The role of growth factors in wound healing

Islet hypertrophy following pancreatic disruption of Smad4 signaling

To investigate the role of transforming growth factor (TGF)-beta family signaling in the adult pancreas, a transgenic mouse (E-dnSmad4) was created that expresses a dominant-negative Smad4 protein driven by a fragment of the elastase promoter. Although E-dnSmad4 mice have normal growth, pancreas weight, and pancreatic exocrine and ductal histology, beginning at 4-6 wk of age, E-dnSmad4 mice show an age-dependent increase in the size of islets. In parallel, an expanded population of replicating cells expressing the E-dnSmad4 transgene is found in the stroma between the enlarged islets and pancreatic ducts. Despite the marked enlargement, E-dnSmad4 islets contain normal ratios and spatial organization of endocrine cell subtypes and have normal glucose homeostasis. Replication of cells derived from primary duct cultures of wild-type mice, but not E-dnSmad4 mice, was inhibited by the addition of TGF-beta family proteins, demonstrating a cell-autonomous effect of the transgene. These data show that, in the adult pancreas, TGF-beta family signaling plays a role in islet size by regulating the growth of a pluripotent progenitor cell residing in the periductal stroma of the pancreas.

The effect of various concentrations of human recombinant epidermal growth factor on split-thickness skin wounds

Epidermal growth factor (EGF) is a potent stimulant of epithelialisation. However, topical application of EGF to achieve facilitated re-epithelialisation in partial thickness wounds has been controversial. A total of 10 pigs, each with eight 4 x 4 cm partial thickness wounds, were treated twice a day for 10 days to observe the effect of human recombinant EGF in concentrations of 0.1, 1, 5, 10, 25 ug/g, vehicle only and two controls. The control and the vehicle-only wounds each demonstrated 100% healing time (HT100) of 9.31 +/- 1.34 and 8.5 +/- 1.12 while the wounds treated with EGF ointment with concentrations of 0.1 (HT100 = 6.4 +/- 0.71), 1 (HT100 = 5.2 +/- 0.63), 5 (HT100 = 5.8 +/- 0.85), 10 (HT100 = 7.1 +/- 1.45) and 25 ug/g (HT100 = 7.4 + 0.57) demonstrated significant reduction in time to achieve re-epithelialisation. Among the EGF-treated wounds, the wounds treated with EGF concentrations of 1 and 5 ug/g achieved the fastest re-epithelialisation with evidence of substantial increase in basal keratinocyte activity observed through Ki-67 activity. In conclusion, this article demonstrates the efficacy of human recombinant EGF in facilitating re-epithelialisation of partial thickness wounds with the most efficient healing found in EGF concentrations of 1 and 5 ug/g.

Expression of matrix metalloproteinases and growth factors in diabetic foot wounds treated with a protease absorbent dressing

Wound healing in diabetes is impaired, and nonhealing ulceration represent clinically relevant complications. Persistently high levels of matrix metalloproteases (MMPs) contribute to wound chronicity. Thus, the topical use of protease inhibitors might influence wound healing and promote transition from a chronic to an acute wound.

METHODS

In this study, 33 patients with chronic diabetic foot lesions (stage 2a of the University of Texas Wound Classification system) were included. Fifteen patients received redundant "good standard wound care." In addition, 18 patients were treated with a protease inhibitory modulating matrix (the OCR/collagen Promogran matrix, Ethicon) with dressings changed on a daily basis. Prior to treatment and at 4 and 8 days after treatment, two 3-mm punch biopsies were taken from the center of the wounds and analyzed using ELISA techniques for MMPs, tissue inhibitor of MMP-2 (TIMP-2), and interleukin-1beta (IL-1beta) levels. In addition, mRNA levels of MMPs as well as IL-1beta and TNF-alpha were detected using quantitative real-time polymerase chain reaction (TaqMan, Applied Biosystems, Weiterstadt, Germany).

RESULTS

No differences were detected between both groups and at the three time points for the mRNA levels of MMPs as well as of IL-1beta and TNF-alpha. In addition, MMP levels in wound tissue (analyzed by ELISA) were also not significantly different between both groups. However, IL-1beta was increased on day 8 in the treatment group (P=.01) only. Interestingly, we found a significant reduction of the MMP-9/TIMP-2 ratio in the group being treated with the ORC/collagen. These wounds exhibited a more rapid healing rate when treated with the ORC/collagen matrix.

CONCLUSIONS

The local treatment with a protease inhibitor has a beneficial effect on wound healing. In contrast to the data on wound fluid, our study demonstrated for the first time the unaltered mRNA levels of MMPs during treatment with a protease inhibitory modulating matrix. At the cellular level, MMPs were also not statistically different. However, the more relevant ratio of MMP-9/TIMP-2 was decreased in the treatment group. An equally important finding was that we did not detect a compensatory increase in the MMP-RNA expression even though wound size was clearly reduced.

Recombinant human epidermal growth factor (EGF) to enhance healing for diabetic foot ulcers

This paper studies the healing effect of recombinant human epidermal growth factor (EGF) on chronic diabetic foot ulcers. A total of 89 patients (65 male and 24 female) aged from 36 to 82 years (average of 54) enrolled for the prospective, open-label trial, crossover study. Predetermined criteria were used for diagnosis and classification of ulcer. The average duration of ulcer was 6 months (range from 3 to 27 months) prior to study. Upon study, the ulcers were debrided and treated with hydrocolloid or composite dressing depending on the condition of the wound. If treatment effect was minimal using advanced dressing for 3 weeks, patients were crossed over to twice-a-day treatment with 0.005% EGF and advanced dressing. Among the patients, 21 patients showed improvement using hydrocolloid or composite dressing alone and 68 patients were crossed over to treatment with EGF and advanced dressing. In the EGF-treated patients, complete healing was noted in 52 patients within an average of 46 days (range from 2 to 14 weeks). Recurrence was not noted during the 6-month observation. But 5 patients showed new lesions different from the prior site. Sixteen patients required further interventions. This paper suggests that topical treatment with EGF combined with advanced dressing may have positive effects in promoting healing of chronic diabetic foot wounds.

The molecular biology of chronic wounds and delayed healing in diabetes

Wound healing is a complicated and integrated process. Although there is some tolerance in terms of redundancy and interrelated control mechanisms, pushing beyond such limits may contribute to delayed wound healing, and in extreme cases lead to chronic wounds/ulcers and thus potentially to lower extremity amputation. Diabetes is associated with such disruption in wound healing. Research in humans and in animal models has identified a large number of changes associated with diabetes at the molecular level in delayed wound healing and to a lesser extent in chronic diabetic ulcers. Better overall understanding of these changes and how they are interrelated would allow for specifically targeted treatment, thus ensuring improved quality of life for patients and providing savings to the high costs that are associated with all aspects of chronic diabetic ulcers. This review examines the work done at the molecular level on chronic diabetic ulcers, as well as considering changes seen in diabetes in general, both in humans and animal models, that may in turn contribute to ulcer formation.

