Five-sixth Nephrectomy in Female Common Marmosets(Callithrix jacchus) as a Chronic Renal Failure Model: -A Longitudinal Course of Serum Biochemical, Hematological and Histopathological Changes-

Establishment of Renal Failure Models by Laparoscopy in Bama Pigs Which Underwent Partial Nephrectomy and Radical Contralateral Nephrectomy

Introduction

The miniature pig possesses unmatched advantages as an animal model because of its high homology with humans. Our experiment aimed to build a chronic renal failure (CRF) model in pigs via laparoscopy.

Material and Methods

Laparoscopic surgery was performed twice to build a CRF model. The first surgery was a left partial nephrectomy and the second was a right radical nephrectomy. Pigs were grouped by the total renal tissue to be resected: ⅔, ¾ or ⅚. Physiological parameters (rectal temperature and heart rate), haematological parameters (WBC and RBC) and renal function (serum creatinine - CR and blood urea nitrogen - BUN) were measured preoperatively and every week postoperatively.

Results

After renal resection the pigs manifested chronic renal failure. Heart rate and body temperature declined to varying degrees over 12 postoperative weeks. No significant difference was observed between the different groups. The result of renal function tests found that postoperative serum CR and BUN in all groups were continuously elevated, and the level of serum CR at two weeks post procedure differed very significantly from its preoperative value (P < 0.05). BUN was significantly elevated at one week (P < 0.05). The renal function decreased significantly faster in the ⅚ group than in the other two groups. The trend of renal function change was similar among groups, but progress was slower in the ⅔ and ¾ groups.

Conclusion

⅚ kidney resection was the optimal miniature pig model of CRF.

Increased Apoptosis in the Paraventricular Nucleus Mediated by AT1R/Ras/ERK1/2 Signaling Results in Sympathetic Hyperactivity and Renovascular Hypertension in Rats after Kidney Injury

Background: The central nervous system plays a vital role in the development of hypertension, but the molecular regulatory mechanisms are not fully understood. This study aimed to explore signaling in the paraventricular nucleus (PVN) which might contribute to renal hypertension.

Methods: Renal hypertension model was established by five-sixth nephrectomy operation (5/6Nx) in male Sprague Dawley rats. Ten weeks afterwards, they were random assigned to no treatment, or intracerebroventricular injection (ICV) with artificial cerebrospinal fluid, losartan [angiotensin II receptor type 1 (AT1R) antagonist], farnesylthiosalicylic acid (Ras inhibitor), PD98059 (MEK inhibitor), or SB203580 (p38 inhibitor) and Z-DEVD-FMK (caspase-3 inhibitor). Before and after treatment, physiological and biochemical indices were measured. Immunohistochemistry, western blot and RT-PCR were applied to quantify key components of renin-angiotensin system, apoptosis-related proteins, Ras-GTP, and MAPKs in the PVN samples. TUNEL assay was used to measure the situ apoptosis in PVN.

Results: The 5/6Nx rats showed significantly elevated systolic blood pressure, urinary protein excretion, serum creatinine, and plasma norepinephrine (p < 0.05) compared to sham rats. The expression of angiotensinogen, Ang II, AT1R, p-ERK1/2, or apoptosis-promoting protein Bax were 1.08-, 2.10-, 0.74-, 0.82-, 0.83-fold higher in the PVN of 5/6Nx rats, than that of sham rats, as indicated by immunohistochemistry. Western blot confirmed the increased levels of AT1R, p-ERK1/2 and Bax; meanwhile, Ras-GTP and p-p38 were also found higher in the PVN of 5/6Nx rats, as well as the apoptosis marker cleaved caspase-3 and TUNEL staining. In 5/6Nx rats, ICV infusion of AT1R antagonist, Ras inhibitor, MEK inhibitor or caspase-3 inhibitor could lower systolic blood pressure (20.8-, 20.8-, 18.9-, 14.3%-fold) together with plasma norepinephrine (53.9-, 57.8-,63.3-, 52.3%-fold). Western blot revealed that blocking the signaling of AT1R, Ras, or MEK/ERK1/2 would significantly reduce PVN apoptosis as indicated by changes of apoptosis-related proteins (p < 0.05). AT1R inhibition would cause reduction in Ras-GTP and p-ERK1/2, but not vice versa; such intervention with corresponding inhibitors also suggested the unidirectional regulation of Ras to ERK1/2.

Conclusion: These findings demonstrated that the activation of renin-angiotensin system in PVN could induce apoptosis through Ras/ERK1/2 pathway, which then led to increased sympathetic nerve activity and renal hypertension in 5/6Nx rats.

Histopathological characterization of renal tubular and interstitial changes in 5/6 nephrectomized marmoset monkeys (Callithrix jacchus)

Common marmosets (Callithrix jacchus) have become a useful animal model, particularly for development of biopharmaceuticals. While various renal failure models have been established in rodents, there is currently no acceptable model in marmosets. We analyzed the damaged renal tubules and tubulointerstitial changes (inflammation and fibrosis) of 5/6 nephrectomized (Nx) common marmosets by histopathological/immunohistochemical methods, and compared these findings to those in 5/6 Nx SD rats. In Nx marmosets and rats sacrificed at 5 and 13 weeks after Nx, variously dilated and atrophied renal tubules were seen in the cortex in common; however, the epithelial proliferating activity was much less in Nx marmosets. Furthermore, the degrees of inflammation and fibrosis seen in the affected cortex were more severe and massive in Nx marmosets with time-dependent increase. Interestingly, inflammation in Nx marmosets, of which degree was less in Nx rats, consisted of a large number of CD3-positive T cells and CD20-positive B cells (occasionally forming follicles), and a few CD68-positive macrophages. Based on these findings, lymphocytes might contribute to the progressive renal lesions in Nx marmosets. Fibrotic areas in Nx marmosets comprised myofibroblasts expressing vimentin and α-smooth muscle actin (α-SMA), whereas along with vimentin and α-SMA expressions, desmin was expressed in myofibroblasts in Nx rats. This study shows that there are some differences in renal lesions induced by Nx between marmosets and rats, which would provide useful, base-line information for pharmacology and toxicology studies using Nx marmosets.