Vascular-mesenchymal cross-talk through Vegf and Pdgf drives organ patterning

Abstract

The initiation of de novo testis cord organization in the fetal gonad is poorly understood. Endothelial cell migration into XY gonads initiates testis morphogenesis. However, neither the signals that regulate vascularization of the gonad nor the mechanisms through which vessels affect tissue morphogenesis are known. Here, we show that Vegf signaling is required for gonad vascularization and cord morphogenesis. We establish that interstitial cells express Vegfa and respond, by proliferation, to endothelial migration. In the absence of vasculature, four-dimensional imaging of whole organs revealed that interstitial proliferation is reduced and prevents formation of wedge-like structures that partition the gonad into cord-forming domains. Antagonizing vessel maturation also reduced proliferation. However, proliferation of mesenchymal cells was rescued by the addition of PDGF-BB. These results suggest a pathway that integrates initiation of vascular development and testis cord morphogenesis, and lead to a model in which undifferentiated mesenchyme recruits blood vessels, proliferates in response, and performs a primary function in the morphogenesis and patterning of the developing organ.organogenesis | sex determination | testis formation E ndothelium-derived signals are required for the development and maintenance of many vertebrate organs. Information about vascular influences on organ budding, tissue-specific celltype specification, and generation of progenitor niches have come from seminal work on the liver, pancreas, and nervous system (1-3). Despite the broad implications of this research, the mechanisms through which endothelial cells influence tissues have been difficult to identify. In several organs, specialized progenitor cells associate with the vasculature and maintain their proliferative status through contact with the ECM that shrouds vessels (4). However, the dynamics and cellular response of less specialized cells that mediate organ morphogenesis are not understood with the same clarity.Endothelial cells influence testis cord morphogenesis in the embryonic mouse gonad (5, 6). The gonad is a uniquely powerful model in which to study the role of vasculature during organ morphogenesis because of the ability to culture and image whole organs during the coincident process of vascularization and epithelial morphogenesis. In the lung, the endothelium is reported to interact with the airway epithelium to induce septae formation in the distal airways (7). However, the potential importance of the mesenchyme was not investigated in that, despite the extensive literature supporting mesenchymal-epithelial interactions as a primary force during lung morphogenesis. In the gonad, Sertoli cells are currently assumed to attract migrating endothelial cells and initiate the hallmark patterning of testis cords, although there is no direct evidence that this is the case.Here we report that cross-talk between the endothelium and nonspecialized mesenchymal cells drives testis morphogenesis. Vegfa is expressed specifically ...

Yolk-sac–derived macrophages regulate fetal testis vascularization and morphogenesis

“…However, macrophage expression of Vegfa (and Angpt1) was lower than that of the nonmacrophage cell populations of the gonad/mesonephros (Fig. S6 D and E), suggesting, in agreement with our previous report (7), that macrophage-derived VEGF is not the major source of VEGF in the gonad. By immunofluorescence, we detected bright VEGFA punctae within gonadal macrophages (Fig.…”

“…The vasculature plays an instructive role in testis morphogenesis (5)(6)(7)(8)39). The first step of this process, the breakdown of the mesonephric vascular plexus, is dependent on gonadal-mesonephric macrophages.…”

“…Pre-Sertoli cells express sex-determining genes, such as sex determining region of chromosome Y (Sry) and sex determining region Y (SRY)-box 9 (Sox9) (3,4), and traditionally have been considered the main driving force in generating testicular architecture. However, recent evidence from our laboratory and others suggests that endothelial and other interstitial mesenchymal cells also play critical roles in testis morphogenesis (5)(6)(7)(8).…”

R-spondin1, WNT4, and the CTNNB1 signaling pathway: strict control over ovarian differentiation

“…This coelomic vessel is usually formed at the surface of the embryonic testis and is required to pattern the gonad and guide sex cord formation (Cool et al 2011). The malelike vasculature of mutant XX gonads suggests that Rspo1 is required to inhibit the crosstalk between mesenchymal and endothelial cells.…”

Assembly of complex cell microenvironments using geometrically docked hydrogel shapes

“…Using the microscale hydrogel system and an image-processing algorithm, we generated a large and reproducible cell vector dataset, to quantitate the rates of migration that increased by ∼40% due to the chemotactic effects of ECs that attracted MSCs. As literature suggests that the PDGF-BB secreted by ECs is a key recruitment signal for MSCs (33,(45)(46)(47)(48)(49), our future experiments will investigate the role of PDGF-BB in EC-MSC interactions, among multiple factors that may be at play in microscale hydrogel environments we describe here.…”