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Novel functional changes during podocyte differentiation: increase of oxidative resistance and H-ferritin expression.

Bányai E, Balogh E, Fagyas M, Arosio P, Hendrik Z, Király G, Nagy G, Tánczos B, Pócsi I, Balla G, Balla J, Bánfalvi G, Jeney V - Oxid Med Cell Longev (2014)

Bottom Line: We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges.Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression.Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Debrecen, Debrecen 4032, Hungary.

ABSTRACT
Podocytes are highly specialized, arborized epithelial cells covering the outer surface of the glomerular tuft in the kidney. Terminally differentiated podocytes are unable to go through cell division and hereby they are lacking a key property for regeneration after a toxic injury. Podocytes are long-lived cells but, to date, little is known about the mechanisms that support their stress resistance. Our aim was to investigate whether the well-known morphological changes during podocyte differentiation are accompanied by changes in oxidative resistance in a manner that could support their long-term survival. We used a conditionally immortalized human podocyte cell line to study the morphological and functional changes during differentiation. We followed the differentiation process for 14 days by time-lapse microscopy. During this period nondifferentiated podocytes gradually transformed into large, nonproliferating, frequently multinucleated cells, with enlarged nuclei and opened chromatin structure. We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges. Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression. Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

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Nuclear expansion and changes in chromatin structure during podocyte differentiation. (a) Representative images show the nuclei of nondifferentiated human podocytes kept under 33°C (permissive condition, left) and the nuclei of differentiated podocytes grown for 14 days at 37°C (nonpermissive condition, right) stained with DAPI. The size of the nucleus increased during the process of differentiation. (b) Chromatin structures in immature and mature podocytes are apparently different. Nuclear preparation of undifferentiated cells contains visible chromosomes with more condensed chromatin structure and several foci of heterochromatin in contrast with the loosely packed chromatin from differentiated cells.
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fig3: Nuclear expansion and changes in chromatin structure during podocyte differentiation. (a) Representative images show the nuclei of nondifferentiated human podocytes kept under 33°C (permissive condition, left) and the nuclei of differentiated podocytes grown for 14 days at 37°C (nonpermissive condition, right) stained with DAPI. The size of the nucleus increased during the process of differentiation. (b) Chromatin structures in immature and mature podocytes are apparently different. Nuclear preparation of undifferentiated cells contains visible chromosomes with more condensed chromatin structure and several foci of heterochromatin in contrast with the loosely packed chromatin from differentiated cells.

Mentions: We observed significant increase both in cellular size and in nuclear size of differentiated podocytes relative to the cell body and nuclei of nondifferentiated cells. Figure 3(a) shows small nondifferentiated (left) and large differentiated nuclei (right) of podocytes after staining with DAPI. This observation corresponds to the idea of a high transcription rate and a low or nonexistent replication rate of differentiated podocytes in the kidney. To further examine whether changes in nuclear size are associated with different chromatin structure, we stained chromatin with DAPI after lysing the nuclei of nondifferentiated and differentiated podocytes. In the nucleoplasm of undifferentiated podocytes there are several dispersed foci of heterochromatin where the transcription of genes is almost inactive (Figure 3(b)). Images also show visible chromosomes referring to a more condensed state of the chromatin, which indicates high mitotic activity. In comparison, in differentiated podocytes the organization of the chromatin structure is more homogeneous; fewer foci of heterochromatin are visible as actively transcribed genes are more loosely packaged. This finding testifies that a high rate of gene transcription and consequent protein synthesis is present in these cells. Tight chromatin packages and visible chromosomes can rarely be observed in mature cells, reflecting a weak tendency of differentiated podocytes to go through the cell cycle. Although it is known to be rare, mature podocytes under certain circumstances go through mitosis but they are unable to carry out cell division. This can be the explanation for the presence of bi- or multinucleated cells visualized by immunofluorescent dyes and very few condensed chromosomes in the nuclear preparations.


