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Molecular and cytological analyses reveal distinct transformations of intestinal epithelial cells during Xenopus metamorphosis.

Okada M, Wen L, Miller TC, Su D, Shi YB - Cell Biosci (2015)

Bottom Line: Here, we carried out different double-staining with a number of cytological and molecular markers during T3-induced and natural metamorphosis in Xenopus laevis.Our studies demonstrated conclusively that the clusters of proliferating cells in the epithelium at the climax of metamorphosis are undifferentiated epithelial cells and express the well-known adult intestinal stem cell marker gene Lgr5.Our findings suggest that morphologically identical larval epithelial cells choose two alternative paths: programmed cell death or dedifferentiation to form adult stem cells, in response to T3 during metamorphosis with apoptosis occurring prior to the formation of the proliferating adult stem cell clusters (islets).

View Article: PubMed Central - PubMed

Affiliation: Section on Molecular Morphogenesis, Program in Cellular Regulation and Metabolism (PCRM), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), 18 Library Dr., Bethesda, MD 20892 USA.

ABSTRACT

Background: The thyroid hormone (T3)-induced formation of adult intestine during amphibian metamorphosis resembles the maturation of the mammalian intestine during postembryonic development, the period around birth when plasma T3 level peaks. This process involves de novo formation of adult intestinal stem cells as well as the removal of the larval epithelial cells through apoptosis. Earlier studies have revealed a number of cytological and molecular markers for the epithelial cells undergoing different changes during metamorphosis. However, the lack of established double labeling has made it difficult to ascertain the identities of the metamorphosing epithelial cells.

Results: Here, we carried out different double-staining with a number of cytological and molecular markers during T3-induced and natural metamorphosis in Xenopus laevis. Our studies demonstrated conclusively that the clusters of proliferating cells in the epithelium at the climax of metamorphosis are undifferentiated epithelial cells and express the well-known adult intestinal stem cell marker gene Lgr5. We further show that the adult stem cells and apoptotic larval epithelial cells are distinct epithelial cells during metamorphosis.

Conclusions: Our findings suggest that morphologically identical larval epithelial cells choose two alternative paths: programmed cell death or dedifferentiation to form adult stem cells, in response to T3 during metamorphosis with apoptosis occurring prior to the formation of the proliferating adult stem cell clusters (islets).

No MeSH data available.


Related in: MedlinePlus

EdU and TUNEL-labeling reveals that apoptotic and proliferating cells are non-overlapping epithelial cells during T3-induced intestinal metamorphosis. Premetamorphic stage 54 tadpoles treated with 10 nM T3 for 0 (A), 3 (B), or 6 days (C) and were sacrificed 1 h after injection with EdU. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–C) are shown in (a′–c′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1). Note that apoptosis in the epithelium occurred prior to the appearance of the clusters (islets) of EdU labeled cells and in distinct epithelial cells during T3 treatment (C, c′)
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Fig7: EdU and TUNEL-labeling reveals that apoptotic and proliferating cells are non-overlapping epithelial cells during T3-induced intestinal metamorphosis. Premetamorphic stage 54 tadpoles treated with 10 nM T3 for 0 (A), 3 (B), or 6 days (C) and were sacrificed 1 h after injection with EdU. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–C) are shown in (a′–c′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1). Note that apoptosis in the epithelium occurred prior to the appearance of the clusters (islets) of EdU labeled cells and in distinct epithelial cells during T3 treatment (C, c′)

Mentions: T3 induces both larval epithelial cell death and adult epithelial development. We next used double-labeling to simultaneously detect apoptotic cells with TUNEL and proliferating cells with EdU. Consistent with earlier reports [27], after 3 days of T3 treatment of premetamorphic tadpoles, larval epithelial cell death could be detected by TUNEL (Fig. 7B) and few apoptotic cells were detected after 6 days, although many EdU positive cells were present (Fig. 7C). No co-staining of any cells by TUNEL and EdU was detected throughout the T3 treatment. Similarly, during natural metamorphosis, there were many TUNEL and EdU positive cells at stage 60 (climax of metamorphosis) but no co-stained cells were detected (Fig. 8B, b′). Like what was observed during T3 treatment, apoptotic labeling peaked before cell proliferation, with little apoptotic signal detected by stage 62 when EdU labeling was the strongest (Fig. 8C, c′). These findings indicate that T3-induced apoptosis occurs earlier than the massive proliferation of the adult stem cells during metamorphosis and that the proliferating cells and apoptotic cells are distinct cell populations in the intestinal epithelium at the climax of metamorphosis.Fig. 7


Molecular and cytological analyses reveal distinct transformations of intestinal epithelial cells during Xenopus metamorphosis.

