| Objective The aim of our study is to evaluate the impact of renal fibrosis on ischemia reperfusion injury(IRI) rats by monitoring the longitudinal renal function changes using dynamic contrast enhanced(DCE) MRI.Materials and Methods The research was approved by Tianjin Medical University General Hospital enthics committee. 28 male Sprague-Dawley rats(provided by Breeding of Peking University health science center) ranged from 250~350g were randomly divided into 4 groups. Group I and group II were healthy rats,whose warm ischemia time were 30 min and 45 min,respectively;group III and group IV were fibrotic rats, whose warm ischemia time were 30 min and 45 min, respectively. 4 rats died accidentally in this study, finally there was 24 rats in this study: the enrolled number of rats in group I, II, III, IV are 6,6,6,5, respectively. The renal interstitial fibrosis of rat was introduced by intraperitoneal injection of cispaltin(4.5 mg/ml)(QIlu pharmaceutical co, LTD, batch number WA2A1210071) 4.5mg/kg, then performed the experiment after the 4 weeks. The microsurgical operation was performed under the microscope with rat surgical instruments. The renal blood flow was blocked by microvascular clip. The time of blocking the left renal artery was related to the group situation above. MR scanning was performed immediately before the induction and on Days 2, 5, 7 and 14 after IRI on a 3.0T scanner(MR750, GE company, US) using an 6cm animal coil(Magtron, Shenzhen, China). Coronal fat suppressed fast recovery fast spin echo(FRFSE) T2-weighted images were acquired after location scan, then performed the DCE-MRI using coronal 3D liver acceleration volume acquisition(LAVA) on bilateral kidneys region. A bolus injection of 0.04 mmol/kg of Gd-DTPA(Magnivist, Bayer-Shcering, Germany) was administrate through a cannula in the tail vein at a rate of 100 ul/s. LAVA scanning were continuously repeated immediately after the administration of Gd-DTPA. The constant rate(kcl) was obtained based on an measurement method proposed by Diana Baumann and Markus Rudin by using the software developed by Northeastern University to help develop software to analyze the LAVA images. One-way analysis of variance(ANOVA) and Bonferroni's post-hoc test was used for intergroup comparisons. Student t-test was used for the longitudinal comparison in the same group. All rats were sacrificed after final MRI examination on D14,bilateral kidneys were sectioned into 5-mm thickness section and stained by hematoxylin and eosin. Tubular damage in the corticomedullary junction area was scored based on the method of Leemans et al. The Kruskal-Wallis H test was used for intergroup comparisons,then the muliple comparation was performed through calibrated P value measured by the method of bonferroni.Result 1.Rate constant(kcl) after the surgery is significantly different for left and right kidney except for group III and the D2 of group IV(P<0.05),however, there was no significant changes between both before I/R injure(P>0.05). The kcl of left kidney in group I,II,IV is lower than preoperative(P<0.05), except for group III. Only the right kidney in group I?II and III after I/R injure had no change compared to pre-operation(P>0.05),whereas there was a mild tendency to decline in group IV. However, except on the Day 2 after the induction of I/R injury, the right kidney of kcl in group IV was lower than pre-operation(P<0.05).2. The constant rate kcl of left kidney in group I decreases to a rock bottom on Day 7 after induction of I/R injury then it has a tendency to recover on Day 14(P<0.05, compared on Day 0 in left kidney), while in condition of group II, the kcl of left kidney decreases after the induction of I/R injury and does not has a tendency to recovery on Day 14(P<0.05, compared on Day 0 in left kidney).3. The kcl of left kidney in group III decreases after IR injury but it has no significant difference(P>0.05, compared on Day 0 in left kidney). The kcl of left kidney in group IV decreases to a rock bottom on Day 7 after induction of I/R injury then it appears to be stable on Day 14(P<0.05, compared on Day 0 in left kidney).4. The pathologic score results between left and right kidney in groups has significant difference(P<0.05). There was a significant difference of left kidney between group I and III?IV and between group II and IV, as well as right kidney(P<0.0083). The pathologic score results of right kidney between group II and III has significant difference, while there was no significant in right kidney(P>0.0083). The pathologic score results of right kidney and left kidney between group I and II has no significant difference(P>0.0083).Conclusion The study demonstrate that when the ischemia time is greater than 30 min, it cause irreversible damage in healthy rats in clamped kidney. Renal fibrosis may cause tolerance with IR injury. |
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