Correlation Between Phenotypic Change In Tubular Epithelium And Renal Allograft Fibrosis

In the past two decades, significant improvement has been achieved in theshort-term survival rate of renal allograft with the improvement of surgical techniquesand combination with new immunosuppressive agents, but the long-term survivalrate has not improved significantly. Chronic graft loss of kidney function caused bychronic renal allograft fibrosis (chronic renal interstitial fibrosis) is still the mainproblem in the transplant and kidney disease academia. Chronic renal allograftfibrosis is an irreversible clinical pathological process, and its pathogenesis iscomplicated. Currently, no biomarker is available to detect interstitial fibrosis in renalallograft at an early stage. In recent years, many researches show that the tubularepithelium express mesenchymal markers, accompanied by the expression ofepithelial markers is decreased or disappeared, means occurrence of the tubularepithelial phenotypic change（EPC), EPC can be involved in the formation of renalinterstitial fibrosis, and plays an essential role in renal allograft fibrosis.Objective: This study used transplant renal biopsy tissue as research material,and confirmed the presence or absence of the EPC in human renal allograft tubularepithelium. We studied the correlation between early phenotypic change in tubularepithelium and chronic renal allograft fibrosis, and whether early tubular EPC aftertransplantation has a good reference value to predicted subsequent renal allograftfibrosis.Methods: This study selected recipients who had undergone a serial graft biopsyat both3and12months after transplantation, and did not have mild to severe renalinterstitial fibrosis at3months. By screening, only eleven cases met the study criteriafrom more than380cases of renal allograft biopsy specimens. Pathological diagnosiswas based on the Banff classification including acute rejection、renal interstitialfibrosis score、tubulitis score and interstitial inflammation score, etc. Epithelialmarkers (E-Cadherin, β-catenin) and mesenchymal markers (α-SMA, vimentin) were detected by immunohistochemistry in renal tubular epithelium. According to theproportion of tubules showing mesenchymal markers, we got EPC score and EPCgroup. We used the difference of interstitial fibrosis score between3months and12months as fibrosis progression score, observed the correlation between early tubularEPC after transplantation and renal allograft fibrosis、fibrosis progression.Result: Our results show that some epitheliums can express mesenchymalmarkers (α-SMA and/or vimentin), meanwhile express little or no epithelial markers(E-cadherin and β-catenin), these epitheliums get mesenchymal phenotype and appearEPC. Tubular EPC is indeed present in human renal allograft tissue, EPC score has atendency to increase with degree of the acute graft rejection appearing.According to EPC score at3months, eleven cases were divided into EPC-positive group and EPC-negative group. Renal interstitial fibrosis score at12monthsin the EPC-positive group was significantly higher than in the EPC-negative group(2.25±0.46vs1.17±0.29; P<0.05).12-month renal interstitial fibrosis scores wereincreasing with the individual EPC scores at3months(r=0.76, P<0.01). Our resultsindicate that early tubular EPC is closely related to renal allograft fibrosis, has apositive correlation with renal allograft fibrosis.Results show that fibrosis progression score in the EPC-positive group was muchhigher than that in EPC-negative group (1.00±0.38vs0.17±0.29, P<0.05), the greaterthe EPC scores at3months, the greater the progression of fibrosis between3monthsand12months (r=0.78, P<0.01). These results further validate that renal allograftfibrosis status were increasing with early tubular EPC, early tubular EPC aftertransplantation has a good reference value to predicted subsequent renal allograftfibrosis.In addition, eleven cases were divided into mild fibrosis group and severefibrosis group based on12-month renal interstitial fibrosis scores, non-progressiongroup and fibrosis progression group based on fibrosis progression score. Wecompared the possible correlation between early tubulitis、interstitial inflammationand subsequent renal allograft fibrosis. Results show that the EPC score, tubulitis (t)score and interstitial inflammation (i) score in severe fibrosis group were highercompared with those in mild fibrosis group respectively（EPC score：2.86±0.69vs 1.25±0.50；t score：0.86±0.89vs0.25±0.50；i score：0.86±0.89vs0.50±0.58）,but only EPC score showed the statistical difference（P<0.05）. Similarly, the EPCscore, tubulitis score and interstitial inflammation score in fibrosis progression groupwere higher than those in non-progression group respectively（EPC score：2.83±0.75vs1.60±0.89；t score：0.83±0.98vs0.40±0.55；i score：0.83±0.98vs0.60±0.55）.Only EPC score had the statistical difference（P<0.05）.12-month fibrosis scores andfibrosis progression scores also have an increasing trend with increased intubulitis andinterstitial inflammation at3months, but compared with the tubulitis score andinterstitial inflammation score, the proportion of tubules EPC was more valuable inpredictive marker for subsequently renal graft fibrosis.Conclusion: Some tubular epitheliums get mesenchymal phenotype and indeedappear EPC in human renal allograft tissue. Chronic renal allograft fibrosis statuswere increasing with early tubular EPC, early EPC in tubular epithelium waspositively correlated with renal allograft fibrosis. Early tubular EPC aftertransplantation has a good reference value to predicted subsequent renal allograftfibrosis. Compared with tubulitis and interstitial inflammation, early tubular EPCcan more accurately predict subsequent renal allograft fibrosis and fibrosisprogression.