The impact of transposable element activity on therapeutically relevant human stem cells

Human stem cells harbor significant potential for basic and clinical translational research as well as regenerative medicine. Currently ~ 3000 adult and ~ 30 pluripotent stem cell-based, interventional clinical trials are ongoing worldwide, and numbers are increasing continuously. Although stem cells are promising cell sources to treat a wide range of human diseases, there are also concerns regarding potential risks associated with their clinical use, including genomic instability and tumorigenesis concerns. Thus, a deeper understanding of the factors and molecular mechanisms contributing to stem cell genome stability are a prerequisite to harnessing their therapeutic potential for degenerative diseases. Chemical and physical factors are known to influence the stability of stem cell genomes, together with random mutations and Copy Number Variants (CNVs) that accumulated in cultured human stem cells. Here we review the activity of endogenous transposable elements (TEs) in human multipotent and pluripotent stem cells, and the consequences of their mobility for genomic integrity and host gene expression. We describe transcriptional and post-transcriptional mechanisms antagonizing the spread of TEs in the human genome, and highlight those that are more prevalent in multipotent and pluripotent stem cells. Notably, TEs do not only represent a source of mutations/CNVs in genomes, but are also often harnessed as tools to engineer the stem cell genome; thus, we also describe and discuss the most widely applied transposon-based tools and highlight the most relevant areas of their biomedical applications in stem cells. Taken together, this review will contribute to the assessment of the risk that endogenous TE activity and the application of genetically engineered TEs constitute for the biosafety of stem cells to be used for substitutive and regenerative cell therapiesS.R.H. and P.T.R. are funded by the Government of Spain (MINECO, RYC-2016- 21395 and SAF2015–71589-P [S.R.H.]; PEJ-2014-A-31985 and SAF2015–71589- P [P.T.R.]). GGS is supported by a grant from the Ministry of Health of the Federal Republic of Germany (FKZ2518FSB403)

Nutritional value and phytotherapeutic relevance of solidaginis herba extracts obtained by different technologies

Solidago canadensis L., (Asteraceae) has been used in European phytotherapy as a urological and antiphlogistical remedy for centuries. The behaviour of dissolution of mineral elements into different tinctures and aqueous extracts obtained from Solidaginis herba was investigated in connection with their quercetin glycoside and organic acid amount. Commonly applied aqueous and alcoholic extracts were analysed for Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, P, Pb, S, Ti, V and Zn content. The concentrations of the minerals examined were determined by inductively coupled plasma emission spectrometry (ICP-OES). Determination of the flavonoids in solidaginis herba and extracts was carried out by a spectrophotometric method, as required by the German Pharmacopoea. For the study of the flavonoid composition of crude drug, the HPLC technique was applied. To determine the relative nutrient contribution of these pharmaceuticals to the diet, data obtained were combined with flavonoid content particulars, then a comparison with U.S Recommended Dietary Allowances (RDA) was made. For evaluation of the phytotherapeutic relevance, k/Na ratio was also calculated. It has been found that the pharmaceuticals examined are important sources of potassium, chromium, manganese, calcium, magnesium, phosphorus and lower sources of iron and zinc, assuming a daily intake of 1-2 l aqueous extracts as recommended for urological diseases. Flavonoid content of the different Solidaginis herba extracts ranged from 62.4 mg l-1 to 305.2 mg l-1

