Oligodendrocyte Migration Research Articles

95 Maturity-Dependent Oligodendrocyte Apoptosis Caused by Hyperoxia

Background: In the developing human brain, periventricular leukomalacia (PVL) is the predominant white matter injury underlying the development of cerebral palsy. PVL has its peak incidence in the premature infant during a well-defined period in human brain development (23–32 weeks, postconceptional age) characterized by extensive oligodendrocyte migration and maturation. We hypothesized that the dramatic rise of oxygen tissue tension associated with mammalian birth may be harmful to immature oligodendrocytes. We therefore investigated the effects of hyperoxia on cultured rat premature, immature and mature oligodendroglia cells. Methods: Flow cytometry was used to assess apoptosis via annexin-V, anti-active caspase-3 antibody, and propidium iodide staining, while cell viability was measured by metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT). Results: Apoptosis was detected at various stages (early: annexin-V, effector: caspase-3) after 24–48 h incubation with hyperoxia (80% O2) in preoligodendrocytes, immature oligodendrocytes (OLN-93) but not in mature oligodendrocytes. These results were confirmed in MTT assays. Conclusion: Hyperoxia directly initiates the apoptotic cascade in immature oligodendrocytes and pre-oligodendroglia cells. This mechanism may contribute to the white matter damage observed in PVL.

A critical role for the protein tyrosine phosphatase receptor type Z in functional recovery from demyelinating lesions

Several lines of evidence suggest that tyrosine phosphorylation is a key element in myelin formation, differentiation of oligodendrocytes and Schwann cells, and recovery from demyelinating lesions. Multiple sclerosis is a demyelinating disease of the human central nervous system, and studies of experimental demyelination indicate that remyelination in vivo requires the local generation, migration or maturation of new oligodendrocytes, or some combination of these. Failure of remyelination in multiple sclerosis could result from the failure of any of these processes or from the death of oligodendrocytes. Ptprz encodes protein tyrosine phosphatase receptor type Z (Ptpz, also designated Rptpbeta), which is expressed primarily in the nervous system but also in oligodendrocytes, astrocytes and neurons. Here we examine the susceptibility of mice deficient in Ptprz to experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. We observe that mice deficient in Ptprz show impaired recovery from EAE induced by myelin oligodendrocyte glycoprotein (MOG) peptide. This sustained paralysis is associated with increased apoptosis of mature oligodendrocytes in the spinal cords of mutant mice at the peak of inflammation. We further demonstrate that expression of PTPRZ1, the human homolog of Ptprz, is induced in multiple sclerosis lesions and that the gene is specifically expressed in remyelinating oligodendrocytes in these lesions. These results support a role for Ptprz in oligodendrocyte survival and in recovery from demyelinating disease.

Chemokines Direct Glial Cells

The organization of the central nervous system (CNS) is complex and requires a finely tuned balance of attractant and repulsive signals for both the neurons and the glia. Tsai et al. determined that the chemokine CXCL1 and its receptor CXCR2 are essential for the proper migration of oligodendrocytes, which are the glial cells responsible for myelination, in the developing CNS. CXCL1 inhibited migration of platelet-derived growth factor-stimulated oligodendrocyte precursor cell (OPC) and promoted cell adhesion in culture. In slice preparations, CXCL1 addition inhibited dorsal migration of the OPCs. In CXCR2 -/- mice, there were fewer OPCs in the developing spinal cord, and their position was displaced toward the pial surface. Finally, experiments in which wild-type or CXCR2 -/- OPCs were injected into wild-type or CXCR2 -/- spinal cord slices confirmed the migration-inhibiting properties of CXCR2 signaling. Thus, chemokines continue to emerge as important migratory control signals in the developing nervous system. H.-H. Tsai, E. Frost, V. To, S. Robinson, C. ffrench-Constant, R. Geertman, R. M. Ransohoff, R. H. Miller, The chemokine receptor CXCR2 controls positioning of oligodendrocyte precursors in developing spinal cord by arresting their migration. Cell 110 , 373-383 (2002). [Online Journal]

