THE GENOTYPE OF BONE-MARROW-DERIVED INFLAMMATORY CELLS DOES NOT ACCOUNT FOR DIFFERENCES IN SKELETAL-MUSCLE REGENERATION BETWEEN SJL J AND BALB/C MICE/

This study determined whether the genotype of bone marrow-derived infl ammatory cells contributes to the more pronounced leukocytic exudation and extensive new muscle formation seen in SJL/J compared with BALB/c mice after a crush-injury (Mitchell et al. 1992). Female SJL/J mice w ere whole-body irradiated and reconstituted with male bone marrow from the BALB/c strain, and irradiated BALB/c females reconstituted with m ale SJL/J bone marrow. The mice were allowed to recover for 3 weeks an d the tibialis anterior muscle (in a leg which had been protected from irradiation) was injured by crushing. At 3 and 10 days after injury t he extent of necrotic debris, mononuclear leukocytic infiltration and new muscle formation was assessed in the muscles. The SJL/J mice recon stituted with BALB/c bone marrow showed extensive mononuclear leukocyt ic infiltration and clearance of necrotic debris when compared with BA LB/c mice reconstituted with SJL/J bone marrow, and these strain-speci fic differences mirrored those seen with control bone marrow reconstit uted hosts and non-irradiated hosts. The results show that the genotyp e of the bone mac-row-derived macrophages is not responsible for the s uperior regeneration of crush-injured skeletal muscle in SJL/J mice, a nd it appears that factors intrinsic to the muscle tissue may be of ce ntral importance.