Our aim was to determine the effect of denervation on repair-associated mRNA levels in the MCL after partial tear. Cohorts of rabbits underwent partial MCL tear with or without concomitant femoral nerve transection. Ligaments were harvested, RNA extracted and RT-PCR was performed using rabbit-specific primers for repair-associated molecules at three days, two wks, six wks and sixteen wks post-injury. Angiogenesis genes MMP3, MMP13, matrix components Collagen I and III and growth factors TGF-ß and NGF mRNA levels were increased in the denervated group at two-weeks post-injury (p<
0.05). Denervation significantly alters mRNA levels during the early stages of rabbit MCL healing. To determine the effect of denervation on repair-associated mRNA levels in the injured medial collateral ligament (MCL). Previous experiments revealed that denervation impairs healing of the MCL. We hypothesized that denervation would decrease repair-associated mRNA levels in the injured MCL when compared with normally innervated injured MCL. Adult, skeletally mature female rabbits were assigned to one of four groups: unoperated control, femoral nerve transection alone (denervated controls), MCL partial tear and denervated MCL partial tear. At three days, two weeks, six weeks or sixteen weeks post-surgery, cohorts of six rabbits from each experimental group were killed. Control rabbits were assessed at two weeks. Ligaments were harvested, RNA extracted and RT-PCR was performed using rabbit-specific primers. In the denervated injury group, mRNA levels of angiogenesis genes MMP-3 and MMP-13, matrix components Collagen I and III and growth factors TGF-ß and NGF had all increased at two-weeks post-injury, in comparison to non-denervated (p<
0.05). We also found increased levels of MMP-3 and NGF mRNA in the denervated group at sixteen weeks post injury (p<
0.05). The mRNA levels of the housekeeping gene GAPDH were increased in the denervated group only at three days post injury (p<
0.05). Of note, TGF-ß mRNA levels were significantly decreased in the denervated group at three days post injury (p<
0.05). Contrary to our initial hypothesis, denervation increases mRNA levels for many important molecules during the early stages of MCL healing. Additional research will be required to explain how and why denervation impairs ligament healing. No previous study has shown that innervation regulates mRNA levels in healing ligament.