Acceleration of wound healing in traumatic ulcers by absorbable collagen sponge containing recombinant basic fibroblast growth factor

The objective of this study was to examine the safety and efficacy of topical application of recombinant basic fibroblast growth factor loaded on a kind of absorbable collagen sponge (rbFGF/ACS) in patients with chronic traumatic ulcers. This double-blind controlled trial included 58 patients with chronic traumatic ulcers. The patients were randomized into two groups. After debridement, the wounds were covered with rbFGF/ACS and then bound up with sterile gauze in the rbFGF/ACS group (n = 30), or bound up with petrolatum sterile gauze in the placebo group (n = 28). The complete closure of the wounds was assessed by photography. The wounds that failed to heal were defined as incomplete healing after 3 weeks. Compared with the placebo group, rbFGF/ACS significantly increased the incidence of complete wound closure by 68% (90.0% versus 53.6%, P = 0.0019) after 3 weeks and shortened the time to achieve complete wound closure by 24% (10.6 days versus 13.9 days, P = 0.0171). There was no difference in side effects between the two groups. rbFGF/ACS significantly increased the incidence of complete wound closure, shortened the complete healing time and improved the healing quality of chronic traumatic ulcers. The safety profile in the rbFGF/ACS group was similar to that in placebo group.

Differential effects of PDGF-BB on matrix metalloproteases and cytokine release in fibroblasts of Type 2 diabetic patients and normal controls in vitro

AIMS/HYPOTHESIS

The complex process of wound healing is regulated by various growth factors. The systemic character of diabetes mellitus favors the chronification of diabetic wounds. In this study, the in vitro effects of platelet-derived growth factor (PDGF)-BB on the expression of cytokines and matrix metalloproteases (MMPs) in fibroblasts of Type 2 diabetic patients and healthy controls were investigated.

METHODS

We studied six Type 2 diabetic patients (mean Hba1(c)=7.5%) and six healthy controls. For proliferation studies, cultivated fibroblasts, prepared from biopsies taken from the thigh, were stimulated with different concentrations of PDGF. After 48 h, the expression of MMPs and cytokines was measured. We analysed the mRNA expression by RT-PCR (TaqMan), tissue protein levels by zymography, and cell supernatant levels by ELISA.

RESULTS

Levels of MMP-mRNA were elevated in diabetic fibroblasts compared with healthy controls. At baseline, MMP-2 protein levels were significantly increased in the fibroblast of diabetic patients (P=.019). For MMP-9, a trend towards higher levels (P=.3) was found. After incubation with PDGF, a significant reduction of MMP-9 (P=.01) and MMP-13 (P=.04) was found. Analysis of cytokine release in cell culture supernatant showed elevated levels of interleukin (IL)-8 at baseline conditions. MMP-1 and MMP-2 levels in the supernatant were concentration-dependently reduced.

CONCLUSIONS

This study, for the first time, demonstrates elevated MMPs in cultivated fibroblasts (derived from intact skin and not from an open wound) of diabetic patients compared with healthy controls under in vitro conditions. Therefore, our data support the hypothesis of alterations of wound healing in diabetic patients on the cellular level, reflecting the systemic character of the disease.

Manifestations of cutaneous diabetic microangiopathy

The etiologies of a variety of skin conditions associated with diabetes have not been fully explained. One possible etiological factor is diabetic microangiopathy, which is known to affect the eyes and kidneys in patients with diabetes. There are many mechanisms by which diabetes may cause microangiopathy. These include excess sorbitol formation, increased glycation end products, oxidative damage, and protein kinase C overactivity. All of these processes occur in the skin, and the existence of a cutaneous diabetic microangiopathy has been well demonstrated. These microangiopathic changes are associated with abnormalities of skin perfusion. Because the skin plays a thermoregulatory role, there is significant capillary redundancy in normal skin. In diabetic patients, loss of capillaries is associated with a decrease in perfusion reserve. This lost reserve is demonstrable under stressed conditions, such as thermal stimulation. The associated failure of microvascular perfusion to meet the requirements of skin metabolism may result in diverse skin lesions in patients with diabetes. Many skin conditions peculiar to diabetes are fairly rare. Necrobiosis lipoidica diabeticorum (NLD) and diabetic bullae occur very infrequently as compared with diabetic retinopathy and nephropathy. Conversely, there is a correlation between diabetic microvascular disease and NLD. This correlation also exists with more common skin conditions, such as diabetic dermopathy. This relationship suggests that diabetic microangiopathy may contribute to these conditions even if it is not primarily causal. Clinically, the major significance of diabetic cutaneous microangiopathy is seen in skin ulceration which is very common and has a major impact on diabetic patients. Many factors contribute to the development of diabetic foot ulcers. Neuropathy, decreased large vessel perfusion, increased susceptibility to infection, and altered biomechanics all play a role, but there is no doubt that inadequate small blood vessel perfusion is a major cause of the inability to heal small wounds that eventually results in ulcer formation. The accessibility of skin capillaries makes cutaneous diabetic microangiopathy an attractive model for research on the evolution of microvascular disease in diabetic patients.

How much do we understand about the effects of ageing on healing?

Poor experimental design has contributed to a perceived association of ageing with delayed wound healing. Continuing research on the influence of ageing will allow more focused therapeutic strategies.

LETTER TO THE EDITOR: The Other Side: Failure in Fair and Balanced Reporting

Matrix metalloproteinases (MMPs) and their tissue inhibitors play important roles in the wound-healing process. An imbalance in the expression of these molecules is thought to contribute to the failure of chronic ulcers to heal. We investigated whether a mitogenic bovine whey extract enriched with growth factors modulated the expression and activity of MMP-2 and -9, and the tissue inhibitor of MMP-2 (TIMP-2) in chronic leg ulcers. Wound fluids and biopsies were collected from chronic leg ulcer patients whose ulcers were treated topically for 4 weeks with placebo or mitogenic bovine whey extract at concentrations of 2.5, 10, and 20 mg/mL. The levels of MMP-2 and -9 in wound fluid samples was assessed by gelatin zymography and showed a decrease in active MMP-2 in the 2.5 and 10.0 mg/mL mitogenic bovine whey extract-treated ulcers compared with placebo (p<0.05). Immunohistochemical analysis of ulcer biopsies for MMP-2, -9, and TIMP-2 expression showed a reduction in the number of MMP-2-positive dermal fibroblasts in the mitogenic bovine whey extract-treated ulcers compared with pretreatment biopsies (p<0.05) that persisted over the course of the study. In contrast, a transient increase in the number of MMP-9- and TIMP-2-positive cells was observed in mitogenic bovine whey extract treated ulcer biopsies compared with pretreatment levels (p<0.05). These results show that topical application of mitogenic bovine whey extract was able to modulate the expression of MMP-2, -9, and TIMP-2 in chronic leg ulcers and that its constituent growth factors may have the potential to redress the proteolytic imbalance observed in nonhealing chronic ulcers.

