Opposite effects of low intensity light of different wavelengths on the planarian regeneration rate.

Planarian freshwater flatworms have the unique ability to regenerate due to stem cell activity. The process of regeneration is extremely sensitive to various factors, including light radiation. Here, the effect of low-intensity LED light of different wavelengths on regeneration, stem cell proliferation and gene expression associated with these processes was studied. LED matrices with different wavelengths (red (λmax = 635 nm), green (λmax = 520 nm) and blue (λmax = 463 nm), as well as LED laser diodes (red (λmax = 638.5 nm), green (λmax = 533 nm) and blue (λmax = 420 nm), were used in the experiments. Computer-assisted morphometry, whole-mount immunocytochemical study and RT-PCR were used to analyze the biological effects of LED light exposure on the planarian regeneration in vivo. It was found that a one-time exposure of regenerating planarians with low-intensity red light diodes stimulated head blastema growth in a dose-dependent manner (up to 40%). The green light exposure of planarians resulted in the opposite effect, showing a reduced head blastema growth rate by up to 21%. The blue light exposure did not lead to any changes in the rate of head blastema growth. The maximum effects of light exposure were observed at a dose of 175.2 mJ/cm2. No significant differences were revealed in the dynamics of neoblasts' (planarian stem cells) proliferation under red and green light exposure. However, the RT-PCR gene expression analysis of 46 wound-induced genes revealed their up-regulation upon red LED light exposure, and down-regulation upon green light exposure. Thus, we have demonstrated that the planarian regeneration process is rather sensitive to the effects of low-intensity light radiation of certain wavelengths, the biological activity of red and green light being dictated by the different expression of the genes regulating transcriptional activity.

[Study of possible involvement of MEK mitogen-activated protein kinase and TGF-ß receptor in planarian regeneration processes using pharmacological inhibition analysis].

Possible involvement of MEK mitogen-activated protein kinase and TGF-ß receptor in the processes of regeneration and morphogenesis in freshwater planarian flatworms Schmidtea mediterranea was studied using a pharmacological inhibitor analysis. It was found that pharmacological inhibitors of these kinases significantly inhibit the regeneration of the head end of the animals and that this effect is realized due to inhibition of proliferative activity of neoblasts, planarian stem cells. It is shown that that the inhibition of the studied protein kinases in regenerating planarians markedly disturbs stem cell differentiation and morphogenesis.

[A role of some intracellular signaling cascades in planarian regeneration activated under irradiation with low-temperature argon plasma].

Using inhibitory analysis the role of some intracellular signaling pathways in activation of planarian regeneration under the influence of low-temperature argon plasma (LTAP) has been investigated. Inactivation of specific inhibitors of intracellular signaling enzymes such as the receptor tyrosine kinase (EGFR), TGF ß receptor, calmodulin, adenylate cyclase, phospholipase A2, phospholipase C, cyclin-dependent protein kinase, JAK2-protein kinase, JNK-protein kinase MEK-protein kinase led to inhibition of the head growth during its regeneration in planarians. Pretreatment with LTAP irradiation provided no inhibitory action of some cascades regulating proliferation. However, the inhibitors of the key regulators of regeneration: TGF ß receptor, calmodulin and MEK-protein kinase completely suppressed the activating effect of plasma. Thus, by the example of regenerating planarians it is shown, that biological activity of low-temperature argon plasma LTAP is caused by modulation of a plurality of cellular signaling systems.

[Retinoic acid as a regulator of planarian morphogenesis].

The effect of retinoic acid on regeneration of two species of asexual planarian races, Girardia tigrina and Schmidtea mediterranea, was studied. It was established that retinoic acids at physiological concentrations (10(-7)-10(-10) M) inhibit the regeneration of the head part of planarians but have no effect on tail blastema growth. It is shown that regeneration of the head part is inhibited as a result of arrest of the cell cycle of neoblasts, proliferating stem cells, during the transition from the G1/G0 to the S phase. Thus, the morphogenetic role of retinoic acids in planarians, primitive bilaterally symmetrical animals, has been demonstrated.

[Melatonin effect on the regeneration of the flatworm Girardia tigrina].

The melatonin effect on the anterior and posterior ends of a free-living flatworm Girardia tigrina was studied, as well as the variability of the mitotic activity of the stem cells (neoblasts) in the anterior and posterior postblasteme. This hormone may inhibit the regeneration of the anterior end of the animal in the physiologic-friendly concentrations of 10(-10)-10(-15) M by suppressing the mitotic activity of the neoblasts. This hormone does not affect the posterior end's regeneration; thus, its regeneration effect is significantly elective.