Baseline values of experimental groups at day 0

<p>The table includes the baseline values of both experimental groups (Bx and Ctrl) at day 0.</p

A new apparatus for standardized rat kidney biopsy.

Survival biopsies are frequently applied in rat kidney disease models, but several drawbacks such as surgical kidney trauma, bleeding risk and variable loss of kidney tissue are still unsolved. Therefore, we developed an easy-to-use core biopsy instrument and evaluated whether two consecutive kidney biopsies within the same kidney can be carried out in a standardized manner. On day 0, 18 Lewis rats underwent a right nephrectomy and 9 of these rats a subsequent first biopsy of the left kidney (Bx group). 9 control rats had a sham biopsy of the left kidney (Ctrl group). On day 7, a second kidney biopsy/sham biopsy was performed. On day 42, all animals were sacrificed and their kidneys were removed for histology. Biopsy cylinders contained 57±28 glomeruli per transversal section, representing an adequate sample size. PAS staining showed that the biopsy depth was limited to the renal cortex whereas surgical tissue damage was limited to the area immediately adjacent to the taken biopsy cylinder. On day 42, the reduction of functional renal mass after two biopsies was only 5.2% and no differences of body weight, blood pressure, proteinuria, serum creatinine, glomerulosclerosis, interstitial fibrosis or number of ED-1 positive macrophages were found between both groups. In summary, our apparatus offers a safe method to perform repetitive kidney biopsies with minimal trauma and sufficient sample size and quality even in experimental disease models restricted to one single kidney

Technical drawing and operational principle of the new biopsy apparatus.

<p><b>A</b>: Longitudinal section. The sleight (in white) and the helve (in dark grey) interact by a slot and key linkage where the tongue of the sleight being located inside snaps into the circular grooves of the helve (arrowheads). <b>B and C</b>: Operational steps 1–3. The cutting filament around the circular blade forms the reference point for the stitch depth (*).</p

Experimental set-up.

<p><b>Day 0</b>: Right nephrectomy in both groups. Subsequent biopsy of the upper pole of the residual kidney in the Bx group and sham biopsy of the residual kidney in the control group. <b>Day 7</b>: Biopsy of the lower kidney pole in the Bx group and second sham biopsy in the control group. <b>Day 42</b>: Animals were sacrificed and kidneys were removed for histology. Body weight, blood pressure, proteinuria and serum creatinine were measured before operations on day 0 and day 42 in both groups (*).</p

Comparison of the biopsy group with the control group on day 42^*.

<p>*Values are expressed as mean ±SD. Bx, biopsy group; Ctrl, control group; Body Wt, body weight; BP, blood pressure; Protein, proteinuria; SCr, serum creatinine; GS score, glomerulosclerosis score (see methods); IF score, interstitial fibrosis score (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115368#s2" target="_blank">methods</a>); Glom ED-1, number of glomerular ED-1 positive macrophages/50 glomeruli; Inter ED-1, number of interstitial ED-1 positive macrophages/mm²; n.a., not applicable. Statistical significance was defined as <i>P</i><0.05.</p><p>Comparison of the biopsy group with the control group on day 42^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115368#nt101" target="_blank">*</a>}.</p