RESUMO
Our understanding of the regulation of vascular development has exploded over the past decade. Prior to this time, our knowledge of vascular development was primarily based on classic descriptive studies. The identification of stem cells, lineage markers, specific growth factors and their receptors, and signalling pathways has facilitated a rapid expansion in information regarding details of the mechanisms that govern development of the vascular system.
Assuntos
Endotélio Vascular/embriologia , Células-Tronco Mesenquimais/citologia , Músculo Liso Vascular/embriologia , Animais , Diferenciação Celular , Linhagem da Célula , Proliferação de Células , Células Endoteliais/citologia , Endotélio Vascular/citologia , Endotélio Vascular/metabolismo , Efrinas/metabolismo , Proteínas Hedgehog/metabolismo , Humanos , Músculo Liso Vascular/citologia , Pericitos/citologia , Transdução de Sinais , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Endothelial-mesenchymal transdifferentiation (EMT) is believed to play a crucial role in embryonic vascular development and intimal thickening, which contributes to the pathogenesis of atherosclerotic lesions. However, the mechanisms by which it occurs, as well as the signals that control it, have not yet been elucidated. Given the important role played by the CD40-CD40 ligand (CD40L) system during the initiation and progress of atherosclerosis, we investigated whether both CD40 and CD40L were present in the aortic wall during EMT and the advanced stages of chicken embryo development. CD40-CD40L expression was found on endothelial cells (ECs), mesenchymal cells, and smooth muscle cells (SMCs) at all stages examined, and appeared to be distributed across the aortic wall. However, some notable differences between the expression patterns were observed. CD40 had a more restricted distribution compared to CD40L, and did not stain every cell type of the aortic wall. According to immunoblotting and enzyme-linked immunosorbent assay (ELISA) analyses, the CD40L content was highest at day 7 of development. An important and novel finding was the expression of CD40L in areas where ECs transdifferentiate into mesenchymal cells. Specifically, CD40L was associated to the surface of cells that were detaching and migrating from the monolayer of ECs, whereas for CD40 a very diffuse subcellular localization was seen at the monolayer and the detaching and migrating cells. These data suggest a possible role for CD40-CD40L interactions during EMT and the remodeling of the aorta.
Assuntos
Aorta/metabolismo , Antígenos CD40/metabolismo , Ligante de CD40/metabolismo , Endotélio Vascular/metabolismo , Mesoderma/metabolismo , Actinas/metabolismo , Animais , Aorta/embriologia , Western Blotting , Diferenciação Celular , Células Cultivadas , Embrião de Galinha , Endotélio Vascular/citologia , Endotélio Vascular/embriologia , Ensaio de Imunoadsorção Enzimática , Técnica Indireta de Fluorescência para Anticorpo , Técnicas Imunoenzimáticas , Mesoderma/citologia , Músculo Liso Vascular/citologia , Músculo Liso Vascular/embriologia , Músculo Liso Vascular/metabolismo , OrganogêneseRESUMO
Morphological studies have hypothesized different origins for the precursors of the vascular smooth muscle cells (SMCs). The intriguing possibility that intimal SMCs may arise from the endothelium has newly emerged. As a first step towards understanding of the possible mechanisms involved in the transdifferentiation of endothelium into smooth muscle cells, we characterized the in vivo phenotype of the cells located in the aortic wall (distal to the aortic arches). This was accomplished using advanced stages of chicken embryo development. Furthermore, we investigated whether the cells present at the intimal thickening derive from the endothelial cell transdifferentiation. Immunolabeling of serial cryosections suggested that mesenchymal cells observed in the intimal thickening may arise from the endothelium. These cells may persist either as non-muscle throughout the development or possibly convert to cells expressing smooth muscle alpha-actin (SM alpha-actin). To determine whether endothelial cells may actually transdifferentiate into mesenchymal cells, aortic explants from 14-day-old chicken embryos (stage 40) were used. We found that explanted endothelial cells lose their