Cell therapy was proposed as a procedure of indirect revascularization for patients with critical ischaemia of lower extremities for whom endovascular and surgical revascularization is impossible. We present herein a review of the state of the art of studies in the field of cell therapy of this cohort of patients.

In proliferating normal and tumor cells, the telomere length (TL) is maintained by high telomerase activity (TA). In the absence of TA the TL maintenance involves a mechanism of alternative lengthening of telomeres (ALT). The aim of this study was to investigate the level of TA, the mTert expression and TL in cultured normal and transformed by γ- and γ,n-irradiation mesenchymal stem cells (MSCs) from mouse bone marrow, in sarcomas that developed after the transplantation of these cells into syngeneic mice, and in fibrosarcoma cell lines obtained from these tumors to find out the role of AT or ALT in maintaining TL in these cells. During prolonged cultivation of normal and transformed under the influence of γ- (1 Gy and 6 Gy) and γ,n-irradiation (0.05 Gy, 0.5 Gy, and 2 Gy) MSCs from mouse bone marrow, a decrease in TA was detected in irradiated cells. Even deeper decrease in TA was found in sarcomas developed after administration of transformed MSCs to syngeneic mice and in fibrosarcoma cell lines isolated from these tumors in which TA was either absent or was found to be at a very low level. TL in three of the four lines obtained was halved compared to the initial MSCs. With absent or low TA and reduced TL, the cells of all the obtained fibrosarcoma lines successfully proliferated without signs of a change in survival. The mechanism of telomere maintainance in fibrosarcoma cell lines in the absence of TA needs further investigation and it can be assumed that it is associated with the use of the ALT. The detected decrease or absence of TA in transformed under the action of irradiation MSCs with the preservation or even an increase in the telomerase gene expression may be associated with the formation of inactive splicing variants, and requires further study. The obtained lines of transformed MSCs and fibrosarcomas with TA and without the activity of this enzyme can be a useful model for studying the efficacy of TA and ALT inhibitors in vitro and in vivo.

Plasmid-mediated gene therapy, being a safe and relatively inexpensive therapeutic strategy, is plagued by a fast silencing of transgene expression. The silencing severely reduces the long-term efficiency of plasmid vectors. We have earlier constructed a low-CpG pMBR2 plasmid vector supporting prolonged expression of transgenes in mesenchymal stem cells in vitro. Long-term expression from the pMBR2 vector was studied for the wild-type mouse secreted alkaline phosphatase gene (mSEAPTwt) and its version devoid of CpGs (mSEAP0) after vector electroporation into mouse hindlimb muscles and hydrodynamic delivery to the liver. The mSEAP levels in the blood were measured over one year. With the pMBR2-mSEAP0 construct, the mSEAP levels in leg muscles increased more than 2.5-fold in the first two months and remained higher than the initial level until the end of the experiment. Far lower expression levels were observed with the control pCDNA3.1-mSEAP0 construct. Expression from pMBR2-mSEAPwt decreased to about 40% after 6 months and remained at similar levels thereafter. In the mouse liver, expression from pMBR2-mSEAP0 was approximately halved within the first 18 weeks and then decrease slowly to the final 17% level. Expression from pMBR2-mSEAPwt initially dropped to 18% and remained at approximately 10% thereafter. In contrast, expression from pCDNA3.1-mSEAP0 sharply dropped to 5% after 2 weeks and remained at nearly zero levels throughout the rest of the experiment. Thus, both vector and transgene should have significantly reduced CpG contents to ensure prolonged plasmid-mediated expression in the liver, while minimizing the vector CpG content is sufficient for expression in skeletal muscles. The results suggested additionally that the localization of S/MAR elements within the transcription unit, in contrast to their outside location, results in significant reduction of the level of secreted, but not cytoplasmic, proteins.

