Effect of central and peripheral nerve injuries on contents of calcitonin gene-related peptide and fracture healing

Objective 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 possible influence on fracture healing. Methods A total of 72 healthy adult SD rats were divided into four groups, ie, left tibial fracture group (Group A), left tibial fracture combined with left sciatic nerve injury group (Group B), left tibial fracture combined with T9-11 spinal cord transection injury group (Group C) and left tibial fracture combined with right cerebral cortex injury group (Group D). The concentration of serum CGRP was measured by radioimmunoassay immediately, 1, 2 and 4 weeks after injury. The concentration of serum CGRP in spinal anterior motor-neuron and dorsal root ganglion was measured and X ray photograph taken at 1,2 and 4 weeks after inju-ry. Bony callus was collected at 2 weeks after injury for HE staining. Results The fracture line was still clear on X-ray of all groups 1 and 2 weeks after injury but disappeared with complete healing four weeks after injury in all groups except for Group B. Two weeks after injury, HE staining showed less bony callus contents in Group B than that of Group A but more bony callus contents in Groups C and D than that of Group A. CGRP concentration in blood plasma and spinal anterior motorneuron represented no apparentstatistical difference among all groups at each time point (P>0.05). Changes of CGRP con-centration in dorsal root ganglion were as follows: one week after injury, there was no apparent statistical difference in Groups B and D compared with Group A (P > 0.05), but Group A showed more CGRP than Group C (P 0.05), but CGRP in Group D was more than that in Group B (P < 0.05) and CGRP in Group C more than Group A (P <0.01); four weeks after injury, CGRP concentration was elevated in all groups especially Group C compared with Group A (P < 0.01). Conclusions When fracture is 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 healing process, when CGRP may exert positive effect. Key words: Wounds and injuries;  Nervous system;  Fracture healing;  Calcitonin gene-re-lated peptide