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Epileptogenic but MRI-normal perituberal tissue in Tuberous Sclerosis Complex contains tuber-specific abnormalities.

Sosunov AA, McGovern RA, Mikell CB, Wu X, Coughlin DG, Crino PB, Weiner HL, Ghatan S, Goldman JE, McKhann GM - Acta Neuropathol Commun (2015)

Bottom Line: Perituberal giant cells and astrocytes together formed characteristic "microtubers".A parallel analysis of tubers showed that many contained astrocytes with features of both protoplasmic and gliotic cells.Microtubers represent a novel pathognomonic finding in TSC and may represent an elementary unit of cortical tubers.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Recent evidence has implicated perituberal, MRI-normal brain tissue as a possible source of seizures in tuberous sclerosis complex (TSC). Data on aberrant structural features in this area that may predispose to the initiation or progression of seizures are very limited. We used immunohistochemistry and confocal microscopy to compare epileptogenic, perituberal, MRI-normal tissue with cortical tubers.

Results: In every sample of epileptogenic, perituberal tissue, we found many abnormal cell types, including giant cells and cytomegalic neurons. The majority of giant cells were surrounded by morphologically abnormal astrocytes with long processes typical of interlaminar astrocytes. Perituberal giant cells and astrocytes together formed characteristic "microtubers". A parallel analysis of tubers showed that many contained astrocytes with features of both protoplasmic and gliotic cells.

Conclusions: Microtubers represent a novel pathognomonic finding in TSC and may represent an elementary unit of cortical tubers. Microtubers and cytomegalic neurons in perituberal parenchyma may serve as the source of seizures in TSC and provide potential targets for therapeutic and surgical interventions in TSC.

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Related in: MedlinePlus

Astrogliosis delineates the border of cortical tubers. (a-c) High levels of GFAP (a) and CD44 (c) and low levels of glutamine synthetase (GS) (b) outline tubers from surrounding normal tissue. Note undulated surface of the tubers and appearance of small gliotic foci (microtubers) nearby (arrows, marked only some). (d) Gliotic tuber astrocytes reveal a profound decrease in EAAT2 and high levels of αB-Crystallin. Note: giant αB-Crystallin immunopositive cells (arrows) are present in tuber and in perituberal area. (e) A difference in the levels of GS and GFAP outline the main body (tuber) and gliotic protuberances (*) which make tuber border highly irregular in shape. (f) Protoplasmic (high levels of GS) and gliotic (high levels of GFAP) astrocytes are neatly segregated at a tuber border (dotted line). Note that giant cells (arrows) show high level of GS expression. (f1) (lower boxed area outlined in f) Only few protoplasmic astrocytes (arrow indicates one protoplasmic astrocyte) are located within the gliotic tuber tissue near the border. (f2) (upper boxed area outlined in f) Long processes of tuber astrocytes penetrate into the perituberal area populated with protoplasmic astrocytes (arrows). (d-f) Confocal microcopy, double immunostaining, counterstaining with Nissl. d’, e’, e”, and f’ represent split d, e, and f images, respectively. In d and d’ only split images obtained from double-immunostained sections are shown. Tuber border is depicted with dotted line. scale bars: 950 μm in a-c; 150 μm in d-f.
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Fig1: Astrogliosis delineates the border of cortical tubers. (a-c) High levels of GFAP (a) and CD44 (c) and low levels of glutamine synthetase (GS) (b) outline tubers from surrounding normal tissue. Note undulated surface of the tubers and appearance of small gliotic foci (microtubers) nearby (arrows, marked only some). (d) Gliotic tuber astrocytes reveal a profound decrease in EAAT2 and high levels of αB-Crystallin. Note: giant αB-Crystallin immunopositive cells (arrows) are present in tuber and in perituberal area. (e) A difference in the levels of GS and GFAP outline the main body (tuber) and gliotic protuberances (*) which make tuber border highly irregular in shape. (f) Protoplasmic (high levels of GS) and gliotic (high levels of GFAP) astrocytes are neatly segregated at a tuber border (dotted line). Note that giant cells (arrows) show high level of GS expression. (f1) (lower boxed area outlined in f) Only few protoplasmic astrocytes (arrow indicates one protoplasmic astrocyte) are located within the gliotic tuber tissue near the border. (f2) (upper boxed area outlined in f) Long processes of tuber astrocytes penetrate into the perituberal area populated with protoplasmic astrocytes (arrows). (d-f) Confocal microcopy, double immunostaining, counterstaining with Nissl. d’, e’, e”, and f’ represent split d, e, and f images, respectively. In d and d’ only split images obtained from double-immunostained sections are shown. Tuber border is depicted with dotted line. scale bars: 950 μm in a-c; 150 μm in d-f.