Expression of Oligodendrocyte-Specific Protein/Claudin-11 in the Human Fetal Forebrain

Oligodendrocyte-specific protein (OSP)/claudin-11, which is the third most abundant CNS myelin protein, is localized to a variant of tight junctions in myelin sheaths. The distribution of this protein was investigated immunohistochemically in 7 human fetal brains (from 24 to 32 weeks of gestation. At 24 weeks of gestation, OSP/claudin-11-immunoreactive (IR) cell bodies are observed in the ganglionic eminence, internal capsule, medial medullary lamina and subthalamic nucleus. Between 30 and 32 weeks of gestation, cellular and fibrous immunolabeling is found in the above-mentioned brain areas. In addition, IR cell bodies are seen in the dorsal thalamus, globus pallidus and striatum. The distribution pattern of OSP/claudin-11-IR structures reflects which regions of the forebrain first display myelin sheaths. In addition, OSP/claudin-11 is expressed in the ganglionic eminence and adjacent cell clusters, indicating a role of this protein in the proliferation and migration of oligodendrocytes. Moreover, it is obvious that OSP/claudin-11 is first restricted to the somata of oligodendrocytes and later accumulates within their processes. This accumulation is in accordance with data in the literature demonstrating that OSP/claudin-11 is a specific protein of myelinic tight junctions. The latter may form a barrier isolating the extracellular compartment between myelin sheaths.

Characterization of the Mouse Peroxisome Proliferator-Activated Receptor δ Gene

Peroxisome proliferator-activated receptors (α, δ and γ) are ligand-activated transcription factors that are involved in multiple cellular responses. The PPARδ subtype is the least understood of all PPAR subtypes. PPARδ is activated by unsaturated fatty acids, PGI2, and by synthetic ligands. PPARδ-regulated genes have not been identified and the factors that control PPARδ expression are not known. The gene that encodes the mouse PPARδ gene is contained in >30 kb DNA sequence and organized in eight exons, six of which encode the PPARδ receptor. A PPARδ-luciferase reporter containing 694 bp 5′ upstream regulatory and 127 bp untranslated was introduced to primary brain cultures to begin a characterization of the DNA sequences that mediate transcriptional regulation of PPARδ. PPARδ-luciferase expression was 10 times higher in oligodendrocyte-containing mature cultures than in immature cultures, indicating that PPARδ may play a role during oligodendrocyte migration, proliferation, and/or maturation.

Development of astrocytes in the lamina cribrosa sclerae of the mouse optic nerve, with special reference to myelin formation.

In the mouse optic nerve, the optic nerve fiber layer in the retina, the optic papilla and the lamina cribrosa sclerae (LCS) just after penetrating the eyeball failed to generate myelin, whereas the optic nerve proper in the orbit was occupied by myelinated nerve fibers. The present study investigated development of the architecture of LCS, where the axons develop from unmyelinated to myelinated type, to elucidate how the initial part of axons was unmyelinated. At the LCS of the adult optic nerve, well developed astrocytes densely formed a cytoplasmic mesh-like frame through which unmyelinated fibers passed. The astrocytes here contained numerous and densely packed intermediate glial filaments and cell organelles. This framework formed by astrocytes appeared to be completed between 7 and 14 postnatal days before oligodendrocyte progenitors, migrated from the chiasm side, reached the proximal end of LCS, and began myelin formation. Thus the failure in myelin formation at the intraocular part and LCS possibly depended upon unsuccessful migration of oligodendrocytes beyond LCS constructed by specialized astrocytes, although other inhibitory factors for myelin formation, such as adhesion molecules distributed around LCS, may be unsolved.

OSP/claudin-11 forms a complex with a novel member of the tetraspanin super family and beta1 integrin and regulates proliferation and migration of oligodendrocytes.

