![]() ![]() Contrarily, we observed that the MD is a monolayer cap of 35–40 cells arranged in five to six layers and extended for about 40 µm using toluidine blue-stained serial semithin sections. Previous observations show that the MD comprise a few cells, about 15–20 cells per nephron. Most of the morphological observations of the MD have been performed in animal models, while few studies have been performed on humans, including our recent morphological studies. In addition, this mechanism is specifically directed to stabilize NaCl absorption from the distal tubule (DT). This negative feedback prevents GFR fluctuation and helps to regulate both the renal blood flow and the GFR. It is known that increased NaCl tubular concentration induces adenosine triphosphate release at the basolateral portion of MD cells, causing afferent arteriole vasoconstriction and consequently producing glomerular filtration rate (GFR) reduction (tubuloglomerular feedback), directly or through breakdown to adenosine. The MD position is strategic, allowing it to detect the alteration of tubular fluid components (e.g., the ionic composition) and to act on the JGA effectors by synthesizing and releasing paracrine mediators. The MD cells have a primary cilium in their apical membrane exposed to the tubular fluid and a basolateral portion in close proximity to the effector cells of the JGA (i.e., the renin-producing granular cells of both afferent and efferent arterioles) and to the contractile cells of the extraglomerular mesangium. The macula densa (MD) cells are renal sensory elements belonging to the juxtaglomerular apparatus (JGA) that plays an important role in regulating renal blood flow, glomerular filtration rate and renin release. Conclusions: The presence of STCs was demonstrated in human adult MD, suggesting that this structure has expansion, self-renewal and epithelial differentiation abilities, similar to all other parts of renal tubules. Although some cells of MD expressed VIM or CD133, none of them co-expressed VIM and CD133. ![]() CD133 was always localized in the apical part of the cells, whereas the VIM expression was evident only in the cellular basal pole. Some of the latter cells were positive both for CD133 and VIM. CD133 and KRT7 were co-expressed in some MD and adjacent DT cells. KRT7-positive cells were identified in MD and adjacent DT cells, while KRT7 positivity was mostly confined in both DT and collecting ducts (CD) in the other areas of the renal parenchyma. ![]() Moreover, CD133 was detected in the parietal epithelial cells of Bowman’s capsule and in some proximal tubules (PT). Results: CD133 was localized in some MD cells and in the adjacent DT cells. The first sections of each set were immunostained for nNOS to identify MD, the second sections were immune-stained for CD133 (specific STCs marker) while the third sections were analyzed for KRT7 (another STCs specific marker) and VIM (that stains the basal pole of the STCs) in the first and second sets, respectively, in order to study the co-expression of KRT7 and VIM with the CD133 marker. Methods: We analyzed two sets of three consecutive serial sections for each sample. The purpose of the present study is to describe the presence of STCs in MD using specific markers such as prominin-1 (CD133), cytokeratin 7 (KRT7) and vimentin (VIM). Although these cells are localized within the proximal (PTs) and distal (DTs) tubules in a normal adult kidney, their presence has never been demonstrated in human macula densa (MD). Background: The scattered tubular cells (STCs) are a population of resident progenitor tubular cells with expansion, self-renewal and epithelial differentiation abilities. ![]()
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