Novel functional changes during podocyte differentiation: increase of oxidative resistance and H-ferritin expression.

Bányai E, Balogh E, Fagyas M, Arosio P, Hendrik Z, Király G, Nagy G, Tánczos B, Pócsi I, Balla G, Balla J, Bánfalvi G, Jeney V - Oxid Med Cell Longev (2014)

Nuclear expansion and changes in chromatin structure during podocyte differentiation. (a) Representative images show the nuclei of nondifferentiated human podocytes kept under 33°C (permissive condition, left) and the nuclei of differentiated podocytes grown for 14 days at 37°C (nonpermissive condition, right) stained with DAPI. The size of the nucleus increased during the process of differentiation. (b) Chromatin structures in immature and mature podocytes are apparently different. Nuclear preparation of undifferentiated cells contains visible chromosomes with more condensed chromatin structure and several foci of heterochromatin in contrast with the loosely packed chromatin from differentiated cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4109136&req=5

fig3: Nuclear expansion and changes in chromatin structure during podocyte differentiation. (a) Representative images show the nuclei of nondifferentiated human podocytes kept under 33°C (permissive condition, left) and the nuclei of differentiated podocytes grown for 14 days at 37°C (nonpermissive condition, right) stained with DAPI. The size of the nucleus increased during the process of differentiation. (b) Chromatin structures in immature and mature podocytes are apparently different. Nuclear preparation of undifferentiated cells contains visible chromosomes with more condensed chromatin structure and several foci of heterochromatin in contrast with the loosely packed chromatin from differentiated cells.
Mentions: We observed significant increase both in cellular size and in nuclear size of differentiated podocytes relative to the cell body and nuclei of nondifferentiated cells. Figure 3(a) shows small nondifferentiated (left) and large differentiated nuclei (right) of podocytes after staining with DAPI. This observation corresponds to the idea of a high transcription rate and a low or nonexistent replication rate of differentiated podocytes in the kidney. To further examine whether changes in nuclear size are associated with different chromatin structure, we stained chromatin with DAPI after lysing the nuclei of nondifferentiated and differentiated podocytes. In the nucleoplasm of undifferentiated podocytes there are several dispersed foci of heterochromatin where the transcription of genes is almost inactive (Figure 3(b)). Images also show visible chromosomes referring to a more condensed state of the chromatin, which indicates high mitotic activity. In comparison, in differentiated podocytes the organization of the chromatin structure is more homogeneous; fewer foci of heterochromatin are visible as actively transcribed genes are more loosely packaged. This finding testifies that a high rate of gene transcription and consequent protein synthesis is present in these cells. Tight chromatin packages and visible chromosomes can rarely be observed in mature cells, reflecting a weak tendency of differentiated podocytes to go through the cell cycle. Although it is known to be rare, mature podocytes under certain circumstances go through mitosis but they are unable to carry out cell division. This can be the explanation for the presence of bi- or multinucleated cells visualized by immunofluorescent dyes and very few condensed chromosomes in the nuclear preparations.

Bottom Line: We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges.Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression.Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Debrecen, Debrecen 4032, Hungary.

ABSTRACT
Podocytes are highly specialized, arborized epithelial cells covering the outer surface of the glomerular tuft in the kidney. Terminally differentiated podocytes are unable to go through cell division and hereby they are lacking a key property for regeneration after a toxic injury. Podocytes are long-lived cells but, to date, little is known about the mechanisms that support their stress resistance. Our aim was to investigate whether the well-known morphological changes during podocyte differentiation are accompanied by changes in oxidative resistance in a manner that could support their long-term survival. We used a conditionally immortalized human podocyte cell line to study the morphological and functional changes during differentiation. We followed the differentiation process for 14 days by time-lapse microscopy. During this period nondifferentiated podocytes gradually transformed into large, nonproliferating, frequently multinucleated cells, with enlarged nuclei and opened chromatin structure. We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges. Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression. Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

Show MeSH
Related in: MedlinePlus