Superficial Nephrons in BALB/c and C57BL/6 Mice Facilitate In Vivo Multiphoton Microscopy of the Kidney

Abstract

Multiphoton microscopy (MPM) offers a unique approach for addressing both the function and structure of an organ in near-real time in the live animal. The method however is limited by the tissue-specific penetration depth of the excitation laser. In the kidney, structures in the range of 100 µm from the surface are accessible for MPM. This limitation of MPM aggravates the investigation of the function of structures located deeper in the renal cortex, like the glomerulus and the juxtaglomerular apparatus. In view of the relevance of gene-targeted mice for investigating the function of these structures, we aimed to identify a mouse strain with a high percentage of superficially located glomeruli. The mean distance of the 30 most superficial glomeruli from the kidney surface was determined in 10 commonly used mouse strains. The mean depth of glomeruli was 118.4±3.4, 123.0±2.7, 133.7±3.0, 132.3±2.6, 141.0±4.0, 145.3±4.3, 148.9±4.2, 151.6±2.7, 167.7±3.9, and 207.8±3.2 µm in kidney sections from 4-week-old C3H/HeN, BALB/cAnN, SJL/J, C57BL/6N, DBA/2N, CD1 (CRI), 129S2/SvPas, CB6F1, FVB/N and NMRI (Han) mice, respectively (n = 5 animals from each strain). The mean distance from the kidney surface of the most superficial glomeruli was significantly lower in the strains C3H/HeN Crl, BALB/cAnN, DBA/2NCrl, and C57BL/6N when compared to a peer group consisting of all the other strains (p<.0001). In 10-week-old mice, the most superficial glomeruli were located deeper in the cortex when compared to 4-week-old animals, with BALB/cAnN and C57BL/6N being the strains with the highest percentage of superficial glomeruli (25% percentile 116.7 and 121.9 µm, respectively). In summary, due to significantly more superficial glomeruli compared to other commonly used strains, BALB/cAnN and C57BL/6N mice appear to be particularly suitable for the investigation of glomerular function using MPM.

New Anti-Nephrin Antibody Mediated Podocyte Injury Model Using a C57BL/6 Mouse Strain

“…Furthermore, many superficial glomeruli were found in C57BL/6 and BALB/c mice [40]. In our case, only small amounts of Abs can induce FSGS in the Balb/c strain compared with the C57BL/6N strain (supplement 2).…”

Intravital imaging of podocyte calcium in glomerular injury and disease

“…The first applications of MPM on the intact living kidney (15) were subsequently improved to directly and quantitatively visualize the permeability of the GFB to albumin and other macromolecules (25,26) as well as podocyte motility/migration in health and disease in vivo (16,19). The feasibility of routinely performing MPM imaging of glomeruli in the intact kidney of several mouse strains has been confirmed by several laboratories (13,14,17,18).…”

“…The basic principles and advantages and the various past applications of this revolutionary, minimally invasive optical sectioning technique for kidney research have been reviewed recently (14). MPM imaging of mouse glomeruli in vivo is now possible (13,(16)(17)(18)(19) and can be applied in generally available transgenic mouse models, including podocin/Cre mice (20) and a variety of fluorescent reporter mice, to establish cell-specific expression of fluorescent proteins in podocytes for imaging applications. For example, several genetically encoded calcium indicators have been developed, including the GFP-based calcium sensor GCaMP family, and their in vivo mouse models have been successfully used for neuronal imaging (21,22).…”

The Role of Renal Interstitial Cells in Proximal Tubular Regeneration

“…Consequently, tubular regeneration has been predominantly investigated in disease models of the tubular system, rather than during the aging of the healthy kidney. The use of serial intravital imaging, however, has markedly expanded our possibilities, thus allowing researchers to address structural and functional changes over prolonged periods of time in the same animal [12,51,52]. For example, the excitation laser used for multiphoton intravital microscopy can be employed as a tool to ablate single tubular cells via focused, high energy laser exposure in an otherwise healthy kidney.…”