Stimulation of the proliferation of human dermal fibroblasts in vitro by a lipidocolloid dressing

OBJECTIVE

The effect of Urgotul on normal human dermal fibroblast proliferation was studied in vitro and compared with that of two other dressings: Mepitel and Tulle Gras.

METHOD

Proliferation was measured by the extent of thymidine incorporation into the replicating DNA of proliferative fibroblasts in contact with the complete dressing.Additional cell viability and metabolism were evaluated using MTT assay. Morphology and ultrastructure analysis were based on immunolabelling and confocal laser microscopy.

RESULTS

Only Urgotul significantly stimulated thymidine incorporation, generally with a maximal proliferative effect at a contact time of 48 hours. This was confirmed by the observation of a greater number of dividing cells (mitotic cells) than in the control cultures. No cytotoxicity was observed following treatment with this dressing. Cells exhibited normal structural and ultrastructural features.

CONCLUSION

Fibroblasts play a key role in dermal wound repair. The ability of Urgotul to promote fibroblast proliferation could explain its efficiency in the healing process of acute and chronic wounds.

DECLARATION OF INTEREST

This study was supported by Urgo Laboratories.

Plateletpheresis does not cause long-standing platelet-derived growth factor release into the donor blood

BACKGROUND

Recently, long-standing elevations of soluble growth factors released from platelets (PLTs) after contact with artificial surfaces during dialysis were described. They could be jointly responsible for the high frequency of death from cardiovascular diseases in dialysis patients. There are no comparable data on the extent and the duration of a growth factor release by plateletpheresis procedures.

STUDY DESIGN AND METHODS

A total of 37 plateletpheresis procedures were performed with two different devices. PLT-derived growth factor (PDGF) isoform AB, transforming growth factor (TGF)-beta1, and beta-thromboglobulin (beta-TG) were measured in the donors' plasma samples, and PLT activation and function were measured by cytometry and aggregometry before and after plateletpheresis and 1 and 24 hours later.

RESULTS

Before apheresis, the following mean plasma levels were found: beta-TG, 98.6 +/- 37.3 IU per mL; PDGF-AB, 71.5 +/- 38.5 pg per mL; and TGF-beta1, 2.24 +/- 0.80 ng per mL. At the end of the apheresis procedures, the mean PDGF-AB level had increased by a factor of 1.8 (p < 0.05). One hour later, the mean PDGF-AB level had normalized again. No significant change in the levels of beta-TG and TGF-beta1 was found by the apheresis procedures. There was no influence of the blood cell separator type on the results.

CONCLUSION

Only a slight and rapidly reversible increase in soluble PDGF-AB was found during plateletpheresis and no increase in soluble TGF-beta1 and beta-TG was found. This change should not be harmful to the donor.

Leukemia inhibitory factor-transfected embryonic fibroblasts and vascular endothelial growth factor successfully improve the skin substitute wound healing by increasing angiogenesis and matrix production

BACKGROUND AND OBJECTIVE

The combined application of cytokines on embryonic fibroblasts and dermal substitute were studied for optimal skin defect coverage. The mechanism of combined treatment of leukemia inhibitory factor (LIF)-transfected embryonic fibroblasts and vascular endothelial growth factor (VEGF) were elucidated and subsequently the in vivo applications of both were tested in an artificial dermal substitute.

METHODS

Mouse embryonic fibroblast cells, BALB-3T3, were stably transfected with mouse full-length LIF cDNA and added to various doses of VEGF for detection of signaling interaction. LIF-transfected cells and VEGF treatment were tested with pig-tendon derived collagen dermal substitute in the backs of BALB/c male mice up to for 14 days.

RESULTS

LIF-transfected cells as well as vector-transfected fibroblasts significantly proliferated by 1, 10, or 100 ng VEGF on days 3 and 5. Erk mitogen-activated protein (MAP) kinase phosphorylation was observed from 1 to 30 min in LIF-transfected and 10 ng of VEFG, and 1 to 60 min in LIF-transfected and 100 ng VEFG treatments. The cellular fibronectin levels also increased in LIF-transfected cells with 10 and 100 ng VEGF additions. In in vivo analyses, LIF-transfected embryonic fibroblasts with 50 microg of VEGF markedly enhanced collagen I expression and CD34 angiogenic marker on days 7 and 14.

CONCLUSION

LIF transfection and VEGF treatment enhanced phosphorylated-Erk-MAP kinase in vitro. In vivo study revealed that the combined application of LIF transfection of embryonic fibroblasts with an angiogenic factor such as VEGF in the template of a dermal substitute induced greater skin collagen production and angiogenesis in the dermal substitute.

Platelet-rich plasma enhances human osteoblast-like cell proliferation and differentiation

PURPOSE

Platelet-rich plasma (PRP) is widely used to promote tissue healing. However, there is no concrete evidence for the biological effects of PRP. This study evaluated the biological effects of PRP on the proliferation and differentiation of 2 human osteoblast-like cell lines.

MATERIALS AND METHODS

Human osteosarcoma cell lines HOS and SaOS-2 were used in this study. PRP was prepared from freshly drawn human venous blood containing a large number of platelets. The MTT assay was used to examine the effects of PRP on osteoblast viability. To evaluate the growth and differentiation, alkaline phosphatase activity was assessed and the expression of procollagen type I, osteopontin, and osteoprotegerin mRNA was measured using semiquantitative reverse transcriptase-polymerase chain reaction. Further, core binding factor alpha 1 (cbfa1/Runx2/AML3/PebpalphaA), a critical regulator of osteoblast differentiation, was also determined.

RESULTS

The administration of PRP enhanced the viability of HOS and SaOS-2 cells in a dose-dependent manner. Alkaline phosphatase activity was suppressed during the cell growth phase, but was strongly enhanced when the cells reached confluence. Semiquantitative reverse-transcription polymerase chain reaction analysis showed that PRP enhanced the levels of procollagen type I, osteopontin, osteoprotegerin, and core binding factor alpha 1 (cbfa1) mRNA.

CONCLUSION

These results suggest that PRP has a favorable effect on human osteoblast-like cells, and acts both to enhance bone regeneration and as an activator in wound healing.

Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.

Epitheliotrophic capacity of a growth factor preparation produced from platelet concentrates on corneal epithelial cells: a potential agent for the treatment of ocular surface defects?

BACKGROUND

Topical application of serum eye drops has been reported to accelerate healing of persistent ocular surface defects. It is supposed that growth factors in serum support the wound healing process. Platelets (PLTs) are rich in growth factors and easily available as PLT concentrates (PCs) from blood banks. Therefore, growth factor preparations from PCs may serve as a new and superior therapeutic agent for such defects.

STUDY DESIGN AND METHODS

After thrombin stimulation for growth factor release, the cell-free supernatant (PLT releasate) of washed PCs (n = 8) was analyzed for epitheliotrophic factors and its wound healing capacity in comparison to serum (n = 8). Human corneal epithelial cells were used as a model to investigate cell growth, migration, and differentiation in response to both blood products.

