Great advances in type 1 diabetes (T1D) and type 2 diabetes (T2D) treatment have been made to this day. However, modern diabetes therapy based on insulin injections and cadaveric islets transplantation has many disadvantages. That is why researchers are developing new methods to regenerate the pancreatic hormone-producing cells in vitro. The most promising approach is the generation of stem cell-derived beta cells that could provide an unlimited source of insulin-secreting cells. Recent studies provide methods to produce beta-like cell clusters that display glucose-stimulated insulin secretion-one of the key characteristics of the beta cell. However, in comparison with native beta cells, stem cell-derived beta cells do not undergo full functional maturation. In this paper we review the development and current state of various protocols, consider advantages, and propose ways to improve them. We examine molecular pathways, epigenetic modifications, intracellular components, and the microenvironment as a possible leverage to promote beta cell functional maturation. A possibility to create islet organoids from stem cell-derived components, as well as their encapsulation and further transplantation, is also examined. We try to combine modern research on beta cells and their crosstalk to create a holistic overview of developing insulin-secreting systems.

Type 2 diabetes mellitus (T2DM) is the most common endocrine disorder (90%) in the world; it has numerous clinical, immunological, and genetic differences from type 1 diabetes mellitus. The pathogenesis of T2DM is complex and not fully clear. To date, animal models remain the main tool by which to study the pathophysiology and therapy of T2DM. Rodents are considered the best choice among animal models, because they are characterized by a small size, short induction period, easy diabetes induction, and economic efficiency. This review summarizes data on experimental models of T2DM that are currently used, evaluates their advantages and disadvantages vis-a-vis research, and describes in detail the factors that should be taken into account when using these models. Selection of a suitable model for tackling a particular issue is not always trivial; it affects study results and their interpretation.

Preclinical studies of human cellular and tissue-based products (HCT/Ps) for transplantation therapy of type 1 diabetes mellitus (T1DM) necessarily involve animal models, particularly mouse models of diabetes induced by streptozotocin (STZ). These models should mimic the clinical and metabolic manifestations of T1DM in humans (face validity) and be similar to T1DM in terms of the pathogenetic mechanism (construct validity). Furthermore, since HCT/Ps contain human cells, modeling of diabetes in immune-deficient animals is obligatory. Here we describe the most simplified diabetes model in Nude mice. Diabetes was induced in 31 males by a single intraperitoneal injection of STZ in normal saline at a medium-to-high dose of 150 mg/kg body weight. Fourteen control animals received only saline. Non-fasting plasma glucose (PG) levels were measured periodically for 50 days. All STZ-treated mice survived beyond 50 days. By day 15 after STZ administration, 22 of 31 (71%) mice developed stable diabetes based on the following criteria: (1) non-fasting PG ≥ 15 mmol/L on consecutive measurements up until day 50; (2) no diabetes remission. The mean non-fasting PG in mice with stable diabetes over the period of 35 days was equal to 25.7 mmol/L. On day 50, mean plasma insulin concentration, mean pancreatic insulin content, and the average number of β-cells in pancreatic islets were 2.6, 8.4, and 50 times lower, respectively, than in the control animals. We consider that our Nude mouse model of diabetes meets face validity and construct validity criteria and can be used in preclinical studies of HCT/Ps.

Сахарный диабет и его осложнения представляют собой самую распространенную эндокринную патологию в большинстве стран мира. Изучение патогенетических механизмов возникновения и прогрессии этого заболевания, а также поиск новых терапевтических средств и способов терапии остаются актуальными на сегодняшний день. Важнейшее значение для изучения сахарного диабета имеют экспериментальные модели. В обзоре обобщены данные о наиболее часто используемых животных моделях. Проанализированы и обсуждены механизмы стрептозотоцинового диабета как наиболее адекватной и легко воспроизводимой экспериментальной модели диабета. Рассмотрены значимые преимущества и недостатки описанных моделей.

The global prevalence of diabetes mellitus and its severe complications is on the rise. The study of the pathogenesis of the onset and the progression of complications related to the disease, as well as the search for new therapeutic agents and methods of treatment, remains relevant. Experimental models are extremely important in the study of diabetes. This survey contains a synthesis of the most commonly used experimental animal models described in scientific literature. The mechanisms of the streptozotocin model are also analyzed and discussed, as it is considered as the most adequate and easily reproducible diabetes model. A review of the significant advantages and disadvantages of the described models has also been conducted.

