transforming-growth-factor-alpha and Tympanic-Membrane-Perforation

Peptide growth factors and cytokines modulate both normal and impaired wound healing. Topical application of growth factors in the form of ear drops may counteract impairment of wound healing in the tympanic membrane (TM). We applied keratinocyte growth factor (KGF), transforming growth factor (TGF)-alpha or basic fibroblast growth factor (bFGF) to the perforated TMs of rats in which healing impairment had been caused by systemic administration of a glucocorticoid. Histologic studies of the injured TM, including anti-5-bromo-2'-deoxyuridine immunohistochemistry, were performed on the third day after wounding. In the control ear, epidermal migration was markedly inhibited by glucocorticoid treatment and no hyperplasia was observed in any layer at the perforation edge. TMs treated with KGF showed marked hyperplasia in the epithelial layer at the perforation edge. In the bFGF- and TGF-alpha-treated groups, hyperplasia was observed in the epithelial and intermediate layers of the TM near the malleus handle and annulus, while no hyperplasia was seen in any layer at the perforation edge. Only KGF, therefore, improved epidermal migration in the TM, while all the growth factors tested induced hyperplasia in the TM.

Topics: Animals; Anti-Inflammatory Agents; Dexamethasone; Fibroblast Growth Factor 2; Fibroblast Growth Factor 7; Fibroblast Growth Factors; Keratinocytes; Male; Rats; Rats, Wistar; Transforming Growth Factor alpha; Tympanic Membrane; Tympanic Membrane Perforation; Wound Healing

The participation of growth factors in wound healing of tympanic membranes (TMs) is established. To determine the possible role of these growth factors in normal healing, we examined the regulation of keratinocyte growth factor (KGF), transforming growth factor-alpha (TGF-alpha), and basic fibroblast growth factor (bFGF) messenger RNA (mRNA) expression in wounded TMs of glucocorticoid-treated rats; these rats have severe wound healing abnormalities. Induction of KGF, TGF-alpha, and bFGF mRNA expression after TM injury was significantly reduced in these rats. Moreover, we found that the average number of bromodeoxyuridine-positive cells in a glucocorticoid-treated group was significantly lower than that in controls. The data suggest that reduced expression of these genes might be partially responsible for the wound healing defects seen in these animals. These results provide a possible explanation for the beneficial effect of exogenous KGF, TGF-alpha, or bFGF in treatment of wound healing disorders of the TM.

Topics: Animals; Anti-Inflammatory Agents; Blotting, Southern; Bromodeoxyuridine; Cell Count; Dexamethasone; Disease Models, Animal; Down-Regulation; Fibroblast Growth Factor 2; Fibroblast Growth Factor 7; Fibroblast Growth Factors; Follow-Up Studies; Gene Expression; Glucocorticoids; Growth Substances; Immunohistochemistry; Injections, Subcutaneous; Male; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA; RNA, Messenger; Staining and Labeling; Time Factors; Transforming Growth Factor alpha; Tympanic Membrane Perforation; Wound Healing

Little is known about the arrested healing of chronic central tympanic membrane perforations and the mechanism involved in this process. Some authors have traced the failure to a growth factor deficiency at the perforation margin. In addition, recently, several growth factors have been tried out to improve tympanic membrane (TM) closure in animals. The authors sought to determine the expression of some well-known growth factor peptides in normal human TM and in TMs with a chronic central perforation.. Total TM specimens were obtained from patients with a normal TM (N = 10) soon after death and from patients with a chronic perforation (N = 20) undergoing myringoplasty with use of an allograft TM. Formaldehyde solution-fixed TMs were analyzed after immunohistochemical staining using highly purified monoclonal antibodies to determine whether epidermal growth factor receptor (EGF-r), transforming growth factor-alpha (TGF-alpha), basic fibroblast growth factor (b-FGF), or transforming growth factor-beta 1 (TGF-beta 1) was expressed in the TMs.. The distribution pattern for EGF-r, TGF-alpha, and b-FGF was similar in perforated and nonperforated TMs. In contrast to this, TGF-beta 1 staining was markedly different in perforated and nonperforated TMs. No or minimal TGF-beta 1 was observed in normal TMs, whereas TGF-beta 1 staining was prominent in perforated membranes, mostly at the perforation border.. The authors experimental findings imply that EGF-r, b-FGF, and TGF-alpha expression are not significantly different in TMs with and without a central chronic perforation. However, for TGF-beta 1, the authors found an increased staining pattern in perforated TMs when compared with that of normal TMs, and staining at the fibrotic and scarred perforation margin was pronounced. Based on these findings, the authors speculate on the possible role of TGF-beta 1 in the development of the fibrotic scar at the perforation margin explaining the deficient healing pattern of tympanic membranes in chronic otitis media. Possible clinical implications for the future, including growth factor therapy, are discussed.

Topics: Antibodies, Monoclonal; Chronic Disease; ErbB Receptors; Female; Fibroblast Growth Factor 2; Humans; Immunohistochemistry; Male; Middle Aged; Otitis Media; Transforming Growth Factor alpha; Tympanic Membrane Perforation

KGF (KGF), synthesized and secreted exclusively by stromal cells in epithelialized organs, specifically promotes proliferation of cells of epithelial origin, including keratinocytes. A related peptide, basic fibroblast growth factor (bFGF), has mitogenic properties for fibroblasts and endothelial cells. KGF expression is stimulated markedly in the skin during wound healing. To investigate the physiologic action of KGF in the healing of TM (TM) perforations, we examined KGF and KGF receptor (KGFR) mRNA transcript levels as well as those of bFGF and transforming growth factor-alpha (TGFalpha) in normal and wounded rat TM at varying intervals, using a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). We found KGF and TGFalpha mRNA expression to be induced rapidly, peaking 3 days after wounding and then declining. Expression of bFGF was induced gradually and remained increased until 7 days. In contrast, we found KGFR to be expressed in normal TM, remaining unchanged during TM repair. These results indicate that KGF and TGFalpha may mediate migration and proliferation of epithelial cells of the outer layer in the early stage of TM repair while bFGF may mediate the connective tissue reaction in the middle layer in a subsequent stage.

Topics: Animals; Base Sequence; Blotting, Southern; Fibroblast Growth Factor 10; Fibroblast Growth Factor 2; Fibroblast Growth Factor 7; Fibroblast Growth Factors; Growth Substances; Keratinocytes; Molecular Sequence Data; Rats; Receptor, Fibroblast Growth Factor, Type 2; Receptors, Fibroblast Growth Factor; Receptors, Growth Factor; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Transforming Growth Factor alpha; Tympanic Membrane; Tympanic Membrane Perforation; Wound Healing

An immunohistochemical study of transforming growth factor-alpha (TGF-alpha) distribution was carried out to clarify the mechanism responsible for accelerated epidermal cell proliferation after perforation of the rabbit tympanic membrane. In the normal tympanic membrane, TGF-alpha expression was not observed, whereas after perforation, over the whole tympanic membrane including the margin of the perforation, TGF-alpha-positive cells appeared and were scattered in the epidermal cell layer. After healing of the perforation, a marked decrease of TGF-alpha-positive cells in the tympanic membrane was observed. This finding suggests that TGF-alpha induces proliferation of epidermal cells after the perforation stimulus.

Topics: Animals; Antibodies, Monoclonal; Cell Division; Immunohistochemistry; Rabbits; Time Factors; Transforming Growth Factor alpha; Tympanic Membrane; Tympanic Membrane Perforation; Wound Healing