RESULTS

PLT releasate contains more epithelial growth factor, PLT-derived growth factor, and transforming growth factor-beta, but less hepatocyte growth factor, fibronectin, and vitamins. Cell growth was significantly better in response to PLT releasate. Migration and differentiation were slightly better supported by serum.

CONCLUSION

Possibly owing to its high content of growth factors, PLT releasate has a distinct superior effect on cell growth. Stimulation of migration and differentiation was slightly inferior but still acceptable. PLT releasate could therefore be a novel treatment option for ocular surface defects.

Effect of an EGF-cancer vaccine on wound healing and inflammation models

BACKGROUND

Epidermal growth factor (EGF) and its receptor (EGF-R) are attractive targets for cancer immunotherapy. Tolerance has been broken with an EGF-vaccine and antibodies against EGF have been produced in animals and in cancer patients. EGF also plays an important role in the inflammation stage of wound healing. Because this therapeutic approach may be of importance after surgery procedures in cancer patients, we decided to investigate the possible role of the EGF-vaccine in the croton-oil-induced ear edema and in the wound healing experimental animal models.

MATERIALS AND METHODS

Mice were immunized with an EGF-vaccine by intramuscular injections and serum titers against EGF were measured through ELISA techniques. Control animals received saline.

RESULTS

Immunized mice produced antibodies against EGF while no antibody titers could be measured in control animals. Croton oil applied to the inner ear surface of EGF-vaccine treated mice caused a 61.3% lower ear punch weight and a 60.2% lower myeloperoxidase activity than control mice. In the EGF-vaccine treated animals, planimetry measurements and histological analysis did not led to significant impairment in tissue repair.

CONCLUSIONS

The EGF-vaccination in mice decreased the normal croton-oil-induced inflammation response, without apparent impairment in tissue healing.

Synthetic Biocompatible Cyclodextrin-Based Constructs for Local Gene Delivery to Improve Cutaneous Wound Healing

The localized, sustained delivery of growth factors for wound healing therapy is actively being explored by gene transfer to the wound site. Biocompatible matrices such as bovine collagen have demonstrated usefulness in sustaining gene therapy vectors that express growth factors in local sites for tissue repair. Here, new synthetic biocompatible materials are prepared and shown to deliver a protein to cultured cells via the use of an adenoviral delivery vector. The synthetic construct consists of a linear, beta-cyclodextrin-containing polymer and an adamantane-based cross-linking polymer. When the two polymers are combined, they create an extended network by the formation of inclusion complexes between the cyclodextrins and adamantanes. The properties of the network are altered by controlling the polymer molecular weights and the number of adamantanes on the cross-linking polymer, and these modifications and others such as replacement of the beta-cyclodextrin (host) and adamantane (guest) with other cyclodextrins (hosts such as alpha, gamma, and substituted members) and inclusion complex forming molecules (guests) provide the ability to rationally design network characteristics. Fibroblasts exposed to these synthetic constructs show proliferation rates and migration patterns similar to those obtained with collagen. Gene delivery (green fluorescent protein) to fibroblasts via the inclusion of adenoviral vectors in the synthetic construct is equivalent to levels observed with collagen. These in vitro results suggest that the synthetic constructs are suitable for in vivo tissue repair applications.

Sample preparation technique and white cell content influence the detectable levels of growth factors in platelet concentrates

BACKGROUND AND OBJECTIVES

Autologous platelet concentrate (PC) is applied locally to improve wound healing and tissue repair. Previous measurements of the growth factor content of platelets have given conflicting results. To date, there is no information on the influence of different preanalytical sample-preparation methods on the detectable amount of growth factors.

MATERIALS AND METHODS

We measured the level of growth factors in PCs obtained by plateletpheresis and by leukapheresis. We subjected aliquots of these components to six different preparation methods: freezing/thawing once or twice; dissolution in 0.5% Triton-X-100; and clot formation by the addition of calcium and thrombin with subsequent incubation for 1 h, for 24 h, or for 1 h followed by freezing and thawing.

RESULTS

In samples dissolved in Triton-X-100, higher levels of growth factors were detected than in the other specimens. In comparison to clot formation, freezing and thawing platelets twice was equivalent with respect to the release of platelet-derived growth factor (PDGF) but superior with respect to the release of transforming growth factor-beta1 (TGF-beta1). Overall, mean levels of 4.77 x 10(-16) g of PDGF-AB, 2.2 x 10(-17) g of PDGF-BB, and 2.41 x 10(-16) g of TGF-beta1 were found per single human platelet in white blood cell (WBC)-poor samples dissolved in Triton-X-100.

CONCLUSIONS

Dissolving PC in Triton-X-100 releases maximum quantities of growth factors from platelets. The release of each growth factor by any sample preparation method should be investigated and interpreted separately. The preanalytical sample-preparation method, as well as the platelet and WBC content, influence the measurable levels of growth factors in PCs. The results implicate the need to correct, considerably upwards, previous estimations of the PDGF content of platelets.

Chicken extract affects colostrum protein compositions in lactating women

This study investigated the effect of supplementation with chicken extract on plasma and colostrum protein compositions in lactating women. Thirty healthy pregnant women were evenly divided into the control (n = 15) or chicken extract (CE) group (n = 15). The CE group was given one bottle (70 mL/bottle) of chicken extract three times a day to provide 18 g protein from the 37th week pregnancy to 3 days postpartum. All women in the CE group consumed chicken extract at least for 2 weeks (18 +/- 5 days). High protein supplement was restricted in the control group. Blood samples were collected during the 37th week pregnancy and 3-day postpartum, and milk was collected during 3-day postpartum. The results showed that plasma total protein was significantly lower by 14% in the CE group compared with that in the control group during 3-day postpartum. Plasma epidermal growth factor (EGF) significantly elevated by 236% during 3-day postpartum compared with those during the 37th week pregnancy in the CE group. The levels of lactoferrin, EGF, and transforming growth factor-beta2 (TGF-beta2) in colostrum significantly increased by 34%, 62%, and 196%, respectively, in the CE group compared with those in the control group. However, the levels of total protein, casein, lactalbumin, and secretory immunoglobulin A in colostrum did not significantly differ between two groups. Therefore, supplementation with chicken extract increased colostrum levels of lactoferrin, EGF, and TGF-beta2, which are important for the growth and immune functions of the infants, in lactating women.