Oligodendrocyte-specific protein (OSP)/claudin-11 is a major component of central nervous system myelin and forms tight junctions (TJs) within myelin sheaths. TJs are essential for forming a paracellular barrier and have been implicated in the regulation of growth and differentiation via signal transduction pathways. We have identified an OSP/claudin-11-associated protein (OAP)1, using a yeast two-hybrid screen. OAP-1 is a novel member of the tetraspanin superfamily, and it is widely expressed in several cell types, including oligodendrocytes. OAP-1, OSP/claudin-11, and beta1 integrin form a complex as indicated by coimmunoprecipitation and confocal immunocytochemistry. Overexpression of OSP/claudin-11 or OAP-1 induced proliferation in an oligodendrocyte cell line. Anti-OAP-1, anti-OSP/claudin-11, and anti-beta1 integrin antibodies inhibited migration of primary oligodendrocytes, and migration was impaired in OSP/claudin-11-deficient primary oligodendrocytes. These data suggest a role for OSP/claudin-11, OAP-1, and beta1 integrin complex in regulating proliferation and migration of oligodendrocytes, a process essential for normal myelination and repair.

The pathobiology of myelin mutants reveal novel biological functions of the MBP and PLP genes.

Substantial biological data indicate that the myelin basic protein (MBP) and myelin proteolipid protein (PLP/DM20) genes produce products with functions beyond that of serving as myelin structural proteins. Much of this evidence comes from studies on naturally-occurring and man-made mutations of these genes in mice and other species. This review focuses upon recent evidence showing the existence of other products of these genes that may account for some of these other functions, and recent studies providing evidence for alternative biological functions of PLP/DM20. The MBP and PLP/DM20 genes each encode the classic MBP and PLP isoforms, as well as a second family of proteins that are not involved in myelin structure. The biological roles of these other products of the genes are becoming clarified. The non-classic MBP gene products appear to be components of transcriptional complexes in the nucleus, and they also may be involved in signaling pathways in T-cells and in neural cells. The non-classic PLP/DM20 gene products appear to be components of intracellular transport vesicles in oligodendrocytes. There is evidence for other functions of the classic PLP/DM20 proteins, including a role in neural cell death mechanisms, autocrine and paracrine regulation of oligodendrocytes and neurons, intracellular transport and oligodendrocyte migration.

Chondroitin sulfates expressed on oligodendrocyte-derived tenascin-R are involved in neural cell recognition. Functional implications during CNS development and regeneration.

Tenascin-R (TN-R), an extracellular matrix constituent of the central nervous system (CNS), has been implicated in a variety of cell-matrix interactions underlying axon growth inhibition/guidance, myelination and neural cell migration during development and regeneration. Although most of the functional analyses have concentrated exclusively on the role of the core protein, the contribution of TN-R glycoconjugates present on many potential sites for N- and O-glycosylation is presently unknown. Here we provide first evidence that TN-R derived from whole rat brain or cultured oligodendrocytes expresses chondroitin sulfate (CS) glycosaminoglycans (GAGs), i.e., C-4S and C-6S, that are recognized by CS-56, a CS/dermatan sulfate-specific monoclonal antibody. Based on different in vitro approaches utilizing substrate-bound glycoprotein, we found that TN-R-linked CS GAGs (1) promote oligodendrocyte migration from white matter microexplants and increase the motility of oligodendrocyte lineage cells; (2) similar to soluble CS GAGs, induce the formation of glial scar-like structures by cultured cerebral astrocytes; and (3) contribute to the antiadhesive properties of TN-R for neuronal cell adhesion in an F3/F11-independent manner, but not to neurite outgrowth inhibition, by mechanism(s) sensitive to chondroitinase or CS-56 treatments. Furthermore, after transection of the postcommissural fornix in adult rat, CS-bearing TN-R was found to be stably upregulated at the lesion site. Our findings suggest the functional impact of TN-R-linked CS on neural cell adhesion and migration during brain morphogenesis and the contribution of TN-R to astroglial scar formation (CS-dependent) and axon growth inhibition (CS-independent), i.e., suppression of axon regeneration after CNS injury.

