The Effect Of Red Light Therapy On The Expression Of IGF-1、IL-1β And PGE2in Rats Local Injured Tissue

Objective:This study investigates the effect of red light therapy (RLT) on acute closed soft tissue injured rat model. Through detecting the pain behavior of rats, histomorphology and immunohistochemistry of the injured tissue, we evaluated the effects of RLT on inflammatory response, mechanical hyperalgesia, and the expression of IGF-1、IL-1β and PGE2in rats local injured tissue.Method:Seventy-eight healthy male Wistar rats weighing between220g and230g were used in the study. The pain thresholds (Mechanical withdrawal threshold, MWT) of all rats were measured using the von Frey filaments two days before building the model of acute closed soft tissue injury. After that, six rats were randomly selected as normal control (n=6). The remaining seventy-two rats were modeled as acute gastrocnemius muscle injury through single strike by home-made "free-falling-mass" device. These injured rats were randomly divided into two groups:muscle injured-non-treatment group (n=36), and muscle injured-with-RLT group (n=36). On the operating day, muscle injured-with-RLT group were implemented RLT for30minutes after2hours awaking from anesthesia. The rats in this group are treated once a day in the following two weeks. Mechanical withdrawal threshold (MWT) was measured respectively using the von Frey filaments on the1st,2ed,3rd,5th and7th days after injury, and the concentration of cytokines IL-1β and PGE2in injured tissue were detected by enzyme-linked immunosorbent assay (ELISA) at the same timepoints. Furthermore, on the1st,2ed,3rd,5th,7th and14th days after the injury, histomorphological changes of injured tissue, as myofiber array, inflammatory infiltration and the proliferation of myoblasts, were observed using Hematoxylin and eosin (H-E) staining. In addition, the expression of insulin-like growth factor-1(IGF-1) was measured using immunohistochemistry.Results: 1、Changes of mechanical pain threshold among three groups Compared with the normal control, the MWT of muscle injured-non-treatment group and muscle injured-with-RLT group reduced significantly (P<0.01) at each time point after muscle injury. During the first two days after muscle injury, the MWT of the two injured groups reduced dramatically, and dropped to the minimum value at the3rd day after muscle injury, but rose again gradually from the5th days after injury. The MWT of rats in injured-non-treatment group reduced notably after injury compared with that of the injured-with-RLT group at each time point mentioned above (p<0.05).2、H-E staining histopathological changes In normal control, skeletal myofibers arranged regularly and in order, and the myofiber appears long-stripe tissue. Compared with injured-non-treatment group, we found that in rats of muscle injured-with-RLT group, the number of inflammatory cells began to decrease, muscle nucleus proliferated in large numbers and arranged like many strings of pearl, and fibroblasts start multiplying on the3rd day after injury. On the5th day after injury, the number of inflammatory cells significantly reduced, and newborn granulation tissue were more apparent. On the7th day after injury, newborn myofibers arranged more regularly, and inflammatory reaction almost absorbed. On the14th day after injury, the injured muscle was healed almost fully, which showed myofibers arranged regularly and in order, and myotubes were formed. In contrast, inflammatory reactions were lasting in rats of injured-non-treatment group until the14th days after injury, and myofibers were arranged in chaos.3、Immunohistochemical changes of the expression of IGF-1On the1st,2cd,3rd,5th, and7th days after injury, the expression of IGF-1in injured-with-RLT group increased significantly compared with normal control and injured-non-treatment group (P<0.01). Compared with the normal control, the expression of IGF-1in injured-with-RLT group had no statistically significant difference on the14th day after injury, but was lower significantly than that of injured-non-treatment group (P<0.01). 4、Changes of the expression of IL-1βAt all the time points, the expression of IL-1β in the injured tissue of rats in the two injured groups showed ascendant trend compared with normal control. The expression of IL-1β in the injured tissue of rats in the injured-non-RLT group was much higher at all time points observed (p<0.01) than normal control and injuried-with-RLT group. On the1st,2ed,3’d, and5th days after injury, the expression of IL-1β in rats of injured-with-RLT group increased significantly in comparison with normal control (p<0.05), but there were no statistically significant difference between these two groups on the7th day after injury (p>0.05).5、Changes of the expression of PGE2At all time points, the expression of PGE2in the injured tissue of rats in the two injured groups was significantly higher than that in normal control (p<0.05). Compared with normal control and the injured-with-RLT group, the expression of PGE2in the injured tissue of rats in the injured-non-RLT group increased significantly at all time points observed (p<0.05).Conclusion:1、RLT promotes muscle regeneration and repair through shortening the duration of acute inflammatory response in trauma tissue and elevating the expression of IGF-1.2、RLT reduces notably the expression of pro-inflammatory and pro-nociceptive cytokines IL-1(3and PGE2, and inhibits significantly the reduction of MWT, which demonstrates that RLT may have an effect of anti-inflammation and analgesis.