Assessment of the Monocyte Subpopulations and M1/M2 Macrophage Ratio in Concentrated Bone Marrow Aspirate

James J Butler; John F Dankert; Laura E Keller; Mohammad T Azam; Jari Dahmen; Gino M M J Kerkhoffs; John G Kennedy

doi:10.1177/19476035241304308

Assessment of the Monocyte Subpopulations and M1/M2 Macrophage Ratio in Concentrated Bone Marrow Aspirate

Cartilage. 2024 Dec 9:19476035241304308. doi: 10.1177/19476035241304308. Online ahead of print.

Authors

James J Butler¹, John F Dankert¹, Laura E Keller², Mohammad T Azam¹, Jari Dahmen³, Gino M M J Kerkhoffs^{4

5}, John G Kennedy¹

Affiliations

¹ Foot and Ankle Division, Department of Orthopaedic Surgery, NYU Langone Health, New York City, NY, USA.
² Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.
³ Department of Orthopaedic Surgery and Sports Medicine, Amsterdam Movement Sciences, Amsterdam UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands.
⁴ Academic Center for Evidence-Based Sports Medicine, Amsterdam UMC, Amsterdam, The Netherlands.
⁵ Amsterdam Collaboration for Health and Safety in Sports, International Olympic Committee Research Center, Amsterdam UMC, Amsterdam, The Netherlands.

Abstract

Objective: The purpose of this study was to determine the M1/M2 macrophage ratio in concentrated bone marrow aspirate (cBMA) in patients undergoing surgical intervention augmented with cBMA for osteochondral lesions of the talus (OLTs).

Design: Samples of peripheral blood (PB), bone marrow aspirate (BMA), and cBMA were collected during the procedure. The samples were analyzed by automated cell counting and multicolor fluorescence-activated cell sorting with specific antibodies recognizing monocytes (CD14+ CD16+) and the M1 (CD86+) and M2 (CD163+CD206+) populations within that monocyte population. Cytokine concentrations within the samples were evaluated with enzyme-linked immunosorbent assay (ELISA). The composition of cBMA was compared between 2 commercially available BMA concentration systems.

Results: Thirty-eight patients with a mean age of 43.2 ± 10.1 years old undergoing a surgical procedure for the treatment of OLTs involving the use of cBMA were included. cBMA had a mean fold increase of 4.7 for all white blood cells, 6.1 for monocytes, 7.9 for lymphocytes, 2.4 for neutrophils, and 9.6 for platelets when compared to BMA. The mean M1/M2 ratio for PB, BMA, and cBMA was 15.2 ± 12.0, 20.8 ± 13.3, and 22.1 ± 16.0, respectively. There was a statistically significant higher concentration of interleukin-1 receptor antagonist (IL-1Ra) in the cBMA sample (8243.3 ± 14,837.4 pg/mL) compared to both BMA (3143.0 ± 2218.5 pg/mL) and PB (1847.5 ± 1520.4 pg/mL) samples. The IL-1Ra/IL-1β ratio for PB, BMA, and cBMA was 790.6 ± 581.9, 764.7 ± 675.2, and 235.7 ± 192.1, respectively. There was no difference in the cBMA M1/M2 ratio (19.0 ± 11.1 vs 24.0 ± 18.3) between the Magellan (Isto Biologics, Hopkinton, Massachusetts) and Angel systems (Arthrex Inc, Naples, Florida).

Conclusion: This prospective study found that the M1/M2 ratio in cBMA was 22.1 ± 16.0, with significant patient to patient variation observed. Overall, there was no statistically significant difference in the M1/M2 ratio across PB, BMA, and cBMA samples. This is the first study to characterize the macrophage subpopulation within cBMA, which may have significant clinical implications in future studies.

Keywords: BMAC; M1/M2 ratio; concentrated bone marrow aspirate; macrophage.