A Single-center Study Of The Spectrum Of Kidney Disease And Tacrolimus-based Therapy For Primary Membranous Nephropathy

BackgroundMembranous nephropathy(MN),also called membranous glomerulonephritis,is a type of diffuse glomerulonephritis belonging to primary glomerular disease(PGD)according to Classification and Atlas of Glomerular Diseases by World Health Organization in 1995.As a pathological term,MN is diagnosed by kidney biopsy,whose main features include capillary wall thickening and normal cellularity on light microscope,IgG and C3 along capillary walls on immunofluorescence,and subepithelial deposits on electron microscopy.The key histological characteristic of MN is the formation of subepithelial immune deposits,associated with variable degrees of alterations in the morphology of glomerular basement membrane(GBM),especially the pathognomonic "spikes" by periodic acid-silvermethenamine(PASM)stain under light microscopy(LM).According to the etiology and pathogenesis,MN is divided into primary membranous nephropathy(PMN)and secondary membranous nephropathy(SMN).PMN,also called idiopathic membranous nephropathy(IMN)previously,accounts for about 80%of all MN cases and SMN accounts for the remaining 20%.Just as the name implies,SMN is caused by secondary disorders such as infections(hepatitis B,hepatitis C,etc),autoimmune diseases(e.g.,systemic lupus erythrematosus and rheumatoid arthritis),malignancy(digestive tract,lungs and breast,especially in patients over 65 years old),drugs/toxins(e.g.,nonsteroidal anti-imflammatory drugs,penicillamine,gold,argentums,lithium and mercury compounds,etc),etc.Wheras PMN is diagnosed by exclusion of SMN,using medical history,physical examination,laboratory tests such as serology and imaging and by careful examination of the renal pathology.Clinically,PMN often occurs in middle-aged and elderly patients with a male predominance,and rare in children(accounts for about 1%-7%renal biopsy patients).Onset of PMN is usually hidden and associated with proteinuria.The majority(80%)of PMN patients manifest nephrotic syndromes(NS)with preserved kidney function in adults,whereas others exhibit subnephrotic proteinuria with a low incidence rate of hematuria.Based on urinary protein excretion(UPE)and severity of PMN,patients are divided into three categories:low risk(UPE<4g/24h with stable GFR),moderate risk(UPE between 4 g/24h and 8g/24h with stable GFR),or high risk(UPE>8g/24h,<50%decline from baseline or>30%decrease in GFR since baseline)categories.Accounting for 20%-50%NS patients,PMN 1s undoubtedly the most common cause of NS in adults.PMN has a varied natural course.Approximately 20%-30%patients undergo spontaneous remission within 2 years depending on the severity of proteinuria.About 15%-30%patients suffer one or more relapses.Some patients showing a persistent proteinuria fluctuating between a nephrotic and a subnephrotic range,however,approximately 34-62%will develop renal insufficiency and 30-40%patients with persistent high-grade porteinuria or NS eventually progress to end-stage renal disease(ESRD)within 10-15 years.In America,the annual incidence of ESRD due to MN is about 1.9/million.Prevalence of MN shows geographical variations globally.In recent several decades,except in a few developed countries such as America,England,Korea and Japan,prevalence of MN keeps increasing in most countries especially developing countries,which is particularly true in China.Incidence rate of MN in China is certainly more than 10/million per year-the mean estimated incidence rate worldwide.Mass data from large epidemiology studies shows that the prevalence of MN has been increasing dramatically and annually in China,associated with a younger age of onset and regional difference(higher in north area than south area).MN was previously regarded as a senile disease and this is clearly outdated at present.Till now,the most authoritative epidemiological study of renal biopsy in China was carried out by Fan Fan Hou et al.By analyzing 71,151 renal biopsies at 938 hospitals spanning 282 cities in China from 2004 to 2014,they found that primary glomerulonephritis(PGN)accounted for 77.5%of all the cases.Accounting for approximately 30.2%of all PGN,MN has become the second most common PGN.Wheras IgA nephropathy(IgAN)accounted for 36.3%and remained the most common type of PGN.The adjusted frequency of MN increased remarkably from 12.2%to 24.9%over the 11 years.However,other types of PGN,such as IgAN,minimal change glomerulopathy(MCD),segmental glomerular sclerosis(FSGS),non-IgAN mesangioproliferative glomerulonephritis(MsPGN)and mesangial proliferative glomerulonephritis(MPGN)remained relatively stable.If things