Magnetic fields and angiogenesis

Abstract

This review belongs to a special issue on magnetic surgery (using magnetic field in surgery), which has developed rapidly in the last few years and showed a great potential to be applied in numerous areas. While magnetic surgery has multiple advantages in surgical processes, including but not limited to shorten surgical procedure and duration, reduce inflammation and bleeding, it also adds another exposure source of relatively strong magnetic field to the human bodies. Consequently, concerns were raised regarding the potential adverse effects of these magnets on our bodies. Moreover, people have increased opportunities to be exposed to various magnetic fields generated by magnetic resonance imaging in hospitals, household magnets, cell phones and power lines, therefore, it is essential to investigate the effects of magnetic fields on human bodies. This review focuses on the effects of magnetic fields on the growth of blood vessels, a process known as angiogenesis. Angiogenesis is involved in a variety of physiological and pathological processes including organ growth and repair, and therefore plays important roles not only in surgical related processes, such as postoperative recovery, but also in other processes such as development and tumor growth. Angiogenesis is regulated by a balance between pro- and anti-angiogenic signals, which is frequently altered in various malignant, inflammatory, ischemic, infectious, and immune disorders. Many studies have investigated the influence of magnetic field on angiogenesis in the last few decades. Here in this review, we summarize, analyze and compare magnetic field parameters, such as strength, gradient and frequency, experimental procedures, biological samples examined and the detailed experimental results. Although there is still no consensus on the effects at cellular level, which is largely caused by a lack of systematic research on different magnetic field parameters, it is interesting that we found the angiogenesis of tumor tissues can be inhibited by both static and dynamic magnetic fields at animal level. In contrast, long-term or high-intensity static magnetic field treatment of non-tumor tissue seems to be able to promote angiogenesis at animal level. Since the experimental evidences are still inadequate, more systematic investigations are needed to further examine this correlation in the future. We also discuss the effect of magnetic field combined with chemotherapy and other treatment methods on angiogenesis and summarize the potential mechanisms of magnetic field on angiogenesis. It has been shown that static magnetic fields can affect multiple aspects of the cell, such as gene expression, cell proliferation, antioxidant defense system, as well as calcium levels. People speculate that magnetic field may regulate angiogenesis by affecting multiple signal transduction pathways including the calcium signaling pathway. Meanwhile there are also studies showing that other molecules could be involved in this process, including ROS (reactive oxygen species, ROS), ERK and membrane-bound receptors. Moreover, the mechanism of the differential effects of magnetic fields on angiogenesis in tumor tissue and non-tumor tissue are still not clear. Although physiological and pathological angiogenesis share many commonalities, there are also multiple different regulation pathways between angiogenesis of tumor vs. non-tumor tissues, such as the dependency of VEGF. In-depth investigations are warranted to better understand the effects and underlying mechanisms of varying magnetic fields with different parameters on angiogenesis in normal and pathological conditions. This review will not only help people to further understand the biological effects of magnetic fields, provide experimental basis for the safe application of magnetic surgery technology, but also lay a foundation for other potential medical applications of magnetic fields in the future.