The Critical Role Of Lysyl Oxidase(LOX) In The Healing Process After Acute Spinal Cord Injury Of Rats

Objectives This study is to explore whether lysyl oxidase(LOX) displays a critical role in the healing process after acute spinal cord injury in rats.Methods 96 healthy SD female rats were divided into four groups: Group A(n=30), damaged rats treated with β-aminopropionitrile(BAPN, an inhibitor of LOX activity); Group B(n=30), damaged rats treated with cobalt chloride(Co Cl2, an enhancer of LOX expression, 30 rats);Group C(n=30)damaged rats with no any treatment(only injury);Group D(n=6), normal rats(sham).Using the Allen ’s methods to establish the acute spinal cord injury model for rats, setting up the same hitting force, injured spinal cords were removed for fixation or protein extraction at different time period after injure(1、3、7、14and 30 days, n=6 for each time point). Expression of LOX was detected by immunohistochemistry(IHC) and immunoblotting using tissues with spinal cord injury, and correlate with the recovery of hind limb movement evaluated by the BBB methods. Results BBB measurements indicated that the higher scales for the recovery of hind limb movement after injury were obtained in rats of the Group B(Co Cl2 treatment) and lower scales in Group A(BAPN treatment) in comparison to those in rats of Groups C(only injury). IHC assays showed that in all experiment time points LOX positive cell numbers in injured groups(A、Band C) were significantly higher than those in the control(D). For example, the average positive cell numbers per tested field in A、B and C groups were 27.46 ± 3.5, 64.67±3.0 and 41.67±2.3, respectively, while the positive cell number in the control was only 6.04±0.2. Furthermore, in all experiment time points, the LOX positive cell numbers in Co Cl2 treated groups were larger than those in the control whereas BAPN treated groups had less positively stained cells in comparison to the control without any treatments. For example, at 3d after injury, LOX positive cells in the only injured group reached the top value as 46.34±3.4, whereas at the same time point, the positive values in Co Cl2 and BAPN treated groups were amounted to 74.81 ± 4.9 and 37.64 ± 3.6, respectively. Westwern blot analyses showed that higher levels of LOX expression were detected in rats treated with Co Cl2(Group B) and lower levels of LOX expression in rats treated with BAPN(Group A)in comparison to those in injured rats without any treatments(Groups C) during the experimental period. Also, LOX expression in all injured groups(A、B、C groups) were upregulated in comparison to the control without spinal cord injury. At the same time point, the difference between two groups was significant statistically.Conclusions Spinal cord injury elevated LOX expression. Co Cl2-enhanced LOX expression facilitated functional recovery of injured spinal cord while BAPN-abolished LOX activity delayed the healing course of damaged spinal cord. Thus, BAPN and Co Cl2 induced alterations in LOX expression in damaged spinal cords of rats modulated recovery conditions of hind limb movement, a marker for spinal cord functions, as determined by BBB assays. These findings suggest that LOX plays an important role in the process of repair in acute spinal cord injuries in human.