Epithelial Tubular Fusion, Measuring Interconnection, and the Quest for Solving the Continuity Problem
The formation of functional epithelial tubules is a central feature of many organ systems. Although it has been well-studied how epithelial cells form tubules, it is not well understood how tubules and related epithelial micro-tissues such as spheroids and organoids interconnect with each other to form functional networks. Currently available model systems that spontaneously undergo epithelial tubular interconnections rely heavily on animal models of organ development, which are time- and resource-intensive, and limit the scope of hypothesis testing. Here we have designed a novel assay to quantitatively examine epithelial tubular interconnection in vitro using epithelial spheroids with fluorescently-tagged apical surfaces and lumens to enable direct visualization of interconnection. We used single cell RNA-Seq data combined with receptor-ligand analyses from mouse kidney tubules that undergo interconnection to build a list of candidate effectors. One such candidate was hepatocyte growth factor (HGF), which has known roles in cell migration, tubulogenesis, and cell proliferation. Addition of HGF robustly induced interconnection of adjacent spheroids. The proliferative effect of HGF neither promoted nor inhibited the interconnections. Additional studies with inhibitors of matrix metalloproteinases (MMPs) revealed a significant role for extracellular matrix turnover in lumen coalescence. These results lay the groundwork for investigating how to promote functional interconnections between tubular epithelia, which has important clinical implications for the intersection of organoid biology and transplant medicine.
Hepatocyte Growth Factor, Kidney Tubules, Proto-Oncogene Proteins c-met, Signal Transduction, Epithelial Cells
University of Texas Southwestern Medical Center
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