Immunophenotypic characterization of bone marrow residing in peripheral artery atherosclerotic plaques

Objective Femoral artery plaques are characterized by a long-standing inflammatory response and advanced calcification and bone formation not seen in other vascular beds as extensively. Our study aimed to characterize and analyze the immune cell profile of bone marrow in femoral artery plaques in order to direct future innovation of therapies targeted at atherosclerosis in peripheral arteries. Methods Atherosclerotic plaques were collected during femoral endarterectomy from 91 patients. Bone marrow was detected in 47.3% of samples and 25 of those with visually largest bone marrow area in hematoxylin and eosin stained samples were re-sectioned and subjected to multiplex immunofluorescence staining for CD34, CD117, CD3, CD56, CD11c, CD20, CD11b, CD68, CD45 and SMA. Machine learning techniques were employed to quantify the cells expressing each surface marker. Patient data were collected from electronic patient records and laboratory measurements were obtained prior to surgery. Magnetic resonance angiography (MRA) imaging of the lower limb arteries obtained prior to surgery were analyzed. Baseline data was collected at time of surgery and for overall mortality patients were followed until 31.10.2024. Results All patients analyzed had extensive atherosclerotic disease in the MRA imaging and 45% of patients had died by the end of follow-up. Bone marrow-like tissue in the plaques was lined by osteoblast-like cells (CD56 + ), was densely vascularized, and in three plaques megakaryocytes were observed. An arterial tertiary lymphoid organ rich in B and T cells was observed. The immune cell composition of the bone marrow-like areas varied with correlations to clinical characteristics. The proportion of CD56 + cells correlated with age, glomerular filtration rate and smoking (rho = -0.597, p =0.005, BH adjusted p=0.0125, rho=0.541, p =0.014, BH adjusted p =0.023 and p =0.005, BH adjusted p =0.0125, respectively) and proportion of B cells (CD20 + ) with alkaline phosphatase (rho= -0.719, p