Glomerulosclerosis and kidney failure in a mouse model of monoclonal immunoglobulin light-chain deposition disease

Abstract

Light chain deposition disease (LCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a monoclonal immunoglobulin (Ig) light chain (LC), leading to nodular glomerulosclerosis and nephrotic syndrome. We developed a transgenic model using site-directed insertion of the variable domain of a pathogenic human LC gene into the mouse Ig kappa locus, ensuring its production by all plasma cells. High free LC levels were achieved after backcrossing with mice presenting increased plasma cell differentiation and no Ig heavy chain (HC) production. Our mouse model recapitulates the characteristic features of LCDD, including progressive glomerulosclerosis, nephrotic-range proteinuria and finally, kidney failure. The variable domain of the LC bears alone the structural properties involved in its pathogenicity. RNA sequencing conducted on plasma cells demonstrated that LCDD LC induces endoplasmic reticulum stress, likely accounting for the high efficiency of proteasome inhibitor-based therapy. Accordingly, reduction of circulating pathogenic LC was efficiently achieved and not only preserved renal function, but partially reversed kidney lesions. Finally, transcriptome analysis of pre-sclerotic glomeruli revealed that proliferation and extracellular matrix remodelling represented the first steps of glomerulosclerosis, paving the way for future therapeutic strategies in LCDD and other kidney diseases featuring diffuse glomerulosclerosis, particularly diabetic nephropathy. Introduction : Monoclonal gammopathies of renal significance (MGRS) are characterized by renal lesions due to monoclonal immunoglobulins produced by a non-malignant B or plasma cell clone (1). Depending on the type and structural properties of the Ig, they comprise tubulopathies caused by LC accumulating in the proximal or distal tubules, or glomerulopathies, most frequently AL amyloidosis and Randall-type monoclonal Ig deposition disease (MIDD) (2). MIDD are characterized by linear amorphous deposits of a monoclonal LC (LCDD) or a truncated HC (HCDD) along the tubular and glomerular basement membranes (BMs), around arteriolar myocytes and in the mesangium, eventually leading to diabetic-like nodular glomerulosclerosis. Clinical manifestations include glomerular proteinuria with progressive kidney failure (3-5). In LCDD, the most frequent form of MIDD, involved LCs are mostly of the kappa isotype, with a striking overrepresentation of the Vk4 variable domain characterized by a long CDR1. Other peculiarities of LCDD LCs are due to somatic hypermutations and include polar to hydrophobic amino-acids replacements, small truncations or abnormal glycosylations (3, 4, 6-10). Moreover, LCDD LCs are characterized by the constant high isoelectric point (pI) of their V domain compared to LCs involved in AL amyloidosis (11).This feature was also confirmed in HCDD and could account for the high avidity of positively charged LCs for anionic heparan sulfates of basement membranes (5). However, little is known about the pathogenic mechanisms i...

A mouse model of cardiac AL amyloidosis unveils mechanisms of tissue accumulation and toxicity of amyloid fibrils

“…The human monoclonal LC genes used in the study were obtained from bone marrow (BM) aspirates as previously described (76,77). The AL λLC cDNA was extracted from a patient with biopsy-proven AL amyloidosis (λS-PT).…”

“…To generate the transgenic mice models (λS-DH and κR-DH) two similar strategies were used as previously described (38,77). For λS-DH, the complete cDNA coding for the selected human monoclonal λLC was introduced in place of the mouse Jκ segments in the κ locus thus generating a fully human LC.…”

“…For λS-DH, the complete cDNA coding for the selected human monoclonal λLC was introduced in place of the mouse Jκ segments in the κ locus thus generating a fully human LC. For κR-DH, only the cDNA coding for the variable/junction domains (VJ) was introduced, generating in the mouse a chimeric human/mouse LC composed of the human VJ domain and the mouse Cκ domain as previously described (38,77).…”

“…Slides were observed on a NiE microscope (Nikon). For electron microscopy (EM) and immunogold studies, tissues were fixed in 3% glutaraldehyde in 0,1M phosphate buffer (pH 7,2) at 4°C and processed as previously described (76,77). For histochemical staining, tissues were fixed in 4% paraformaldehyde and paraffin-embedded as previously described (77).…”

“…Total RNA was extracted from the apical part of the hearts of λS-DH and DH-LMP2A mice using the miRNeasy Mini Kit (Qiagen) on the TRIzol reagent and the purity of the samples was assessed on the Bioanalyzer RNA 6000 Nano (Agilent) before generating the libraries and performing the RNAsequencing as previously described (77). Paired-end reads were processed through the bioinformatic pipeline nf-core/rnaseq v3.12 (80) in reverse strandedness mode.…”