Low level laser therapy promotes bone regeneration by coupling angiogenesis and osteogenesis

Abstract

Background Bone tissue engineering is a new concept bringing hope for the repair of large bone defects, which remains a major clinical challenge. The formation of vascularized bone is key for bone tissue engineering. Growth of specialized blood vessels termed type H is associated with bone formation. In vivo and in vitro studies have shown that low level laser therapy (LLLT) promotes angiogenesis, fracture healing, and osteogenic differentiation of stem cells by increasing reactive oxygen species (ROS). However, whether LLLT can couple angiogenesis and osteogenesis, and the underlying mechanisms during bone formation, remains largely unknown. Methods Mouse bone marrow mesenchymal stem cells (BMSCs) combined with biphasic calcium phosphate (BCP) grafts were implanted into C57BL/6 mice to evaluate the effects of LLLT on the specialized vessel subtypes and bone regeneration in vivo. Furthermore, human BMSCs and human umbilical vein endothelial cells (HUVECs) were co-cultured in vitro. The effects of LLLT on cell proliferation, angiogenesis, and osteogenesis were assessed. Results LLLT promoted the formation of blood vessels, collagen fibers, and bone tissue and also increased CD31hiEMCNhi-expressing type H vessels in mBMSC/BCP grafts implanted in mice. LLLT significantly increased both osteogenesis and angiogenesis, as well as related gene expression (HIF-1α, VEGF, TGF-β) of grafts in vivo and of co-cultured BMSCs/HUVECs in vitro. An increase or decrease of ROS induced by H2O2 or Vitamin C, respectively, resulted in an increase or decrease of HIF-1α, and a subsequent increase and decrease of VEGF and TGF-β in the co-culture system. The ROS accumulation induced by LLLT in the co-culture system was significantly decreased when HIF-1α was inhibited with DMBPA and was followed by decreased expression of VEGF and TGF-β. Conclusions LLLT enhanced vascularized bone regeneration by coupling angiogenesis and osteogenesis. ROS/HIF-1α was necessary for these effects of LLLT. LLLT triggered a ROS-dependent increase of HIF-1α, VEGF, and TGF-β and resulted in subsequent formation of type H vessels and osteogenic differentiation of mesenchymal stem cells. As ROS also was a target of HIF-1α, there may be a positive feedback loop between ROS and HIF-1α, which further amplified HIF-1α induction via the LLLT-mediated ROS increase. This study provided new insight into the effects of LLLT on vascularization and bone regeneration in bone tissue engineering.

Comparative Investigation of Photobiomodulation in Diabetes-Impaired Alveolar Bone healing; A Histomorphometrical and Molecular Study

“…Recent studies suggest a photobiomodulation-induced coupling role of angiogenesis and osteogenesis, as well as related gene expression including HIF-1α and VEGF, both in vivo and in vitro. This evidence was derived from the observation of reactive oxygen species (ROS)-triggered increase in irradiated cells, which resulted in the subsequent crosstalk between angiogenesis and osteogenesis [29]. Our results also showed that photobiomodulation succeeded to simultaneously enhance both VEGF and OCN mRNA expression densities in diabetic tooth extraction sockets, proposing a latent mechanism of photobiomodulationmediated wound healing improvement in diabetic rats.…”

Regulating Macrophage Polarization in High Glucose Microenvironment Using Lithium‐Modified Bioglass‐Hydrogel for Diabetic Bone Regeneration

“…Simple bone fractures or defects can be repaired and recovered by the body itself, but in diabetic microenvironment, fractures tend to take a long time to repair, as the ability of the body is limited. [ 27 ] Thus, we examined hydrogel biomaterials for the acceleration of bone reconstruction.…”

Understanding Reactive Oxygen Species in Bone Regeneration: A Glance at Potential Therapeutics and Bioengineering Applications

“…Through further investigation, it was found that these effects were induced through the ROS/ Hif-1α signaling pathway, emphasizing LLLT's production of ROS as the key feature in promoting angiogenesis and osteogenesis. While their results highlight the increase in ROS being beneficial to angiogenesis and osteogenesis, the study emphasizes a suitable window for osteogenic differentiation, with higher ROS levels damaging osteogenic differentiation at later timepoints (Bai et al, 2021).…”

“…Rather than focusing on reducing ROS, others have acknowledged that an increase in ROS is necessary for osteogenesis, especially for the formation of blood vessels to adequately vascularize bone. Bai et al demonstrated the use of low-level laser therapy (LLLT) in promoting coupled angiogenesis and osteogenesis by use of a BMSC and biphasic calcium phosphate graft implanted into mice and an endothelial and bone marrow stem cell coculture (Bai et al, 2021). Both in vivo and in vitro studies demonstrated a significant increase in angiogenesis and osteogenesis as well as upregulation of VEGF, TGF-β, and Hif-1α.…”