Wound healing. The role of platelet-derived growth factor and transforming growth factor beta

Delayed wound healing in immunodeficient TGF-beta 1 knockout mice

Previous studies showed that full-thickness wounds in transforming growth factor-beta1-deficient mice initially heal normally. Unfortunately, transforming growth factor-beta1 deficiency leads to a multifocal inflammatory disease affecting most organs of the body, which ultimately interferes with later stages of wound healing in these mice. As this inflammatory disease is eliminated in transforming growth factor-beta1-deficient mice lacking T and B cells (Tgfb1-/- Scid-/- mice), we hypothesized that wound repair in the latter would proceed normally, even at later stages of healing. Unexpectedly, Tgfb1-/- Scid-/- mice demonstrate a major delay of approximately 1 wk in each of the major phases of wound healing: inflammation, proliferation, and maturation. Immuno- deficient Scid-/- mice that have the wild-type Tgfb1 allele do not experience this delay in wound healing. One interpretation of these findings is that lymphocytes and transforming growth factor-beta1 affect compensatory pathways in wound healing. An alternative interpretation is that the delayed expression of Tgfb2 and Tgfb3 that occurs in the absence of transforming growth factor-beta1 results in the delayed wound healing, suggesting that transforming growth factor-beta2 and/or transforming growth factor-beta3 play important parts in wound healing.

Effect of topical rh-TGF-beta 1 on second intention wound healing in horses

OBJECTIVE

To investigate the effects on wound healing of transforming growth factor-beta 1 as a topical treatment to full-thickness, excisional wounds of the distal limb of horses.

DESIGN

A randomised block study using four horses, each with wounds assigned to four treatment groups.

ANIMALS

Four adult Standardbred geldings.

PROCEDURE

Four, 4 cm2, full-thickness wounds were created on the dorsomedial and dorsolateral aspect of the metacarpus or metatarsus of each limb of four horses, giving a total of 64 wounds. For each limb, wounds were randomly assigned to four treatment groups: no treatment (control), carrier (Methyl Cellulose gel), 50 ng/wound rhTGF-beta 1 in carrier, and 500 ng/wound rhTGF-beta 1 in carrier. Wounds were treated on day 0 and day 8. Effects of treatment were evaluated on the basis of the presence of exuberant granulation tissue requiring excision, number of times excision was required, total wound area, area of epithelialisation, area of granulation, and histological evaluation of biopsy samples of wounds on day 8 and excised wounds on day 21.

RESULTS

Topical application of TGF-beta 1 at the two concentrations studied had no significant effect on the total area of wounds (P = 0.7), the area of granulation tissue (P = 0.78), the area of epithelialisation (P = 0.92), histological assessment or subjective clinical assessment of wounds.

CONCLUSION

TGF-beta 1 had no beneficial effects on wound healing. Additional trials are needed to test if it has value for wound treatment in horses.

Bone- and non-bone-derived growth factors and effects on bone healing

In the future, it may be possible to manipulate the fracture site with exogenous growth factors to allow successful union of the bone ends without additional surgery. The complex interaction of growth factors, the timing of their appearance and disappearance at the wound site, and the concentrations necessary to achieve specific effects must be studied more thoroughly. For growth factors to find widespread clinical use, there must be evidence that healing is enhanced. It may be difficult to enhance the healing of fresh fractures in normal animals, and it may also be difficult to demonstrate the healing of nonunion fractures. Because of the great variability in fractures of clinical patients, studies designed to determine the effect of growth factors on bone healing must be carefully designed with appropriate attention given to randomizing patients based on the risk of delayed healing and other patient characteristics.

Preparation of autologous platelets for the ophthalmologic treatment of macular holes

BACKGROUND

Platelet concentrates were recently used for ophthalmologic treatment of macular holes. This strategy was investigated to define standardized blood bank components.

