Morphological Assessment of Spatially Modulated Er:yag Laser Ablation (Recosma) on Arterial Re-Endothelialization After Mechanical Injury: An Experimental Study

Background . Endothelial injury is one of the key factors contributing to thrombosis, intimal hyperplasia, and restenosis after vascular interventions. The Er:YAG laser equipped with a spatially modulated ablation (SMA) handpiece is used to stimulate soft-tissue repair; however, its effect on arterial wall healing after mechanical injury has not previously been investigated. Objective . This study aimed to evaluate the morphological features of vascular wall repair and endothelial layer restoration after mechanical injury to the rabbit femoral artery following transadventitial Er:YAG laser irradiation delivered via an SMA handpiece. Materials and Methods . The experiment was performed in 42 rabbits; 84 femoral artery segments were examined. Two injury models were used: compression injury and arteriotomy followed by vascular suturing. Laser irradiation was applied from the adventitial side using the following parameters: wavelength 2940 nm, pulse duration 0,3 ms, fluence 2.1 J/cm 2 , SMA handpiece. Morphological assessment was performed on days 3, 14, 30, and 60. Results. On day 3 after mechanical injury, endothelial denudation, focal intimal and medial injury, and inflammatory infiltration were observed. Isolated SMA exposure of intact arteries was not associated with morphologically detectable damage to the vascular wall. By day 14, the lasertreated groups demonstrated earlier restoration of a continuous endothelial layer: in 80 % of segments after compression injury and in 100 % of segments after suture injury, without signs of thrombosis. In the control groups, inflammatory changes and luminal obliteration by organizing thrombotic material persisted. At later time points after SMA exposure, remodeling was predominantly limited to the intima, whereas in the control groups hyperplasia extended into the medial layer. Conclusion. Transadventitial Er:YAG-SMA exposure after mechanical arterial injury was associated with earlier re-endothelialization, absence of thrombosis in the suture injury model, and less pronounced pathological remodeling of the vascular wall. These findings support further preclinical evaluation of this technology as a local method for modulating vascular repair.