Ramon Muñoz-Chápuli - Academia.edu (original) (raw)

Papers by Ramon Muñoz-Chápuli

Medicinal Research Reviews, 2006

Angiogenesis, the generation of new capillaries through a process of pre-existing microvessel spr... more Angiogenesis, the generation of new capillaries through a process of pre-existing microvessel sprouting, is under stringent control and normally occurs only during embryonic and post-embryonic development, reproductive cycle, and wound repair. However, in many pathological conditions (solid tumor progression, metastasis, diabetic retinopathy, hemangioma, arthritis, psoriasis and atherosclerosis among others), the disease appears to be associated with persistent upregulated angiogenesis. The development of specific anti-angiogenic agents arises as an attractive therapeutic approach for the treatment of cancer and other angiogenesis-dependent diseases. The formation of new blood vessels is a complex multi-step process. Endothelial cells resting in the parent vessels are activated by an angiogenic signal and stimulated to synthesize and release degradative enzymes allowing endothelial cells to migrate, proliferate and finally differentiate to give rise to capillary tubules. Any of these steps may be a potential target for pharmacological intervention. In spite of the disappointing results obtained initially in clinical trials with anti-angiogenic drugs, recent reports with positive results in phases II and III trials encourage expectations in their therapeutic potential. This review discusses the current approaches for the discovery of new compounds that inhibit angiogenesis, with emphasis on the clinical developmental status of anti-angiogenic drugs. © 2006 Wiley Periodicals, Inc. Med Res Rev, 26, No. 4, 483–530, 2006

Experientia, 2004

Endothelial cells receive multiple information from their environment that eventually leads them ... more Endothelial cells receive multiple information from their environment that eventually leads them to progress along all the stages of the process of formation of new vessels. Angiogenic signals promote endothelial cell proliferation, increased resistance to apoptosis, changes in proteolytic balance, cytoskeletal reorganization, migration and, finally, differentiation and formation of a new vascular lumen. We aim to review herein the main signaling cascades that become activated in angiogenic endothelial cells as well as the opportunities of modulating angiogenesis through pharmacological interference with these signaling mechanisms. We will deal mainly with the mitogen-activated protein kinases pathway, which is very important in the transduction of proliferation signals; the phosphatidylinositol-3-kinase/protein kinase B signaling system, particularly essential for the survival of the angiogenic endothelium; the small GTPases involved in cytoskeletal reorganization and migration; and the kinases associated to focal adhesions which contribute to integrate the pathways from the two main sources of angiogenic signals, i.e. growth factors and the extracellular matrix.

Histochemical Journal, 1999

We report morphological and immunohistochemical evidence for a translocation of cells from the co... more We report morphological and immunohistochemical evidence for a translocation of cells from the coelomic mesothelium to the aortic wall between the developmental stages HH16 and HH22 of the quail embryos. The coelomic mesothelial cells closest to the aorta showed, at these stages, increased mitotic activity, reduced intercellular adhesion, loss of tight junctions, and long basal cytoplasmic processes. Coinciding with these morphological traits, cytokeratin immunoreactivity was found in the mesothelium, in cells of the aortic wall and throughout the ventral periaortic mesenchyme (but not in the lateral and dorsal aortic regions). Vimentin immunoreactivity colocalized with cytokeratin in the mesothelial cells adjacent to the aorta. In the ventral aortic wall, cytokeratin colocalized with smooth muscle α-actin and with the 1E12 antigen (a smooth muscle-specific α-actinin isoform). We think that the morphological and immunolocalization data observed are compatible with an epithelial–mesenchymal transition by which mesothelial-derived cells contribute to the splanchnic mesoderm and aortic wall. The precise coincidence between the mesothelial contribution and the emergence of the aortic smooth muscle cells progenitors, as well as the immunolocalization data, suggest a potential relationship of the mesothelial-derived cells with this cell lineage. This may explain the observed ventrodorsal asymmetry in the distribution of smooth muscle cells progenitors in the aortic wall.