A brief review of current data on the molecular biology of stem cells forming meristems and differentiating into various organs of angiosperms is presented. Different primary and secondary meristems are compared. The interactions of some hormones, regulatory gene networks, and signaling pathways in different types of meristems are described.

The currently used classification of eye burns was proposed in 1973 by N.A. Puchkovskaya and V.M. Nepomnyashaya. Recent emergence of the concept of limbal stem cells of the corneal epithelium and its application in clinical practice has significantly expanded the possibilities for diagnosis, treatment, and visual rehabilitation of patients with eye burns. In 1997, Dr. Michael Wagoner proposed a classification of eye burns in which the grade of burn severity is determined by the degree of damage to the limbal stem cells. Considering this approach, the authors conducted a comparative analysis of the classifications of eye burns used in Russia (in different years) and those that have appeared in the Western countries in recent years. In this regard, a new classification of eye burns is being proposed.

Cancer stem cells (CSCs) are the most malignant subpopulation of tumor cells that possess a tumorigenic potential and resistantance to chemotherapy. These properties make CSCs a promising target for the development of targeted antitumor therapy which is especially in demand in highly aggressive cancers. However, the correct identification of cancer cells with stem properties remains a challenge. A newly developed lentivirus-based reporter SORE6 allows to directly identify CSCs by measuring gene expression of the embryonic stem cell factors SOX2 and OCT4. In the current study the reporter was modified to enable isolation of SOX2^(+)/OCT4^(+) cells by immunomagnetic separation and then was used to transduce HCC1806 and MDA-MB-453 triple-negative breast cancer (TNBC) cell lines. To validate the modified reporter, SOX2^(+)/OCT4^(+) populations were isolated and analyzed for the content of NANOG, a key transcription factor of pluropotency which expression is regulated by SOX2/OCT4. The percentage of SOX2^(+)/OCT4^(+) cells was assessed for each cell line. An increased content of NANOG protein was found in isolated SOX2^(+)/OCT4^(+) cell fractions indicating that the modified reporter is suitable for further studying the CSC subset.

In hepatocellular carcinoma (HCC), the presence of cancer stem cells (CSCs) have been linked to drug resistance, epithelial-mesenchymal transition (EMT), and cancer relapse. This study investigates the expression profile of ZEB1, ZEB2, ABCG2 in HCC-CSCs, and the role of EMT promoter ZEB2 in cells treated with resveratrol. The expression of ZEB1, ZEB2 and ABCG2 transcripts were analyzed in CD133^(+)/CD44^(+) cells isolated from the PLC/PRF/5 cell line. ZEB2-dependent ABCG2 gene expression and the effects of resveratrol on proliferation, cell cycle and apoptosis were explored in SNU398 cell clones. An inverse correlation between ZEB1/ZEB2 and ABCG2 levels were observed both in CSCs and in ZEB2-knock-down cells. The resveratrol treatment significantly decreased cell viability, while promoting cell cycle arrest in ZEB2-independent manner. Interestingly, resveratrol-treated cells with low levels of ZEB2 were resistant to apoptosis. The interplay of expression levels of ABCG2 and ZEB family EMT transcription factors may play a role in establishing CSC-like phenotype in HCC cells resistant to resveratrol.

Using flow cytometry GD2 ganglioside expression was evaluated both on colorectal adenocarcinoma cell lines and on tumor tissue samples from colorectal cancer patients. The marker was found on EpCAM-positive tumor cells in 6 of 12 patients' samples but not on the HT29 and CaCo-2 cell lines. GD2 expression was not an exceptional feature of cancer stem cells, since its expression level was similar on CD133-positive and CD133-negative tumor cells. Thus, the presence of GD2 ganglioside was revealed on colorectal adenocarcinoma cells for the first time. This finding makes it possible to use targeted therapy to treat this disease.

