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Cell-autonomous defects in thymic epithelial cells disrupt endothelial-perivascular cell interactions in the mouse thymus.

Bryson JL, Griffith AV, Hughes B, Saito F, Takahama Y, Richie ER, Manley NR - PLoS ONE (2013)

Bottom Line: We show that endothelial cells initially enter the thymus at E13.5, with PDGFR-β(+) mesenchymal cells following at E14.5.At subsequent stages there were fewer capillaries, leaky blood vessels, disrupted endothelium - perivascular cell interactions, endothelial cell vacuolization, and an overall failure of vascular organization.These data further demonstrate a novel TEC-mesenchyme-endothelial interaction required for proper fetal thymus organogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Biology, University of Georgia, Athens, Georgia, USA.

ABSTRACT
The thymus is composed of multiple stromal elements comprising specialized stromal microenvironments responsible for the development of self-tolerant and self-restricted T cells. Here, we investigated the ontogeny and maturation of the thymic vasculature. We show that endothelial cells initially enter the thymus at E13.5, with PDGFR-β(+) mesenchymal cells following at E14.5. Using an allelic series of the thymic epithelial cell (TEC) specific transcription factor Foxn1, we showed that these events are delayed by 1-2 days in Foxn1 (Δ/Δ) mice, and this phenotype was exacerbated with reduced Foxn1 dosage. At subsequent stages there were fewer capillaries, leaky blood vessels, disrupted endothelium - perivascular cell interactions, endothelial cell vacuolization, and an overall failure of vascular organization. The expression of both VEGF-A and PDGF-B, which are both primarily expressed in vasculature-associated mesenchyme or endothelium in the thymus, were reduced at E13.5 and E15.5 in Foxn1 (Δ/Δ) mice compared with controls. These data suggest that Foxn1 is required in TECs both to recruit endothelial cells and for endothelial cells to communicate with thymic mesenchyme, and for the differentiation of vascular-associated mesenchymal cells. These data show that Foxn1 function in TECs is required for normal thymus size and to generate the cellular and molecular environment needed for normal thymic vascularization. These data further demonstrate a novel TEC-mesenchyme-endothelial interaction required for proper fetal thymus organogenesis.

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Thymus vascular patterning altered in Foxn1Δ mice.Immunofluorescence analysis on frozen sagittal sections of Foxn1+/Δ and Foxn1Δ/Δ newborn thymus for CD31+ (red) and PDGFR-β+ (green) cells in (A–C) Foxn1+/Δ and (D–F) Foxn1Δ/Δ mice. (G) Average mean fluorescence intensity for CD31 in Foxn1+/Δ (n = 8) Foxn1Δ/Δ (n = 6) thymus sections. Asterisks denote statistical significance (P<0.05). Scale bar, 50 µm; n = 3.
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pone-0065196-g006: Thymus vascular patterning altered in Foxn1Δ mice.Immunofluorescence analysis on frozen sagittal sections of Foxn1+/Δ and Foxn1Δ/Δ newborn thymus for CD31+ (red) and PDGFR-β+ (green) cells in (A–C) Foxn1+/Δ and (D–F) Foxn1Δ/Δ mice. (G) Average mean fluorescence intensity for CD31 in Foxn1+/Δ (n = 8) Foxn1Δ/Δ (n = 6) thymus sections. Asterisks denote statistical significance (P<0.05). Scale bar, 50 µm; n = 3.

Mentions: Thymic vascular patterning requires the formation of a primary blood vessel network and subsequent vascular pruning. This process culminates with the establishment of a capillary-rich cortex that connects to PCVs at the CMJ and within the medulla (Figure 6A–C). However, patterning of the thymus vascular network was defective in newborn Foxn1Δ/Δ mutants (Figure 6D–F), which displayed medium-large sized blood vessels throughout the organ, compared to controls. This apparent increase in CD31+ vasculature in mutant thymi was statistically significant (p<0.05), as shown by comparing the average mean fluorescence intensity measurements (Figure 6G) from Foxn1+/Δ (n = 8) and Foxn1Δ/Δ (n = 6) mutants.