Anatomy and Embryology, 2000

Slug is a transcription factor involved in processes such as the formation of mesoderm and neural... more Slug is a transcription factor involved in processes such as the formation of mesoderm and neural crest, two developmental events that imply a transition from an epithelial to a mesenchymal phenotype. During late cardiac morphogenesis, mesenchymal cells originate from two epithelia – epicardial mesothelium and cushion endocardium. We aimed to check if Slug is expressed in these systems of epithelial-mesenchymal transition. We have immunolocated the Slug protein in the heart of quail embryos between Hamburger and Hamilton stages HH16 and HH30. In the proepicardium (the epicardial primordium), Slug was detected in most cells, mesothelial as well as mesenchymal. Slug immunoreactivity was strong in the mesenchyme of the endocardial cushions and subepicardium from its inception until HH24, but the immunoreactivity disappeared in later embryos. Only a small portion of the endocardial cells located in the areas of epithelial-mesenchymal transition (atrioventricular groove and outflow tract) were immunolabelled, mainly between HH16 and HH20. Endocardial cells from other cardiac segments were always negative, except for a transient, weak immunoreactivity that coincided with the development of the intertrabecular sinusoids of the ventricle. In contrast, virtually all cells of the epicardial mesothelium were immunoreactive until stage HH24. The mesenchymal cells that migrate to the heart through the spina vestibuli were also conspicuously immunoreactive. The myocardium was not labelled in the stages studied. Our results stress the involvement of Slug in the epithelial to mesenchymal transition. We suggest that Slug can constitute a reliable marker of the cardiac epithelial cells that are competent to transform into mesenchyme as well as a transient marker of the epithelial-derived mesenchymal cells in the developing heart.

Developmental Dynamics, 1997

A study about the hypothetical contribution of the epicardial cells to the subepicardial mesenchy... more A study about the hypothetical contribution of the epicardial cells to the subepicardial mesenchyme was carried out in Syrian hamster embryos of 9-12 days post coitum (dpc) and chick embryos of 3-5 days of incubation. In the epicardium and subepicardium of these embryos we have immunolocated the proteins cytokeratin (CK), vimentin (VIM), fibronectin (FN), and two antigens related to the transformation of endocardial cells into valvuloseptal mesenchyme, ES/130 and JB3. In the hamster embryos, CK ؉ subepicardial mesenchymal cells (SEMC) were apparently migrating from the primitive epicardium from 9.5 dpc at the atrioventricular (AV) groove and proximal outflow tract (OFT). The morphological signs of delamination extended by 11 dpc to the epicardium of the interventricular groove and the dorsal part of the ventricle. The relative abundance of the CK ؉ SEMC decreased in embryos of 12 dpc. VIM colocalized with CK in most SEMC, and in some epicardial mesothelial cells, mainly at the areas of delamination. CK immunoreactivity was also found in some early subepicardial capillaries. Similar observations were made in the chick embryos studied. The immunoreactive patterns obtained at the subepicardium with anti-FN, ES/130, and JB3 antibodies were similar to those reported in the areas of endothelial transformation of the endocardial cushions. We suggest that these observations are compatible with an epithelial-mesenchymal transformation involving the epicardial mesothelium and originating at least a part of the SEMC. Dev.

Anatomy and Embryology, 1998

Cardiac morphogenesis involves substantial remodeling processes that include cell transdifferent... more Cardiac morphogenesis involves substantial remodeling processes that include cell transdifferentiation and migration. The c-ets-1 protooncogene codes for a transcription factor that can transactivate a number of genes involved in developmental processes such as degradation of extracellular matrices and cell migration. We have immunolocated the ets-1 protein in the heart of quail and chick embryos between the Hamburger and Hamilton stages HH16 and HH37. In HH16–17 embryos, the ets-1 transcription factor was only detected in some endocardial cells and in most mesothelial and mesenchymal cells of the proepicardium. Ets-1 immunoreactivity increased markedly in the developing endocardial cushions, myocardium, epicardium and early subepicardial mesenchyme of HH18–19 embryos. By HH20–24 the immunoreactivity was found throughout the heart, with a stronger intensity in the areas of epithelial-mesenchymal transition of the endocardium and epicardium. In embryos between HH26 and HH33, ets-1 immunoreactivity increased in the cushion mesenchyme, atrioventricular endocardium, ventricular epicardium and subepicardial mesenchyme cells, but not in other areas of the heart. The immunoreactivity declined in the innermost part of the endocardial cushions. The subepicardial mesenchyme was particularly immunoreactive in these stages, coinciding with the development of the subepicardial vascular network. In fact, ets-1 colocalized with the quail vascular marker QH1 in the subepicardial mesenchymal cells. Ets-1-negative cells were abundant in the subepicardium and valvuloseptal tissue of the HH37 embryos. The results suggest that ets-1, probably through transactivation of genes such as urokinase-type plasminogen activator and matrix metalloproteinases, might play a crucial role in the differentiation of the cushion and subepicardial mesenchyme, the formation of the intratrabecular sinusoids and the early development of the cardiac vessels.

