Epidermal growth factor accelerates connective tissue wound healing in the perforated rat mesentery

Growth factors in wound healing: the present and the future?

Numerous clinical studies have confirmed the pivotal role growth factors play in wound healing and their diminished levels in the chronic wound. Despite promising early studies treating chronic wounds with growth factors, results with traditional bolus dosing of a single growth factor have yielded insignificant results. Disappointing results have been theorized to be the result of growth factors inherent short half-life, a hostile microenvironment rich in protease activity, and poor delivery mechanisms failing to deliver effective dosages in an appropriate temporal manner. Advances in tissue engineering and regenerative medicine have provided technologies capable of delivering multiple growth factors in a spatially oriented approach. These technologies include polymer systems, scaffolds, and hydrogels that have demonstrated improved response by target tissues when growth factors are delivered in this biomimetic fashion. With improved delivery systems, treatment of chronic wounds with growth factors has the potential to accelerate healing in a manner not previously realized with traditional delivery approaches.

Genomics of corneal wound healing: a review of the literature

Corneal wound healing is a complex process: its mechanisms and the underlying genetic control are not fully understood. It involves the integrated actions of multiple growth factors, cytokines and proteases produced by epithelial cells, stromal keratocytes, inflammatory cells and lacrimal gland cells. Following an epithelial insult, multiple cytokines are released triggering a cascade of events that leads to repair the epithelial defect and remodelling of the stroma to minimize the loss of transparency and function. In this review, we examine the literature surrounding the genomics of corneal wound healing with respect to the following topics: epithelial and stromal wound healing (including inhibition); corneal neovascularisation; the role of corneal nerves in wound healing; the endothelium; the role of aquaporins and aptamers. We also examine the effect of ectasia on corneal wound healing with regard to keratoconus and following corneal surgery. A better understanding of the cellular and molecular changes that occur during repair of corneal wounds will provide the opportunity to design treatments that selectively modulate key phases of the healing process resulting in scars that more closely resemble normal corneal architecture.

Growth factors in corneal wound healing following refractive surgery: A review

The first part of this review article aims to provide important basic definitions of growth factor terminology, and to put forward a model for understanding the role of growth factors in a wound healing context. In the second part of the paper, we review the literature on growth factors in the cornea, including that on changes associated with wound healing following refractive surgery in the epithelial, stromal, and endothelial layers. The role of growth factors in stromal removal, corneal neovascularization, corneal innervation and wound healing is considered. The importance of the epithelial-stromal interaction is discussed, including the role of growth factors in keratocyte apoptosis. In the final section, we review the current literature on endogenous and exogenous modulation of growth factors in corneal wound healing. This includes important in vitro work but aims to emphasize clinically relevant results. Photorefractive keratectomy (PRK) may have short-term complications such as pain and haze, whereas laser in situ keratomilieusis (LASIK) may have longer-term adverse effects on corneal biomechanics. The emerging technique of laser epithelial keratomilieusis (LASEK) provides an interesting alternative wound which may be less susceptible to the inherent complications of PRK and LASIK. At present, the phenomenon of iatrogenic keratectasia following LASIK is not fully understood, but these features of wound healing following PRK may be amenable to growth factor modulation.

Stimulation of protracted connective tissue repair in normal mice by transforming growth factor beta 1

The repair and contraction during connective tissue repair of mesenteric perforations is prolonged in mice compared with rats. In the present study the stimulating effect of transforming growth factor beta 1 (TGF-beta 1) on different aspects of such repair of the mouse mesentery was assessed. The number of closed mesenteric perforations were counted on different days after operation and the free peritoneal cells were counted, the mitotic index was assessed, and actin distribution of fibroblasts around the perforation was studied with laser scanning confocal microscopy. TGF-beta 1 significantly increased the speed of closure and seemed to induce more actin in fibroblasts at the wound margin. It did not significantly influence the mitotic index, but fewer free peritoneal cells were obtained in mice treated with TGF-beta 1. We conclude that TGF-beta 1 is a potent stimulator of connective tissue repair and contraction in mice. The different methods of closure in rats and mice implicate different molecular responses in wounds and further studies on the stimulating effect of TGF-beta 1 may indicate basic fibroblastic cellular mechanisms that are active during contraction in connective tissue repair.

Formation of healing tissue and angiogenesis in repair of connective tissue stimulated by epidermal growth factor

Epidermal growth factor (EGF) has been shown to stimulate connective tissue repair in the perforated mesentery of rats. The aim of the present investigation was to study the effect of EGF on the formation of healing tissue and angiogenesis in such repair. After laparotomy standardised perforations were made in the centre of the mesenteric "windows" with a scalpel. The rats were given intraperitoneal injections of either 10 micrograms EGF dissolved in phosphate-buffered saline (PBS), or PBS alone, twice daily for four consecutive days beginning on the day of operation. In the first experiment, healing tissue formation and angiogenesis was quantified morphometrically in perpendicularly cut mesenteric windows on days 1 to 10 after operation. Treatment with EGF caused the formation of significantly more healing tissue on days 2 to 7, but no stimulation of angiogenesis. In the second experiment, angiogenesis was quantified morphometrically on days 14 and 21. Mesenteric windows were spread out on objective slides after the capillary bed had been visualised by perfusion of carbon ink. Perforation caused a significant increase of microvascular density in the centre of the mesenteric windows on days 14 and 21. Treatment with EGF did not stimulate angiogenesis at any observation point. In conclusion, treatment with EGF significantly increased the formation of healing tissue in connective tissue repair in the perforated mesentery of rats, but did not affect angiogenesis.

Growth factors and wound healing: biochemical properties of growth factors and their receptors

Wound healing is a complex biologic process that involves chemotaxis and division of cells, neovascularization, synthesis of extracellular matrix proteins, and remodeling of scar. Peptide growth factors have been shown to regulate many of these processes in vitro, leading to the hypothesis that peptide growth factors also regulate important phases of wound healing in vivo. Part I of this two-part series presents an overview of the biochemical properties of five families of peptide growth factors that are thought to be involved in wound healing: epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and fibroblast growth factor (FGF).