Photobiomodulation mitigates diastolic dysfunction, reduces perivascular fibrosis and inflammation, and enhances mitochondrial metabolism and angiogenesis in a mouse model of HFpEF

Abstract Introduction Emerging molecular evidence implicates mitochondrial dysfunction, systemic inflammation, and capillary rarefaction as pivotal contributors to the pathophysiology of HFpEF. Photobiomodulation (PBM) has garnered attention for its potential to augment mitochondrial metabolism, attenuate inflammation, and foster angiogenesis. This investigation aims to delineate the effects of PBM on the pathophysiology of HFpEF in a murine model. Methods To induce HFpEF, 3-month-old male C57BL/6 mice were subjected to a '2-hit model' involving a high-fat diet combined with the vasoconstrictor nitric oxide synthase inhibitor, N(G)-Nitro-L-arginine methyl ester (L-NAME). PBM therapy was administered transdermally over the cardiac region thrice weekly for a duration of 10 weeks using a 904nm super-pulsed laser, with each session lasting 90 seconds and delivering an energy density of 4.2J/cm^2 per diode to a cohort of 12 mice. A sham group of 13 mice underwent identical procedures with the laser deactivated. An additional control group of 10 mice was maintained on a standard diet without any interventions. Echocardiographic assessments were performed at the outset, 7th and 10th week time. Following the 10-week period, mice were euthanized, their hearts harvested and serum withdrawn for further analysis. Results Echocardiography of PBM-treated animals demonstrated significant attenuation of deterioration of diastolic parameters (E’) compared to the sham-treated control group (E’[mm/sec], baseline-vs-10w: PBM, -32.1±5.9-vs- -27.9±6.4; sham, -32.9±8.6-vs- -22.5±5.7; p=0.037). Histological analysis of the cardiac tissue involving picrosirius red staining for collagen revealed that 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). Multiplex analysis of HFpEF mice showed significantly higher levels of inflammatory chemokines than controls that were attenuated by PBM (mean±SD log[pg/ml] of the chemokine (C-X-C motif) ligand-1 (CXCL-1): PBM=2.52±0.29, Control=2.14±0.35; monocyte chemotactic protein (MCP-1): PBM=0.87±0.46, HFpEF=1.5±0.58, Control=0.8±0.6; p<0.001 and p=0.003 respectively). RNA sequencing revealed 551 genes with significant differential expression (DE) between PBM and Controls (adjusted p-value [padj]<0.1). Ingenuity Pathway Analysis (IPA) analysis revealed that PBM upregulated genes pertaining to mitochondrial metabolism and down-regulated genes active in mitochondrial dysfunction (qPCR [GAPDH] 2–∆∆Ct fold change PBM/Sham: Ndufv2=3.7, Atp5md=3.5, Dnhd1=0.5). Relevant DE genes were validated by quantitative real-time PCR (qPCR). Conclusions PBM attenuated Diastolic dysfunction, fibrosis, pro-inflammatory chemokine secretion and upregulates mitochondrial metabolism in a mouse model of HFpEF.Study designResults