Cell-autonomous defects in thymic epithelial cells disrupt endothelial-perivascular cell interactions in the mouse thymus.

Bryson JL, Griffith AV, Hughes B, Saito F, Takahama Y, Richie ER, Manley NR - PLoS ONE (2013)

Thymus vascular patterning altered in Foxn1Δ mice.Immunofluorescence analysis on frozen sagittal sections of Foxn1+/Δ and Foxn1Δ/Δ newborn thymus for CD31+ (red) and PDGFR-β+ (green) cells in (A–C) Foxn1+/Δ and (D–F) Foxn1Δ/Δ mice. (G) Average mean fluorescence intensity for CD31 in Foxn1+/Δ (n = 8) Foxn1Δ/Δ (n = 6) thymus sections. Asterisks denote statistical significance (P<0.05). Scale bar, 50 µm; n = 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672159&req=5

pone-0065196-g006: Thymus vascular patterning altered in Foxn1Δ mice.Immunofluorescence analysis on frozen sagittal sections of Foxn1+/Δ and Foxn1Δ/Δ newborn thymus for CD31+ (red) and PDGFR-β+ (green) cells in (A–C) Foxn1+/Δ and (D–F) Foxn1Δ/Δ mice. (G) Average mean fluorescence intensity for CD31 in Foxn1+/Δ (n = 8) Foxn1Δ/Δ (n = 6) thymus sections. Asterisks denote statistical significance (P<0.05). Scale bar, 50 µm; n = 3.
Mentions: Thymic vascular patterning requires the formation of a primary blood vessel network and subsequent vascular pruning. This process culminates with the establishment of a capillary-rich cortex that connects to PCVs at the CMJ and within the medulla (Figure 6A–C). However, patterning of the thymus vascular network was defective in newborn Foxn1Δ/Δ mutants (Figure 6D–F), which displayed medium-large sized blood vessels throughout the organ, compared to controls. This apparent increase in CD31+ vasculature in mutant thymi was statistically significant (p<0.05), as shown by comparing the average mean fluorescence intensity measurements (Figure 6G) from Foxn1+/Δ (n = 8) and Foxn1Δ/Δ (n = 6) mutants.

Bottom Line: We show that endothelial cells initially enter the thymus at E13.5, with PDGFR-β(+) mesenchymal cells following at E14.5.At subsequent stages there were fewer capillaries, leaky blood vessels, disrupted endothelium - perivascular cell interactions, endothelial cell vacuolization, and an overall failure of vascular organization.These data further demonstrate a novel TEC-mesenchyme-endothelial interaction required for proper fetal thymus organogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Biology, University of Georgia, Athens, Georgia, USA.

ABSTRACT
The thymus is composed of multiple stromal elements comprising specialized stromal microenvironments responsible for the development of self-tolerant and self-restricted T cells. Here, we investigated the ontogeny and maturation of the thymic vasculature. We show that endothelial cells initially enter the thymus at E13.5, with PDGFR-β(+) mesenchymal cells following at E14.5. Using an allelic series of the thymic epithelial cell (TEC) specific transcription factor Foxn1, we showed that these events are delayed by 1-2 days in Foxn1 (Δ/Δ) mice, and this phenotype was exacerbated with reduced Foxn1 dosage. At subsequent stages there were fewer capillaries, leaky blood vessels, disrupted endothelium - perivascular cell interactions, endothelial cell vacuolization, and an overall failure of vascular organization. The expression of both VEGF-A and PDGF-B, which are both primarily expressed in vasculature-associated mesenchyme or endothelium in the thymus, were reduced at E13.5 and E15.5 in Foxn1 (Δ/Δ) mice compared with controls. These data suggest that Foxn1 is required in TECs both to recruit endothelial cells and for endothelial cells to communicate with thymic mesenchyme, and for the differentiation of vascular-associated mesenchymal cells. These data show that Foxn1 function in TECs is required for normal thymus size and to generate the cellular and molecular environment needed for normal thymic vascularization. These data further demonstrate a novel TEC-mesenchyme-endothelial interaction required for proper fetal thymus organogenesis.

Show MeSH
Related in: MedlinePlus