go on like this,MN will probably surpass IgAN in the near future.They also found that increased risk of MN was connected with long-term exposure to air pollution especially fine particulate matter of<2.5 ?m(PM2.5)induced by rapid urbanization.Moreover,the increased prevalence and diagnosis rate of MN may also be related to improvement of renal biopsy technology as well as people's health care consciousness.Having been the second most PGN,MN is an important cause of chronic kidney disease(CKD)as well as ESRD without doubt China is a country with 1.4 billion people(comprising 20%of the world population),continuous surge of MN has made this disease become a public health problem in China.Therefore,further understanding of MN mechanisms and optimization of its treatment regimen have become clinical issues that Chinese clinicians are facing and need to be solved urgently.PMN is recognized as an organ-specific autoimmune glomerular disease mediated by specific antibodies to podocyte antigens such as neutral endopeptide(NEP),M-type phospholipase A2 receptor(PLA2R)and Thrombospondin Type-1 Domain-Containing 7A(THSD7A),etc.From the initial establishment of Heymann nephritis(HN)model in rats to worldwide clinical application of antibodies to PLA2R and THSD7A nowadays,our understandings concerning MN pathogenesis have undergone a long and great journey—from hypotheses to evidence and from bench to bedside.PMN is also called"idiopathic" membranous nephropathy initially due to the unknown pathogenesis of the disease.In 1959,Walter Heymann reported that experimental MN was caused by injecting kidney extracts combined with Freund's adjuvant in rats,which is later known as active HN model.Passive HN model was then designed for further studies.In 1982,the first podocyte antigen in HN model was identified—GP330(megalin),which was expressed on the proximal tubular brush borders.Based on those abundant findings from animal experiment which may also apply to human,the following hypotheses were put forward:There are intrinsic glomerular antigens expressed on human podocytes,the corresponding antibodies bind to target antigens and form immune deposits in situ,subsequent formation of membrance attack comples(C5b-9)induce podocyte injury then lead to protenuria and other clinical manifestations.In 2002,Hanna Debiec et al.confirmed the first podocyte antigen responsible for human MN—neutral endopeptidase(NEP)in the case report published in N Engl J Med.The maternal anti-NEP antibodies generated by the previous pregnancy were transferred from NEP-deficient mother to the fetus and caused alloimmune neonatal MN.In 2009,Laurence H.Beck Jr.reported that approximately 70%of adult PMN patients have IgG4 antibodies(both in the circulation and glomerulus)to podocyte-expressed PLA2R antigen.Since then,outpouring studies have shown that anti-PLA2R antibodies are detected in 70%?80%IMN patients all over the world.By providing the previous hypotheses with solid evidence,Dr.Beck's finding is a milestone beyond doubt in the history of MN.In 2014,a second podocyte membrane antigen THSD7A with similar properties to PLA2R was identified by Nicola M.Tomas et al.They found that anti-THSD7A antibodies presented in about 2.5%?5%of patients with PMN,and may be related with malignancy.Confirmed as reliable diagnostic and prognostic markers of IMN,detection of both anti-PLA2R antibodies and anti-THSD7A antibodies are applied to clinical practice promptly and widely.Insight into PMN enters a new era with discovery of the two autoantigens.The term IMN is no longer equal to PMN and should be superseded by the term autoimmune MN(AMN).However,PLA2R and THSD7A may represent only 80%?90%of adult PMN,leaving 10%?20%with potential autoantigens remain to be defined.The most common manifestation of adult PMN is NS,usually with edema of both lower limbs as the main complaint.Although course and prognosis of PMN are different,some patients may have spontaneous remission,nephrotic PMN patients are mostly at moderate or high risk and need treatment.Remission of NS predicts long-term renal survival(the mean 10-year renal survival rate is about 80%?90%).Persistent NS increases risk of progression to ESRD,infection,thromboembolic events,and progressive cardiovascular disease(CVD).Based on the pathogenesis mentioned above,the fundamental treatment for PMN should be immunosuppressive therapy(IST),aiming at inducing NS remission and protecting renal function.As described in KIDIGO guidelines,IST should be started in patients with nephrotic PMN if the UPE persistently exceeds 4 g/24h with>50%of the baseline value after supporting treatment(SC)such as angiotensin converting enzyme inhibitor/angiotensin