Mitochondrial stress in primary amyloidogenic PCs. Assessment of mitochondrial morphology and homeostasis in primary BM PCs purified from AL and MM patients by EM and transcripts analysis. (A) Representative EM images of BM PCs in AL, MM, and MGUS patients and analysis of cellular distribution of mitochondria. The percentage of perinuclear mitochondria was arbitrarily estimated as the proportion of mitochondria within half of the distance between perinuclear and plasma membrane (>20 PCs per patient; 9 AL, 6 MM, 3 MGUS primary samples per group). (B-C) Abundance of transcripts encoding HO-1 and organelle-resident redox sensors (B) and effectors of the mitochondrial UPR (C) assessed by quantitative reverse transcription PCR (8 AL and 7 MM patients). Histograms show mean values ± standard error. *P < .05; **P < .005 (Student t test). ClpP, caseinolytic mitochondrial matrix peptidase proteolytic subunit; ClpX, caseinolytic mitochondrial matrix peptidase chaperone subunit; Hsp60, heat shock protein 60; PDI, protein disulfide isomerase; Prdx3, peroxiredoxin 3; Prdx4, peroxiredoxin 4; Ubl5, ubiquitin-like 5.