The Influence of Brain Injury or Peripheral Nerve Injury on Calcitonin Gene-Related Peptide Concentration Variation and Fractures Healing Process

To investigate the changes of calcitonin gene-related peptide (CGRP) in rat's blood plasma, spinal anterior motorneuron, and dorsal root ganglion (DRG) after fractures combined with central or peripheral nerve injuries and its influence on fracture healing, 72 healthy adult SD rats (male or female) were divided into 4 groups (18 rats in each group): group A, simple(left) tibial fracture; group B, left tibial fracture combined with left sciatic nerve injury; group C, left tibial fracture combined with T9-11 spinal cord transection injury; group D, left tibial fracture combined with right cerebral cortex injury. Group A was the control group. The concentration of serum CGRP was measured immediately, 1w, 2w, and 4w after injury using radio immunoassay. X-ray photograph was taken at 1w, 2w, and 4w after injury to assess fracture healing. The concentration of serum CGRP in spinal anterior motorneuron and dorsal root ganglion was measured 1w, 2w, and 4w after injury. Bony callus at 2w after injury using H.E.staining was observed. 1w and 2w after injury, the fracture line was still clear on the X-ray of all groups, but 4w after injury the fracture line disappeared with complete healing except the peripheral nerve injury group. By H.E. staining, we found lesser bony callus contents in the peripheral nerve injury group than the simple fracture group at 2w after injury; irregular bone trabecula and healing defect were found in the former group. While the spinal injury group and cerebral cortex injury group represented more bony callus than the simple fracture group, increased bone trabecula and regularity, medullary cavity occluded and finally solid bony connections were found. CGRP concentration in blood plasma and spinal anterior motorneuron represented no apparent differences among all groups during each observation period. For the dorsal root ganglion group, 1w after fracture, there was no apparent difference of CGRP concentration in the peripheral nerve injury group and cerebral cortex group compared with the control group (P 0.05), but the spinal injury group showed more CGRP than the control group (P 0.01). 2w after injury, the peripheral nerve injury group and cerebral cortex group also showed no difference compared with the control group, but the cerebral cortex group had more CGRP contents than the peripheral nerve injury group (P 0.05), and the spinal injury group showed more CGRP than the control group (P 0.01). 4w after injury, the peripheral nerve group, spinal injury group, and cerebral cortex injury group all showed higher concentration of CGRP than the control group. Among the 3 groups, the spinal injury group is the highest (P 0.01). When fracture combined with peripheral nerve injury, the healing process can be slowed down. In contrast, fracture combined with spinal injury and cerebral cortex injury will accelerate the healing process. The CGRP in dorsal root ganglion in spinal injury group and cerebral cortex injury group increased, which may have positive effects on fracture healing.