Untitled

Abstract

The human mesonephros is currently regarded as a simplified version of the foetal metanephros, primarily due to the close morphological resemblance between these two structures. The aim of the present study was to define whether human mesonephric and foetal metanephric nephrons share immunophenotypical traits in their corresponding structures (glomeruli, proximal and distal tubules). For this purpose we first investigated immunohistochemically the overall expression and topographical distribution of cytokeratins 7, 8, 18, 19, and 20, vimentin and alpha-smooth muscle actin in mature mesonephric nephrons and compared the results with those obtained in maturing-stage foetal metanephric nephrons. No expression of cytokeratins 7 and 20 was found. Cytokeratins 8, 18, and 19 and vimentin showed a restricted and basically coincident expression along the different components of both mesonephric and metanephric nephrons. These findings indicate that the intermediate filament protein profile of human mature mesonephric nephrons closely recapitulates that observed in developing metanephros and thereby strengthens the concept that human mesonephros, a transient ontogenic structure, is largely similar to the foetal metanephros. The sole difference between human mesonephros and foetal metanephros was the divergent expression of alpha-smooth muscle actin. This protein exhibited an increasingly accentuated mesangial expression paralleling the morphological maturation of metanephric glomerulus, whereas it was absent from the mesonephric one. This would suggest that the mesangial cells in these two renal structures have a different function during the foetal life.

Differential expression of epithelial and smooth muscle lineage‐specific markers of metanephros in one‐humped camel foetuses

“…In addition, α-SMA exhibited an increasingly mesangial expression, paralleling the morphological maturation of the metanephric glomerulus (Magro et al, 2001).…”

“…The schematic classification of metanephrogenesis in camel embryos is divided into four stages, based on the characteristic features of each developmental stage previously reported by Osman et al (2014). The present work investigates the immuno‐localization of some significant proteins such as α‐SMA, as a cytoskeleton marker (Alpers et al, 1992; Oliver and Awqati 2000; Naruse et al, 2000 and Magro et al, 2001); CD34, as an endothelial marker (Naruse et al, 2000); Osteopontin, an important factor in tubulogenesis (Xie et al, 2001); and E‐cadherin, as cell–cell adhesion molecule (Cho et al, 1998; Ulf et al, 2002; Terada et al, 2017). The analysis revealed that all the proteins examined were detected as either membranous or cytoplasmic proteins.…”

“…Although the specific cell types that express α‐SMA have yet to be determined, it is widely believed that myofibroblasts are among those capable of expressing it (Atkins et al, 1996), or transdifferentiated epithelial cells (Ng et al, 1999). In addition, α‐SMA exhibited an increasingly mesangial expression, paralleling the morphological maturation of the metanephric glomerulus (Magro et al, 2001) .…”

“…α‐SMA is the actin isoform that predominates within vascular smooth muscle cells and plays a crucial role in fibrogenesis. It is also considered a mesangial marker during the formation of human kidney glomeruli (Alpers et al, 1992; Bennett & Matsell, 1998) and an indicator for arterial pre‐glomerular vessels (arcuate arteries) in rat embryos (Magro et al, 2001). In the human embryo, α‐SMA was detected in the afferent arterioles and mesangium, but it was not detected in the medulla (Stefanska et al, 2016) While in the rat embryo, the cells expressing α‐SMA appeared in the arcuate arteries (Sauter et al, 2008).…”