Mentions: To discriminate between perituberal cortex and tubers, it is first critical to demarcate the cortical tubers themselves in histological sections. Based on immunohistochemical analysis, we have found that astrogliosis is the best criterion for morphological discrimination between tubers and the surrounding neocortical parenchyma (Figure 1). In addition to providing a clear histological delineation of tubers, this proposal is in line with MRI data where both T1- and T2-weighted images correlate with the level of tissue sclerosis/gliosis [13]. Several markers of astrocytes were used to determine tuber astrogliosis and accordingly tuber borders. These included markers typical for gray matter protoplasmic astrocytes such as glutamine synthetase (GS) and the astrocyte specific glutamate transporters (EAAT1 and EAAT2), all of which showed profoundly lower levels in tubers (Figure 1). In addition, markers that are seen in reactive/gliotic astrocytes such as glial fibrillary acidic protein (GFAP), vimentin, CD44, αB-Crystallin, and S100 revealed striking increases in tuber tissue (Figure 1, only some shown). Tuber borders were thus clearly outlined, segregating perituberal protoplasmic astrocytes from tuber gliosis (Figure 1). We observed that the borders of tubers were not always smooth, displaying uneven profiles with many peripheral protrusions (Figure 1a,b,c,e). Long processes of tuber astrocytes penetrated into the perituberal parenchyma and intermingled with neighboring protoplasmic astrocytes (Figure 1f). Furthermore, small foci of astrogliosis (microtubers, see below) were regularly found near the tuber borders (Figure 1a,b,c).Figure 1


Epileptogenic but MRI-normal perituberal tissue in Tuberous Sclerosis Complex contains tuber-specific abnormalities.

Sosunov AA, McGovern RA, Mikell CB, Wu X, Coughlin DG, Crino PB, Weiner HL, Ghatan S, Goldman JE, McKhann GM - Acta Neuropathol Commun (2015)