Involvement of OSP/claudin-11 in oligodendrocyte membrane interactions: role in biology and disease.

Oligodendrocyte-specific protein (OSP/claudin-11) is a four transmembrane protein concentrated in central nervous system myelin. Recent evidence has emerged suggesting that OSP/claudin-11 is involved in membrane interactions at tight junctions and with the extracellular matrix. OSP/claudin-11 seems to modulate proliferation and migration of oligodendrocytes presumably through these interactions. Furthermore, evidence is presented implicating OSP/claudin-11 as an autoantigen in the development of autoimmune demyelinating disease.

N-Cadherin Influences Migration of Oligodendrocytes on Astrocyte Monolayers

Oligodendrocyte cell migration is required for the development of the nervous system and the repopulation of demyelinated lesions in the adult central nervous system. We have investigated the role of the calcium-dependent adhesion molecules, the cadherins, in oligodendrocyte-astrocyte interaction and oligodendrocyte progenitor migration. Immunostaining demonstrated the expression of N-cadherin on the surfaces of both oligodendrocytes and astrocytes, and oligodendrocyte-like cells adhered to and spread on N-cadherin substrates. The blocking of cadherin function by antisera or specific peptides reduced adhesion of oligodendroglia to astrocyte monolayers, diminished contact time between oligodendrocyte processes and individual astrocytes, and significantly increased the migration of oligodendrocyte-like cells on astrocyte monolayers. Furthermore, a soluble cadherin molecule without adhesive properties increased oligodendroglial proliferation on various extracellular matrix substrates. These data suggest that cadherins are at least partially responsible for the poor migration-promoting properties of astrocytes and that decreasing cell–cell adhesion might effect repopulation of demyelinated multiple sclerosis lesions by oligodendrocyte progenitors.

Developmental migration of oligodendrocytes in the embryonic chick retina

The temporal changes in intensity of myelination of the nervous pathways in 0 to 42-day-old Wistar rats were quantitatively analyzed by immunohistochemistry with anti-proteolipid protein and compared with that obtained by immunohistochemistry with anti-myelin basic protein. Immunohistochemistry was performed on paraffin-embedded tissue according to the standard ABC technique. Intensity of myelination was examined by an image analyzing system. We analyzed nine nervous pathways: corpus callosum, optic tract, internal capsule, spinal tract of the trigeminal nerve, inferior cerebellar peduncle, cerebellar white matter, pyramidal tract, medial longitudinal fasciculus, and cuneate fasciculus. The presence of immunoreactive fibers for proteolipid protein (PLP) in the spinal tract of the trigeminal nerve, medial longitudinal fasciculus and cuneate fasciculus was noted on postnatal day 0. Those of the corpus callosum, inferior cerebellar peduncle, cerebellar white matter, pyramidal tract and internal capsule were noted on day 7, and that of optic tract on day 14. The time required to reach the intensity of myelination of day 42 was day 14 for the cuneate fasciculus, day 21 for the spinal tract of the trigeminal nerve, inferior cerebellar peduncle and medial longitudinal fasciculus, day 28 for the optic and pyramidal tracts, day 35 for the corpus callosum and day 42 for the internal capsule and cerebellar white matter. The appearance of immunoreactive fibers for PLP was usually earlier than that for myelin basic protein (MBP) and the pattern of difference between PLP and MBP can be classified into three groups: (1) their time of appearance and progress are almost the same, as in the optic tract; (2) the appearance and progress of PLP occur earlier than those of MBP, as in the pyramidal tract; (3) the appearance of PLP occurs earlier than that of MBP, but their progress is the same. Our findings revealed that the time of appearance and progress of myelination as measured by PLP are different among the nervous pathways, and that there is also a difference between PLP and MBP. This difference between PLP and MBP may indicate a functional difference between them.

