Effect Of Microencapsulated Rabbit Sciatic Nerve Xenotransplantation On Cells Apoptosis And Its Correlative Gene Expression After Spinal Cord Injury In Rats

Objective To observe the effect of microencapsulated rabbit sciatic cells xenotransplantation on neurocyte apoptosis and explore its protective mechanism during the period of secondary affection. Methods Hemisection injury at the T10 level was performed on Sprage Dawley (SD) rats and immediately, the microcapsules which were absorbed into gelfoams(absorbable gelatin sponge),were grafted into the lesion site. All the rats were randomly divided into 4 groups: normal control group; A injury control group; B free-cell microcapsule group and C microcapsule grafted group( rats were transplanted with gelfoams which have absorbed microcapsulated rabbit sciatic cells) .At 8hr and 1,3,7,14 days after injury , a 10mm cord segment centered at the lesion site was removed ,was placed in the same fixative overnight, and was embedded in paraffin. Serial 5μm crosssections were cut and stained with the methods of the terminal deoxynucleotidal transferase-mediated DUTP-biotin nick endlabeling(TUNEL ), and the Bcl-2 proteinexpression of neurocyte was measured immunohistochemically.Moreover, at the first four times, a 10mm cord was removed in the same way, then was used for flow cytometry(FCM) study. Results TUNEL-positive neurons were noted primarily restricted to the injury area 8-24 hr after lesion , with a maximum presence at 8 hr after injury. However 7 d after injury , a second wave of TUNEL-positive glial cells was noted in the white matter peripheral to the lesion and extanding at least several millimeters from the lesion site. The FCM showed that there are two apoptosis peaks, the first one appeared 1 d after injury ,the second peak appeared 7 d after injury. All the apoptosis of the Microcapsule grafted group are lower than of A and B group, and the distinction reached its maximum 7d after injury.Meanwhile,the Bcl-2 protein expression of the Microcapsule grafted group reached its peak 7 d after SCIand maintains its high level until 2 weeks later, however, the Bcl-2expression of injury control group decreased dramatically 3 d after injury. Conclusion Microcapsulated rabbit sciatic tissue cells transplantation can inhibit the apoptosis after SCI and improve the Bcl-2 protein expression on SD rats. It seemed that the implants upregulate the expression level of gene Bcl-2 and inhibit the apoptosis of neurons and glial cells.Perhaps the inhibition of demyelination due to oligodendrocytes apoptosis plays a great role in the secondary injury after SCI in white matter.