Astrogliosis delineates the border of cortical tubers. (a-c) High levels of GFAP (a) and CD44 (c) and low levels of glutamine synthetase (GS) (b) outline tubers from surrounding normal tissue. Note undulated surface of the tubers and appearance of small gliotic foci (microtubers) nearby (arrows, marked only some). (d) Gliotic tuber astrocytes reveal a profound decrease in EAAT2 and high levels of αB-Crystallin. Note: giant αB-Crystallin immunopositive cells (arrows) are present in tuber and in perituberal area. (e) A difference in the levels of GS and GFAP outline the main body (tuber) and gliotic protuberances (*) which make tuber border highly irregular in shape. (f) Protoplasmic (high levels of GS) and gliotic (high levels of GFAP) astrocytes are neatly segregated at a tuber border (dotted line). Note that giant cells (arrows) show high level of GS expression. (f1) (lower boxed area outlined in f) Only few protoplasmic astrocytes (arrow indicates one protoplasmic astrocyte) are located within the gliotic tuber tissue near the border. (f2) (upper boxed area outlined in f) Long processes of tuber astrocytes penetrate into the perituberal area populated with protoplasmic astrocytes (arrows). (d-f) Confocal microcopy, double immunostaining, counterstaining with Nissl. d’, e’, e”, and f’ represent split d, e, and f images, respectively. In d and d’ only split images obtained from double-immunostained sections are shown. Tuber border is depicted with dotted line. scale bars: 950 μm in a-c; 150 μm in d-f.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
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Fig1: Astrogliosis delineates the border of cortical tubers. (a-c) High levels of GFAP (a) and CD44 (c) and low levels of glutamine synthetase (GS) (b) outline tubers from surrounding normal tissue. Note undulated surface of the tubers and appearance of small gliotic foci (microtubers) nearby (arrows, marked only some). (d) Gliotic tuber astrocytes reveal a profound decrease in EAAT2 and high levels of αB-Crystallin. Note: giant αB-Crystallin immunopositive cells (arrows) are present in tuber and in perituberal area. (e) A difference in the levels of GS and GFAP outline the main body (tuber) and gliotic protuberances (*) which make tuber border highly irregular in shape. (f) Protoplasmic (high levels of GS) and gliotic (high levels of GFAP) astrocytes are neatly segregated at a tuber border (dotted line). Note that giant cells (arrows) show high level of GS expression. (f1) (lower boxed area outlined in f) Only few protoplasmic astrocytes (arrow indicates one protoplasmic astrocyte) are located within the gliotic tuber tissue near the border. (f2) (upper boxed area outlined in f) Long processes of tuber astrocytes penetrate into the perituberal area populated with protoplasmic astrocytes (arrows). (d-f) Confocal microcopy, double immunostaining, counterstaining with Nissl. d’, e’, e”, and f’ represent split d, e, and f images, respectively. In d and d’ only split images obtained from double-immunostained sections are shown. Tuber border is depicted with dotted line. scale bars: 950 μm in a-c; 150 μm in d-f.
Mentions: To discriminate between perituberal cortex and tubers, it is first critical to demarcate the cortical tubers themselves in histological sections. Based on immunohistochemical analysis, we have found that astrogliosis is the best criterion for morphological discrimination between tubers and the surrounding neocortical parenchyma (Figure 1). In addition to providing a clear histological delineation of tubers, this proposal is in line with MRI data where both T1- and T2-weighted images correlate with the level of tissue sclerosis/gliosis [13]. Several markers of astrocytes were used to determine tuber astrogliosis and accordingly tuber borders. These included markers typical for gray matter protoplasmic astrocytes such as glutamine synthetase (GS) and the astrocyte specific glutamate transporters (EAAT1 and EAAT2), all of which showed profoundly lower levels in tubers (Figure 1). In addition, markers that are seen in reactive/gliotic astrocytes such as glial fibrillary acidic protein (GFAP), vimentin, CD44, αB-Crystallin, and S100 revealed striking increases in tuber tissue (Figure 1, only some shown). Tuber borders were thus clearly outlined, segregating perituberal protoplasmic astrocytes from tuber gliosis (Figure 1). We observed that the borders of tubers were not always smooth, displaying uneven profiles with many peripheral protrusions (Figure 1a,b,c,e). Long processes of tuber astrocytes penetrated into the perituberal parenchyma and intermingled with neighboring protoplasmic astrocytes (Figure 1f). Furthermore, small foci of astrogliosis (microtubers, see below) were regularly found near the tuber borders (Figure 1a,b,c).Figure 1

Bottom Line: Perituberal giant cells and astrocytes together formed characteristic "microtubers".A parallel analysis of tubers showed that many contained astrocytes with features of both protoplasmic and gliotic cells.Microtubers represent a novel pathognomonic finding in TSC and may represent an elementary unit of cortical tubers.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Recent evidence has implicated perituberal, MRI-normal brain tissue as a possible source of seizures in tuberous sclerosis complex (TSC). Data on aberrant structural features in this area that may predispose to the initiation or progression of seizures are very limited. We used immunohistochemistry and confocal microscopy to compare epileptogenic, perituberal, MRI-normal tissue with cortical tubers.

Results: In every sample of epileptogenic, perituberal tissue, we found many abnormal cell types, including giant cells and cytomegalic neurons. The majority of giant cells were surrounded by morphologically abnormal astrocytes with long processes typical of interlaminar astrocytes. Perituberal giant cells and astrocytes together formed characteristic "microtubers". A parallel analysis of tubers showed that many contained astrocytes with features of both protoplasmic and gliotic cells.

Conclusions: Microtubers represent a novel pathognomonic finding in TSC and may represent an elementary unit of cortical tubers. Microtubers and cytomegalic neurons in perituberal parenchyma may serve as the source of seizures in TSC and provide potential targets for therapeutic and surgical interventions in TSC.

Show MeSH
Related in: MedlinePlus