During the recent decades of studies on stem cells, there has been a considerable interest in mesenchymal stem cells (MSCs), which are notable unique properties. These characteristics make MSCs a promising instrument for regenerative medicine. According to the official data of the US National Institutes of Health (https://clinicaltrials.gov/), the number of clinical trials involving the use of MSCs has doubled in five recent years However, most registered clinical trials using MSC therapy to treat different human diseases have not met expectations, regardless of hopeful pretrial results in the investigations with different models of animal diseases. This fact explains the urgency of studies on searching for ways to enhance the therapeutic potential of MSCs. The MSCs from the human umbilical cord have been chosen as the study object since they have several advantages over MSCs obtained from other sources. The aim of the work was to develop ways of enhancing the therapeutic efficiency of MSCs from the human umbilical cord and to research the effectiveness of MSCs with enhanced therapeutic potential using animal models of several diseases.
The following tasks were formulated to achieve the abovementioned aim:
1. To obtain the models of liver damage in rats and aseptic acute peritonitis in mice and to characterize their specificities.
2. To investigate the therapeutic potential of the initial MSCs of the human umbilical cord and MSCs, encapsulated into alginate capsules, using the simulated hepatic cirrhosis in rats.
3. To study the specificities of the impact of MSCs from the human umbilical cord on acute inflammation in the abdominal cavity of mice, to develop a fast and effective way of determining the therapeutic efficiency of MSCs, which helps compare the therapeutic potential of different preparations based on MSCs of the human umbilical cord and the impact of some factors thereon.
4. To study in vivo the interaction between the initial and preconditioned MSCs of the human umbilical cord with intraperitoneal macrophages using the peritonitis model in mice.
5. To develop the model of acute pancreatitis in rats and to characterize the exocrine and endocrine functions of the pancreas.
6. To compare the therapeutic efficiency of initial MSCs from the human umbilical cord and the ones preconditioned with hydrogen peroxide, using the model of acute pancreatitis of rats.
The hepatic cirrhosis in rats was induced by intraperitoneal injections of the CCl4 solution with olive oil for 13 weeks. The presence of hepatic cirrhosis was proven using histological and molecular biological methods. According to our data, the hepatic fibrosis started developing within the first weeks of administering CCl4. The development of hepatic fibrosis was confirmed by the study of the expression of some genes, which are markers for the state of the liver. These are genes EGF, α-SMA, GFAP, and eNOS. The results were compared in dynamics after 3, 8, and 13 weeks of using both ways of administering MSCs of the human umbilical cord in terms of their therapeutic effect on the rat hepatic cirrhosis. Therefore, the intraperitoneal administration of the encapsulated MSCs of the human umbilical cord resulted in restoring the rat liver after cirrhosis faster than the systematic administration of MSCs of the human umbilical cord. The next task was to select a convenient model to study the effect of MSCs preconditioning with various factors on their therapeutic efficacy in order to compare the efficiency of different MSC preparations. The model of acute peritonitis in miсe is induced by the intraperitoneal administration of the proteose peptone solution. Our comparison of the impact of MSC preconditioning on the anti-inflammatory effect demonstrated that the factor, reliably enhancing the therapeutic efficiency of MSCs, was H2O2 in the concentration of 30 µmol. After the model of acute peritonitis demonstrated that the preconditioning of MSCs using H2O2 had the highest impact on their therapeutic potential, the next task was to compare the therapeutic efficiency of the initial and H2O2-preconditioned MSCs of the human umbilical cord using the model of acute pancreatitis of rats to confirm the effectiveness of this approach. Acute pancreatitis in rats was induced by intraperitoneal administration of L-arginine. The clinical signs of the disease were observed three days later. The initial and Н2О2-preconditioned MSCs of the human umbilical cord were transplanted intraperitoneally three days later. The therapeutic effect was evaluated in dynamics 3, 7, and 14 days after the MSC administration. The obtained results demonstrated the high therapeutic efficiency of MSCs from the human umbilical cord in inhibiting acute inflammation of the pancreas and its regeneration. At the same time, the anti-inflammatory and restorative effect of MSCs, preconditioned by H2O2, developed twice faster than in the variant with initial MSCs.
