A new view of macula densa cell microanatomy

Abstract

Although macula densa (MD) cells are chief regulatory cells in the nephron with unique microanatomical features, they have been difficult to study in full detail due to their inaccessibility and limitations in earlier microscopy techniques. The present study used a new mouse model with a comprehensive imaging approach to visualize so far unexplored microanatomical features of MD cells, their regulation and functional relevance. MD-GFP mice with conditional and partial induction of green fluorescent protein (GFP) expression, which specifically and intensely illuminated only single MD cells were used with fluorescence microscopy of fixed tissue and live MD cells in vitro and in vivo with complementary electron microscopy (EM) of rat, rabbit, and human kidney. An elaborate network of major and minor cell processes here named maculapodia were found at the cell base, projecting towards other MD cells and the glomerular vascular pole. The extent of maculapodia showed up-regulation by low dietary salt intake and female gender. Time-lapse imaging of maculapodia revealed highly dynamic features including rapid outgrowth and an extensive vesicular transport system. EM of rat, rabbit, and human kidneys, and three-dimensional (3D) volume reconstruction in optically cleared whole-mount MD-GFP mouse kidneys further confirmed the presence and projections of maculapodia into the extraglomerular mesangium and the afferent and efferent arterioles. The newly identified dynamic and secretory features of MD cells suggest the presence of novel functional and molecular pathways of cell-to-cell communication in the juxtaglomerular apparatus (JGA) between MD cells and between MD and other target cells.

Intravital imaging reveals glomerular capillary distension and endothelial and immune cell activation early in Alport syndrome

“…In chronic studies, H (200 U, as above) was given iv every other day for a total of three times as described recently (10). The ACE inhibitor (ACEi) enalapril was administered at a dose of 10 mg/day/mouse via drinking water (150mg/L) as described before (32). Animals were treated with H, ACEi or vehicle (PBS given iv) for one week followed by intravital MPM imaging and tissue harvest as described above.…”

Physiological activation of the nephron central command drives endogenous kidney tissue regeneration

“…Future work is needed to dissect their roles in MD cells. The known structural and neuron-like functional heterogeneity between individual MD cells (7,11,35) was reflected also in their regenerative gene profile established by single-cell transcriptome analysis (Fig. 2C).…”

“…We next aimed to identify the molecular signature of the MD cell tissue remodeling program in both control and physiological activation states using MD and control cell isolation from MD-GFP mouse kidneys as established and validated recently (11), followed by bulk and single-cell RNA sequencing and transcriptomic analysis (Fig. 2A).…”

“…Vectastain Elite ABC-HRP Kit was used to perform horseradish-peroxidase labeling (PK6101, Vector Laboratories, Burlingame, CA). Sections were examined with Leica TCS SP8 (Leica Microsystems, Wetzlar, Germany) confocal/multiphoton laser scanning microscope systems as described previously (11). Imaging software (Image J, National Institutes of Health and the Laboratory for Optical and Computational Instrumentation (LOCI, University of Wisconsin) was used to calculate the percent area of colocalization to determine the changes in the proportion of NG2 + cells in each cell type, as well as the proportional distribution of NG2 + cell types.…”

Renal cell markers: lighthouses for managing renal diseases

“…However, a recent study by Gyarmati et al developed a method to analyze live MD cells. A chimera of MD specific marker, nNOS, and a tamoxifen inducible membrane targeted green fluorescent protein was generated and using this, they were able to visualize the 3-D projections (also called as maculopodia) of the MD cells (112).…”