Remodeling Phenotype of Macrophages in steroid-induced osteonecrosis: switching from M1 to M2 polarization

Abstract

Osteonecrosis, a common orthopaedic disease, is a worldwide medical problem need to be conquered. Over the past decades, major advances have occurred in the pathophysiological mechanisms of osteonecrosis, however, its etiology is still complex and not clear. A number of different theories have been developed to explain the pathogenic mechanisms of steroid-induced osteonecrosis, including Microcirculation embolism and bone marrow cell hypertrophy induced by thrombus, fat, abnormal red blood cells, nitrogen, etc.. Among them, theory of fat metabolism disorder is generally recognized among the kinds of theories of steroid-induced osteonecrosis. However, the pathogenesis of femoral head osteonecrosis very complicated, and it’s difficult to be explained using the single theory. The polarization of Macrophages are involved in many important pathophysiologic processes, such as necrosis and regeneration. Our hypothesis is that M1-polarised Macrophages appear to be disruptive in the early and middle stage of steroid-induced osteonecrosis of femoral head (SANFH), while M2-polarised Macrophages appear to be protective in the late stage, which play an important role in developing SANFH. Our hypothesis could help to explain the pathogenic mechanism of steroid-induced osteonecrosis, and deserves further studies.