Developmental Biology, 1998

It has been proposed that the subepicardial mesenchymal cells (SEMC) originate from the primitive... more It has been proposed that the subepicardial mesenchymal cells (SEMC) originate from the primitive epicardium and also from migration of extracardiac mesenchyme from the liver area. We have studied the possibility of an origin of SEMC through transformation of the proepicardial mesothelium, as well as the potential of the early proepicardium to generate epicardium and SEMC in quail-chick chimeras. The study was carried out in quail and chick embryos between HH16 and HH29 stages. Most proepicardial cells, mesothelial as well as mesenchymal, were cytokeratin and vimentin immunoreactive, suggesting a cytoskeletal shift from the epithelial to the mesenchymal type. Furthermore, we immunolocated, in the proepicardial mesothelium, three proteins specifically expressed during the endothelial-mesenchymal transition of the endocardial cushions, namely the JB3/fibrillin-associated antigen, the ES/130 protein and the smooth muscle cell ␣-actin. Grafts of proepicardial tissue from HH16 -17 quail embryos into chick embryos of the same age originated large areas of donor-derived epicardium, including mesothelial, mesenchymal, and vascular cells. The donor-derived primitive epicardium showed segment-specific features, being squamous and adhered to the myocardium on the atrial wall and showing morphological signs of ingression in the atrioventricular groove and outflow tract. These morphological traits together with the distribution of vimentin, the ES/130 protein, and the JB3/fibrillin-associated antigen suggested a localized transformation of some epicardial mesothelial cells into mesenchyme. Most of the donor-derived cells, mesothelial and mesenchymal, showed the vascular marker QH1, which frequently colocalized with cytokeratin. Heterotopic grafts of quail splanchnopleura into the pericardial cavity of chick embryos originated a squamous, epicardial-like, cytokeratin-immunoreactive cell layer on the heart surface, as well as a few QH1 ؉ subepicardial and intramyocardial cells. The results suggest that a substantial part of the subepicardial mesenchyme, including the progenitors of the cardiac vessels, originates from the transformation of proepicardial and epicardial mesothelial cells into mesenchyme, and that the epicardial transition could be driven by a segment-specific myocardial signal.

Faseb Journal, 2001

+)-Aeroplysinin-1, an antibacterial brominated compound produced by certain sponges, was selected... more +)-Aeroplysinin-1, an antibacterial brominated compound produced by certain sponges, was selected during a blind high-throughput screening for new potential antiangiogenic compounds obtained from marine organisms. In a variety of experimental systems, representing the sequential events of the angiogenic process, aeroplysinin-1 treatment of endothelial cells resulted in strong inhibitory effects. Aeroplysinin-1 inhibited the growth of endothelial cells in culture and induced endothelial cell apoptosis. Capillary tube formation on Matrigel was completely abrogated by addition of aeroplysinin-1 at the low micromolar range. Aeroplysinin-1 also exhibited a clear inhibitory effect on the migration capabilities of endothelial cells. Zymographic assays showed that aeroplysinin-1 treatment produced a decrease in the concentration of matrix metalloproteinase-2 and urokinase in conditioned medium from endothelial cells. Finally, aeroplysinin-1 exhibited a dose-dependent inhibitory effect on the in vivo chorioallantoic membrane assay, showing potent apoptosis-inducing activity in the developing endothelium. The in vivo inhibition of angiogenesis by aeroplysinin-1 was confirmed by the Matrigel plug assay. Together, our data indicate that aeroplysinin-1 is a compound that interferes with key events in angiogenesis, making it a promising drug for further evaluation in the treatment of angiogenesisrelated pathologies.

Journal of Fish Biology, 1990

A study was carried out on the serum levels of cholesterol [total (TC) and that associated with h... more A study was carried out on the serum levels of cholesterol [total (TC) and that associated with high-density lipoproteins (HDLC)] and triglyceride (TG) in 127 specimens of Scyliorhinus canicula. The values obtained were correlated with sex, size, liver weight and reproductive stage. Results showed that male dogfish have higher levels of TC and HDLC, and lower TG than female. In adult males, TC increased and HDLC decreased with both size and spermatogenesis. Females carrying capsulated eggs showed a noticeable increase in TG together with a decrease of the HDLC levels, which were apparently not related with size.

