A Study On Differentially Expressed Genes Between Olfactory Ensheathing Cells And Schwann Cells In Rats

Both olfactory ensheathing cells (OECs) and Schwann cells(SCs) provide cellularenvironments that support the growth of damaged axons following transplantation intoexperimental models of CNS injury. Moreover, both cell types are able to remyelinate axonsfollowing transplantation into experimental models of demyelination, producing newmyelin sheaths that are indistinguishable from one another. Besides the similarites infunctions OECs are common with SCs in phenotypic properties and secretion ofneurotrophic factors such as nerve growth factor (NGF), brain derived neurotrophic factor(BDNF), ciliary-derived nerve growth factor(CNTF). However it has been demonstratedthat OECs are preferable to transplant after CNS injury than SCs in several aspects.OECs are specialized cells which support axons that leave the olfactory epithelium andproject though the peripheral nervous system into the olfactory bulb of the CNS and theyshould have some unique properties which allow them to guide and enhance regeneratingCNS axons though a normally growth inhibitory environment. Interactions between SCsand astrocytes have an adverse effect on regeneration following SCs transplantation into theCNS. For example, transplanted Schwann cells show limited migration into a host lesionenvironment characterized by reactive or scarring astrocytes, with the result that fewregenerating axons are able to exit the graft and reenter the host tissue and SCs can alsoarousing greater increase in the expression of axon growth inhibitory chondroitin sulfateproteoglycans (CSPGs). In contrast, OECs may exhibit greater compatibility withastrocytes than do Schwann cells. Transplanted OECs appear to elicit a less severe reactionin host astrocytes and less CSPGs expression, which may allow more axons to traversegraft–host boundaries and to penetrate further into the lesion environment. It will be usefulto understand CNS regeneration with establishing how the behavior of the two cells maydiffer and why one cell type might be preferable to transplant than the other given the broadsimilarity in the CNS repair of the two cells.In this project, some differentially expressed genes between OECs and SCs that may 2第三军医大学博士学位论文be beneficial to further exploitation in CNS regeneration have been identified usingsuppressed subtraction hybridization (SSH) method. Immunocytochemistry and electronmicroscopy are applied to study morphological characteristics of OECs acquired bydissecting ONL from olfactory bulb (OB) and purified with complements treatmentfollowing anti-Thy1.1 incubation. The main results are as follows:1.A population of OECs with 95% purity is acquiredMany cells supposed as fibroblasts, endothelium and neurons retract and detach fromculture dishes in 2 hours after purification. Few fibroblasts and endothelium can beobserved 24h later and the purity of OECs determined by anti-P75NGFr staining is 95% ormore. Purification procedure may repeat 6 days later to maintain the high purity.2. Immunocytochemical properties and ultrastructure of OECsCultured OECs show immunoreactivity to P75NGFr, N-CAM and GFAP.Ultrastructure of OECs shows an irregularly-shaped nucleus and the chromatin is uniformlydistributed throughout the karyoplasms. The cytoplasm contains abundant ribosomes andrough endoplasmic reticulum, and the plasma membrane shows a typical ruffledappearance.3. Four differentially expressed genes are obtained using SSH methodSequencing and BLAST of 45 clones result in 4 genes with known functions. Theproteins coded include hepatic leukemia factor (Hlf) which plays a role in synaptogenesis,Phr1(PAM) which also functions in synaptogenesis, gap junction membrane channel proteinalpha1 (Gja1,connexin43) which takes part in intercellular interactions andGlycosylphosphatidylinositol phospholipase D1 (GPLD1)one of whose functions is torelease proteins from their glycosylphosphatidylinositol (GPI) anchors at the cell surface.GPLD1 may destroy some proteins...