The Roles Of Fibrocytes In The Progressive Renal Fibrosis Induced By Adriamycin And Effects Of Rapamycin On Them In This Model Of Rats

Background and objective Renal fibrosis is the common pathway of chronic kidney diseases(CKD) running to end-stage renal disease (ESRD) resulting from various reasons.Glomerular sclerosis and tubulointerstitial fibrosis are known as classical changes of renal fibrosis. Unfortunately, the intimate mechanisms leading to the development and progression of renal injury are not yet fully known. Previous studies were reptored that some types of cells ,such as myofibroblast and fibroblast, have the key roles in the development and procession of renal fibrosis,wheras the special type of the peripheral blood cells, fibrocyte, is shown as a precursor of myofibroblast and fibroblast. It may be effective to ameliorate the process of renal fibrosis by blocking the migration, transformation of fibrocyte. It is the reason why some studies are focus on fibrocyte, recently. Rapamycin(RAPA) is a new, potent immunosuppressive agent. it possesses a variety of pharmacological functions, including anti-inflammation, anti-virus,anti-proliferation and protecting vascular. Some researches have shown that RAPA has significant protective positive effects on renal fibrosis in various animal models of chronic renal disease. Our study was to investigate the effect of fibrocytes and chemokine recepter 7(CCR 7) in the process of renal fibrosis induced by adriamycin in rats. Moreover, to observe the effect of RAPA on some cytokines relating with fibrocyte to explore the potential protective mechanism in renal fibrosis.Methods Sixty-two Male Sprague-Dawley( SD) rats 8 weeks old were divided to three groups randomly, normal control group (group A, n=20) ,model group (group B,n=32) and RAPA treatment group(group C, n=10). Group B and C were injected with 4 mg/ kg of adriamycin via tail vein on the first day of the 1st and 2nd wk respectively,while group A received 0. 9 % sodium chloride solution injection of equal volume at the same time. Group C received RAPA treatment 1.5 mg/(kg·d) orally in the 2 nd wk after the first adriamycin injection. The changes of 24 h urine protein and renal pathological were evaluated in the end of 7 wk after the first administration of adriamycin. In group B, the urine and serum samples were measured at the end of 4 wk,7 wk,10 wk and 13 wk after the first administration of adriamycin to observe biochemical changes, including serum total cholesterol(TC), serum triglyceride(TG), serum albumin(ALb) and 24 h urine protein excretion rate, while the renal tissue of rats was obtained to evaluate renal histological and ultrastructural changes by glomerulosclerosis index(GSI) and tubulointerstitial index(TII), and analyze the expression of CD45 and CCR7 by immunohistochemistry. The samples, which were mentioned above, were measured in the end of 7 wk after the first administration of adriamycin in group C.Results1. Levels of TG, TC and ALb Comparing with group A, there were increasing levels of TC(6.79±1.47 vs 1.29±0.27, P<0.01) and TG(2.57±1.19 vs 0.76±0.11, P<0.01) , wherea s Alb (21.41±2.11 vs 34.64±0.96, P<0.01)decreased significantly in the end of 7 wk in group B.2. 24 h urine protein excretion rate Comparing with group A, there were increasing levels of 24 h urine protein excretion rate (568±102 vs 21±6,P<0.01 ) in group B, and they rose further as the disease-process progressed(P<0.01). 24 h urinary protein excretion rate in group C was decreased significantly compared with it in group B in crossponding time (P<0.01).3. Renal pathologic morphology The proliferation of the mesangial cells, the accumulation of the extracellular matrix and atrophyin or extension of renal tubules in group B were more remarkable than that in groupA, while these changes were signicantly ameliorated by theatment with RAPA(P<0.01).4. Fibrocyte In group B ,we observed the serial sections of renal tissue by immunohistochemistry and found that in renal cortical interstitium, there were some cells which expressed CD45 and collagen I simultaneously.5. The expression of CD45 In group B, interstitial infiltrate of CD45+ cells appeared in the end of 4 wk, reached a maximum in the end of 7 wk (P<0.01)and gradually decreased afterward(P<0.05).The number of CD45+ cells was lower in group C than in group B in crossponding time(P<0.01).6. The expression of CCR7 In group B, interstitial infiltrate of CCR7+ cells appeared in the end of 4 wk, reached a maximum in the end of 7 wk (P<0.01)and gradually decreased afterward(P<0.05). In crossponding time ,the number of CCR7+ cells was lower in group C than in group B(P<0.01).Conclusions1. Fibrocytes may be involved in the earlier and intermediate stage of kidney fibrosis.The immigration of this population from peripheral blood to renal lesion site is possible to be associated with the expression of CCR7 protein.2. RAPA could ameliorate renal fibrosis induced by adriamycin in rats, and the effects is likely to be correlated with the downregulation of CCR7 protein.