Anti-Collagen Type IV monoclonal antibody

Age-related macular degeneration (AMD) and related macular dystrophies (MDs) are a major cause of vision loss. However, the mechanisms underlying their progression remain ill-defined. This is partly due to the lack of disease models recapitulating the human pathology. Furthermore, in vivo studies have yielded limited understanding of the role of specific cell types in the eye vs. systemic influences (e.g., serum) on the disease pathology. Here, we use human induced pluripotent stem cell-retinal pigment epithelium (hiPSC-RPE) derived from patients with three dominant MDs, Sorsby's fundus dystrophy (SFD), Doyne honeycomb retinal dystrophy/malattia Leventinese (DHRD), and autosomal dominant radial drusen (ADRD), and demonstrate that dysfunction of RPE cells alone is sufficient for the initiation of sub-RPE lipoproteinaceous deposit (drusen) formation and extracellular matrix (ECM) alteration in these diseases. Consistent with clinical studies, sub-RPE basal deposits were present beneath both control (unaffected) and patient hiPSC-RPE cells. Importantly basal deposits in patient hiPSC-RPE cultures were more abundant and displayed a lipid-and protein-rich "drusen-like" composition. Furthermore, increased accumulation of COL4 was observed in ECM isolated from control vs. patient hiPSC-RPE cultures. Interestingly, RPE-specific up-regulation in the expression of several complement genes was also seen in patient hiPSC-RPE cultures of all three MDs (SFD, DHRD, and ADRD). Finally, although serum exposure was not necessary for drusen formation, COL4 accumulation in ECM, and complement pathway gene alteration, it impacted the composition of drusen-like deposits in patient hiPSC-RPE cultures. Together, the drusen model(s) of MDs described here provide fundamental insights into the unique biology of maculopathies affecting the RPE-ECM interface.

The glomerular basement membrane (GBM) is a critical component of the kidney's blood filtration barrier. Alport syndrome, a hereditary disease leading to kidney failure, is caused by the loss or dysfunction of the GBM's major collagen type IV (COLA) isoform alpha(3),alpha(4),alpha(5). The constituent COL4 alpha-chains assemble into heterotrimers in the endoplasmic reticulum before secretion into the extracellular space. If any one of the alpha(3)-,alpha(4)- or alpha(5)-chains is lost due to mutation of one of the genes, then the entire heterotrimer is lost. Patients with Alport syndrome typically have mutations in the X-linked COL4A5 gene or uncommonly have the autosomal recessive form of the disease due to COL4A3 or COL4A4 mutations. Treatment for Alport syndrome is currently limited to angiotensin-converting enzyme inhibition or angiotensin receptor blockers. Experimental approaches in Alport mice have demonstrated that induced expression of COL4A3. either widely or specifically in podocytes of Col4a3(-/-) mice, can abrogate disease progression even after establishment of the abnormal GBM. While targeting podocytes in vivo for gene therapy is a significant challenge, the more accessible glomerular endothelium could be amenable for mutant gene repair. In the present study, we expressed COL4A3 in Col4a3(-/-) Alport mice using an endothelial cell-specific inducible transgenic system, but collagen-alpha(3)alpha(4)alpha(5) (IV) was not detected in the GBM or elsewhere, and the Alport phenotype was not rescued. Our results suggest that endothelial cells do not express the Col4a3/a4/a5 genes and should not be viewed as a target for gene therapy.