Pathologic heterogeneity persists in early active multiple sclerosis lesions

Abstract

Objective: Multiple sclerosis (MS) lesions demonstrate immunopathological heterogeneity in patterns of demyelination. Previous cross-sectional studies reported immunopatterns of demyelination were identical among multiple active demyelinating lesions from the same individual, but differed between individuals, leading to the hypothesis of intraindividual pathological homogeneity and interindividual heterogeneity. Other groups suggested a time-dependent heterogeneity of lesions. The objective of our present study was to analyze tissue samples collected longitudinally to determine whether patterns of demyelination persist over time within a given patient.

Methods: Archival tissue samples derived from patients with pathologically confirmed central nervous system inflammatory demyelinating disease who had undergone either diagnostic serial biopsy or biopsy followed by autopsy were analyzed immunohistochemically. The inclusion criteria consisted of the presence of early active demyelinating lesions--required for immunopattern classification--obtained from the same patient at 2 or more time points.

Results: Among 1,321 surgical biopsies consistent with MS, 22 cases met the study inclusion criteria. Twenty-one patients (95%) showed a persistence of immunopathological patterns in tissue sampled from different time points. This persistence was demonstrated for all major patterns of demyelination. A single patient showed features suggestive of both pattern II and pattern III on biopsy, but only pattern II among all active lesions examined at autopsy.

Interpretation: These findings continue to support the concept of patient-dependent immunopathological heterogeneity in early MS and suggest that the mechanisms and targets of tissue injury may differ among patient subgroups. These observations have potentially significant implications for individualized therapeutic approaches.

Figure 1. Early active demyelinating MS lesion

Early MS lesions are characterized by cellular lesions infiltrated by numerous macrophages and the presence of reactive gliosis (A: HE). Lesions are demyelinated and display LFB-positive degradation products within macrophages, indicating recent myelin breakdown (B: LFB/PAS). T cell inflammation is variable and may be low (C: anti-CD3), whereas macrophages are abundant (D: KiM1P staining). Early active demyelinating lesions, which represent the earliest lesion stage, contain macrophages immunoreactive for minor myelin proteins (E: anti-MOG, F: anti-MAG, single of the numerous myelin laden macrophages are indicated by arrows). Original magnifications: A–D: ×20, E/F: ×40; Scale bars: A: 200µm, E: 100µm.

Figure 2

Bar plot of symptoms leading to initial biopsy overall and relative to immunopattern. Percentages shown are based on 19 subjects with documented symptoms. (We could not ascertain symptoms for three subjects.) Subjects can have multiple symptoms.

Figure 3. Persistence of pattern I pathology

Pattern I immunopathology was observed in both biopsies from the same MS patient performed at different time points (interval 3mo 28days, patient #2) and from different lesion locations (left occipital and right parieto-occipital). Early active lesions in both specimens revealed demyelination with similar loss of myelin proteins (A/C/E/G: anti-MOG, B/D/F/H: anti-MAG). Minor myelin proteins within macrophages indicate early active demyelination (arrows in C,D,G,H). Complement activation products within macrophages were absent (not shown). Original magnifications: A/B: ×10, C/D/G/H: ×40, E/F: ×20; Scale bars: A: 500µm, C: 100µm, E: 200µm.

Figure 4. Persistence of pattern II pathology

Pattern II immunopathology was observed in both biopsies from the same MS patient performed at different time points and same lesion location (interval 1mo 8days, patient #18). Early active lesions in both specimens revealed demyelination with similar loss of myelin proteins (A/D: anti-MOG, B/E: anti-MAG, inserts in higher magnification to show minor myelin proteins within macrophages), as well as complement activation products within macrophages (C/F: anti-TCC). Original magnifications: A/B: ×20, C/F: ×40, D/E: ×10; Scale bars: A: 200µm, C: 100µm, D: 500µm.

Figure 5. Persistence of pattern III pathology

Pattern III pathology is observed in subsequent biopsies from the same patient (interval 20days, patient #21) with the same lesion biopsied twice. Both specimens were characterized by a preferential loss of MAG (B/F, MAG loss indicated by arrows) relative to MOG (A/E). Numerous apoptotic oligodendrocytes were present in areas of MAG loss (arrows, C: anti-CNPase, G: anti-PLP). Minor myelin proteins within macrophages indicate early active demyelinating activity (arrows; D/H: anti-MOG). Original magnifications: A/B/E/F: ×4, C/G: upper regions ×60, lower regions ×100, D/H: ×40; Scale bars: A: 500µm, C: 50µm for upper region and 10µm for lower region, D: 20µm.

Figure 6

Relationship of immunopatterns relative to time of biopsy and/or autopsy. To better show the data, the x-axis is linear for the first twelve months and logarithm thereafter. Question marks indicate unknown second biopsy date.