The Role of Low-Level Laser Therapy in Bone Healing: Systematic Review

Abstract

Low-level laser therapy (LLLT) is a treatment that is increasingly used in orthopedics practices. In vivo and in vitro studies have shown that low-level laser therapy (LLLT) promotes angiogenesis, fracture healing and osteogenic differentiation of stem cells. However, the underlying mechanisms during bone formation remain largely unknown. Factors such as wavelength, energy density, irradiation and frequency of LLLT can influence the cellular mechanisms. Moreover, the effects of LLLT are different according to cell types treated. This review aims to summarize the current knowledge of the molecular pathways activated by LLLT and its effects on the bone healing process. A better understanding of the cellular mechanisms activated by LLLT can improve its clinical application.

Keywords: bone fracture healing; bone healing; bone regeneration; low-level laser therapy (LLLT); orthopedics treatments; photo-biomodulation; phototherapy.

Figure 1

PRISMA flow diagram that included searches of databases, registers and other sources [12].

Figure 2

Schematic representation of molecular pathways activated by Low-Level Laser Therapy (LLLT). Abbreviations: VEGF (vascular endothelial growth factor); FGF (Fibroblast Growth Factors); PDGF (Platelet-Derived Growth Factor); TGF-ß (tumor growth factor- ß); BMPs (bone morphogenetic proteins); AKT (AKT Serine/Threonine Kinase 1); PI3K(Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Delta); MAPK (mitogen-activated protein kinase); ERK (extracellular signal-regulated kinase 1/2); SMAD proteins (small mothers against decapentaplegic); runx-2 (runt-related transcription factor gene); col1 (collagen type 1 gene); ocn (osteocalcin gene); opn (ostepontin gene); ibsp (bone sialoprotein gene).