Proteomic identification of intracellular vesicle trafficking and protein glycosylation requirements for lumen inflation in Ciona notochord

Lumen formation and inflation are crucial steps for tubular organ morphogenesis, yet the underling mechanism remains largely unrevealed. Here, we applied 4D proteomics to screen the lumenogenesis-related proteins and revealed the biological pathways potentially that are involved in lumen inflation during notochord lumen formation in the ascidian Ciona savignyi. In total, 910 differentiated expressed proteins (DEPs) were identified before and after notochord lumen formation utilizing Mfuzz analysis. Those DEPs were grouped into four upregulated clusters based on their quantitative expression patterns; the functions of these proteins were enriched in protein metabolic and biosynthetic process, the establishment of localization, and vesicle-mediated transport. We analyzed the vesicle trafficking cluster and focused on several vesicle transport hub proteins. In vivo function-deficient experiments showed that mutation of vesicle transport proteins resulted in an abnormal lumen in notochord development, demonstrating the crucial role of intracellular trafficking for lumen formation. Moreover, abundant extracellular matrix proteins were identified, the majority of which were predicted to be glycosylated proteins. Inhibition of glycosylation markedly reduced the lumen expansion rate in notochord cells, suggesting that protein glycosylation is essential for lumenogenesis. Overall, our study provides an invaluable resource and reveals the crucial mechanisms in lumen formation and expansion.

Natural Vascular Scaffolding Treatment Promotes Outward Remodeling During Arteriovenous Fistula Development in Rats

Following creation, an arteriovenous fistula (AVF) must mature (i.e., enlarge lumen to allow high blood flow) before being used for hemodialysis. AVF maturation failure rates are high, and currently, there are no effective therapy to treat this problem. The maturation process is likely affected by the integrity of the vascular extracellular matrix (ECM). Natural Vascular Scaffolding (NVS) Therapy is a new technology that interlinks collagen and elastin via photoactivation of a locally delivered small molecule (4-amino-1,8-naphtalamide). We hypothesized that NVS Therapy may improve AVF remodeling by preserving ECM integrity. AVFs were created in Wistar male rats by connecting the femoral vein (end) to femoral artery (side) in the same limb. Immediately after blood flow was restored to dilate the femoral vein by arterial pressure, a 10 μl-drop of the NVS compound (2 mg/ml) was placed on the anastomosis perivascularly. Following 5-min incubation, the NVS treated area was exposed to 1-min illumination by 450-nm light. The control group received 10 μl-drop of phosphate buffered saline (PBS) and the same light activation. The skin was closed, and rats were euthanized 4 weeks (n = 6-9 per group) post-AVF creation for histology, morphometry, immunohistochemistry (IHC), and multiphoton microscopy for second-harmonic-generation evaluation of collagen fibers. The vascular thickness was similar in both groups. The AVF vein's open lumen area and % open lumen area in NVS-treated rats were significantly larger than in PBS-treated rats (4.2-fold p = 0.014 and 2-fold p = 0.009, respectively). The inflammatory markers IL-6 and MMP-9 in the AVF walls were significantly decreased in the NVS group than the PBS group. Collagen fibers in the vascular wall trended toward perpendicular alignment to the lumen circumference in the NVS-treated AVFs, with more defined shape but less area than in the PBS-treated AVFs. These results indicate that the NVS Therapy exerted changes in collagen, which may influence AVF maturation. Rats tolerated the NVS treatment well, and the lack of cell death by the treatment was confirmed in cell culture experiments. These results suggest that NVS treatment is safe and may have therapeutic potential by facilitating lumen expansion to enhanced AVF maturation in patients.

A Grainyhead-Like 2/Ovo-Like 2 Pathway Regulates Renal Epithelial Barrier Function and Lumen Expansion

Grainyhead transcription factors control epithelial barriers, tissue morphogenesis, and differentiation, but their role in the kidney is poorly understood. Here, we report that nephric duct, ureteric bud, and collecting duct epithelia express high levels of grainyhead-like homolog 2 (Grhl2) and that nephric duct lumen expansion is defective in Grhl2-deficient mice. In collecting duct epithelial cells, Grhl2 inactivation impaired epithelial barrier formation and inhibited lumen expansion. Molecular analyses showed that GRHL2 acts as a transcriptional activator and strongly associates with histone H3 lysine 4 trimethylation. Integrating genome-wide GRHL2 binding as well as H3 lysine 4 trimethylation chromatin immunoprecipitation sequencing and gene expression data allowed us to derive a high-confidence GRHL2 target set. GRHL2 transactivated a group of genes including Ovol2, encoding the ovo-like 2 zinc finger transcription factor, as well as E-cadherin, claudin 4 (Cldn4), and the small GTPase Rab25. Ovol2 induction alone was sufficient to bypass the requirement of Grhl2 for E-cadherin, Cldn4, and Rab25 expression. Re-expression of either Ovol2 or a combination of Cldn4 and Rab25 was sufficient to rescue lumen expansion and barrier formation in Grhl2-deficient collecting duct cells. Hence, we identified a Grhl2/Ovol2 network controlling Cldn4 and Rab25 expression that facilitates lumen expansion and barrier formation in subtypes of renal epithelia.