The success of cell therapy is directly related to the viability of cells used for transplantation. The cells used for transplantation are in some cases injected in suspension. However, the optimal conditions for the preservation of cell viability upon the preparation and storage of cell suspensions for transplantation have not been defined yet. The aim of the present work consisted in the selection of optimal conditions for the storage of suspensions of human submandibular salivary gland cells, differentiated cells of the submandibular salivary gland, and dermal fibroblasts in biocompatible solutions. Standard procedures of cell isolation and cultivation were used in the study. An automatic cell counter from BioRad was used to count the cells, and viability of the cells was assessed using staining with 4% Trypan Blue. The biocompatible solutions tested included phosphate-buffered saline, physiological saline for injections, and a 2% solution of human albumin in phosphate-buffered saline. The study showed that the human cells under investigation remained viable in suspension at both +4°С and +25°С for at least 24 hours, regardless of the carrier solution used. The highest content of viable cells of the salivary gland (more than 50%) at both temperatures examined was observed when cells were suspended in phosphate-buffered saline. However, the adhesive and proliferative properties of the salivary gland cells were better preserved at +4°С in case of 24 hours of incubation under the conditions described above. Fibroblasts maintained in physiological saline formed a homogeneous single-cell suspension that remained stable for 30 hours at +4°С; virtually no loss of cell viability was observed. The addition of 2% albumin resulted in a decrease of the viability of fibroblasts. Thus, storage and transportation in phosphate- buffered saline at +4°С can be recommended for suspensions of cells of the human submandibular salivary gland, whereas human fibroblast suspensions should be maintained at +4°С in physiological saline.

Diabetes affects over 350 million people worldwide, with the figure projected to rise to nearly 500 million over the next 20 years, according to the World Health Organization. Insulin-dependent diabetes mellitus (type 1 diabetes) is an endocrine disorder caused by an autoimmune reaction that destroys insulin-producing β-cells in the pancreas, which leads to insulin deficiency. Administration of exogenous insulin remains at the moment the treatment mainstay. This approach helps to regulate blood glucose levels and significantly increases the life expectancy of patients. However, type 1 diabetes is accompanied by long-term complications associated with the systemic nature of the disease and metabolic abnormalities having a profound impact on health. Of greater impact would be a therapeutic approach which would overcome these limitations by better control of blood glucose levels and prevention of acute and chronic complications. The current efforts in the field of regenerative medicine are aimed at finding such an approach. In this review, we discuss the time-honored technique of donor islets of Langerhans transplantation. We also focus on the use of pluripotent stem and committed cells and cellular reprogramming. The molecular mechanisms of pancreatic differentiation are highlighted. Much attention is devoted to the methods of grafts delivery and to the materials used during its creation.

The studies of cell plasticity and differentiation abilities are important problems in modern cellular biology. The use of histone deacetylase inhibitor - valproic acid is a promising approach to increasing the differentiation efficiency of various cell types. In this paper we investigate the ability of mouse submandibular salivary gland cells to differentiate into the hepatic direction and the effect of valproic acid on the efficiency of this differentiation. It was shown that the gene expression levels of hepatocyte markers (Aat, Afp, G6p, Pepck, Tat, Cyp3a13) and liver-enriched transcription factors (Hnf-3α, Hnf-3β, Hnf-4α, Hnf-6) were increased after differentiation in salivary gland cells. Valproic acid increases the specificity of hepatic differentiation, reducing the expression levels of the ductal (Krt19, Hhex1, Cyp7a1) and acinar (Ptf1a) markers. After valproic acid exposure, the efficiency of hepatic differentiation also increases, as evidenced by the increase in the gene expression level of Alb and Tdo, and increase in urea production by differentiated cells. No change was found in DNA methylation of the promoter regions of the genes; however, valproic acid treatment and subsequent hepatic differentiation largely affected the histone H3 methylation of liver-enriched genes. Thus, mouse submandibular salivary gland cells are capable of effective differentiation in the hepatic direction. Valproic acid increases the specificity and efficiency of the hepatic differentiation of these cells.

Изучение фенотипической пластичности и дифференцировочных способностей клеток является важной задачей клеточной биологии. В представленной работе исследована способность клеток поднижнечелюстной слюнной железы мыши к дифференцировке в гепатоцитарном направлении, а также проанализировано влияние вальпроевой кислоты, ингибитора гистон-деацетилаз, на эффективность дифференцировки. Показано, что после дифференцировки в клетках слюнной железы возрастает экспрессия генов гепатоцитарных маркеров (Aat, Afp, G6p, Pepck, Tat, Cyp3a13) и факторов транскрипции (Hnf-3α, Hnf-3β, Hnf-4α, Hnf-6). Вальпроевая кислота увеличивает специфичность гепатоцитарной дифференцировки, снижая экспрессию протоковых (Krt19, Hhex1, Cyp7a1) и ацинарных (Ptf1a) маркеров. После воздействия вальпроевой кислоты усиливается также эффективность гепатоцитарной дифференцировки, о чем говорит повышение уровня Alb и Tdo2 и увеличение секреции мочевины дифференцированными клетками. Изменений в характере метилирования промоторных областей генов не обнаружено, однако обработка вальпроевой кислотой и гепатоцитарная дифференцировка в значительной степени затрагивают метилирование гистона H3, ассоциированного с генами, ключевыми для гепатоцитарной дифференцировки. Таким образом, клетки поднижнечелюстной слюнной железы мыши способны к дифференцировке в гепатоцитарном направлении, а вальпроевая кислота увеличивает специфичность и эффективность их дифференцировки.