STUDY DESIGN AND METHODS

Two different, highly concentrated autologous platelet components, one from whole-blood preparation and the other from plateletpheresis, were evaluated. In the first procedure, platelet-rich plasma was obtained from 250 mL of whole blood. After storage for 20 hours, platelet-rich plasma was concentrated in a second centrifugation step and adjusted to 10 x 10(9) platelets per mL. In the second procedure, platelets were collected by apheresis, stored overnight, centrifuged, and adjusted to 20 x 10(9) platelets per mL. The respective component was instilled during vitrectomy and gas tamponade in patients with stage II to IV macular holes. Patients were followed for 9 months.

RESULTS

With regard to the various preparation procedures and final concentrations of platelets in the components, no differences in wound healing were observed. An anatomic closure of the macular hole was achieved in 18 of 19 treated patients. Visual acuity improved in 14 patients.

CONCLUSION

Both types of highly concentrated platelet components were effective in achieving high closure rates of macular holes. These autologous platelet components possess the quality standard of blood bank components and could be of great benefit for initiating wound healing in other clinical settings.

Establishment of prostatic cell line "Pro9ad" from a p53-deficient mouse

BACKGROUND

We demonstrated that p53-deficiency is sufficient for immortalization of fetal uterine cells. In the present study, we further extended our previous observations to prostate tissues from a young p53-deficient adult mouse.

METHODS

Cell lines were established from the ventral prostate of a p53-deficient male mouse and maintained in medium containing 10% heat-inactivated fetal calf serum supplemented with insulin (10 microg/ml), transferrin (10 microg/ml), cholera toxin (10 ng/ml), and selenium (10(-8) M).

RESULTS

Pro9ad, one of the lines established, exhibits a typical epithelial morphology in culture. Despite the possession of androgen receptors, the growth of Pro9ad was not stimulated by 5alpha-dihydrotestosterone. Hepatocyte growth factor (HGF) slightly stimulated proliferation, whereas fibroblast growth factor-1 (FGF-1), keratinocyte growth factor (KGF), and platelet-derived growth factor AB (PDGF-AB) had no stimulating effect on growth. However, FGF-2, epidermal growth factor (EGF), and insulin-like growth factor-1 (IGF-1) accelerated proliferation in a dose-dependent manner. EGF and IGF-1 additively stimulated growth.

CONCLUSIONS

These results suggest that Pro9ad shares characteristics in common with primary prostatic epithelial cells despite p53-deficiency, and that p53-deficiency alone allows establishment of clonal cell lines of the prostate epithelium. Furthermore, the prostates of p53-deficient mice are useful sources for obtaining cell lines.

Effect of topical anti-transforming growth factor-beta on corneal stromal haze after photorefractive keratectomy in rabbits

PURPOSE

To determine the relationship between anti-transforming growth factor-beta (anti-TGF-beta) antibodies and the amount of corneal stromal haze after excimer laser photorefractive keratectomy (PRK).

SETTING

Wills Eye Hospital, Philadelphia, Pennsylvania, USA.

METHODS

Nineteen rabbits had bilateral PRK. Dichlorotriazinyl fluorescein was used to stain the exposed stroma; all rabbits were then treated with antibiotic ointment for 4 days. Ten rabbits were randomized to treatment with topical anti-TGF-beta1, -beta2, and -beta3 antibody 50 microg three times a day for 4 days; the others received diluent three times a day for 4 days. Stromal haze was graded weekly for 8 weeks on a 0 to 4+ scale. At the end of the study, all corneas were examined histopathologically.

RESULTS

All treated eyes developed appreciable haze. Seven control rabbits and one antibody-treated rabbit had an epithelial erosion (P = .00001). Antibody-treated rabbits had significantly less haze at 3, 4, and 5 weeks (right eyes) and 3, 4, 5, 7 and 8 weeks (left eyes) (P < .05). Histopathology and fluorescence microscopy showed subepithelial collagen deposition consistent with clinical haze.

CONCLUSIONS

Topical anti-TGF-beta antibody reduced stromal haze after PRK in the rabbit model and may be clinically beneficial in humans.

