Molecular patterns of diffuse and nodular parathyroid hyperplasia in long-term hemodialysis

Secondary hyperparathyroidism is well known complication manifested in end-stage renal disease (ESRD). Both nodular and diffuse parathyreoid hyperplasia occur in ESRD patients. Distinct molecular mechanisms involved in parathyreoid hyperplasia remain poorly understood. Microarray screening proved homogeneity of gene transcripts in hemodialysis patients as compared to transplant cohort and primary hyperparathyreoidism, therefore further studies were performed in hemodialysis patints only. Enrichment analysis conducted on 485 differentially expressed genes between nodular and diffuse parathyreoid hyperplasia revealed highly significant differences in GO terms and KEGG database in ribosome structure (p=3.70-18). Next, RT-qPCR validation of microarray analysis proved higher expression of RAN guanine nucleotide release factor (RANGRF, p<0.001), calcyclin binding protein (CACYBP, p<0.05) and exocyst complex component 8 (EXOC8, p<0.05) and lower expression of peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (PIN1, p<0.01) mRNA in nodular hyperplasia. Multivariate analysis revealed RANGRF and PIN1 expression along with parathyroid weight to be associated with nodular hyperplasia. Higher expression of genes associated with ribosomal structure and function underline extended translation mechanisms involved in parathyreoid nodular formation in long-term hemodialysis treated patients. Parathyroid tissue obtained from ESRD hyperparathyroidism patients who had undergone parathyroidectomy were used for transcriptome screening (Illumina HumanHT-12 v4.0 Expression BeadChips) and subsequently for discriminatory gene analysis, pathway mapping and gene-annotation enrichment analyses. Results were verified on enlarged group of hemodialysis patients with nodular (n=20) and diffuse (n=20) hyperplasia using RT-qPCR method.