Carcinogenesis and tumor progression are not caused not only by malignant epithelial cells, but also by the tumor stroma around cancer stem cells which performs regulatory, nutritional and 'framework' functions. It is represented by mesenchymal cells of various types predominantly by cancer-associated fibroblasts (CAF). αSMA, FAP-1, desmin, podoplanin, neuron-glial antigen 2 (NG2), PDGFR-α and -β are used for CAF identification but there is no universal markers due to the plasticity of the cell population that underlies the subpopulation division CAF. CAF subpopulations are not described for many tumor types. Recently, evidence has accumulated that CAFs mediate many adverse processes in the tumor, including can support stromal inflammation and cause fibrosis. By forming a niche in cancer stem cells, CAFs mediate chemoresistance and the appearance of dormant metastases. The study of the role of CAF will allow not only to form a fundamentally new understanding of the mechanisms of carcinogenesis, but also to create new diagnostic and therapeutic targets for treating tumors.

Hematopoietic stem cells (HSCs) exist in a close contact with their specific microenvironment, called a niche, which supports the HSC function and significantly influences the HSC properties. The existence of the HSC niche, which was proposed as a purely theoretical concept in 1978, finds increasing experimental evidence and is now generally accepted by specialists in the field of hematopoiesis. The review briefly describes various cell components of the HSC niche in bone marrow, considers the metabolic states of the niche and HSCs, and discusses other aspects of niche biology. Increasing knowledge of the HSC niche will help to create in vitro cell models of the HSC niche, to modulate the HSC properties, and to achieve multifold HSC expansion in culture for further applications in therapeutic practice.

Ischemic cardiomyopathy is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ischemic cardiomyopathy. Several stem cell types, including cardiac-derived stem cells, bone marrow-derived stem cells, mesenchymal stem cells, skeletal myoblasts, CD34+ and CD133+ stem cells have been used in clinical trials. Clinical effects mostly depend on transdifferentiation and paracrine factors. One important issue is that a low survival and residential rate of transferred stem cells blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ischemic cardiomyopathy mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical conditions, the particular microenvironment onto which the cells are delivered, and clinical conditions remain to be addressed. Here we provide an overview of modern methods of stem cell delivery, types of stem cells and discuss the current state of their therapeutic potential.

Allogenic transplantation of hemopoetic stem cells (allo-THSC) is one of the most effective treatment methods for Hurler syndrome, aimed at maximal correction of complications related to the genetic disorder. Presence of infection in the recipient is an adverse risk factor, affecting the possibility of starting the conditioning regimen and THSC peforming in general.

Retinitis pigmentosa (RP) is a degenerative retinal disease that leads to blindness. Recently, treatment methods based on new technologies have emerged. Among them is stem cells transplantation (SC).

Retinal diseases associated with damage to retinal pigment epithelium (PPE) are the most frequent causes of irreversible loss of vision in adults. Since there is no therapeutic treatment available that could repair RPE and its connections with the adjacent photoreceptors, the review focuses on various methods of surgical treatment. One of the most promising methods at present is the use of stem cells derivatives. Results of numerous experimental and clinical trials show that use of human induced pluripotent stem cells in the treatment of degenerative diseases of the retina can be considered effective and promising.

Neurogenesis is a complex process which governs embryonic brain development and is importants for brain plasticity throughout the whole life. Postnatal neurogenesis occurs in neurogenic niches that regulate the processes of proliferation and differentiation of stem and progenitor cells under the action of stimuli that trigger the mechanisms of neuroplasticity. Cells of glial and endothelial origin are the key regulators of neurogenesis. It is known that physiological neurogeneses is crucial for memory formation, whereas reparative neurogenesis provides partial repair of altered brain structure and compensation of neurological deficits caused by brain injury. Dysregulation of neurogenesis is a characteristics of various neurodevelopmental and neurodegenerative diseases, particularly, Alzheimer's disease which is very important medical and social problem. In the in vitro model of the neurogenic niche using hippocampal neurospheres as a source of stem/progenitor cells and astrocytes, we studied effects of astrocyte activation on the expression of markers of different stages of cell proliferation and differentiation. We found that aberrant mechanisms of development of stem and progenitor cells, caused by the beta-amyloid (Aβ1-42), can be partially restored by targeted activation of GFAP-expressing cells in the neurogenic niche.