An overview of the topical management of wounds

Wounds in animals are a common and frequent reason for seeking veterinary attention. The way in which wounds are managed affect the rate of healing, the time to return to normal function, the final cosmetic appearance, and hence the satisfaction of customers. The management of wounds depends on the stage of wound healing and can include irrigation, mechanical and chemical debridement, the use of antiseptics and antimicrobials, adherent and nonadherent dressings, and miscellaneous topical applications such as aloe vera, honey and live yeast cell derivative. The advantages, disadvantages and indications for initial wound management, topical applicants and dressings are discussed.

Diabetic periodontitis: possible lipid-induced defect in tissue repair through alteration of macrophage phenotype and function

BACKGROUND

Diabetes mellitus is a major health problem in the United States affecting approximately 13 million people. The five 'classic' complications which have historically been associated with the condition are microangiopathy, neuropathy, nephropathy, microvascular disease, and delayed wound healing. Recently, periodontal disease (PD) has been declared the 'sixth' major complication of diabetes as diabetics demonstrate an increased incidence and severity of PD. The cellular and molecular basis for diabetic PD is unknown.

HYPOTHESIS

Recent evidence suggests that PD and delayed dermal wound healing may be manifestations of the same general systemic deficit in diabetes involving impairment of the cellular and molecular signal of wounding via alterations in macrophage phenotype. Diabetes-induced hyperlipidemia may interfere with the normal cellular and molecular signal of wounding by alteration of macrophage function and subsequent dysregulation of cytokines at the wound site.

RESULTS

Preliminary data in both animal models and humans suggests that hyperglycemia, in combination with elevations of serum low density lipoproteins and triglycerides, leads to formation of advanced glycation end products (AGEs) which may alter macrophage phenotype. This may be responsible for dysregulation of macrophage cytokine production and increased inflammatory tissue destruction and alveolar bone loss.

IMPLICATIONS

Future investigations will consider diabetic PD in the context of a generalized systemic wound healing deficit that manifests as PD in the face of constant pathologic wounding of the gingiva (bacterial plaque) or delayed dermal wound healing in instances of periodic traumatic wounding to other parts of the body. These types of studies will provide information concerning defective tissue repair in diabetics that will have clinical relevance for the understanding of PD and delayed dermal healing as well as applications of appropriate and specific therapies.

Effects of growth factors and L-arginine on ischemic skin flaps in rats

This study determined the effect of the polypeptide growth factors transforming growth factor-beta (TGF-beta), insulin-like growth factor-I (IGF-I), and growth hormone (GH) alone and in combination with dietary L-Arginine HCL (ARG) on skin flap survival in rats. Caudally based dorsal skin flaps were created in 110 Sprague-Dawley rats. The rats were randomly assigned into three treatment groups, based on drinking water supplementation. Group 1 (n = 50) received ARG in their drinking water, group 2 (n = 50) received tap water alone, and group 3 (n = 10) received N-omega-nitro-L-arginine (L-NA) and hydralazine. Groups 1 and 2 were divided into subgroups of 10 rats each based on treatment with either: TGF-beta, IGF-I, GH, or IGF-I + GH. All subgroups that received GH had significantly greater (P < .0001) median body weight gains when compared with subgroups not receiving GH. L-arginine HCL when added to IGF-I negated the positive effects of IGF-I on both flap survival and weight gain. Although the rats in all subgroups from groups 1 and 2 had an increase in mean percent skin flap survival when compared with the water alone subgroup, only rats receiving IGF-I, or the combination of ARG with either TGF-beta or GH, had statistically significant enhanced skin flap survival. Rats in group 3 did not show an increase in skin flap survival when compared with the control subgroup.

Impaired wound healing in the cancer patient: effects of cytotoxic therapy and pharmacologic modulation by growth factors

This article reviews the experimental and clinical data regarding the effects of chemotherapy on wound healing. In addition, the role of growth factors in the normal wound healing process and their therapeutic potential to optimize wound healing in the cancer patient are discussed.