ZNF185 Prevents Stress Fiber Formation Through the Inhibition of RhoA in Endothelial Cells

respectively. mTG had minimal effect on molecular transport during diffusive transport. Native GBM behaved as a compressive filter, restricting large molecule transport at high pressure. This effect was mitigated in enzymatically crosslinked GBM due to the decreased degree of compressibility suggesting that disease mediated enzymatic crosslinking may

Background: IgA nephropathy (IgAN) is characterized by galactose deficient IgA (gd-IgA1) containing immune complexes in the mesangium, leading to activation of the cells, proliferation, matrix expansion and local inflammation.The exact composition of the mesangial matrix and its role in disease progression is not fully known.One important group of proteins in matrixes are proteoglycans (PGs).PGs are composed of a core protein to which glycosaminoglycan (GAG) side chains are attached.The most common GAGs are heparan sulfate (HS) and chondroitin sulfate (CS).Both the core protein and GAGs determine the properties of PGs and changes in PG composition could be of importance for disease progression.In this study, we aimed to elucidate the role of changes in the PG expression in IgAN.
Methods: Human MCs expression of PGs after stimulation with gd-IgA1 was investigated using a glycoproteomics which gives information about both the core protein identity and the the GAGs attached.Immunoflourescens was used for quantification of GAGs.ELISA was used to investigate specific PGs.In vivo and in vitro validation was done using a previously published transcriptomic data set of glomeruli from patients with IgAN in combination with a proteomic data set of HMCs treated with gd-IgA (Liu et al JASN 2017).
Results: Glycoproteomics identified 13 PGs in the medium and 5 in the cell lysate and their corresponding GAGs, of which the majority was CS PGs.More PGs were identified in the cells treated with control IgA (cIgA) or gd-IgA1 than the controls.Immunohistochemistry revealed that gd-IgA1 treatment of MCs does not lead to a total increase in GAGs, but rather to a switch from HS to CS GAGs.This was found to be true also in the already published proteomic data set on MCs treated with gd-IgA1.In vivo validation revealed that in IgAN there are more CS upregulated than HS in IgAN.Bikunin, the most upregulated CS PG, expression was validated using ELISA, and found to not be expressed by cells before stimulation with IgA, but then highly upregulated.

Conclusions:
In conclusion, this study gives a comprehensive view of the PGs expressed by MCs and their alterations in response to gd-IgA1 as part of the expansion of the mesangium in IgAN.The switch of HS GAGs to CS GAGs could be involved in driving inflammation/proliferation but the role of this switch needs further investigation.

TH-PO427 Poster Thursday
Glomerular Diseases: Inflammation and Fibrosis

Pathological Changes After Methylprednisolone (MP) Pulse Therapy in IgA Nephropathy
Byoung-Soo Cho.Dr. Cho's Kidney Clinic, Seoul, Republic of Korea.
Background: IgA nephropathy is one of the most common chronic glomerulonephritis and 30-45% fall into CKD over a period of 20-25 years.Lots of therapeutic regimens are tried such as ACEi, ARB, omega-3, corticosteroids, MP pulse therapy and recently many kinds of complement inhibitors, Nefecon, Atacicept, Atrasentan etc., however need a longterm follow up studies to confirm the efficacy.Up to now most centers regarded proteinuria as a most imporatant prognostic marker in IgA nephropathy.In order to confirm the efficacyof proteinuria as a prognostic marker, we performed follow up renal biopsy who showed normalized proteinuria aDuring last 7 yearsour clinic performed 1,500 cases of renal biopsyfter MP pulse therapy Methods: During last 7 years our clinic performed 1,500 cases of renal biopsies at OPD level, of which 494 cases (32.9%) were IgA nephropathy patients.We performed follow up renal biopsy in 120 cases who showed normalized urinalysis findings Renal biopsy findings were divided into 3 groups, Group A: improved pathological findings.Group B : no significant pathologic changes.Group C: aggravated pathological findings such as increased glomerulossclerosis, tubulointerstitial changes, tubular atrophy etc.One cycle of MP pulse therapy consist of methylprednisolone (20-30mg/kg, max 1gm/day) IV for 3 conscutive days.Depends on pathologic findings we performed 3 to 15 cycles.
Results: Male to female ratio were 59:61, Mean age were 31.1 years old.Of the 120 follow up renal biopsies, 60 cases (50%) showed improved pathological findings (Group A) such as reduced or disappearance of electron dense deposits, restoration of foot processes, decreased mesangial proliferation, 50 cases (40%) showed no significant pathological changes compare to initail pathological findings (Group B), 10 cases (10%) showed aggravated pathological findings such as increased glomerulosclerosis, aggravated intrerstitial fibrosis and tubular atrophy even though clinically improved such as normalized urinalysis findings, stabilized BPand improvement of eGFR.(Group C) Conclusions: Only 50% of the clinically improved IgA nephropathy patients showed improved pathological findings Decresed proteinuria could not be a prognostic marker of improvement of IgA nephropathy Follow up renal biopsy might be mandatory procedure even though clinically improved such as disappearance of proteinuria Funding: Private Foundation Support

TH-PO428 Poster Thursday
Glomerular Diseases: Inflammation and Fibrosis

Interstitial LRP1 Expression Is Associated With Glomerular Disease
Marwin Groener, 1,2 Tilman Jobst-Schwan, 3 Mario Schiffer.Background: Low density lipoprotein receptor-related protein 1 (LRP1) is a large evolutionarily conserved endocytic transmembrane receptor that is ubiquitously expressed.However, little is known about its function in the kidney.The goal of this study was to investigate LRP1 expression in different nephron segments in healthy and diseased human renal tissue as well as the developing kidney.
Methods: Immunohistochemistry with two antibodies targeted towards the intracellular and extracellular domains of LRP1 were used to assess spatial distribution of LRP1 in healthy human renal tissue and in biopsies of minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy.Perinatal and adult mouse kidneys were assessed with immunohistochemistry for LRP1.Published kidney RNA and ATAC sequencing databases were used to evaluate LRP1 transcription levels in different renal cell types.
Results: In healthy human tissue, intracellular LRP1 signal was detected in distal tubules (DT), loop of Henle (LH), and collecting ducts (CD), whereas extracellular domain signal was found in proximal tubules (PT) and weaker in LH.No glomerular or interstitial signal was found with either antibody.Surprisingly, marked glomerular and interstitial LRP1 expression was seen in all glomerulopathies.Glomerular expression did not co-localize with nephrin and had a mesangial pattern.Interstitial LRP1 was pronounced in the peritubular space.In P0 mouse kidneys, LRP1 signal was primarily found in the interstitium and S-shaped body, whereas adult mouse tissue predominantly expressed LRP1 in the PT.RNA and ATAC sequencing database analysis indicated preferential transcription of LRP1 in mesangial cells and fibroblasts.
Conclusions: Interstitial LRP1 expression is markedly induced in human proteinuric glomerulopathies.Interestingly, the developing mouse kidney has similar interstitial LRP1 expression which is lost in mature renal tissue.Our findings demonstrate an association of interstitial LRP1 with glomerular disease and kidney development.Further research is needed to elucidate the role of LRP1 in renal disease and its potential as a drug target.