Adenovirus Encoding Human Platelet-Derived Growth Factor-B Delivered in Collagen Exhibits Safety, Biodistribution, and Immunogenicity Profiles Favorable for Clinical Use

We have developed a therapeutic approach to wound repair involving immobilization of gene transfer vectors within biocompatible matrices (gene-activated matrix, or GAM). The matrix also serves as a scaffold for cellular in-growth and subsequent gene uptake and expression. An adenoviral vector encoding human platelet-derived growth factor-B delivered in collagen (AdPDGF-B/GAM) has demonstrated efficacy in models of wound repair. The safety, biodistribution, and immunogenicity profiles of AdPDGF-B/GAM were examined using a rabbit dermal wound model. Four weekly doses at 1 x 10(10) and 1 x 10(11) viral particles/cm2 of wound surface stimulated dose-related increases in granulation tissue formation and cell proliferation. In situ hybridization and immunostaining demonstrated concordant expression of human PDGF-B mRNA and protein. No treatment-related changes in hematology, serum chemistry, or histopathology were observed. Although AdPDGF-B DNA and PDGF-B mRNA were detected in wounds and axillary lymph nodes of treated animals, no AdPDGF-B was detected in blood or other organs. No immunologic responses against collagen were observed; however, as expected, IgG responses to AdPDGF-B and human PDGF-BB protein were detected. In adenovirus-preimmunized rats, attenuation of the wound healing response was modest (approximately 16%). Collectively, these observations indicate that repeat doses of AdPDGF-B/GAM are well tolerated and lead to robust, localized tissue repair.

Moist exposed therapy: an effective and valid alternative to occlusive dressings for postlaser resurfacing wound care

BACKGROUND

Laser resurfacing has now become an accepted and important component of facial rejuvenation. With the introduction of computerized scanning systems, the actual laser resurfacing technique has been greatly simplified; however, the final outcome still depends to a large extent on the efficiency of the postlaser wound care in promoting wound healing and preventing early and late complications. It has been repeatedly confirmed that a moist environment is the single most important external factor affecting the rate of re-epithelialization. Occlusive moisture-retentive dressings, however, are difficult to apply and maintain in position and may as well be complicated by serious infections.

OBJECTIVE

Moist exposed burn ointment has been shown to maintain adequate moisture for optimal healing by frequent ointment application without the need for a secondary overlying dressing. It would be ideal for postoperative laser care.

METHODS

Twenty-eight consecutive patients treated with coherent ultrapulse CO2 laser in Toulouse, France, were included in the trial. Moisture-retentive ointment was applied over the treated areas every 4 to 6 hours. Healing was assessed clinically and with repeated transepidermal water loss measurements. Swab cultures were taken, and pain was evaluated with a visual analog scale. Colorimetric analysis of pictures taken was statistically compared with picture analysis of 20 patients treated earlier with an occlusive dressing.

RESULTS

Uneventful timely healing occurred in all patients with minimal pain and discomfort. Healing with moist exposed therapy resulted in faster recovery of cutaneous erythema, as evidenced by colorometry.

CONCLUSION

Moist exposed burn ointment application can be safely considered a good and valid alternative to occlusive dressings for postoperative laser care.

Effect of Platelet-Rich Plasma on the Peri-implant Bone Response:

Platelet-rich plasma (PRP) is used as a source of growth factors to stimulate and accelerate bone formation and soft tissue healing. The use of PRP in bone regeneration, both around dental implants and in periodontic treatments, has become particularly appealing. The aim of this study was to evaluate the effect of PRP in an experimental model of osteogenesis around laminar implants. Fifteen male Wistar rats, weighing 90 +/- 10 g, were used in this study. One milliliter of blood was obtained from each animal by intracardiac puncture and transferred into Eppendorf tubes containing 10% sodium citrate. The tubes were centrifuged at 1500 rpm for 15 minutes and PRP was prepared. The laminar test was used to evaluate the bone peri-implant response. PRP and a titanium laminar implant were introduced into the right tibia (Ti/PRP group), whereas the left tibia (control) received only a laminar implant (Ti group). Thirty days postimplantation, the tibiae were resected, radiographed, and processed for embedding in acrylic resin. Ground sections (50 microm) were stained with toluidine blue. The peri-implant bone volume was evaluated histomorphometrically. Statistical analysis of the data was performed. The amount of newly formed bone in the Ti/PRP group (30 +/- 7 cm) was significantly greater than in the Ti group (16 +/- 3 cm). A greater volume of peri-implant bone was observed when PRP was used in the laminar implant test model.

Bilaterally increased VEGF-levels in muscles during experimental unilateral callus distraction

Angiogenesis is essential for wound healing and proliferative processes such as bone formation and repair. Since increased expression of the vascular endothelial growth factor (VEGF) stimulates bone formation, it can be hypothesized that surgical procedures leading to a systemic increase of VEGF for instance during wound healing, influence enchondral ossification processes and might be responsible for observed growth phenomena during callus distraction. To study the mechanisms of angiogenesis in soft tissue during unilateral callus distraction, lengthening of the right tibia was performed in 12 beagles. After osteotomy, application of a ring fixator and after five latency days, distraction was started for 25 days. A control group of four additional beagles underwent no surgical procedure. Subsequent to the distraction period (Group A), muscle samples from six beagles were taken from the distracted side (ds) and the contralateral non-distracted side (n-ds), six beagles underwent an additional consolidation period of 25 days (Group B). Samples were analyzed for VEGF, VEGFR-1 and VEGFR-2 mRNA expression using real-time PCR and protein expression using Western Blot analysis. Muscles from both extremities showed significantly increased expression of VEGF and its cognate receptors VEGFR-1/2. Expression decreased significantly after the consolidation period, whereby the level at the non-distracted side decreased more than the level at the distracted side. Interestingly VEGF and VEGFR-1 levels at the non-distracted side were significantly higher than at the distracted side. In contrast VEGFR-2, the receptor that mediates endothelial cell proliferation, showed higher levels at the distracted than at the non-distracted side. These findings indicate that callus distraction results not only in locally increased expression of VEGF and its receptors, but leads also to increased VEGF and VEGFR-1/2 levels at distant sides and might therefore be responsible for the observed growth phenomena during callus distraction.

Evaluation of the mechanism of vascular endothelial growth factor improvement of ischemic flap survival in rats

This study evaluated the effects of exogenous vascular endothelial growth factor (VEGF) on the regulation of cytokines in a rat dorsal ischemic skin flap model. Exogenous VEGF (1 microg/ml) was injected subdermally into the flaps of 12 rats before the flaps were sutured back in place. Another 12 rats with flaps received saline injections, as a control group. Biopsy specimens were obtained from the flaps treated with VEGF or saline solution, at positions 2.5, 5.5, and 8.5 cm from the distal edge of the flaps, at 12 hours (n = 6 for each group) and 24 hours (n = 6 for each group) after suturing of the flaps. Expression of cytokine, growth factor, and inducible nitric oxide synthase was measured. The results demonstrated that expression of tumor necrosis factor-alpha and nitric oxide synthase in the distal part of the VEGF-treated flaps was significantly decreased, compared with the control values, at 12 and 24 hours postoperatively. It was concluded that administration of exogenous VEGF could protect flaps from ischemia-reperfusion injury through the regulation of proinflammatory cytokines and the inhibition of cytotoxic nitric oxide production.

