Vascular endothelial growth factor stimulates embryonic urinary bladder development in organ culture

Abstract

OBJECTIVES To determine whether vascular endothelial growth factor A (VEGF) and its receptors are expressed during bladder development in mice when capillaries are forming, and whether exogenous VEGF might enhance the growth of endothelia and other types of bladder cells, using an embryonic organ‐culture model. MATERIALS AND METHODS Whole bladders from wild‐type mice, at embryonic day (E) 14, were grown in serum‐free organ culture in an air/5% CO2 atmosphere; some cultures were supplemented with VEGF and/or with VEGF receptor 1/Fc chimera (VEGFR1/Fc), which blocks VEGF bioactivity. Organs were harvested after 6 days and the expression of VEGF and related molecules assessed using immunohistochemistry. RESULTS VEGF, VEGFR1 and VEGFR2 positive cells were immunodetected in E14 and E18 bladders. Exogenous VEGF increased whole‐organ growth, as assessed by explant areas, total cell numbers, DNA and protein content; proliferation was enhanced, and apoptosis decreased, in urothelium and surrounding tissues. VEGF also increased the proportions of cells expressing endothelial (CD31) and smooth muscle (α smooth muscle actin) markers. VEGFR1/Fc blocked the growth‐enhancing effects of exogenous VEGF. CONCLUSIONS In organ culture, exogenous VEGF not only stimulated embryonic bladder endothelial cells but also strikingly enhanced the growth of the whole organ. Whether the effects of VEGF on diverse bladder cell populations are direct or indirect requires further investigation. The finding that VEGF protein is present in embryonic bladders in vivo raises the possibility that it has similar actions during normal development. The results also illuminate the pathobiology of certain bladder diseases in which VEGF levels have been shown to be increased.

VEGF receptors and neuropilins are expressed in the urothelial and neuronal cells in normal mouse urinary bladder and are upregulated in inflammation

“…As judged by colocalization of Cy5.5 fluorescence with immunofluorescent staining for lineage-specific markers, VEGF receptors and coreceptors in both structures, the tracer preferentially tagged urothelial and neuronal cells, but not vascular or lymphatic endothelial cells. Although there are several reports on immunohistochemical detection of VEGF receptors in urinary bladder (13,14,29), our findings in vivo, for the first time, identify these receptors as accessible and functionally active. Importantly, our findings that in vivo tagged urothelial cells display both VEGF receptors and NRP Fig.…”

Generating Elastin-Rich Small Intestinal Submucosa–Based Smooth Muscle Constructs Utilizing Exogenous Growth Factors and Cyclic Mechanical Stimulation

“…Although the exact signaling mechanisms between the urothelium and BSMC in culture are unclear, it has been noted previously that soluble growth factors are likely involved. 6,7 Burgu et al demonstrated the importance of vascular endothelial growth factor (VEGF) in the development of murine embryonic bladders in culture. 7 Further, Master et al 6 highlighted the importance of epithelial mesenchymal signaling in the ingrowth of fibroblasts into bladder acellular matrix.…”

“…6,7 Burgu et al demonstrated the importance of vascular endothelial growth factor (VEGF) in the development of murine embryonic bladders in culture. 7 Further, Master et al 6 highlighted the importance of epithelial mesenchymal signaling in the ingrowth of fibroblasts into bladder acellular matrix. Therefore to increase cellular penetration, growth factors that are released in culture by the urothelium may be utilized.…”

Teashirt 3 is necessary for ureteral smooth muscle differentiation downstream of SHH and BMP4

“…In situ hybridisation using digoxigenin-labelled or radioactive probes was performed on sections as described (Caubit et al, 2005). Probes Embryonic ureter culture and video microscopy E15.5 ureters were dissected and explanted onto platforms (Millipore; pore size 0.4 μm) and cultured in defined, serum-free media, as described for embryonic mouse urinary bladders (Burgu et al, 2006). The timelapse imaging is detailed in the movie legends (see supplementary material).…”