Evolution & Development, 2008

SUMMARY The epicardium is the outer layer of the vertebrate heart. Both the embryonic epicardium ... more SUMMARY The epicardium is the outer layer of the vertebrate heart. Both the embryonic epicardium and its derived mesenchyme are critical to heart development, contributing to the coronary vasculature and modulating the proliferation of the ventricular myocardium. The embryonic epicardium arises from an extracardiac, originally paired progenitor tissue called the proepicardium, a proliferation of coelomic cells found at the limit between the liver and the sinus venosus. Proepicardial cells attach to and spread over the cardiac surface giving rise to the epicardium. Invertebrate hearts always lack of epicardium, and no hypothesis has been proposed about the origin of this tissue and its proepicardial progenitor in vertebrates. We herein describe the epicardial development in a representative of the most basal living lineage of vertebrates, the agnathan Petromyzon marinus (lamprey). The epicardium in lampreys develops by migration of coelomic cells clustered in a paired structure at the roof of the coelomic cavity, between the pronephros and the gut. Later on, these outgrowths differentiate into the pronephric external glomerulus (PEG), a structure composed of capillary networks, mesangial cells, and podocytes. This observation is consistent with the conclusion that the primordia of the most anterior pair of PEG in agnathans have been retained and transformed into the proepicardium in gnathostomes. Glomerular progenitor cells are highly vasculogenic and probably allowed for the vascularization of a cardiac tube primarily devoid of coronary vessels. This new hypothesis accounts for the striking epicardial expression of Wt1 and Pod1, two transcription factors essential for development of the excretory system.

Evolution & Development, 2005

Circulatory systems of vertebrate and invertebrate metazoans are very different. Large vessels of... more Circulatory systems of vertebrate and invertebrate metazoans are very different. Large vessels of invertebrates are constituted of spaces and lacunae located between the basement membranes of endodermal and mesodermal epithelia, and they lack an endothelial lining. Myoepithelial differentation of the coelomic cells covering hemal spaces is a frequent event, and myoepithelial cells often form microvessels in some large invertebrates. There is no phylogenetic theory about the origin of the endothelial cells in vertebrates. We herein propose that endothelial cells originated from a type of specialized blood cells, called amoebocytes, that adhere to the vascular basement membrane. The transition between amoebocytes and endothelium involved the acquisition of an epithelial phenotype. We suggest that immunological cooperation was the earliest function of these protoendothelial cells. Furthermore, their ability to transiently recover the migratory, invasive phenotype of amoebocytes (i.e., the angiogenic phenotype) allowed for vascular growth from the original visceral areas to the well-developed somatic areas of vertebrates (especially the tail, head, and neural tube). We also hypothesize that pericytes and smooth muscle cells derived from myoepithelial cells detached from the coelomic lining. As the origin of blood cells in invertebrates is probably coelomic, our hypothesis relates the origin of all the elements of the circulatory system with the coelomic wall. We have collected from the literature a number of comparative and developmental data supporting our hypothesis, for example the localization of the vascular endothelial growth factor receptor-2 ortholog in hemocytes of Drosophila or the fact that circulating progenitors can differentiate into endothelial cells even in adult vertebrates.

Differentiation, 1999

The existence of the hemangioblast, a common progenitor of the endothelial and hematopoietic cell... more The existence of the hemangioblast, a common progenitor of the endothelial and hematopoietic cell lineages, was proposed at the beginning of the century. Although recent findings seem to confirm its existence, it is still unknown when and how the hemangioblasts differentiate. We propose a hypothesis about the origin of hemangioblasts from the embryonic splanchnic mesothelium. The model is based on observations collected from the literature and from our own studies. These observations include: (1) the extensive population of the splanchnic mesoderm by mesothelial-derived cells coinciding with the emergence of the endothelial and hematopoietic progenitors; (2) the transient localization of cytokeratin, the main mesothelial intermediate filament protein, in some embryonic vessels and endothelial progenitors; (3) the possible origin of cardiac vessels from epicardial-derived cells; (4) the origin of endocardial cells from the splanchnic mesoderm when this mesoderm is an epithelium; (5) the evidence that mesothelial cells migrate to the hemogenic areas of the dorsal aorta. (6) Biochemical and antigenic similarities between mesothelial and endothelial cells. We suggest that the endothelium-lined vascular system arose as a specialization of the phylogenetically older coelomic cavities. The origin of the hematopoietic cells might be related to the differentiation, reported in some invertebrates, of coelomocytes from the coelomic epithelium. Some types of coelomocytes react against microbial invasion and other types transport respiratory pigments. We propose that this phylogenetic origin is recapitulated in the vertebrate ontogeny and explains the differentiation of endothelial and blood cells from a common mesothelial-derived progenitor.& b d y :

