PREVENTION BY ANTI-LFA-1 OF ACUTE MYOBLAST DEATH FOLLOWING TRANSPLANTATION

Myoblast transplantation is a potential treatment for Duchenne muscula r dystrophy, One of the problems possibly responsible for the limited success of clinical trials is the rapid death of the myoblasts after t ransplantation. To investigate this problem, myoblasts expressing beta -galactosidase were injected in the tibialis anterior muscles of mice, beta-galactosidase activity was reduced by 74.7% after 3 days, Myobla st death observed at 3 days was reduced to 57.2% when the hosts were i rradiated, This result suggested that host cells were contributing to this phenomenon, Transplantation in SCID and FK506-treated mice did no t reduce cell death, indicating that mortality was not due to an acute specific reaction, In contrast, administration of the anti-LFA-1 (TIB -213) mAb markedly reduced myoblast death at 3 days without altering l eukocyte tissue infiltration, We postulated that neutrophils were medi ating myoblast mortality by an LFA-1-dependent mechanism, To test this hypothesis, IL-1 beta-activated myoblasts were loaded with 6-carboxy- 2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethylester) (DC FH), a marker for oxidative stress, Addition of neutrophils and zymosa n-activated serum resulted in a time-dependent DCFH fluorescence; this neutrophil-induced oxidation was considerably inhibited by TIB-213, T hese results indicate that an effective control of the inflammatory re action will be necessary for any new clinical trials of myoblast trans plantation and suggest that neutrophil-mediated myoblast injury occurs by an LFA-1-dependent pathway.