Modality And Altrastructure Changes Of Motor Neurons In Spinal Cord Anterior Horn After Peripheral Nerve Injury

Objective:To observe the death rules and ultrastructural changes of motor neurons in spinal cord horn after peripheral nerve injury through establish rat sciatic nerve injury model. Preliminary discussion peripheral nerve defects after autologous nerve transplantation,if distal anastomotic resection could mobilize the ability of repair and regeneration in central neurons.Method:1. Thirty adult male and female wistar rats were randomly diveded into two groups, five in control group,twenty-five in experimental group.The experimental group was diveded into five subgroups according with the time of specimens after operation, five in each group.2. The rats of experimantal group were cut the sciatic nerve from the piriformis zero-to-five cm,and then were anastomisis. Ten rats were cut the sciatic nerve again from the fist anastomitic one cm,ananstomisis. For the control group,the sciatic nerve was only exposed.3. At 3,14,28days afrer the first operation and 14,28days after the second operation, specimen was obtained from the spinal cord(L4-L6) under deeply general anaesthesia.The change of number and morphology of motor neurons were observed on HE-stained sections; the number of apoptosis motor neurons was detected on Tunel;the ultrastructural change of spinal cord anterior horn motor neurons was observed with transmission electronic microscope.Results:1. All experimental group animals displayed unilateral lower limb paralysis postoperatively and other limbs were not affectde. Ulcer could be saw in the plantar.2. At each time point postoperatively, the HE—stained transverse sections showed:the number of motor neumns decreased significantly with soma swollen and atrophied. Cell nucleus pyknosised, disslove deven disappeaed. At 4 weeks postoperitively, the nmber of lost motor neurons in the experimental group was the most. The number of motor neurons in the experimental group was lower than the control group at all time points(P<0.05).3.Apoptotic cells in the experimental group were found at three days postoperation and gradually increased with time. The glial cells of maker-positive could be found at the same time. The number of apopototis cells reached the peak at the four weeks, then began to decrease.The number of apopototic cells in the experimental group was higher than the control group at all time points(P<0.05).4. The cell organelles of normal neurons in the spinal cord anterior horn were ditributed uniform in the perinuclear. A series of changes occurred to the ultrastructure of motor neuron since the three days postoperation. The cellular damage was the most severely at four weeks after the nerve injury. Rough endoplasmic reticulum zonal arrangement, expansion of endoplasmic reticulum pools, and degranulation.Ribosomal particles dispersed,moderate degenerative changes in mitochondria, most of the cristae membrane was unclear or even disappear.The volume of Golgi complex was small.There was a moderate amount of lipofuscin granules.The nocleolus was small too. From the fourteen days to the twenty-eight days after the second operation,the electron microscope image showed the damaged neurons begin to recovery, the survival neurons closed to normal nuclear morphology. The number of mitochondria were increased. Rough endoplasmic reticulum gradually returned to normal lamellar arrangement,which reflected the strong favor of cell synthesis of functional repair of axons.Conclusion:1.After peripheral nerve injury,the spinal cord motor neurons degeneration even death would occur,the number of neurons degree,apoptosis was the main form of neuronal death. The damaged neurons begun to recovery after four weeks.2.After peripheral nerve injury,the ultrastructural degeneration of cell organelles in spinal cord motor neurons gradually increased with the extend of time.As part of the re-establishment of neural feedback went to the same way, the damaged neurons gradually returned to normal shape after four weeks.3.If autologous nerve graft distal anastomosis resection could mobilize the ability of repair and regeneration in the central neurons remained to be further observed and deeply research.