Gene Therapy (1999) 6 , 1015–1020  1999 Stockton Press All rights reserved 0969-7128/99 $12.00 http:/ / www.stockton-press.co.uk/ gt IGF-I gene transfer in thermally injured rats MG Jeschke 1,2 , RE Barrow 1,2 , HK Hawkins 1,2 , K Yang 4 , RL Hayes 4 , BJ Lichtenbelt 1,2 , JR Perez-Polo 3 and DN Herndon 1,2 1 Shriners Hospital for Children; Departments of 2 Surgery and 3 Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston; and 4 Department of Neurosurgery, University of Texas Medical School, Houston, Texas, USA Exogenous insulin-like growth factor-I (IGF-I) is known to rhIGF-I protein. Body weights and wound healing were improve the pathophysiology of a thermal injury, however, measured. Muscle and liver dry/wet weights and IGF-I con- deleterious side-effects have limited its utility. Cholesterol- centrations in serum, skin and liver were measured by containing cationic liposomes that encapsulate comp- radioimmunoassay. Transfection was confirmed by histo- lementary DNA (cDNA) are nonviral carriers used for in chemical staining for -galactosidase. Rats receiving the vivo gene transfection. We propose that liposome IGF-I IGF-I cDNA constructs exhibited the most rapid wound re- gene transfer will accelerate wound healing in burned rats epithelialization and greatest increase in body weight and and attenuate deleterious side-effects associated with high gastrocnemius muscle protein content (P  0.05). Local levels of IGF-I. To test this hypothesis IGF-I gene con- IGF-I protein concentrations in the skin were higher when structs, encapsulated in liposomes, were studied for their compared to liposomes containing only the lacZ gene efficacy in modulating the thermal injury response. Thirty (P  0.05) Transfection was apparent in the cytoplasm of adult male Sprague–Dawley rats were given a 60% TBSA myofibroblasts, endothelial cells and macrophages of the scald burn and randomly divided into three groups to granulation tissue. Liposomes containing the IGF-I gene receive weekly subcutaneous injections of liposomes plus constructs proved effective in preventing muscle protein the lacZ gene coding for -galactosidase, liposomes plus wasting and preserving total body weight after a severe cDNA for IGF-I and -galactosidase or liposomes plus the thermal injury. Keywords: growth factor; insulin-like growth factor-I; liposomes; trauma; wound healing Introduction Gene transfection is a promising approach to the treat- ment of various clinical disorders. There are, however, several obstacles to overcome before this approach can be effective. 1 One major obstacle is the selection of an appropriate vector for gene delivery. 2 Viruses have been used as delivery vectors due to the specificity with which they can bind to and infect cells. 2 The most common viruses used for transfection have been the retroviruses, adenoviruses and adeno-associated viruses. 1–3 Viral infec- tion-associated toxicity, immunologic compromise, and possible mutagenic or carcinogenic effects, however, make this approach potentially dangerous. 1 The use of naked DNA not encapsulated or plasmid DNA con- structs alone, without viral genes present, have been used topically or delivered with a pneumatic ‘gene gun’. Both have proven to be inefficient at transferring genes, per- haps due to the fragility of the naked DNA constructs in the extracellular environment and the traumatic conse- quences of ‘gene gun’ discharges on cellular integrity. 1,4 When liposomes were discovered by Bangham, 5 their in vivo utility was largely met with skepticism. 6 Although the nonviral nature of liposomes and their stability in vivo are attractive, their use has been limited to in vitro due Correspondence: MG Jeschke, Shriners Hospital for Children, 815 Market Street, Galveston, Texas 77550, USA Received 21 August 1998; accepted 5 February 1999 to the low in vivo transfection efficiencies. 4 Modification of the standard liposomal structure to a cationic structure and the inclusion of cholesterol, together with the use of cytomegalovirus promoters in the cDNA constructs used for gene transfer, have increased the efficacy and trans- genic expression levels to those previously achieved with adenovirus constructs. 4,7 A thermal injury is a particularly severe form of trauma characterized by high cardiac output, increased oxygen consumption, and protein and fat wasting. 8 This vulnerable hypermetabolic state compromises the immune system and attenuates wound healing. 9 Insulin- like growth factor-I (IGF-I) is an anabolic growth factor shown to improve metabolic rate, gut mucosal function and protein loss after a burn injury. 9–11 IGF-I is known to mediate the actions of growth hormone in the hypermeta- bolic state by attenuating lean body mass loss, improving the immune response, attenuating the acute phase response, and by enhancing wound healing. 9,12–16 A key determinant of patient outcome after a burn injury is the wound healing process. 14 Fibroblasts and keratinocytes have IGF-I receptors which probably mediate IGF-I stimulation of mitogenicity and proliferative activity. 17,18 There are, however, side-effects, such as hypoglycemia, mental status changes, edema, fatigue and headache, that are caused by the large amounts of systemic IGF-I needed for the desired therapeutic effects. These adverse side- effects limit the therapeutic utility of IGF-I in the treat- ment of burns. 19,20 We propose that delivery systems that rely on gene