MS Abstracts 12-99

Elucidation of the mechanisms involved in the regeneration of Oligodendrocytes and ReMyelination is a central issue in Multiple Sclerosis (MS) research.

We recently identified a novel alternatively spliced, developmentally regulated Oligodendrocyte-specific protein designated MicroTubule-Associated Protein-2+13 [MicroTubule-Associated Protein-2 expressing exon 13 (MAP-2+13)].

MAP-2+13 is expressed in human fetal Oligodendrocytes during process extension and Myelination but is minimally expressed in normal mature CNS.

To test the hypothesis that MAP-2+13 is reexpressed in regenerating Oligodendrocytes in MS lesions, we examined the Brains of MS patients for the expression of this protein.

By ImmunoCytoChemistry using a series of MonoClonal AntiBodies specific for MAP-2+13, we determined that MAP-2+13 expression was up-regulated in all 31 lesions from 10 different MS Brains.

MAP-2+13 was expressed in regenerating Oligodendrocytes associated with DeMyelinated Lesions, with the highest counts found in regions of extensive ReMyelination.

By electron microscopy, MAP-2+13 was localized to Oligodendrocytes engaged in ReMyelination, evident by their process extension and association with thinly Myelinated (ReMyelinated) and DeMyelinated Axons.

These results suggest a hitherto unsuspected role for this MicroTubule-Associated Protein in Oligodendrocyte function during development and Myelin repair.

Adhesion Molecules are important in the trafficking of peripheral Leukocytes into the Central Nervous System, a major event in the PathoGenesis of Multiple Sclerosis, which is an Inflammatory and DeMyelinating Disease.

The latest MRI evidence supports clinical divergence between forms of Multiple Sclerosis With Relapses and the Primary/Progressive form Without Relapses, which shows fewer and smaller Inflammatory lesions.

With the aim of elucidating whether different Pathogenic mechanisms are involved in Primary/Progressive Multiple Sclerosis, in 89 patients:

1. 39 with the Primary/Progressive form
2. 25 with the Secondary/Progressive form
3. 25 with the Relapsing/Remitting form
4. 38 healthy controls

We compared membrane expression of the Adhesion Molecules ICAM-1 (CD54), LFA-1alpha (CD11a), VLA-4 [alpha(4)/ß(1) Integrin (CD49d/CD29)], L-Selectin (CD62L) and ICAM-3 (CD50) in peripheral blood and the Serum-soluble forms ICAM-1, L-Selectin, VCAM-1 and ICAM-3.

We found a significant decrease in Leucocyte surface expression of most of the Adhesion Molecules tested and an increase in soluble ICAM-1 and L-Selectin levels in Secondary/Progressive and Relapsing/Remitting Multiple Sclerosis compared with Primary/Progressive Multiple Sclerosis, which gave results similar to those in controls.

These results, which are supported by MRI evidence, show that trafficking of AutoReactive Leucocytes through the Blood-Brain Barrier is crucial to the PathoGenesis of Secondary/Progressive and Relapsing/Remitting forms of Multiple Sclerosis.

Whereas, other mechanisms leading to progressive Axonal damage would account for Primary/Progressive forms of the disease.

We studied quantitatively the fate of Oligodendrocytes (OGs) during lesion formation in 395 lesion areas from biopsy and autopsy tissue of 113 Multiple Sclerosis cases.

The density of OGs in Multiple Sclerosis lesions was variable at all stages of DeMyelinating activity, ranging from nearly complete loss to values exceeding those in the PeriPlaque White Matter (range 0-970 OGs/mm(2)).

To determine whether there were distinct patterns of OG pathology in different patients, we restricted our analysis to the 56 cases.

In which the longitudinal extent of the lesion extended from PeriPlaque White Matter into the active DeMyelinating edge and inactive plaque center.

Two major groups of OG pathology were defined by the presence or absence of increased OGs within the lesion:
1. In 70% (39 out of 56) of the cases, OGs were variably reduced during active stages of Myelin destruction, but reappeared within inactive or ReMyelinating areas.
2. In the remaining 30% (17 out of 56) of the cases, extensive destruction of Myelinating Cells at active sites of DeMyelination was observed, but OGs were absent in inactive plaque areas without ReMyelination.

In inactive areas, an increased number of OGs expressing ProteoLipid Protein (PLP) mRNA compared with those expressing Myelin Oligodendrocyte Glycoprotein (MOG) suggested these cells may have been derived from the Progenitor pool.

In all lesions from a given patient the pattern of OG pathology remained consistent.

A highly significant negative correlation was observed between number of Macrophages in lesions and number of MOG- and PLP mRNA-labelled OGs (MOG: r = -0.32, P < 0.0000118; PLP mRNA: r = -0.23, P < 0.00238).

OG density did not correlate with T-Cell and Plasma Cell inflammation, or Axonal Loss.

The profound Heterogeneity in extent and topography of OG destruction in active DeMyelinating Lesions suggests that in subsets of Multiple Sclerosis patients, Myelin, mature OGs and possibly OG Progenitors are differentially affected.

InterLeukin-10 (IL-10) is an AntiInflammatory Cytokine which may modulate disease expression in Multiple Sclerosis (MS).

Three dimorphic polymorphisms within the IL-10 promoter region at positions - 1082, - 819 and - 519 have previously been identified.

The - 1082*A allele has been associated with low and the - 1082*G allele with high in vitro IL-10 production.

We have genotyped 185 Caucasian MS patients and 211 ethnically matched controls for each of these three dimorphisms. MS patients were stratified for severity of disease outcome.

No associations were found for any IL-10 promoter polymorphisms when the MS cases were compared with controls or with disease outcome with regards to disability.