Growth factor profiles in intraperitoneal drainage fluid following colorectal surgery: relationship to wound healing and surgery

Cytokines and growth factors are important at each stage of wound healing. This study aims to determine the changing profiles of these factors in intraperitoneal drainage, acute wound fluid, following colorectal surgery, and to correlate levels to wound healing and surgical outcomes. Acute wound fluid samples (n = 52 patients) were collected daily from postoperative day 1 until drain removal. Levels of cytokines (interleukins-6 and -1beta and tumor necrosis factor-alpha) and epidermal growth factor, platelet-derived growth factor, vascular endothelial derived growth factor, basic fibroblast growth factor, and transforming growth factor-beta1 were determined by enzyme-linked immunosorbent assay. A significant negative correlation emerged between the levels of interleukin-6, epidermal growth factor, platelet-derived growth factor, and basic fibroblast growth factor and the postoperative day, e.g., basic fibroblast growth factor : day 1, 695, median (29-2,806, range) pg/ml; day 2, 249 (1-1,784); day 3, 94 (0-722); day 7, 22 (0-326) (p < 0.05, Spearman's correlation). Levels appeared to relate to the stage of wound healing. Several factors, in particular interleukin-1beta and tumor necrosis factor-alpha levels, correlated with surgical outcomes such as the need for a defunctioning stoma and/or postoperative complications. Cytokines and growth factors are involved in normal wound healing, and their levels in acute wound fluid may act as markers of wound healing and surgical outcome.

Regulation of wound healing by growth factors and cytokines

Cutaneous wound healing is a complex process involving blood clotting, inflammation, new tissue formation, and finally tissue remodeling. It is well described at the histological level, but the genes that regulate skin repair have only partially been identified. Many experimental and clinical studies have demonstrated varied, but in most cases beneficial, effects of exogenous growth factors on the healing process. However, the roles played by endogenous growth factors have remained largely unclear. Initial approaches at addressing this question focused on the expression analysis of various growth factors, cytokines, and their receptors in different wound models, with first functional data being obtained by applying neutralizing antibodies to wounds. During the past few years, the availability of genetically modified mice has allowed elucidation of the function of various genes in the healing process, and these studies have shed light onto the role of growth factors, cytokines, and their downstream effectors in wound repair. This review summarizes the results of expression studies that have been performed in rodents, pigs, and humans to localize growth factors and their receptors in skin wounds. Most importantly, we also report on genetic studies addressing the functions of endogenous growth factors in the wound repair process.

Adeno-associated viral vector-mediated human vascular endothelial growth factor gene transfer stimulates angiogenesis and wound healing in the genetically diabetic mouse

AIMS/HYPOTHESIS

We studied the gene therapy efficacy of diabetes-associated wound healing disorder with an adeno-associated virus (AAV) vector expressing the 165-amino acid isoform of human vascular endothelial growth factor-A (VEGF-A) by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJ db+/db+ mice and their normal littermates ( db+/+m).

METHODS

Animals were randomized to receive intradermally into the wound edges either rAAV-LacZ (a control gene), or rAAV-VEGF165. Animals were killed on different days (7 and 14 days after skin injury) and wounded skin tissues were used for gene marker studies, histological evaluation and immunohistochemistry, and wound breaking strength analysis. Furthermore we studied the VEGF mature protein in the wounds.

RESULTS

We found that AAV vectors are highly efficient for gene transfer to the mouse skin, displaying an exquisite tropism for the panniculus carnosus by using the beta-galactosidase activity assay. We confirmed the increased expression of the angiogenic factor at day 7 by measuring the wound content of the mature protein. Delivery of VEGF165 to incisional skin wounds of diabetic mice resulted in a remarkable induction of new vessel formation with consequent improvement in the wound healing process. The rAAV-VEGF165 gene improved wound healing in diabetic mice through the stimulation of angiogenesis, reepithelization, synthesis and maturation of extracellular matrix. Moreover the recombinant AAV encoding the human VEGF165 increased the breaking strength of the wound and enhanced the wound content of VEGF.

CONCLUSION/INTERPRETATION

Our study suggests that VEGF gene transfer might represent a new approach to treat wound healing disorders associated with diabetes.

Effect of recombinant adeno-associated virus vector-mediated vascular endothelial growth factor gene transfer on wound healing after burn injury

OBJECTIVE

The purpose of this study was to investigate the effect of recombinant adeno-associated viral (rAAV) vector-mediated human vascular endothelial growth factor (VEGF165) transfer on experimental burn wounds.

DESIGN

Randomized experiment.

SETTING

Research laboratory.

SUBJECTS

C57BL/6 male mice weighing 25-30 g.

INTERVENTIONS

Mice were immersed in 80 degrees C water for 10 secs to achieve a partial-thickness scald burn. Animals were randomized to receive at two injection sites on the edge of the burn either 1011 copies of the rAAV-VEGF165 or the vector carrying the control and inert gene beta-galactosidase (rAAV-LacZ). On day 14 the animals were killed. Burn areas were used for histologic examination, evaluation of VEGF expression (immunohistochemistry) and VEGF wound content (enzyme-linked immunosorbent assay), determination of wound nitrite, and measurement of messenger RNA (mRNA) for endothelial and inducible nitric oxide synthase (eNOS and iNOS).

MEASUREMENTS AND MAIN RESULTS

rAAV-VEGF165 increased epithelial proliferation, angiogenesis, and maturation of the extracellular matrix. Furthermore, gene transfer enhanced VEGF expression, studied by immunohistochemistry, and the wound content of the mature protein (rAAV-LacZ, 11 +/- 5 pg/wound; rAAV-VEGF165, 104 +/- 7 pg/wound). Moreover, VEGF165 gene transfer increased wound content of nitrate. Finally, rAAV-VEGF165 administration enhanced the messenger RNA for eNOS (rAAV-VEGF165, 1.1 +/- 0.2 relative amount of eNOS mRNA; rAAV-LacZ, 0.66 +/- 0.3 relative amount of eNOS mRNA) and iNOS (rAAV-VEGF165, 0.8 +/- 0.09 relative amount of iNOS mRNA; rAAV-LacZ, 0.45 +/- 0.05 relative amount of iNOS mRNA).

CONCLUSION

Our study suggests that rAAV-VEGF gene transfer may be an effective therapeutic approach to improve clinical outcomes after thermal injury.

