Changes of autophagosomes of podocytes in idiopathic membranous nephropathy and its clinical significance

Objective To observe the quantity change of autophagosomes in podocytes and expressions of autophagy-related gene Beclin-1 and microtubule-associated protein 1 light chain 3 (LC3) in different pathological stages of idiopathic membranous nephropathy (IMN), and to explore how autophagy is related to podocyte injury, the occurrence of proteinuria and the disease progression in IMN. Methods Clinical data of 26 patients who were diagnosed as IMN (14 IMN stage 1 and 12 IMN stage 2) admitted to Zhejiang Provincial people's Hospital from January 2013 to December 2014 were retrospectively analyzed. Normal renal tissue from 15 cases of kidney neoplasms with nephrectomy was collected as control. The changes of kidney tissue pathology were detected after PAS and PASM staining by light microscope. The autophagosomes of podocyte were detected by transmission electron microscopy. Expressions of Beclin-1 and LC3 protein were detected by immunohistochemistry. Expressions of LC3 and synaptopodin were detected by immunofluorescence. The correlation of autophagosomes and clinical pathologic factors in IMN patiens was analyzed. Results There were fewer autophagosomes of podocytes and lower expression of Beclin-1 and LC3 protein in IMN group than those in control group (P=0.034, P=0.011, P=0.013, respectively). Moreover, these effects were more obvious with the development of IMN. Compared with those in control group, autophagosomes, Beclin-1 and LC3 protien were reduced in IMN stage 2 group (P=0.009, P=0.030, P=0.015); the number of autophagosomes and the expressions of LC3 and Beclin-1 were decreased in IMN stage 1 group as well, however statistically insignificant (P=0.352, P=0.087, P=0.128); Comparisons between IMN stage 2 patients and IMN stage 1 patients shown significant difference in the number of autophagosomes (P=0.030), but no significant difference in expressions of Beclin-1 and LC3 (P=0.355, P=0.181). Autophagosomes number was not correlated with serum creatinine, serum urea nitrogen, 24-hour urinary protein and eGFR (all P＞0.05). The expressions of synaptopodin and LC3 protein were lower in IMN group than those in control group. Conclusion Autophagy may contribute to podocyte injury and the production of protein urine in IMN, and may be closely related to the progression of disease.