Early development of the oligodendrocyte in the embryonic chick metencephalon

It has been demonstrated that the spinal cord oligodendrocytes in the vertebrates arise in the ventral ventricular zone adjacent to the floor plate in their early development. Because of the similarities of basic structures in the spinal cord and metencephalon, it is probable that the mode of early oligodendrocyte development in the metencephalon is the same as that in the spinal cord. We examined this possibility in chick embryos, using monoclonal antibodies O1 and O4, markers for oligodendrocyte lineage. An O4-positive (O4+) cell focus was observed in the medial ventricular zone of E5 chick ventral metencephalon (the earliest stage examined), adjacent to the floor plate. At E6, O4+ cells were dispersed from the medial to the lateral pons and, at E7, to the cerebellar anlagen. O4+ cells in the E6 brainstem and in the E7 cerebellum were unipolar in shape, whereas one day later, some of the labeled cells were multipolar with a few thin processes. O1 + oligodendrocytes first appeared at E8 in the ventromedial part of the pons and were distributed throughout the pons at E10 and in the cerebellum at E12. Explants from three subdivisions of the metencephalon (medial and lateral pons, and cerebellum) from E5 to E8 chick embryos were separately cultured to confirm the potential for generation of oligodendrocyte lineage. O4+ cells appeared in the culture of the E5 medial pons (the earliest stage examined), in the E6 lateral pons, and in the E7 cerebellum. In addition, E7 was the youngest stage from which cerebellar explants were able to generate O1+ oligodendrocytes. Our results clearly demonstrated the in vivo morphology of oligodendrocyte precursors in the metencephalon and their developmental appearance in a ventral-to-dorsal manner. From the bipolar morphology of O4+ cells and the spacio-temporal continuity of the dispersion, it is inferred that the initial dispersion of O4+ cells may involve oligodendrocyte migration from the focus of the medial pons to the lateral and dorsal parts of the metencephalon. J. Neurosci. Res. 48:212–225, 1997. © 1997 Wiley-Liss, Inc.

Early development of the oligodendrocyte in the embryonic chick metencephalon

It has been demonstrated that the spinal cord oligodendrocytes in the vertebrates arise in the ventral ventricular zone adjacent to the floor plate in their early development. Because of the similarities of basic structures in the spinal cord and metencephalon, it is probable that the mode of early oligodendrocyte development in the metencephalon is the same as that in the spinal cord. We examined this possibility in chick embryos, using monoclonal antibodies O1 and O4, markers for oligodendrocyte lineage. An O4-positive (O4+) cell focus was observed in the medial ventricular zone of E5 chick ventral metencephalon (the earliest stage examined), adjacent to the floor plate. At E6, O4+ cells were dispersed from the medial to the lateral pons and, at E7, to the cerebellar anlagen. O4+ cells in the E6 brainstem and in the E7 cerebellum were unipolar in shape, whereas one day later, some of the labeled cells were multipolar with a few thin processes. O1+ oligodendrocytes first appeared at E8 in the ventromedial part of the pons and were distributed throughout the pons at E10 and in the cerebellum at E12. Explants from three subdivisions of the metencephalon (medial and lateral pons, and cerebellum) from E5 to E8 chick embryos were separately cultured to confirm the potential for generation of oligodendrocyte lineage. O4+ cells appeared in the culture of the E5 medial pons (the earliest stage examined), in the E6 lateral pons, and in the E7 cerebellum. In addition, E7 was the youngest stage from which cerebellar explants were able to generate O1+ oligodendrocytes. Our results clearly demonstrated the in vivo morphology of oligodendrocyte precursors in the metencephalon and their developmental appearance in a ventral-to-dorsal manner. From the bipolar morphology of O4+ cells and the spacio-temporal continuity of the dispersion, it is inferred that the initial dispersion of O4+ cells may involve oligodendrocyte migration from the focus of the medial pons to the lateral and dorsal parts of the metencephalon.