receptor blocker,antihypertensive agents,statins and anticoagulant drug.The best evidence-supported regimen is alternating monthly cycles of glucocorticoids(GCs)plus alkylating agents(cyclophosphamide,CTX is recommended)for at least 6 months.Calcineurin inhibitor(CNIs)regimen of cyclosporine(CsA)or tacrolimus(TAC)is recommended as the alternative initial therapy.Other non-first-line treatments include Rituximab,Mycophenolate Mofetil(MMF),adrenocorticotropin(ACTH)and so on.Traditional Chinese medicine Tripterygium wilfordii also exerts favorble effects on in PMN patients.Known as the second generation immunosuppressants,CNIs mainly affects the activation and proliferation of T cells by inhibiting the intracellular calcineurin activity,thus inhibiting the immune response.CNls not only reduce the level of serum anti-PLA2R antibody in PMN patients,but also directly act on the glomerular podocytes by stabilizing their actin skeletons,thus significantly reducing urinary protein.Compared with CsA,TAC has stronger immunosuppressive effects(10-100 fold)and fewer side effects.To our knowledge,TAC is quite effective in the treatment of PMN,either used alone or combined with GCs.Although there are some side effects(relapse,elevated blood glucose and nephrotoxicity)and the price is relatively high,TAC takes effect quickly with high remission rates(averaging about 65%?89%after 12 months of treatment)as well as good drug safety.With development of social economy,improvement of national health care and implementation of the two-child policy,more and more PMN patients choose TAC as the initial therapy allowing for adverse effects of high-dose GCs and CsA that may affect appearance or reproductive ability.Under these circumstances,we designed and conducted this retrospective study to observe changes of MN frequency inTaian City Central Hospital and treatment of TAC-based therapy in young adults with nephrotic PMN(nPMN).Part 1.Study of the spectrum of kidney diseases in Taian City Central Hospital from 2012 to 2018ObjectivesTo evaluate changes in renal histopathological spectrum over time in Taian City Central Hospital using renal biopsy-proven cases,we performed this retrospective study.MethodsFrom January 1st,2012 to December 31th,2018,patients over the age of 14 years who were diagnosed with kidney diseases by renal biopsy in Taian City Central Hospital were analyzed.Biopsies containing Iess than 10 glomeruli were excluded.The study was divided into 2 periods:2012-2014(Period 1,PI)and 2015-2018(Period 2,P2).Results1.From January 2012 to December 2018,584 patients underwent renal biopsy in Taian City Central Hospital,and 578 qualified renal biopsy specimens were enrolled in this study.Annual biopsies were 26,72,89,91,95 and 105,respectively.Among the 578 patients,313 were males and 265 were females.Average age at the time of biopsy was 43.9±14.1.2.Among the 578 qualified cases of renal biopsy,465 patients were diagnosed with PGN,comprising 80.4%of all biopsies.PGN remained the most frequent type of histologic diagnosis during the study.While secondary glomerulonephritis(SGN),tubulointerstitial nephropathy(TIN)and hereditary renal diseases(HRD)accounted for 17.5%,1.9%and 0.2%,respectively.3.Among the 465 PGN patients,PMN(49.5%)was the most common type,and IgAN(24.7%)ranked second,followed by MCD(15.1%)and FSGS(5.8%).The remaining 2.6%patients belonged to other PGN types such as MsPGN,MPGN and CreGN,etc.4.From 2012 to 2018,annual frequencies of main PGN types were as follows:IgAN/PGN was 50%,38.6%,31%,22.7%,17.6%,20.9%and 14.50%,respectively.PMN/PGN was 8.3%,28.1%,38%,58.9%,55.4%,58%and 65.1%,respectively.MCD/PGN was 20.8%,19.3%,23.9%,9.3%,14.9%,13.6%and 10.8%respectively.FSGS/PGN was 16.7%,3.5%,5.6%,4%,6.8%,7.4%and 3.6%,respectively.5.From Period 1(2012-2014)to Period 2(2015-2018),main PGN types changed as follows:During Period 1,IgAN(36.8%)was the most frequent PGN;PMN(29.6%)was the second,followed by MCD(21.7%)and FSGS(6.6%).During Period 2,PMN(59.1%)surpassed IgAN and became the most frequent PGN;while IgAN(18.8%)became the second,followed by MCD(12.1%)and FSGS(5.4%).6.Among the 230 PMN patients,134 were male(58.3%)and 96(41.7%)were female,the ratio of male to female was 1.4:1.As for the pathological staging,189(82.2%)patients were in stagell and 23(10%)patients were in stage ?.15(6.5%)and 3(1.3%)patients belonged to stage ? and stage ?,respectively.Of all the 230 PMN patients,185(80.4%)manifested NS,followed by proteinuria(11.3%)and chronic glomerulonephritis(8.3%).17 patients showed impaired renal function at the time of onset,occupying 7.4%of all PMN patients.The average age of PMN patients changed from 45.5±15.8 in Period 