Antioxidant activity of medicinal plants used in phytotherapy

Oxygen free radicals play an important role in the development of different disorders like inflammatory-immune injury, carcinogenesis, hepatic toxicity and artherosclerosis. The antioxydant role of a wide spectrum of natural products has been established. Flavonoids and other phenolic compounds (proanthocyanidins, rosmarinic acid, hydroxicinnamic derivatives, catechines, etc.) of plant origin have been reported as scavengers and inhibitors of lipid peroxidation. We have studied the antioxidant activity as well as content and composition of natural phenolics in a series of medicinal plants with phytotherapeutical significance. Thus we determined the total phenol contents and studied the composition of flavonoids, polyphenols, phenolic acids of different vegetative and reproductive organs of medicinal plants: Anthriscus cerefolium (L.) Hoffm., Petroselinum crispum L., Cichorium intybus L., Helichrysum arenarium D.C.„cempervivum tectorum L., Taravacum officinale Web. Characteristic constituents in the various crude drugs were determined by chromatographic (TLC, HPLC) and spectroscopic (UV, UV-VIS) methods. The non specific scavenger activities of the medicinal plant extracts were studied by the chemiluminometric technique. The changes of chemiluminescence intensity of the H,G,•0H-luminol system at increasing concentrations of the H702/ -OH were measured. Inhibitory effects of selected standardized fractions from plants were tested on ascorbic acid induced lipid peroxidation in rat liver and homogenates. The best correlation were established with total phenolics in some medicinal plants (S. tectorum, T. officinale) while activities in other cases seem to be influenced by flavonoids (P. crispum, H. arenarium, A. cerefolium) and by hydroxicinnamic derivatives (C. intybus). &nbsp

Antioxidant activity of medicinal plants used in phytotherapy

Oxygen free radicals play an important role in the development of different disorders like inflammatory-immune injury, carcinogenesis, hepatic toxicity and artherosclerosis. The antioxydant role of a wide spectrum of natural products has been established. Flavonoids and other phenolic compounds (proanthocyanidins, rosmarinic acid, hydroxicinnamic derivatives, catechines, etc.) of plant origin have been reported as scavengers and inhibitors of lipid peroxidation. We have studied the antioxidant activity as well as content and composition of natural phenolics in a series of medicinal plants with phytotherapeutical significance. Thus we determined the total phenol contents and studied the composition of flavonoids, polyphenols, phenolic acids of different vegetative and reproductive organs of medicinal plants: Anthriscus cerefolium (L.) Hoffm., Petroselinum crispum L., Cichorium intybus L., Helichrysum arenarium D.C.„cempervivum tectorum L., Taravacum officinale Web. Characteristic constituents in the various crude drugs were determined by chromatographic (TLC, HPLC) and spectroscopic (UV, UV-VIS) methods. The non specific scavenger activities of the medicinal plant extracts were studied by the chemiluminometric technique. The changes of chemiluminescence intensity of the H,G,•0H-luminol system at increasing concentrations of the H702/ -OH were measured. Inhibitory effects of selected standardized fractions from plants were tested on ascorbic acid induced lipid peroxidation in rat liver and homogenates. The best correlation were established with total phenolics in some medicinal plants (S. tectorum, T. officinale) while activities in other cases seem to be influenced by flavonoids (P. crispum, H. arenarium, A. cerefolium) and by hydroxicinnamic derivatives (C. intybus). &nbsp

Dynamic ABCG2 expression in human embryonic stem cells provides the basis for stress response

ABCG2 is a plasmamembrane multidrug transporter with an established role in the cancer drug resistance phenotype. This protein is expressed in various tissues, including several types of stem cells. Although ABCG2 is not essential for life, knock-out mice were found to be hypersensitive to xenobiotics and had reduced levels of the side population of hematopoietic stem cells. Previously we have shown that ABCG2 is present in human embryonic stem cell (hESC) lines while exhibiting a heterogeneous expression pattern. In the present study we examined the role and function of this heterogeneity, and investigated whether it is related to stress responses in hESCs. We did not find any difference between the expression of pluripotency markers in ABCG2 positive and negative hESCs, however, ABCG2 expressing cells had a higher growth rate following cell separation. We found that certain harmful conditions (physical stress, drugs and UV light exposure) are tolerated much better in the presence of ABCG2 protein. This property can be explained by the transporter function which eliminates potential toxic metabolites accumulated during stress conditions. In contrast, mild oxidative stress in hESCs caused a rapid internalization of ABCG2, indicating that certain environmental factors may induce the removal of this transporter from the plasmamembrane. In the light of these results we suggest that a dynamic balance of ABCG2 expression at the population level has an advantage to promptly respond to changes in the cellular environment. Such an actively maintained heterogeneity might be evolutionarily favorable to protect special cell types, including pluripotent stem cells