THE DYNAMICS OF MACROPHAGE RECRUITMENT AFTER NERVE TRANSECTION

In the present study rat sciatic nerves (n = 60) were transected: in h alf of the animals the nerve was allowed to regenerate freely, in the other half the regeneration was prevented by suturing beside the point of transection. Macrophages were stained with ED-1 antibody and count ed (number/mm(2)) in both the epi- and endoneurium 3, 7, 14, 48 and 56 days post transection. Macrophages were observed first in the epineur ium; the local density of macrophages was considerably higher in the e pineurium than in the endoneurium during the first few days. The numbe r of macrophages in the epineurium was maximal at 3 days (1000-2000/mm (2)), and thereafter it declined sharply. In the endoneurium macrophag es were most abundant after 2 weeks (1000/mm(2)), after which their nu mber declined steadily. A migration of epineurial macrophages appeared to take place through the perineurium from epineurial areas containin g a high concentration of macrophages. Initially an endoneurial accumu lation of macrophages was noted in the subperineurial area. These find ings suggest an alternative route for macrophages into the endoneurial space. No statistical difference was observed between the regeneratin g and non-regenerating experimental groups. The present study indicate s that regenerating axons do not have an effect on the number of macro phages in either the epineurium or the endoneurium.