Origin and migration of the optic nerve oligodendrocyte in the chick embryo

Origin and migration of the optic nerve oligodendrocyte in the chick embryo

Acquired peripapillary myelination associated with chronic papilledema

A patient with papilledema due to idiopathic intracranial hypertension developed bilateral progressive peripapillary myelination. This acquired myelination suggests a breakdown of the normal barrier to oligodendrocyte migration into the retina. However, ultrastructural studies of developmental and acquired myelination in animals have consistently found that the myelin is formed by peripheral nervous system myelin forming cells (Schwann cells) rather than central nervous system oligodendrocytes.

1202 Eary development and migration of oligodendrocyte in the metencephalon

1202 Eary development and migration of oligodendrocyte in the metencephalon

Oligodendrocyte precursors originate from both the dorsal and the ventral parts of the spinal cord

Oligodendrocytes have been recently claimed to originate from bilateral columns of precursors whose extension is limited to the ventral region of the neuroepithelium. We designed an experiment in which the developmental capabilities of the different regions of the ventricular epithelium could be tested. We exchanged isotopically and isochronically defined sectors of the E2 spinal cord between quail and chick embryos and followed the production and migration of oligodendrocytes by using a quail-specific cDNA probe encoding the oligodendrocyte marker Schwann cell myelin protein. We showed that oligodendrocytes are generated in vivo from both ventral and dorsal halves of the neural tube. Moreover, extensive ventro-dorsal, as well as dorsoventral, migrations of oligodendrogenic cells take place during spinal cord differentiation.

Myelination of the rat retina by transplantation of oligodendrocytes into 4-day-old hosts

Oligodendrocyte transplantation into the retina enables us to investigate the early events in myelin formation in a new in vivo system. The axons of rat retinal ganglion cells are unmyelinated in the eye but should express a myelination initiation signal since they acquire myelin posterior to the globe. The lamina cribrosa may block the migration of oligodendrocytes from the optic nerve into the retina. Animals that lack a lamina cribosa such as the rabbit have myelinated retinas. We have bypassed the lamina cribrosa by using transplantation techniques and inserted freshly isolated syngeneic 3-week-old rat oligodendrocytes into the unmyelinated 4-day-old rat retina during the period of active optic nerve myelination. The animals are sacrificed at 1-week intervals for 8 weeks. The retinas are examined immunocytochemically for myelin with an antibody to myelin basic protein (MBP). MBP-positive cells are seen extending processes at 1 and 2 weeks. Three and four week retinas show the formation of thicker and longer myelin sheaths oriented along the same radial path as the retinal ganglion axons with maximal MBP staining intensity seen by 5 weeks. Transplanted retinas are negative when stained for Po, a Schwann cell antigen, ruling out Schwann cell myelination of our retinas. We have shown that rat cerebral oligodendrocytes survive, mature, and express a myelin-specific protein in the retinal environment in a pattern consistent with myelination of ganglion cell axons. Retinal transplantation provides a new in vivo model to study oligodendrocyte development and axonal-glial interactions, free from the difficulties inherent in culture systems.

Patchy myelination pattern in the jimpy mouse brain: Immunohistochemical study

The jimpy (jp) mutation of the mouse leads to a dramatic decrease of myelination in the hemizygous mutant central nervous system (CNS). Several descriptions based on classical histology, immunohistochemistry, and electron microscopy (EM) have demonstrated the scarcity of myelin formation in the different parts of the CNS. The immunohistochemical study presented here showed a very singular patchy pattern of myelin distribution in the different areas of the whole mutant brain. The myelin patches are randomly dispersed without bilateral symmetry, and their density and location vary from one animal to another. No reproducible pattern of myelination could be found among the population observed. This distribution has been compared with observations on young heterozygotes and wild-type homozygotes from the same strain. A similar patchy and random distribution of myelin could be observed in heterozygotes, which present an intermediate level of myelination. This strongly suggests that a migration of precursors or immature oligodendrocytes (ODCs) from the periventricular zone followed by local multiplication of colonies of ODCs before myelination is a general feature in normal as well as pathological conditions.