Increased satellite cell apoptosis in vastus lateralis muscle after anterior cruciate ligament reconstruction.

Objective: Recovery of the quadriceps femoris muscle after anterior ligament reconstruction is im-paired. The aim of this study was to investigate satellite cell content and function of the vastus lateralis muscle after anterior ligament reconstruction.
Methods: Biopsies were obtained from the vastus lateralis muscle of 16 recreational athletes immediately before and again 12 weeks after anterior ligament reconstruction. Total satellite cell number (Pax7+), activated (Pax7+/MyoD+), differentiating (Pax7-/MyoD+), and apoptotic (Pax7+/TUNEL+) satellite cells, myofibers expressing myosin heavy chain (MHC) I and II, and neonatal MHC (MHCneo) were determined immunohistochemically.
Results: After anterior ligament reconstruction, the number of apoptotic satellite cells was significantly (p = 0.019) increased, concomitant with a significant (p < 0.001) decrease in total satellite cell number, with no change in activated and differentiating satellite cell number. MHCneo+ myofibers tended towards an increase.
Conclusion: Satellite cell apoptosis and the reduction in the satellite cell pool might provide an explanation for prolonged quadriceps muscle atrophy after anterior ligament reconstruction.