Remyelination capacity of the MS brain decreases with disease chronicity

Objective: To analyze and compare the extent of remyelination in lesions from patients with multiple sclerosis (MS) who have a short (early MS lesions) or a long (chronic MS lesions) disease duration and to determine the influence of anatomic localization on the extent of remyelination. In early MS lesions, remyelination has been described as a relatively frequent event, in contrast to chronic MS lesions, where remyelination is absent or limited to the lesion border in the majority of lesions. However, no studies have been published that have quantified and compared the extent of remyelination in early and chronic MS lesions. Methods: We analyzed the occurrence of remyelination in 52 biopsies from 51 patients (early MS) and in 174 lesions from 36 autopsy cases (chronic MS) by immunohistochemistry for myelin proteins, and correlated our findings with anatomic localization, sex, age, and disease duration. Results: Significantly more lesions were remyelinated in early than in chronic MS (80.7% vs 60%). In chronic MS, subcortical lesions showed more extensive remyelination than periventricular lesions. The majority of cerebellar lesions were completely demyelinated. Conclusion: In summary, our data demonstrate that remyelination is a frequent event in early multiple sclerosis lesions. Furthermore, the anatomic localization of a lesion might influence the extent of remyelination. CNPase = 2,3-cyclic nucleotide 3-phosphodiesterase; LFB = Luxol fast blue; MBP = myelin basic protein; MOG = myelin oligodendrocyte protein; MS = multiple sclerosis; OPC = oligodendrocyte progenitor cell;PAS = periodic acid-Schiff; PBS = phosphate-buffered saline; PLP = proteolipid protein.