1 to 48.4±14.5 in Period 2,showing a significantly increasing trend.7.Of all the 35 SMN patients,14(40%)patients were secondary to SLE,10(3 1.4%)patients were secondary to Hepatitis B,7(20%)patients were secondary to diabetes and the remaining 4(8.6%)patients were secondary to psoriasis,Sjogren syndrome(SS),ANCA-associated vasculitis and thyroid cancer,respectively.8.From 2014 to 2018,the annual PM2.5 in Taian city was 76(?g/m3,69?g/m3,66?g/m3,57?g/m3 and 52?g/m3,respectively.There were no significant relations between PM2.5 and frequency of MN in our hospital.Conclusions1.From 2012 to 2018,patients undergoing renal biopsy increased year after year,from 26 cases in 2012 to 105 cases in 2018.2.During the observation time,PGN remained the most common type of histologic diagnosis,comprising 80.4%of all renal biopsies.PMN,IgAN,MCD and FSGS were the leading PGN types.Spectrum of PGN changed during the observation time.PMN increased sharply and nearly doubled from Period 1 to Period 2.IgAN and MCD decreased significantly while frequency of FSGS remained stable during the entire period.3.The ratio of male to female in PMN patients was 1.4:1,showing a male predominance.And stage ? was the leading histologic diagnoses in PMN patients.The most common presentation of PMN was NS clinically,followed by proteinuria and CGN.The vast majority of patients had normal renal function at onset of PMN.4.Main causes of SMN in our hospital were SLE,HBV and DM successively.5.From 2014 to the year 2018,PM2.5 in Taian city had no significant relations with frequency of PMN.Part 2.Study of tacrolimus-based therapy for nephrotic PMN in young adults.ObjectivesWe designed this study to investigate efficacy and safety of tacrolimus-based treatment for nephrotic PMN(nPMN)in young adults.MethodsFrom January 2012 to December 2018,biopsy-proven nPMN patients aged between 15 and 40 in Taian City Central Hospital treated with tacrolimus were retrospectively analyzed.12-month follow-up data were collected.Forty patients in the TAC group received tacrolimus medication with the dose of 0.05 to 0.1 mg/kg/day initially.Forty-six patients in the TAC+Pred group received TAC combined with oral prednisone(0.5 mg/kg/day initially).Indexes of patients in the two groups at baseline,after treatment of 3 months,6 months and 12 months were collected and compared.Results1.Baseline charicteristicsA total of 86 patients(40 patients in the TAC group and 46 patients in the TAC+Pred group)were included in the study.Demographic,clinical and laboratory charicteristics between the two groups were comparable at baseline.2.Primary outcomesAfter 3 months of initial therapy,in the TAC group,2(5%)patient achieved CR and 6(12.5%)patients achieved PR.In the TAC+Pred group,3(6.52%)patient achieved CR and 10(21.7%)patients achieved PR.TR rates were 20%and 28.3%,respectively.No significant difference was observed between the two groups.At the end of the 6th month,in the TAC group,3(7.5%)patients achieved CR and 11(27.5%)patients achieved PR.In the TAC+Pred group,11(23.9%)patient achieved CR and 15(32.6%)patients achieved PR.TR rates were 35%and 56.5%,respectively.Compared with the TAC group,both CR rate and TR rate in the TAC+Pred group was statistically higher.At the end of the 12-month follow-up,in the TAC group,7(17.5%)patients exhibited CR and 24(60%)patients exhibited PR.In the TAC+Pred group,17(36.9%)patient exhibited CR and 20(43.5%)patients exhibited PR.TR rates in the two groups were 77.5%and 80.4%,respectively.Patients in the TAC+Pred group had a significantly higher CR rate compared with the TAC group,whereas TR rates were comparable between the two groups.The multivariate logistic regression analysis showed that the probability of CR at 6 and 12 months as well as TR at 6 months were significantly higher in TAC+Pred group compared with TAC group,which further confirmed the above results.The multivariate logisticregression model also showed gender(male vs female,OR 0.306,95%Cl 0.113-0.826)was independently associated with TR at 12 months.3.Secondary outcomesUPE,ALB and eGFR between groups were comparable during the follow-up.Decrease in proteinuria was significantly greater in the TAC+Pred group.Relapse occurred in two(5%)patients in the TAC group and no relapse was reported in the TAC+Pred group during the 12-month follow-up,while there was no significant difference between the two groups.4.Adverse effectsAdverse effects in both groups were mild and controllable.ConclusionsBoth tacrolimus monotherapy and tacrolimus combined with medium-dose prednisone are effective and safe for young adults with nPMN,while TAC+Pred regimen brings more benefits and is recommended for clinical use.