we removed the bandage from wounds at times after application ranging from 1 hour to 9 days. Three days application gave the earliest wound closure, and all application times gave a faster healing slope after removal compared with control wounds. Chitosan acetate bandage reduced the number of inflammatory cells in the wound at days 2 and 4, and had an overall beneficial effect on wound healing especially during the early period where its antimicrobial effect is most important.     

TGF-beta1 alters the healing of cutaneous fetal excisional wounds.

BACKGROUND/PURPOSE: In a number of species, fetal wound healing differs from the adult in the absence of inflammation, fibrosis, scar formation, and excisional wound contraction. The lack of inflammation also may explain the relative absence of any cytokine levels at the wound site, such as transforming growth factor (TGF)-beta, and therefore the unique characteristics of fetal wound healing. The authors hypothesized that exogenous TGF-beta1 would induce contraction, inflammation, fibrosis, and scar formation in cutaneous excisional wounds in the fetal rabbit. METHODS: Cellulose discs (3 mm in diameter) were formulated with either 1.0 microg TGF-beta1 (n = 6) or bovine serum albumin (BSA; n = 7), as a control, for sustained-release over 3 days. Each disc was implanted into the subcutaneous tissue on the backs of fetal New Zealand White Rabbits in utero on day 24 of gestation (term, 31 days). A full-thickness, 3-mm excisional wound (7.4 mm2) was then made next to the implanted cellulose disc. All wounds were harvested 3 days later. RESULTS: At harvest, the excisional wounds in the TGF-beta1 group had contracted (5.6 +/- 2.0 mm2), whereas those in the control group had expanded (13.5 +/- 1.2 mm2, P< .01). The surrounding dermis in the TGF-beta1 group had 16.3 inflammatory cells per grid block compared with 12.4 cells in the control group (not significant). In addition, a greater amount of fibrosis was induced by the TGF-beta1 implant (1.7 +/- 0.3) than the control implant (0.4 +/- 0.2) on a scale of 0 to 3, P < .01. In situ hybridization analysis showed an increase in procollagen type 1alpha1 gene expression in the surrounding dermis of the TGF-beta1 group (36.7 +/- 3.6 grains per grid block) compared with the control group (7.1 +/- 0.9 grains per grid block, P < .001). CONCLUSIONS: These results demonstrate that the cytokine TGF-beta1 can induce fetal excisional wounds to contract, stimulate fibrosis, and increase procollagen type 1alpha1 gene expression. These findings further suggest that the absence of TGF-beta1 atthe wound site may be responsible in part for the lack of a postnatal healing response.     

Fetal diaphragmatic wounds heal with scar formation

Fetal wound healing is fundamentally different from wound healing in the adult. Although experimental work in mice, rats, rabbits, monkeys, and sheep has demonstrated that fetal healing occurs without inflammation and scarring, all of these studies have been limited to fetal skin wounds. Whether all fetal tissues heal in a regenerative-like fashion is unknown. Amniotic fluid exposure may play an important role in scarless fetal skin wound healing, but the effect of amniotic fluid on fetal mesothelial wound healing has not been characterized. To investigate these questions we created bilateral linear diaphragmatic wounds in 100-day gestation fetal lambs (term = 145 days). The right thoracotomy was closed to exclude amniotic fluid. In contrast, the left thoracotomy was fashioned into an Eloesser flap which permitted the left diaphragmatic wound to be continually bathed in amniotic fluid. Wounds were harvested after 1, 2, 7, or 14 days and analyzed by light microscopy and immunohistochemistry with antibodies to collagen types I, III, IV, and VI. Whether bathed in or excluded from amniotic fluid, the mesothelial-lined diaphragm healed with scar formation and without evidence of muscle regeneration. Interestingly, diaphragmatic wounds exposed to amniotic fluid were covered by a thick fibrous collagen peel similar to that seen in gastroschisis bowel. These findings indicate that not all fetal tissues share the unique scarless healing properties of fetal skin.     

Evaluation of autologous bone marrow‐derived nucleated cells for healing of full‐thickness skin wounds in rabbits

The aim of the study was to evaluate the potential of autologous bone marrow‐derived nucleated cells to enhance the rate of healing of full‐thickness excisional skin wounds in rabbits. The study was conducted on 20 New Zealand white rabbits of either sex. Two, 2 × 2 cm full‐thickness skin (thoracolumabar region) excisional wounds were created; one on each side of the dorsal midline in each animal. The wounds were randomly assigned to either injection of autologous bone marrow‐derived nucleated cells into the wound margins (BI), or topical application of sterile saline solution (normal saline, NS), which served as control. The wound healing was assessed by evaluation of granulation tissue formation, wound contraction, epithelisation and histopathological and histochemical changes up to 28 days after creation of the wound. Granulation tissue appeared significantly faster in BI‐treated wounds (3.22 ± 0.22 days) than in NS‐treated wounds (4.56 ± 0.47 days). Better epithelisation was seen histologically in BI wounds than in NS‐treated wounds. Wound contraction was significantly more in BI wounds when compared with NS wounds on 21 post‐surgery. Histopathological examination of the healing tissue showed early disappearance of inflammatory reaction, significantly more neovascularisation, and more fibroplasias and early lay down and histological maturation of collagen in BI wounds than in control wounds. It was concluded that injection of autologous bone marrow‐derived nucleated cells in the wound margins induced faster and better quality healing of excisional skin wounds in rabbits when compared with normal saline. The injection of autologous bone marrow‐derived nucleated cells can be used to promote healing of large full‐thickness skin wounds in rabbits.     

The local effects of cachectin/tumor necrosis factor on wound healing.

Previous experimental studies have suggested that tumor necrosis factor (TNF) may have either a beneficial or a detrimental role in wound healing. Control and doxorubicin-treated (6 mg/kg, intravenously) rats underwent paired dorsal 5-cm linear wounds and had either vehicle or recombinant (r)TNF (0.5, 5, or 50 micrograms) applied locally to the wound. Paired wounds were harvested at 7 and 14 days after wounding and analyzed for wound-bursting strength (WBS) and activity of the gene for type 1 collagen and TNF. Doxorubicin treatment decreased WBS at 14 days but not at 7 days after wounding. Local application of 50 micrograms of rTNF decreased WBS in saline-treated rats and concentrations of 5 and 50 micrograms decreased WBS in doxorubicin-treated rats when measured 7 days after wounding. These effects dissipated when WBS was measured 14 days after wounding. Doxorubicin decreased wound collagen gene expression and local TNF treatment decreased wound collagen gene expression in saline-treated rats and further decreased it in doxorubicin-treated rats. The decrement in collagen gene expression induced by rTNF increased as the local dose of rTNF increased. The gene for TNF was not detectable in wounds from normal or doxorubicin-treated rats at 3, 7, 10, or 14 days after wounding. These data suggest that the gene for TNF is not expressed in wounds and that the local application of TNF is detrimental to wound healing as it decreases WBS and activity of the gene for collagen.