Both sugarcane and rice contain amorphous silica nanoparticles (SiNPs) that can be released into the air following burning, where they can be inhaled, or potentially seep into the groundwater, where they may be ingested.
Unlike crystalline silica, which is larger in size and causes lung disease, amorphous silica nanoparticles can pass through the lung to the kidney, where they can induce inflammation and chronic kidney disease in rats.
We therefore performed a pilot study to determine if SiNPs are increased in the kidney tissue of individuals with Mesoamerican nephropathy (MeN), a type of CKDu from Central America.
Kidney biopsies from patients hospitalized at Hospital Rosales in San Salvador carrying a diagnosis of CKDu (n = 6) and biopsies from patients with other diseases (n = 16) were randomly evaluated. A blinded analysis for silica nanoparticle content and size distribution was performed using single-particle inductively coupled plasma mass spectrometry and expressed as nanoparticles per volume of tissue (see Item S1 in supplementary material). All kidney biopsies were performed for clinical indications and leftover tissues deidentified. Clinical information and occupational exposures were extracted from the chart by the treating physician (RL). Institutional review board approval was obtained both from Hospital Rosales and the Colorado Multiple Institution Review Board, who waived the requirement for personal consent. Data are expressed as mean ± standard error of the mean and a Mann-Whitney test was used to compare groups.
Six cases were consistent with MeN, while 16 control biopsies showed focal segmental glomerulosclerosis (n = 6), membranous glomerulonephritis (GN) (n = 3), systemic lupus erythematosus (n = 3), and 1 each of IgA nephropathy, postinfectious GN, membranoproliferative GN, and thin basement membrane disease. A diagnosis of MeN was defined as biopsy showing chronic tubulointerstitial fibrosis, tubular atrophy, and inflammation associated with variable glomerular hypertrophy and glomerulosclerosis in the absence of hypertension, diabetes, or known kidney disease. A consensus on the diagnoses were made by the renal pathologist at Hospital Rosales (LS), the Karolinska Institute (AW), and the University of Colorado (SL).