Homocysteine Induced Rat Renal Fibrosis Model And MRI Evaluation

Objective:Rat models of renal fibrosis were established by intravenous injection of homocysteine?Hcy?through the tail vein.T₂WI signal intensity standardized by psoas major muscle signal intensity and Gd-DTPA,MnO₂@BSA dynamic MRI enhanced parameters were used to evaluate and monitor the degree of renal fibrosis in rats.The results were compared with the final histopathological results.The feasibility of MnO₂@BSA enhanced MRI in assessing and monitoring the progression of renal fibrosis was compared with conventional MRI parameters.Materials and Methods:The subjects were 38 healthy male Sprague-Dawley?SD?rats?200g-300g,226±25g?.4.5mg/kg Hcy solution were injected through rat tail vein.Six rats died after injection of Hcy solution,3 rats died accidentally after anesthesia,and the remaining 29 rats completed all MRI examinations and were included in the study.Under anesthesia with intramuscular injection of 2%pentobarbital sodium?0.15ml/100g body weight?,Fast recovery fast spin echo?FRFSE?T₂WI and coronal Gd-DTPA DCE MRI were performed using 3.0T MRI?HD750 General Electric Medical Company,Milwaukee,USA?and 5.0cm pore animal coil?Jiangsu Wankang Medical Technology Co.,Ltd.?before and 1st,2nd,3rd,6th,11th,16th,20th and27th days after injection of Hcy solution,and MnO₂@BSA enhanced MRI was performed before and on the 1st,3rd,6th,11th,16th,20th and 27th days after injection of Hcy solution.The signal intensity of hilar horizontal cortex?CO?,outer stripe of the outer medulla?OSOM?,inner stripe of the outer medulla?ISOM?and psoas major muscle?psoas major?were measured on T2WI images using image J software?National Institutes of Health?.The signal intensity was calibrated by the ratio of average signal intensity of each kidney to that of psoas major muscle.Standardlized signal intensity?SSI?is obtained.SPSS17.0 analysis software was used to compare the SSI values in CO,OSOM,ISOM regions,Gd-DTPA DCE MRI and MnO₂@BSA enhanced MRI T₁WI CO and M signal intensity values at different time points.The difference was considered statistically significant when P<0.05.In addition to the normal group,2-4 rats were randomly selected at each time point for histopathological examination.Result:1.Characteristics of T₂SSI changes in rats with renal fibrosis:before injection of Hcy solution,CO signal intensity?2.48±0.36?and OSOM signal intensity?2.41±0.36?were indistinguishable and showed moderate signal intensity,while ISOM signal intensity showed relatively high signal intensity?2.91±0.46?.Two days after injection of Hcys solution,CO showed a bandy high signal?3.19±0.098,P<0.05?,and the boundary between CO and ISOM was clear.At 3rd day,CO signal intensity decreased slightly?2.69±0.40?,but was still higher than normal?P<0.05?.After then,CO signal intensity increased continuously?P<0.05?.The changes of OSOM and ISOM signal intensity were the same as CO.2.Changes of Gd-DTPA DCE MRI in renal fibrosis of rats:On the first day after modeling,the Kcl of kidney began to decrease sharply which was obviously lower than the normal level.On the second day,Kcl continued to decrease.On the third day,Kcl increased slightly,but was still significantly lower than the normal level.After then Kcl maintained at a plateau.3.Changes in MRI examination of renal fibrosis in rats with MnO₂@BSA enhancement:before Hcy injection,the renal cortex and medulla of rats were significantly enhanced,and the medullary enhancement was higher than that of cortex.After Hcy injection,the enhancement of renal cortex and medulla decreased slightly on 1st day.Thereafter,the enhancement of renal cortex and medulla continued to increase.The difference between the degree of renal medullary enhancement and that of the pre-modeling rats represents the leakage of MnO₂@BSA from the glomerulus,which increased continuously 3 days after modeling.4.Histopathological changes of renal fibrosis rats:1-2 days after homocysteine injection,the glomerular capillary endothelial cells swelled and the renal tubular epithelial cells in various regions were evidently edematous.Three days later,the structure of renal tubular epithelial cells was disordered and the glomerular structure was damaged.Eleven days later,the glomerular structure was destroyed.Sixteen days later,the glomerular injury was serious and the epithelial cells of renal tubules were vacuolated and degenerated.Conclusion:1.Injection of Hcy solution through tail vein can induce renal fibrosis in rats.2.MRI T₂WI signal intensity can be used to monitor renal damage in rats exposed to Hcys solution.Analysis of T₂WI corrected signal intensity with histopathology showed that renal damage induced by Hcy was a dynamic and multiphase process.3.Gd-DTPA DCE-MRI enhanced MRI showed that renal Kcl began to decrease sharply 1-2 days after modeling,and maintained a plateau after the 3rd day,which was significantly lower than normal level.4.MnO₂@BSA enhanced MRI showed the leakage of MnO₂@BSA continuously increased in rats after modeling.,which was consistent with the pathological findings that the lesions of Hcy kidney were mainly located in the glomerulus.