Photobiomodulation attenuates myocardial fibrosis and diastolic dysfunction in a mouse model of heart-failure with preserved ejection fraction

Abstract Introduction Photobiomodulation (PBM) has been shown to positively effect pathways associated with heart failure with preserved ejection fraction (HFpEF), such as reducing inflammation and increasing NO, microvascular flow, mitochondrial membrane potential, and ATP synthesis. Purpose This study aimed to determine whether PBM can mitigate myocardial fibrosis and diastolic dysfunction in a mouse model of HFpEF. Methods HFpEF was induced in 26, 3-month-old C57/black male mice by a ‘2-hit-model’ that includes high-fat diet and inhibition of NO-synthase by L-NAME (Nω-nitro-l-arginine-methyl-ester). Transcutaneous PBM was administered 3X/week[wk] for 10wks using a 904nm super-pulsed laser (90-seconds, 4.2J/cm2 per diode, n=13). 10 non-model control mice were also included. Echocardiography was performed at baseline, 7wks, and 10wks. Mice were sacrificed at ten weeks. Histological cardiac sections were stained for collagen with picrosirius red and scanned in X40 resolution. The positive pixel count algorithm of the Aperio ImageScope software (Leica Biosystems Inc.) was used to analyzed each vessel and measured the area of adventitial collagen (AC), perimeter of the external and internal elastic lamina (EEL, IEL). %Media=100*(EEL area-IEL area)/EEL Area; %Lumen=(IEL area/EEL area); and Standardized adventitial collagen = Area of AC / EEL perimeter were calculated. Significance was determined by 1-way ANOVA by group for %media, %lumen, and EEL area, and by 1-way ANCOVA by group with EEL area as a covariate for the standardized AC to take into account the variability in vessel sizes. p<0.05 was considered significant. Results Mice that were subjected to the HFpEF 2-hit model had a significant increase in the medial area of the coronary vessels and a concomitant decrease in the lumen area compared to mice that were not subjected to the model (Mean ±SD, %Media: control 50%±11; sham: 64%±11; PBM: 63%±12, p<0.001 control vs HFpEF). The model did not affect the overall vessel area defined by the EEL (p=0.547). The HFpEF model induced a significant increase in the standardized adventitial collagen compared to controls, which was attenuated by PBM: control 3.0±1.6; HFpEF sham: 3.9±1.8; PBM: 3.4±1.9, p=0.008 control vs sham, p=0.055 PBM vs control; p=0.396 control vs PBM). Moreover, diastolic flow parameters demonstrated that E’ deteriorated significantly in the sham group but not in the PBM group (E’[mm/sec], baseline-vs-10w: sham; -32.9±8.6-vs- -22.5±5.7, p=0.004; PBM; -32.1±5.9-vs- -27.9±6.4, p=0.262, p=0.037), and delayed deterioration in E/E’ (Δbaseline-7w, PBM vs sham: -3.6±7.0-vs-7.6±15.4, p=0.006). Conclusions PBM attenuated perivascular fibrosis and diastolic parameters deterioration in a mice model of HFpEF. Further investigations into the biomolecular and histological mechanisms are performed.Trial designResults