Okada M, Wen L, Miller TC, Su D, Shi YB - Cell Biosci (2015)

EdU and TUNEL-labeling reveals that apoptotic and proliferating cells are non-overlapping epithelial cells during T3-induced intestinal metamorphosis. Premetamorphic stage 54 tadpoles treated with 10 nM T3 for 0 (A), 3 (B), or 6 days (C) and were sacrificed 1 h after injection with EdU. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–C) are shown in (a′–c′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1). Note that apoptosis in the epithelium occurred prior to the appearance of the clusters (islets) of EdU labeled cells and in distinct epithelial cells during T3 treatment (C, c′)
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Fig7: EdU and TUNEL-labeling reveals that apoptotic and proliferating cells are non-overlapping epithelial cells during T3-induced intestinal metamorphosis. Premetamorphic stage 54 tadpoles treated with 10 nM T3 for 0 (A), 3 (B), or 6 days (C) and were sacrificed 1 h after injection with EdU. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–C) are shown in (a′–c′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1). Note that apoptosis in the epithelium occurred prior to the appearance of the clusters (islets) of EdU labeled cells and in distinct epithelial cells during T3 treatment (C, c′)
Mentions: T3 induces both larval epithelial cell death and adult epithelial development. We next used double-labeling to simultaneously detect apoptotic cells with TUNEL and proliferating cells with EdU. Consistent with earlier reports [27], after 3 days of T3 treatment of premetamorphic tadpoles, larval epithelial cell death could be detected by TUNEL (Fig. 7B) and few apoptotic cells were detected after 6 days, although many EdU positive cells were present (Fig. 7C). No co-staining of any cells by TUNEL and EdU was detected throughout the T3 treatment. Similarly, during natural metamorphosis, there were many TUNEL and EdU positive cells at stage 60 (climax of metamorphosis) but no co-stained cells were detected (Fig. 8B, b′). Like what was observed during T3 treatment, apoptotic labeling peaked before cell proliferation, with little apoptotic signal detected by stage 62 when EdU labeling was the strongest (Fig. 8C, c′). These findings indicate that T3-induced apoptosis occurs earlier than the massive proliferation of the adult stem cells during metamorphosis and that the proliferating cells and apoptotic cells are distinct cell populations in the intestinal epithelium at the climax of metamorphosis.Fig. 7

Bottom Line: Here, we carried out different double-staining with a number of cytological and molecular markers during T3-induced and natural metamorphosis in Xenopus laevis.Our studies demonstrated conclusively that the clusters of proliferating cells in the epithelium at the climax of metamorphosis are undifferentiated epithelial cells and express the well-known adult intestinal stem cell marker gene Lgr5.Our findings suggest that morphologically identical larval epithelial cells choose two alternative paths: programmed cell death or dedifferentiation to form adult stem cells, in response to T3 during metamorphosis with apoptosis occurring prior to the formation of the proliferating adult stem cell clusters (islets).

View Article: PubMed Central - PubMed

Affiliation: Section on Molecular Morphogenesis, Program in Cellular Regulation and Metabolism (PCRM), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), 18 Library Dr., Bethesda, MD 20892 USA.

ABSTRACT

Background: The thyroid hormone (T3)-induced formation of adult intestine during amphibian metamorphosis resembles the maturation of the mammalian intestine during postembryonic development, the period around birth when plasma T3 level peaks. This process involves de novo formation of adult intestinal stem cells as well as the removal of the larval epithelial cells through apoptosis. Earlier studies have revealed a number of cytological and molecular markers for the epithelial cells undergoing different changes during metamorphosis. However, the lack of established double labeling has made it difficult to ascertain the identities of the metamorphosing epithelial cells.

Results: Here, we carried out different double-staining with a number of cytological and molecular markers during T3-induced and natural metamorphosis in Xenopus laevis. Our studies demonstrated conclusively that the clusters of proliferating cells in the epithelium at the climax of metamorphosis are undifferentiated epithelial cells and express the well-known adult intestinal stem cell marker gene Lgr5. We further show that the adult stem cells and apoptotic larval epithelial cells are distinct epithelial cells during metamorphosis.

Conclusions: Our findings suggest that morphologically identical larval epithelial cells choose two alternative paths: programmed cell death or dedifferentiation to form adult stem cells, in response to T3 during metamorphosis with apoptosis occurring prior to the formation of the proliferating adult stem cell clusters (islets).

No MeSH data available.


Related in: MedlinePlus