rhBMP2 alone does not induce macrophage polarization towards an increased inflammatory response

Abstract

Once thought to have revolutionized therapeutic intervention in surgery, Recombinant Human Bone Morphogenic Protein 2 (rhBMP2) is now in its second decade of sustained controversy over the side effects associated with its use. Side effects associated with clinical use of rhBMP2 (Infuse, Medtronic Inc) include a marked inflammatory response, pain, therapeutic failures, ectopic bone, tissue degradation, and death. What is missing, despite the depth of literature on the subject, is a direct interrogation of rhBMP2, specifically for inflammation. Here we set out to determine if rhBMP2 alters traditional macrophage markers associated with pro-inflammatory responses, and pro-reparative responses to injury. Based on our previous work, we hypothesized there would be no direct effect of peptide on macrophage polarization. Here we utilized commercially available murine macrophages, RAW 264.7, and treated these cells with rhBMP2 in standard growth media or macrophage polarizing media (M1 and M2) at several doses of the peptide. Our readouts were cell viability, apoptosis, gene expression of M1 and M2 markers, and ELISA for M1 marker iNOS, and M2 marker Arg1. Our data give very little evidence to support an alteration in macrophage phenotype by rhBMP2 alone, or alteration of the phenotype when cultured in enriched M1 or M2 media. These results further suggest that other factors associated with the clinical use of Infuse, likely supraphysiological rhBMP2 doses and off label usage, are more likely the culprit for poor outcomes. This further reinforces the utility of rhBMP2 and other peptides in tissue engineering therapies when conditions are tightly controlled.

Bioresorbable Chitosan-Based Bone Regeneration Scaffold Using Various Bioceramics and the Alteration of Photoinitiator Concentration in an Extended UV Photocrosslinking Reaction

“…The first commercially available and FDA-approved growth factor delivery system for bone healing treatment is known as Medtronic Infuse ® , which incorporates recombinant bone morphogenetic protein-2 (rhBMP-2) in a collagen sponge carrier [ 29 ]. However, this system requires intra-operative preparation and is associated with high burst release that can lead to unwanted adverse effects, including higher rates of implant displacement, subsidence, infection, ectopic bone formation, osteolysis, and thus may result in ineffective treatment of non-unions [ 30 , 31 , 32 , 33 ].…”

The Body’s Cellular and Molecular Response to Protein-Coated Medical Device Implants: A Review Focused on Fibronectin and BMP Proteins

“…In their study, the authors hypothesized that BMP-2 mediates immunoregulation through macrophage polarization. However, another study presents evidence that BMP-2 itself would not alter the macrophage phenotype, nor augment pro- or anti-inflammatory status in M1 or M2 macrophages, respectively [ 118 ]. Therefore, the influence of BMP-2 on macrophages and the immune environment around an implanted site needs further investigation.…”

Bio-clickable mussel-inspired peptides improve titanium-based material osseointegration synergistically with immunopolarization-regulation

“…The motivation for the combined use of RGD and BMP-2 mainly comes from the fact that in addition to promoting MSCs adhesion, pieces of evidences have indicated that RGD-integrin interaction could also enhance the osteoinductivity of BMP-2 via increasing the phosphorylation of Smad1/5/8, thus synergistically accelerating the osteodifferentiation of MSCs [ [29] , [30] , [31] , [32] ]. Furthermore, BMP-2 protein can also regulate the transition of macrophages from the pro-inflammatory M1phenotype to the anti-inflammatory M2 phenotype [ [33] , [34] , [35] , [36] ]. Previous studies by us and others have demonstrated that M2 macrophages can inhibit inflammation and osteoclast differentiation by secreting anti-inflammatory factor IL-10, and secrete VEGF-A and TGF-β to promote angiogenesis and differentiation of MSC into osteoblasts, so as to promote osteogenesis [ [33] , [34] , [35] , [36] , [37] ].…”

“…Furthermore, BMP-2 protein can also regulate the transition of macrophages from the pro-inflammatory M1phenotype to the anti-inflammatory M2 phenotype [ [33] , [34] , [35] , [36] ]. Previous studies by us and others have demonstrated that M2 macrophages can inhibit inflammation and osteoclast differentiation by secreting anti-inflammatory factor IL-10, and secrete VEGF-A and TGF-β to promote angiogenesis and differentiation of MSC into osteoblasts, so as to promote osteogenesis [ [33] , [34] , [35] , [36] , [37] ].…”