Planarians as an In Vivo Experimental Model for the Study of New Radioprotective Substances

Abstract

Ionising radiation causes the death of the most actively dividing cells, thus leading to depletion of the stem cell pool. Planarians are invertebrate flatworms that are unique in that their stem cells, called neoblasts, constantly replace old, damaged, or dying cells. Amenability to efficient RNAi treatments, the rapid development of clear phenotypes, and sensitivity to ionising radiation, combined with new genomic technologies, make planarians an outstanding tool for the discovery of potential radioprotective agents. In this work, using the well-known antioxidant N-acetylcysteine, planarians are, for the first time, shown to be an excellent model system for the fast and effective screening of novel radioprotective and radio-sensitising substances. In addition, a panel of measurable parameters that can be used for the study of radioprotective effects on this model is suggested.

A Study on the Planarian Model Confirms the Antioxidant Properties of Tameron against X-ray- and Menadione-Induced Oxidative Stress

“…It is known that planarian regeneration depends on neoblasts, which are capable of proliferating and differentiating into all types of planarian cells [ 18 ]. Being completely eliminated at doses higher than 30 Gy, they retain some viability and mitotic activity at sublethal doses of 10–15 Gy, which we have used in our work [ 25 ]. We could observe that sublethal X-ray doses drastically reduce the mitotic index (number of mitotic cells per 1 mm 2 ) in planarians, but the presence of Tameron in a concentration of 10 −4 M saves the phenotype, retaining 3 to 5 times more neoblasts on the first day after irradiation.…”

“…The same principles are applicable not only to ionizing radiation studies but also to studies of chemically induced oxidative stress. Our model has been previously proven to be robust and effective for testing new radioprotectors and antioxidants in the example of a classical antioxidant, N-acetylcysteine [ 25 ]. In the present work, we have tested the antioxidant, radioprotective, and pro-regenerative properties of Tameron on models of X-ray- and chemically induced oxidative stress in the Schmidtea mediterranea planarian.…”

Mitogen-like Cerium-Based Nanoparticles Protect Schmidtea mediterranea against Severe Doses of X-rays

“…The planarians were treated with cerium-containing nanoparticles overnight and fixed in PBS containing 4% formaldehyde and 0.3% Triton X100 for 20 min. In addition, the planarian staining for detecting mitotic cells was performed according to the protocol provided by Newmark and Alvarado [ 31 ]. In labeling mitotic cells, a primary antibody was used for phosphorylated histone H3 (Santa Cruz, Dallas, TX, USA) at a 1/1000 dilution.…”

“…The polymerase chain reaction was carried out using a BioRad CFX-96 amplifier (USA). The expression of 46 genes that control the early stages of regeneration and the proliferative activity of neoplasms, divided into four classes (W1, W2, W3, and W4), was measured [ 31 ]. In addition, the expression of another 15 key genes involved in regeneration was measured: ζ-class neoblast subpopulations (ancestors of all neoblasts), σ-class (epidermal progenitors), and γ-class (interstitial cell progenitors).…”

“…The rapid development of pure phenotypes and high sensitivity to ionizing radiation, combined with new genomic technologies, make planarians a unique experimental model for the discovery of potential radioprotective agents [ 30 ]. It is well known that ionizing radiation has a pronounced and measurable effect on planarians that can be easily monitored and quantified, such as the rate of blastema regeneration, the number of neoblasts and their mitotic activity, the degree of DNA damage, and the intracellular ROS level [ 31 ]. Recently, CeO 2 and CeF 3 nanoparticles were shown to act as inorganic mitogens in regenerating planarians [ 32 ].…”