Purpose: The purpose of this study was to determine the desmin characteristics of fibers infiltrated by CD11b-leukocytes in fast- and slow-twitch murine muscles after eccentric contractions.
Methods: We developed a computer image analysis procedure to quantify the percentage of intramyofiber CD11b-leukocyte infiltration. Only CD11b-positive fibers that exhibited identifiable borders were examined. Patterns of leukocyte infiltration of these fibers were distinguished and confirmed quantitatively by determining the mean percentage of leukocyte infiltration. We examined the desmin characteristics of these fibers with the same image analysis system and quantified the percentage of the fiber that demonstrated antidesmin staining. The influence of sex and muscle type on desmin characteristics and percentage of CD11b-leukocyte infiltration also was analyzed.
Results: The percentage of CD11b-leukocyte infiltration was less than 50% for the majority of fibers. Three intramyofiber leukocyte infiltration patterns were identified that had significantly different mean percentages of leukocyte infiltration: 14%, 27%, and 47% (P < 0.001). Of the three desmin characteristics (normal, increased, and decreased) that were observed, almost three fourths of the fibers exhibited increased desmin. A significant difference in the percentage of increased desmin was found among the CD11b-leukocyte infiltration patterns (P = 0.01). Fibers with the least amount of CD11b-leukocyte infiltration showed the greatest amount of increased desmin. Sex and muscle type did not influence any of these findings.
Conclusion: Increased desmin appears to be associated with an early stage of intramyofiber leukocyte infiltration after eccentric contractions.