Cells Tissues Organs, 2001

Questions on the embryonic origin and developmental significance of the epicardium did not receiv... more Questions on the embryonic origin and developmental significance of the epicardium did not receive much recognition for more than a century. It was generally thought that the epicardium was derived from the outermost layer of the primitive myocardium of the early embryonic heart tube. During the past few years, however, there has been an increasing interest in the development of the epicardium. This was caused by a series of new embryological data. The first data showed that the epicardium did not derive from the primitive myocardium but from a primarily extracardiac primordium, called the proepicardial serosa. Subsequent data then suggested that the proepicardial serosa and the newly formed epicardium provided nearly all cellular elements of the subepicardial and intermyocardial connective tissue, and of the coronary vasculature. Recent data even suggest important modulatory roles of the epicardium and of other proepicardium-derived cells in the differentiation of the embryonic myocardium and cardiac conduction system. The present paper reviews our current knowledge on the origin and embryonic development of the epicardium.

Developmental Biology, 2007

Previous studies of knock-out mouse embryos have shown that the Wilms' tumor suppressor gene (Wt1... more Previous studies of knock-out mouse embryos have shown that the Wilms' tumor suppressor gene (Wt1) is indispensable for the development of kidneys, gonads, heart, adrenals and spleen. Using OPT (Optical Projection Tomography) we have found a new role for Wt1 in mouse liver development. In the absence of Wt1, the liver is reduced in size, and shows lobing abnormalities. In normal embryos, coelomic cells expressing Wt1, GATA-4, RALDH2 and RXRα delaminate from the surface of the liver, intermingle with the hepatoblasts and incorporate to the sinusoidal walls. Some of these cells express desmin, suggesting a contribution to the stellate cell population. Other cells, keeping high levels of RXRα immunoreactivity, are negative for stellate or smooth muscle cell markers. However, coelomic cells lining the liver of Wt1-null embryos show decreased or absent RALDH2 expression, the population of cells expressing high levels of RXRα is much reduced and the proliferation of hepatoblasts and RXRα-positive cells is significantly decreased. On the other hand, the expression of smooth muscle cell specific α-actin increases throughout the liver, suggesting an accelerated and probably anomalous differentiation of stellate cell progenitors. We describe a similar retardation of liver growth in RXRα-null mice as well as in chick embryos after inhibition of retinoic acid synthesis. We propose that Wt1 expression in cells delaminating from the coelomic epithelium is essential for the expansion of the progenitor population of liver stellate cells and for liver morphogenesis. Mechanistically, at least part of this effect is mediated via the retinoic acid signaling pathway.

Journal of Molecular and Cellular Cardiology, 2003

Transposition of great arteries in humans is associated with a wide spectrum of coronary artery p... more Transposition of great arteries in humans is associated with a wide spectrum of coronary artery patterns. However, no information is available about how this pattern diversity develops. We have studied the development of the coronary arteries in mouse embryos with a targeted mutation of perlecan, a mutation that leads to ventriculo-arterial discordance and complete transposition in about 70% of the embryos. The perlecan-deficient embryos bearing complete transposition showed a coronary artery pattern consisting of right and left coronary arteries arising from the morphologically dorsal and ventral sinuses of Valsalva, respectively. The left coronary artery gives rise to a large septal artery and runs along the ventral margin of the pulmonary root. In the earliest embryos where transposition could be confirmed (12.5 d post coitum), a dense subepicardial vascular plexus is located in this ventral margin. In wild-type mice, however, capillaries are very scarce on the ventral surface of the pulmonary root and the left coronary artery runs dorsally to this root. We suggest that the establishment of the diverse coronary artery patterns is determined by the anatomical arrangement and the capillary density of the peritruncal vascular plexus, a plexus that spreads from the atrio-ventricular groove and grows around the aortic or pulmonary roots depending on the degree of the short-axis aortopulmonary rotation. This simple model, based on very few assumptions, might explain all the observed variation of the coronary artery patterns in humans with transposition, as well as our observations on the perlecan-deficient and the normal mice.

