Hildur Rún Helgudóttir, Runólfur Pálsson, Viðar Örn Eðvarðsson and Þórarinn Guðjónsson
Introduction
Adenine phosphoribosyltransferase (APRT) deficiency is a rare genetic disorder that results in excessive generation and excretion of 2, 8-dihydroxyadenine (DHA), leading to kidney stone disease and crystal nephropathy. This condition causes inflammation and fibrosis in the kidneys. Despite research on other crystal nephropathies, the mechanism of DHA-induced kidney cell injury remains unclear. This study aimed to establish a comprehensive cell culture model to investigate DHA crystal-induced kidney injury.
Methods
Three cell lines, MDCK, HK-2, and HEK293, were studied in both 2D and 3D cultures. Cells were exposed to DHA at concentrations that matched those observed in patients with APRT-deficiency. Cell viability and migration assays, RT-PCR, and immunostaining were employed as read-out assays. Immunohistochemistry (IHC) was used to analyze kidney tissue samples from APRT deficiency patients and healthy controls obtained from the Landspitali-The National University Hospital Biobank.
Results
DHA exposure decreased kidney cell viability and migration across all cell lines. Expression of CD44 increased with higher DHA concentrations, suggesting enhanced crystal-binding potential of the exposed cells. DHA reduced barrier function via reduced trans-epithelial electrical resistance (TEER) in liquid-liquid interface (LLl) cultures. Analysis of patient kidney tissue samples revealed increased collagen I and III expression, well-known markers of fibrosis, in APRT deficiency patients.
Conclusions
These findings demonstrate the deleterious effects of DHA on kidney cell health and barrier function, and its potential role in promoting fibrosis in APRT deficiency. Future studies in 3D cultures will focus on further exploring the phenotypic changes in kidney cells after exposure to DHA.