A novel controlled drug-delivery system for growth hormone applied to healing skin wounds in diabetic rats

Controlled release systems for drugs, hormones and growth factors can be particularly useful in tissue repair processes. These systems act as a biodegradable support containing the substance to be delivered, allowing their gradual release. In the past years, the local application of growth factors has acquired special relevance as a therapeutic option for use in subjects who show deficient tissue scarring, the hormone dose being the limiting factor for its success. In this study, the in vitro biocompatibility of a copolymer formed by vinylpyrrolidone and 2-hydroxyethyl methacrylate, used as an administration vehicle for hGH, was evaluated. The system was then tested in vivo in terms of its capacity for healing incisional wounds in healthy and diabetic rats. For the in vitro studies, polymer and hormone degradation rates were determined, and polymer biocompatibility was evaluated in fibroblast cultures. In the in vivo experiments, an incision was made in the back of the animals, and polymers discs with/without hGH, were introduced in the aperture. Morphological, immunohistochemical and morphometric evaluations were performed on wound tissue specimens 3-10 days after surgery. In vitro, the polymer was found to be biodegradable and showed no toxic effects on fibroblasts, the hormone being slowly released to the culture medium. In untreated diabetic rats, a delayed skin scarring and cell response were observed, compared to that noted in healthy animals. Skin closure, keratinisation and fibrosis occurred earlier in the presence of the polymer-hGH system. The use of this co-polymer as an administration vehicle for hGH improves the wound scarring process in the pathological setting of diabetes.

Wound healing and diabetes mellitus

Diabetes mellitus is one of the major contributors to chronic wound healing problems. When diabetic patients develop an ulcer, they become at high risk for major complications, including infection and amputation. The pathophysiologic relationship between diabetes and impaired healing is complex. Vascular, neuropathic, immune function, and biochemical abnormalities each contribute to the altered tissue repair. Despite treatment of these chronic wounds, which involves tight glucose control and meticulous wound care, the prognosis for their healing is quite poor. Newer modalities that deliver natural or engineered growth factors show a great deal of promise. All of the studies clearly show the continued need for well-controlled clinical trials.

Skin blood flow response in the rat model of wound healing: expression of vasoactive factors

BACKGROUND

Although the microvascular blood flow response to wounding is predominantly vasodilation at skin sites with nutritive capillary perfusion (NUTR), there is a significant vasoconstrictive response at sites with high arteriovenous perfusion (AV). There may be a difference between NUTR and AV sites in the vasoactive factors which mediate the blood flow response to wounding. We measured the levels of mRNA expression of several potential mediators of the blood flow response to assess this possible difference.

MATERIALS AND METHODS

We measured skin blood flow at wounds placed at the back, a NUTR site, and at the paw, an AV site, in 12 Wistar Kyoto rats. Measurements were performed at baseline and then at 7 days post wounding. There was a significant increase in blood flow at back wound sites, with a rise from 4.1 +/- 0.3 ml/min/100 g to 9.8 +/- 1.9 ml/min/100 g. At the undisturbed wound perimeter, outside the zone of granulation tissue, flow rose to 7.3 +/- 1.1 ml/min/100 g. At the paw wound site, Day 0 flow was 8.8 +/- 0.8 ml/min/100 g. At 7 days, there was a significant decrease in flow at wound center to 5.5 +/- 0.5 ml/min/100 g. We measured the levels of inducible nitric oxide synthetase (iNOS), endothelin, endothelin receptor, vascular endothelial growth factor (VEGF), and keratinocyte growth factor (KGF) gene mRNAs using reverse transcriptase PCR.

RESULTS

There was a 10-fold increase in NOS mRNA in granulation tissue of both wounds on Day 7. There was a lesser but still substantial increase in the wound perimeter tissue. Levels of endothelin mRNA in the wound and wound perimeter were significantly lower at the paw than at the back. At baseline, the level of endothelin receptor B (ETrB) mRNA was greater at the back than at the paw. Wounding resulted in a substantial increase in EtrB mRNA levels in granulation tissue, reaching the same level at the back and paw wounds. There was also a substantial rise in EtrB mRNA levels at the paw wound perimeter, so that there was a reversal of the baseline condition, with paw levels actually surpassing the levels at the back perimeter.

CONCLUSIONS

Thus, we have found significant changes in mediators both of vasoconstriction and vasodilation affecting the healing wound. These changes affect NUTR and AV sites in different ways. These results demonstrate the complexity of the regulatory processes controlling microvascular blood flow in wound healing.

Critiquing clinical research of new technologies for diabetic foot wound management

Healing the diabetic foot ulcer has been a challenge. Over the past 20 years, researchers have gained significant knowledge about the biochemical mechanisms that underlie the process of wound repair. A literature review of the latest advanced technologies, devices, and therapies is provided. In addition, clinical decision-making insights for clinicians to evaluate research and to assist in choosing the correct modality for each of their diabetic foot ulcer patients are discussed.

Angiogenesis induction and regression in human surgical wounds

Angiogenesis in human wound healing is not well characterized, with only sparse information available regarding the maturation and fate of vessels formed as a consequence of human tissue repair. Therefore, this study aimed to establish the temporal profile of angiogenesis in human dermal wounds. Punch biopsies were obtained under local anesthesia from 45 patients following breast surgery. Scars were predominantly between 2 and 52 weeks after surgery but in five patients were > 52 weeks. Control samples were taken from breast skin peroperatively (n = 24). Quantification of vascular density was performed using the Chalkley grid, following antibody staining for platelet endothelial cell adhesion molecule. Vascular patterns, wound cellularity and morphology were also determined. Cumulative microvessel density was increased in all samples when compared to controls (p < 0.05). This was greatest 2 to 24 weeks following surgery 17 (15-21) median (range), decreased thereafter, but remained elevated compared to controls even in the mature scars > 52 weeks. Control tissue showed an ordered morphological arrangement of dermal structures, collagen, and elastic fibers. However, wounding resulted in marked structural distortion for up to 15 weeks. In conclusion, this study shows for the first time the prolonged persistence of both microvessels and cellularity (fibroblastic cells), in addition to structural distortion in human dermal wounds, which is in contrast to previous in vitro and in vivo studies.

The management of surgical wounds in a community setting

Many patients are now having minor surgical procedures carried out in the community and those patients who undergo surgery in hospital are likely to be discharged earlier due to increasing pressure on hospital beds. This article discusses the management of surgical wounds healing by both primary and secondary closure, in the community setting. Understanding the complex process of wound healing is essential if nurses are to recognize abnormalities and select appropriate treatments for patients. The stages of wound healing will be discussed in detail, including the patient's presentation. Factors that influence this process within the patient (e.g. age, nutrition, medication and pain) and those at the wound bed (e.g. exudate, tissue type and infection) will be highlighted. Choosing the correct type of surgical wound dressing for the type of wound can contribute to wound healing, patient comfort and the cost-effectiveness of treatment. Factors that need to be taken into consideration when choosing a dressing will be outlined and suggestions made for the type of dressings that would be most appropriate. The importance of accurate and detailed documentation will be highlighted as part of this process.