Cell and Tissue Research, 2001

The Wilms' tumour suppressor gene WT1 encodes a zinc-finger transcription factor which is essenti... more The Wilms' tumour suppressor gene WT1 encodes a zinc-finger transcription factor which is essential for the development of kidney, gonads, spleen and adrenals. WT1-null embryos lack all of these viscerae and they also show a thin ventricular myocardium and unexpectedly die from cardiac failure between 13 and 15 days post coitum. We studied the localization of the WT1 protein in chick and quail embryos between stages HH18 and HH35. In early embryos, WT1 protein was located in specific areas of the coelomic mesothelium adjacent to the nephric ducts, the myocardium or the primordia of the endodermal organs (gut, liver and lungs). These mesothelial areas also showed localized expression of Slug, a zinc-finger transcription factor involved in epithelial-mesenchymal transitions. WT1+ mesenchymal cells were always found below the immunoreactive mesothelial areas, either forming a narrow band on the surface of the endodermal organs (gut, liver and lungs) or migrating throughout the mesodermal organs (mesonephros, metanephros, gonads, spleen and heart). In the developing heart, the invasion of WT1+ cells started at stage HH26, and all the ventricular myocardium was pervaded by these cells, presumably derived from the epicardium, at HH30. We suggest that WT1 is not required for the epithelial-mesenchymal transition of the coelomic mesothelium, but it might be a marker of the mesothelial-derived cells, where this protein would be acting as a repressor of the differentiation.

Developmental Biology, 2002

The first aim of the study was to determine the tissue-specific distribution of two molecules tha... more The first aim of the study was to determine the tissue-specific distribution of two molecules that are thought to play a crucial function in the interaction between EPDCs and other cardiac tissues, namely the Wilms' Tumor transcription factor (WT1) and retinaldehyde-dehydrogenase2 (RALDH2). This study was performed in normal avian and in quail-to-chick chimeric embryos. It was found that EPDCs that maintain the expression of WT1 and RALDH2 initially populate the subepicardial space and subsequently invade the ventricular myocardium. As EPDCs differentiate into the smooth muscle and endothelial cell lineage of the coronary vessels, the expression of WT1 and RALDH2 becomes downregulated. This process is accompanied by the upregulation of lineage-specific markers. We also observed EPDCs that continued to express WT1 (but very little RALDH2) which did not contribute to the formation of the coronary system. A subset of these cells eventually migrates into the atrioventricular (AV) cushions, at which point they no longer express WT1. The WT1/ RALDH2-negative EPDCs in the AV cushions do, however, express the smooth muscle cell marker caldesmon. The second aim of this study was to determine the impact of abnormal epicardial growth on cardiac development. Experimental delay of epicardial growth distorted normal epicardial development, reduced the number of invasive WT1/RALDH2-positive EPDCs, and provoked anomalies in the coronary vessels, the ventricular myocardium, and the AV cushions. We suggest that the proper development of ventricular myocardium is dependent on the invasion of undifferentiated, WT1-positive, retinoic acid-synthesizing EPDCs. Furthermore, we propose that an interaction between EPDCs and endocardial (derived) cells is imperative for correct development of the AV cushions. © 2002 Elsevier Science (USA)

Anatomical Record Part A-discoveries in Molecular Cellular and Evolutionary Biology, 2006

Proepicardial/epicardial-derived cells are the main origin of the early embryonic coronary vascul... more Proepicardial/epicardial-derived cells are the main origin of the early embryonic coronary vascular bed. In vivo coronary vasculogenesis, which is a fast-occurring event, can be mimicked in vitro by culturing proepicardial tissue in different ways. The in vitro vasculogenic model presented in this study (a proepicardial suspension culture assay) partially reproduces coronary vascular development from its cellular precursors, a process known to be highly dependent on cell migration, cell differentiation, cell adhesion/sorting, and tissue fusion phenomena. The main aim of this study is to study the triggering signals and the cellular dynamics that regulate the differentiation of proepicardial cells into the angioblastic/endothelial lineage and their in vitro vasculogenic potential. Our results indicate that hanging drop-cultured proepicardia, which have an intrinsic vascular potential, behave like self-assembling cell aggregates or spheroids that can fuse to give rise to complex vascularized 3D structures. We believe that these self-assembling cell aggregates are an optimal choice to study the differentiation of coronary angioblasts, as well as a good method to reproduce vascular development in vitro. Finally, we propose the proepicardium as a suitable cellular source for vascular tissue engineering. Anat Rec Part A, 288A:700–713, 2006. © 2006 Wiley-Liss, Inc.