THE HOST ENVIRONMENT DETERMINES STRAIN-SPECIFIC DIFFERENCES IN THE TIMING OF SKELETAL-MUSCLE REGENERATION - CROSS-TRANSPLANTATION STUDIES BETWEEN SJL J AND BALB/C MICE/

The difference in the timing of the regeneration process of skeletal m uscle between SJL/J and BALB/c mice was investigated using grafts of w hole skeletal muscle (both autografts and allografts). Histological, a utoradiographic and immunohistochemical techniques were used in the in vestigation. Infiltration of leucocytes into autografts, numbers of de smin-positive myogenic cells and myotube formation were all more advan ced in the SJL/J compared with BALB/c mice. Furthermore, autoradiograp hic evidence showed that myoblasts in the SJL/J autografts were synthe sising DNA 12 h earlier than myoblasts in BALB/c autografts. In allogr afts, where SJL/J host mice received BALB/c grafts, and vice versa, le ucocyte infiltration and myotube formation occurred earlier in the BAL B/c muscles grafted into SJL/J hosts, than in the reverse situation wi th BALB/c hosts. The results show that, at least for whole muscle graf ts, it is the host environment which determines the speed and outcome of the regenerative process.