The goal of this project is to determine whether axons of a damaged spinal cord can be induced to regenerate by the administration of exogenous macrophages (Mphi). The Mphi are activated by lipopoly~saccharide (LPS) or phytohemaglutinin (PHA), with the intent of promoting their secretion of growth factors over that of proteases. The exogenous, isogeneic Mphi should provide growth factors that might promote axonal regeneration across the lesion. The spinal cord of adult rats is crushed epidurally , at the T~7 segment of rats, by compressing the cord between the blades of a fine forceps. The blades are separated by an adjustable distance. The activated Mphi are labeled with a lipid soluble, fluorescent dye and are now injected intravenously at different times over a 1 to 4 week period following the injury. In other injured rats, the Mphi are injected, first, directly into the cord at the lesion site and then intravascularly thereafter. The exogenous, activated Mphi are attracted to and accumulate at the injured site. As the pathological changes in damaged cords are variable so are the number and position of intact axons. Consequently, spared axons must be distinguished from regrowing ones. There is now a method, the immunostaining of GAP~43 with antibodies at high dilution, which, in preliminary findings, appears to distinguish normal from regenerating axons. To date, only a few such axons are discernible. The next steps are to find the reagents that optimally release the Mphi growth factors and to identify the cytokines that may also be secreted by these Mphi and which may be prime effectors of tissue repair.
