For many years, photobiomodulation in cancer patients has been used empirically, based on the positive clinical experience. When using PBM for the prevention and treatment of early radiation toxicity, exposure can occur directly in the area of the tumor site. For that reason, the data is need about a potential influence of low-intensity red light as on the normal as well on the tumor cells exposed to ionizing radiation. The aim of the work was to study the effects of photobiomodulation (PBM) in the red spectrum (640 nm) with fluences from 3 mJ/cm2 to 2 J/cm2 in combination with ionizing radiation at doses of 2–6 Gy against human BJ-5ta-hTERT cells – postnatal fibroblasts. The cells were exposed to low-intensity red light before or after their exposure to IR, the viability of the cells was determined by MTT-test 24 hours after the last exposure. The effects of PBM depend on the fluence of PBM, the dose of IR and the sequence of the actions of these physical factors on cells. The adaptive effect of PBM was observed only for high fluences – 1 and 2 J/cm2 when exposed to PBM and subsequent irradiation of IR. At the same time, the stimulating effect of PBM was observed only for low fluences from 3 to 300 mJ/cm2 under IR irradiation and subsequent (after 1 hour) exposure to PBM. These data should be taken into account when using PBM for the correction of adverse events of radiation therapy in a clinic.
Using optoacoustic microscopy, a radiation-induced increase in the fragmentation of experimental tumor small vessels, as well as the formation of large hemoglobin-containing structures were revealed within first days after treatment.
The possibilities of optoacoustic microscopy for comparison of vascular network of different tumor models as well as for investigation of tumor vessels response to radiation therapy were demonstrated.
Development of a number of diseases is accompanied by changes in the blood vessels’ structure and the investigation of tissue vascular pattern remains one of the most essential problems in experimental and clinical medicine. Hybrid methods of optoacoustic (OA) imaging enable label-free optical-contrast angiography at optical penetration depths with ultrasonic resolution. We used OA to study vascular network of experimental tumor during growth and after treatment as well as to study the dynamics of blood content of human skin during functional tests. Optoacoustic angiography was performed using raster-scan system in reflection mode with 532 nm laser source and wideband PVDF detector. The sensitivity of the system allowed to visualize 50 µm blood vessels at up to 2.1 mm depth. Minimally detected diameter of blood vessel located at the surface of a soft tissue was 15 µm. Imaging of colon tumor models CT26 and HT-29 revealed peculiarities of vascular system development. Irradiation-induced increase of small tumor vessels segments number and parallel decrease in the number of large hemoglobin-containing structures were demonstrated. The fraction of blood-filled vessels of the human skin was assessed during cuff occlusion and temporarily filling with blood became clearly visible on OA images. To study the effects of local mechanical compression on human skin vasculature we varied external pressure and revealed the gradual drop in OA signal from blood vessels. We demonstrated the possibilities of raster-scan angiography for in vivo analysis of vessels structure, for monitoring of neoangiogenesis and for dynamical investigation of blood content under external actions.
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