Human pluripotent stem cells, which include embryonic stem cells and induced pluripotent cells (iPSCs), are capable of unlimited division and differentiation into all cells of the body. These cells are considered as a potential source of various types of cells for transplantations. The use of autologous iPSCs is not potentially associated with immune rejection and does not require immunosuppression required for allogeneic grafts. However, the high cost of this technology and the duration of obtaining iPSCs and differentiated cells may limit the use of autologous iPSCs in clinical practice. In addition, full equivalence and immunological compatibility of autologous iPSCs and their derivatives have been repeatedly questioned. One approach to solving the problem of the immunological compatibility of allogeneic derivatives of iPSCs can be the establishment of cell lines with reduced immunogenicity. Differentiated derivatives of such iPSCs may be suitable for transplantation to any patient. This review discusses the strategies for evading immune surveillance in normal and tumor processes that can be used to establish stem cell lines with reduced immunogenicity.

Blood is extremely important for a multicellular organism: it connects all organs and tissues, supplies them with nutrients and oxygen, removes carbon dioxide and metabolic products, maintains homeostasis, and provides protection against infections. That is why studies on blood have always drawn a great deal of attention. In ancient times, it was believed that the soul was in the blood and that it sometimes "sank into the stomach." Initially, the study of blood was limited to morphological methods, to which physiological and cellular research were added in the twentieth century. With their help, researchers established that mature blood cells are formed from a rare population of hematopoietic stem cells (HSCs), which are located in the bone marrow. The development of molecular biology methods and their combination with classical physiological ones allowed a breakthrough in understanding the structure of the hematopoietic system, which changed our understanding not only of hematopoiesis but also about the nature of adult stem cells. This review describes the molecular assays used in experimental hematology, and how their application has gradually been expanding our knowledge of blood formation and continues to provide new information about it.

To assess the safety and efficacy of umbilical cord blood (UCB) cells in the treatment of schizoasthenia and comorbid negative disorders.

Oncogenesis can be caused by an increase in the activity of genes responsible for initiating tumor growth in stem or progenitor cells, as well as a reduction in the functioning of suppressor genes. Endogenous estrogen exposure is associated with an increased risk of breast cancer in both pre- and postmenopausal women. The most important step in the understanding of the pathogenesis of breast cancer was the development of the theory of the switching of estrogen's effect from hormonal to genotoxic, in which the main culprits of carcinogenesis are not chemical metabolites of estrogens, but their derivatives, corresponding to chemical procarcinogens according to their damaging characteristics. The origin of these substances and the formation of estrogen genotoxicity lies in the disruption of the inactivation process of catechol estrogens in methylation reactions. The main epigenetic modification of the human genome is the methylation of cell DNA molecules. DNA methylation does not alter the primary sequence of nucleotides, but is necessary for the functional suppression of certain genes. The phenomenon of hypomethylation-hypermethylation underlies the long-term silencing of various genes, including tumor suppressor genes. Nutrition and a lifestyle associated with smoking and the consumption of excessive quantities of alcohol determine estrogen metabolism and the availability of methyl groups in the body, as well as epigenetic changes in the DNA of the genome. The assessment of individual risk of breast cancer on the basis of an assay for the expression and methylation of the COMT gene responsible for estrogen metabolism seems relevant.

To date, descension of the pelvic floor is a fairly common gynecological pathology that requires surgical treatment. The development of cellular technologies suggests that the use of multipotent mesenchymal stem cells (MMSC) in the treatment of this pathology can stimulate the regeneration of damaged tissue and contribute to the reconstruction of the structures of the pelvic floor.