Mouse submandibular salivary gland cells and liver progenitor cells from long-term in vitro cultures with a high proliferation potential were side-by-side compared by methods of immunocytochemistry, quantitative real-time PCR, flow cytometry, and transcriptome analysis. The two cell types were found to be similar in expressing cell markers such as EpCAM, CD29, c-Kit, Sca-1, and c-Met. In addition, both cell types expressed cytokeratins 8, 18, and 19, alpha-fetoprotein, and (weakly) albumin. Unlike the liver cells, however, the salivary gland cells in culture showed high-level expression of cytokeratin 14 and CD49f, which was indicative of their origin from salivary gland ducts. Quantitative real-time PCR and deep-sequencing transcriptome analysis revealed similarities in the expression pattern of transcription factors between the two cell types. In this respect, however, the cultured salivary gland cells proved to be closer to exocrine cells of the pancreas than to the liver progenitor cells. Thus, ductal cells of postnatal submandibular salivary glands in culture show phenotypic convergence with progenitor cells of endodermal origin, suggesting that these glands may serve as a potential cell source for cellular therapy of hepatic and pancreatic disorders. The results of this study provide a deeper insight into the molecular features of salivary gland cells and may help optimize procedures for stimulating their differentiation in a specified direction.

Transplantation of the submandibular gland under the renal capsule of mice with streptozotocin-induced diabetes mellitus stimulated the compensatory function of the recipient submandibular gland. An increase in insulin I and insulin II gene expression in the submandibular gland after transplantation was demonstrated by PCR. More intensive production and extrusion of these proteins in the apical and basal directions in granular compartment cells of the submandibular gland was confirmed by electron microscopy. All these changes led to a reduction of blood glucose levels in diabetic animals as soon as 2-2.5 weeks after transplantation.

A cell culture that preserves its phenotype up to the 20th passage was obtained from mouse submandibular salivary glands. An analysis of the heterogeneous culture indicates the existence of several morphological types of cells, including small, densely packed cells of cuboidal or polygonal shapes and large, rounded cells. Epithelial cells of the submandibular gland cultured for several weeks were able to form tubular structures. Our studied cell culture of glandulocytes (cells of glandular epithelium) was represented by K19- and NGF-positive cells. It is important to note that, using both immunocytochemical staining and PCR, the expression of genes that encode the proinsulin and insulin proteins is revealed in the studied cell population.

The effect of gangliosides and phenylephrine synchronizing the protein synthesis rhythm was preserved in hepatocytes cultured in the normal serum-free medium for one-two days. Hence, the membrane signal triggers intracellular, as was shown by us earlier, calcium-dependent processes, which regulate the kinetics of protein synthesis for a certain time after the signal perception.

Cell interactions have been studied in cultures pf hepatocytes from young and old rats. The rhythm of protein synthesis is an index of cell interaction and synchronization in culture, while the amplitude of oscillations characterized cell cooperation in an aggregate rhythm. The mean rhythm amplitude in the culture of hepatocytes from old rats is twice lower than that from young rats. Gangliosides (mixture, bovine brain gangliosides) and alpha1-adrenomimetic phenylephrine enhanced synchronization of cultures of the cells from old rats and increased the amplitude of oscillations to the level of young animals. Addition of rat blood serum (10%) to the medium revealed the rhythm of protein synthesis in the culture, asynchronous in the control, i.e., led to their synchronization. In media with young and old rat blood sera, oscillations were intense, with high amplitudes, and low, respectively. Addition of bovine brain gangliosides to a medium with old rat blood serum increased the amplitudes of oscillations to a level of the rhythm stimulated by the young rat serum. Thus, the cells of old animals can fully perceive synchronizing factors and, in the case of their increased concentration, the rhythm of protein synthesis in old animals did not differ from that in young rats. Current data on biochemical mechanisms underlying intercellular cooperation in the formation of population rhythm of protein synthesis have been discussed.

Previously we demonstrated synchronized oscillations of protein synthesis rate in hepatocyte cultures upon accumulation of monosialoganglioside GM1 in the medium or after introduction of exogenous GM1 to the medium. The synchronized oscillations of the protein synthesis rate in dense hepatocyte cultures were blocked 30 min after their treatment with 10–20 μM BAPTA-AM, a chelating agent of cytoplasmic calcium. Enzyme immunoassay for GM1 demonstrated similar amounts of GM1 in the medium conditioned for 3 h by dense hepatocyte cultures pretreated with 20 μM BAPTA-AM for 1 h and in the medium of normal dense cultures: 0.0060 ± 0.0005 and 0.0055 ± 0.0005 pmol/1000 cells, respectively. The content of GM1 was also similar in the normal and BAPTA-AM-pretreated hepatocytes: 0.158 ± 0.013 and 0.183 ± 0.014 pmol/1000 cells, respectively. The synchronized rhythm of protein synthesis has been confirmed in the diluted cultures in the medium conditioned by the normal dense cultures. However, the medium conditioned by the dense cultures pretreated with BAPTA-AM induced no synchronization of the diluted cultures. Since GM1 concentration was normal in this medium, we propose the effect of a physicochemical form of the gangliosides accumulated in the medium on their ability to synchronize the rhythm of protein synthesis.