Ultrastructural Study of the Kidney in the CoelacanthLatimeria chalumnae(Rhipidistia: Coelacanthini)

Activation of MST1 protects filtration barrier integrity of diabetic kidney disease in mice through restoring the tight junctions of glomerular endothelial cells

As a pathological feature of diabetic kidney disease (DKD), dysregulated glomerular filtration barrier function could lead to the increased levels of proteinuria. The integrity of tight junctions (TJs) of glomerular endothelial cells (GECs) is a guarantee of physiological function of glomerular filtration barrier. Mammalian sterile 20-like kinase (MST1) is a key regulatory protein in the blood-brain barrier (BBB), and it regulates the expression of TJs-related proteins in cerebral vascular endothelial cells. Our previous study showed that MST1 was involved in renal tubulointerstitial fibrosis of DKD. In the present study we investigated the role of MST1 in barrier function of GECs of DKD, and explored its regulatory mechanisms. In kidney tissue section of DKD patients and db/db mice, and high glucose (HG)-cultured mouse glomerular endothelial cells (mGECs), we showed that MST1 was inactivated in the GECs of DKD accompanied by disrupted glomerular endothelial barrier. In db/db mice and HG-cultured mGECs, knockdown of MST1 increased proteinuria levels, and disrupted glomerular endothelial barrier through decreasing TJs-related proteins, whereas MST1 overexpression restored glomerular endothelial barrier through regaining TJs-related proteins. In db/db mice and HG-cultured mGECs, we demonstrated that MST1 inhibition induced TJs's disruption of GECs via activating YAP1/TEAD signaling. Verteporfin (an inhibitor of YAP1-TEAD interaction) and PY-60 (a YAP1 agonist) were used to verify the role of YAP1/TEAD signaling in the regulation effect of MST1 on barrier function of mGECs. In conclusion, MST1 activation recovers glomerular endothelial barrier of DKD by regaining TJs-related proteins via inhibiting YAP1/TEAD signaling. This study highlights the multiple regulation of MST1 activation on kidney injury.

An update on the evolutionary origin of aglomerular kidney with structural and ultrastructural descriptions of the kidney in three fish species

The kidney of fish contains numerous nephrons, each of which is divided into the renal corpuscle and renal tubules. This glomerular structure is the filtration unit of the nephron and is important for the kidney function, but it has been reported that the renal corpuscle was lost in at least four independent linages of fish (i.e., aglomerular kidney). In this study, the authors newly described renal structures for three species by histological and ultrastructural observations: two aglomerular kidneys from a seahorse Hippocampus barbouri and a toadfish Allenbatrachus grunniens and a glomerular kidney from a snake eel Pisodonophis boro. The renal development of H. barbouri was also described during 1-35 days after birth. In all species tested, the anterior kidney was comprised of haematopoietic tissues and a few renal tubules, whereas the posterior kidney contained more renal tubules. Although the glomerular structure was present in P. boro, light microscopic observations identified no glomeruli in the kidney of H. barbouri and A. grunniens. Ultrastructurally, abundant deep basal infoldings with mitochondria in the renal tubules were observed in A. grunniens compared to H. barbouri and P. boro, suggesting the possible role of basal infoldings in maintaining the osmotic balance. By integrating the results from the three species and comprehensive literature search, the authors further showed that 56 species have been reported to be aglomerular, and that the aglomerular kidney has evolved at least eight times in bony fishes.

Fish sperm biology in relation to urogenital system structure

Morphology of the urogenital system has evolved during fish speciation. Chondrostei (sturgeons and paddlefishes) possess an excretory system which is called "primitive" in that the sperm ducts enter the kidneys and share the excretory ducts where sperm is mixed with urine before it is released into the spawning environment. Further, in this group of fishes there are also physiological characteristics which are associated with these anatomical features where the mixing of sperm and urine is a prerequisite for the final sperm maturation rather than contamination. In the Holostei (gars and bowfins) which are closely related to the Chondrostei, sperm also naturally mixed with urine, but the physiological role of such mixing for sperm biology has not been described. In contrast, urinary and sperm ducts in the more evolved Teleostei are completely separate, and sperm and urine are not mixed before being released during spawning. Thus, urine constitutes an inappropriate environment which can be a source of problems when sperm is collected during fisheries practices. In this review, the consequences of such divergent conditions in the urogenital anatomy will be considered in relation to general features of fish sperm biology and in relation to aquaculture and fisheries practices.