Recombinant AAV vector encoding human VEGF165 enhances wound healing

Delivery of therapeutic genes represents an appealing possibility to accelerate healing of wounds that are otherwise difficult to treat, such as those in patients with metabolic disorders or infections. Experimental evidence indicates that in such conditions potentiation of neo-angiogenesis at the wound site might represent an important therapeutic target. Here we explore the efficacy of gene therapy of wound healing with an adeno-associated virus (AAV) vector expressing the 165 amino acid isoform of vascular endothelial growth factor-A (VEGF-A). By gene marker studies, we found that AAV vectors are highly efficient for gene transfer to the rat skin, displaying an exquisite tropism for the panniculus carnosus. Gene expression from these vectors is sustained and persistent over time. Delivery of VEGF165 to full thickness excisional wounds in rats resulted in remarkable induction of new vessel formation, with consequent reduction of the healing time. Histological examination of treated wounds revealed accelerated remodeling of epidermis and dermis, with formation of a thick granular layer, containing numerous newly formed capillaries, as well as vessels of larger size. These data underline the importance of neo-angiogenesis in the healing process and indicate that VEGF gene transfer might represent a novel approach to treat wound healing disorders.

Augmentation of wound healing with translation initiation factor eIF4E mRNA

BACKGROUND

Initiation of translation is the rate-limiting step in protein synthesis; eIF4E increases translational efficiency by facilitating ribosome scanning. eIF4E is present in cells in rate-limiting amounts; chronic overexpression of eIF4E causes cell transformation by upregulating growth-related proteins. Biolistic delivery of epidermal growth factor (EGF) increases wound healing; transiently increasing wound eIF4E levels with biolistic mRNA transmission may further augment wound healing without oncogenesis.

PATIENTS AND METHODS

Midline fascial wounds were created in rats and biolistically treated with gold particles carrying mRNA encoding for hEGF with or without eIF4E prior to suture closure; control animals received blank bullets. The animals were sacrificed at 7 or 14 days for determination of peak wound bursting strength on a tensiometer. Results are expressed as means +/- standard deviation; statistics were via analysis of variance.

RESULTS

[Table: see text].

CONCLUSIONS

Simultaneous biolistic delivery of EGF mRNA with eIF4E mRNA significantly increases wound breaking strength compared to that in control animals or treatment with EGF mRNA alone without risk of cellular transformation. Further studies of translational activation to augment wound healing are warranted.

Stress-induced susceptibility to bacterial infection during cutaneous wound healing

Psychological stress delays wound healing and decreases immune/inflammatory responses required for bacterial clearance. To determine if stress increases the susceptibility to wound infection, female SKH-1 mice were subjected to restraint stress (RST) beginning 3 days prior to the placement of cutaneous wounds. Viable bacteria were quantified from harvested wounds. RST delayed healing by 30% and caused a 2- to 5-log increase in opportunistic bacteria (e.g., Staphylococcus aureus) when compared to wounds from control animals (p <.05). By day 7, 85.4% of the wounds from RST mice had bacterial counts predictive of infection compared to 27.4% from control mice (p <.001). To assess the role of RST-induced glucocorticoids in bacterial clearance, mice were treated with the glucocorticoid receptor antagonist RU486. RU486 reduced opportunistic bacteria by nearly 1 log in wounds from RST mice (p <.05). Thus, stress impairs bacterial clearance during wound healing, resulting in a significant increase in the incidence of opportunistic infection.

Becaplermin: recombinant platelet derived growth factor, a new treatment for healing diabetic foot ulcers

Chronic or non-healing lower extremity ulcerations in diabetics are a significant cause of morbidity and mortality, and account for a large proportion of the financial burden related to the care of diabetics. Lower extremity ulcerations develop primarily as a consequence of neuropathy and the goal in addressing any wound is to re-establish tissue integrity as soon as possible. The healing of wounds is a complex procedure involving multiple growth factors, some of which have multiple effects on different cell types, in particular, platelet derived growth factor (PDGF) is a prominent agent, active in all stages of the healing process. Becaplermin (0.01% Regranex gel) is a homodimeric protein produced by recombinant DNA technology through the insertion of the gene for the B chain PDGF into the yeast Saccharomyces cerevisiae. The biological activity of becaplermin is similar to that of indigenous PDGF-BB, specifically, the promotion of chemotactic recruitment and the proliferation of cells involved in wound repair. Becaplermin has undergone extensive animal and human studies, demonstrating that it is highly effective as an adjunctive measure for the healing of ulcerations in the feet of diabetics when used in conjunction with standard wound healing practices. Specifically these practices include the provision of a moist environment free of debris and necrotic tissue, control of infection and optimal weight displacement from the affected area. Becaplermin is safe and easy to use, being applied once-daily and at present, becaplermin is the only growth factor licensed for use in wound healing.

Sustained release of human growth hormone (hGH) from collagen film and evaluation of effect on wound healing in db/db mice

Collagen films containing human growth hormone (hGH) were prepared and the release of hGH from these films and their effect on healing of full-thickness wounds in db/db mice were evaluated. The release profiles of hGH from the collagen films varied with composition and preparation conditions. The film prepared by air-drying of the mixture of hGH and collagen solution released hGH continuously over 3 days both in vitro and in vivo. By application of collagen film containing 3 mg of hGH twice at an interval of 6 days to wounds, area of wounds on day 21 was significantly reduced compared with that of non-treated wounds. Application of hGH alone at the same dose had no significant effect on wound healing. The maximum serum hGH concentration after single administration of the hGH collagen film was lower than that with hGH alone, and hGH persisted in serum over 3 days. These results suggest that hGH collagen film may be a useful topical formulation for the treatment of wounds.

Recombinant human platelet-derived growth factor gel speeds healing of acute full-thickness punch biopsy wounds

BACKGROUND

Recombinant human platelet derived growth factor-BB gel (PDGF gel) has been shown to be effective in the treatment of diabetic neuropathic ulcers. It is also being used off-label to speed wound healing of flaps, grafts, and wounds from Mohs micrographic surgery.

OBJECTIVE

The purpose of the study was to compare the rate of healing in wounds treated with PDGF gel and with wounds treated with conventional therapy (antibiotic ointment).

METHODS

A double-blind controlled study of 7 healthy volunteers was performed. With a 4-mm skin punch biopsy instrument, two full-thickness wounds were made on each arm of each volunteer. Fourteen wounds treated with PDGF gel were compared with 14 wounds treated with antibiotic ointment. Healing was evaluated by visual determination of the global percentage healed and wound depth.

RESULTS

Wounds treated with PDGF gel showed a significantly faster rate of healing on each of the initial 6 follow-up visits. The greatest difference was on day 10 when PDGF-treated wounds were 71% healed compared with 28% for antibiotic-treated wounds (P =.0005). At days 22 and 24, 92.9% and 100% of the PDGF gel-treated wounds were healed, compared with 50% and 57%, respectively (P =.0313 and P =.0313), in the antibiotic ointment group. By day 29, both PDGF gel and antibiotic-treated wounds were healed. PDGF also decreased wound depth compared with wounds treated with antibiotic ointment at days 8 and 10 with P values <.0313 and <.0020, respectively.

CONCLUSION

We conclude that PDGF gel speeds healing of acute full-thickness wounds compared with antibiotic ointment.