cobblestone-appearance and migrate toward cell-free area. Some of these cells maintain the vWf immunoreactivity, whereas other cells coordinately lose vWf and gain SM alpha-actin expression (transitional cells). Taken together these findings strongly support the possibility that embryonic aortic endothelial transdifferentiate into mesenchymal cells, some of which express SM alpha-actin. Since TGFbeta-3 is considered an essential factor during epithelial to mesenchymal transitions in earlier chicken heart development, we also investigated the distribution of this growth factor at day 14. Our observations indicated that the immunoreactivity for TGFbeta-3 in this stage may be associated with migrating mesenchymal cells and that this immunoreactivity appears to decrease as cell differentiation advances. Therefore, the present study provides evidence that could help to explain 1) the presence of cells displaying a phenotype reminiscent of fetal-like cells in the normal chicken aorta and in the intimal region of the human aorta; 2) the SM lineage diversity in the chicken embryo reported by others; 3) a subpopulation of immature cells in the subendothelial region of the main pulmonary arteries of fetal, neonatal and adult bovines; and 4) the presence of intimal cushions, intimal pads, eccentric and diffuse intimal thickening that are observed in mammalian and avian vessels at birth.
Assuntos
Aorta Torácica/embriologia , Endotélio Vascular/embriologia , Mesoderma , Músculo Liso Vascular/embriologia , Túnica Íntima/embriologia , Actinas/metabolismo , Animais , Aorta Torácica/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Técnicas de Cultura de Células , Diferenciação Celular , Movimento Celular , Embrião de Galinha , Endotélio Vascular/metabolismo , Técnicas Imunoenzimáticas , Mesoderma/citologia , Mesoderma/metabolismo , Proteínas dos Microfilamentos , Músculo Liso Vascular/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Túnica Íntima/metabolismo , Vimentina/metabolismo , Fator de von Willebrand/metabolismo , CalponinasRESUMO
Clear differences exist in the incidence and severity of atherosclerotic plaques that arise in different segments of the arterial tree. Aortic homograft transplant experiments in dogs showed that the greater incidence of plaque formation in the abdominal versus the thoracic aorta was due to intrinsic differences in the cell populations in these two segments rather than to hemodynamic factors. What is the basis for SMC diversity within a common vessel wall? Recent lineage analysis studies in the avian and mammalian embryo indicate that two distinct SMC lineages contribute to the formation of the major elastic outflow arteries including the aorta. A mixture of unique SMC types of diverse developmental lineages within a common vessel wall raises new questions about the potential for SMC type-specific responses to growth factors and cytokines involved in human atherosclerosis and restenosis.
Assuntos
Angioplastia Coronária com Balão/efeitos adversos , Doença das Coronárias/patologia , Doença das Coronárias/terapia , Modelos Animais de Doenças , Matriz Extracelular/patologia , Músculo Liso Vascular/patologia , Animais , Aorta Abdominal/patologia , Aorta Torácica/patologia , Linhagem da Célula , Citocinas/fisiologia , Cães , Substâncias de Crescimento/fisiologia , Humanos , Músculo Liso Vascular/embriologia , Neovascularização Patológica/fisiopatologia , Ratos , RecidivaRESUMO
Clear differences exist in the incidence and severity of atherosclerotic plaques that arise in different segments of the arterial tree. Aortic homograft transplant experiments in dogs showed that the greater incidence of plaque formation in the abdominal versus the thoracic aorta was due to intrinsic differences in the cell populations in these two segments rather than to hemodynamic factors. What is the basis for SMC diversity within a common vessel wall? Recent lineage analysis studies in the avian and mammalian embryo indicate that two distinct SMC lineages contribute to the formation of the major elastic outflow arteries including the aorta. A mixture of unique SMC types of diverse developmental lineages within a common vessel wall raises new questions about the potential for SMC type-specific responses to growth factors and cytokines involved in human atherosclerosis and restenosis