[Corneal regeneration: is there a place for tissues of perinatal origin?] / Regeneratsiya rogovitsy: est' li mesto dlya tkanei perinatal'nogo proiskhozhdeniya?

The article reviews the main properties of the cornea and the mechanisms of its physiological regeneration and repair in response to damage and describes the most promising methods of treatment aimed at stimulating limbal stem cells and based on the use of native tissues of perinatal origin, umbilical cord mesenchymal stromal cells, and cell-free therapeutic products.

Mild or Moderate COVID-19 during Pregnancy Does Not Affect the Content of CD34+ Hematopoietic Stem Cells in Umbilical Cord Blood of Newborns.

The study included umbilical cord blood samples (n=64) intended for cryogenic storage of hematopoietic stem cells and obtained from patients with a history of mild and moderate forms of COVID-19 during pregnancy. The control group was composed of samples (n=746) obtained from healthy women in labor. A comparative analysis of the volume of cord blood collected, the total leukocyte count, the relative and absolute content of cells with the CD34+/CD45+ phenotype revealed no significant differences between the groups.

Human Umbilical Cord Tissue-Derived Multipotent Mesenchymal Stromal Cells Exhibit Maximum Secretory Activity in the Presence of Umbilical Cord Blood Serum.

Using multiplex analysis, we performed a comparative study of cytokine and growth factor production by human umbilical cord tissue-derived multipotent mesenchymal stromal cells (UC-MSC) cultured under standard conditions and in the presence of human umbilical cord blood serum (UCBS). It was found that the secretion of most studied molecules, including well-known inductors of regeneration HGF, G-CSF, GM-CSF, and VEGF by UCMSC considerably increased in the presence of 5% UCBS. The use of UCBS allows not only obtaining xenogenic-free cellular and cell-free therapeutic products, but also increasing the secretion of most biologically active molecules capable of stimulating repair processes.

Human Umbilical Cord Blood Serum/Plasma: Cytokine Profile and Prospective Application in Regenerative Medicine.

The concentrations of cytokines and growth factors in human umbilical cord blood serum and plasma samples were measured by multiplex analysis. It was found that in comparison with peripheral blood serum of adult donors, umbilical cord blood serum and plasma contain significantly higher concentrations of the most studied molecules including IL-4, 5, 6, 7, 10 and 15, MCP-1, SCF, and SDF, as well as growth factors directly involved in the processes of regeneration (G-CSF, HGF, PDGF-BB, and VEGF). Thus, umbilical cord blood plasma and especially serum are a rich source of cytokines and growth factors with anti-inflammatory, anti-apoptotic, and angiogenic effects and can be used in various fields of regenerative medicine.

Effect of Storage Conditions on the Integrity of Human Umbilical Cord Mesenchymal Stromal Cell-Derived Microvesicles.

We studied the effect of storage conditions on the safety of microvesicles produced by human multipotent umbilical cord mesenchymal stromal cells into the conditioned medium. It was found that microvesicles can be stored without serious degradation for up to 1 week at 4°Ð¡, but were almost completely destroyed during freezing and thawing cycles irrespective of the storage temperatures (-20°Ð¡, -70°Ð¡, or -196°Ð¡). Similar results were obtained for lyophilized medium conditioned by human multipotent umbilical cord mesenchymal stromal cells. Addition of a cryoprotectant (5-10% DMSO) followed by freezing and/or lyophilization preserved microvesicles at a nearly initial level. These findings indicate that during storage, microvesicles, being membrane structures, behave similar to living cells and require appropriate conditions for prolonged storage.

Comparative Analysis of Secretome of Human Umbilical Cord- and Bone Marrow-Derived Multipotent Mesenchymal Stromal Cells.

Production of cytokines and growth factors by cultured human umbilical cord tissue- and bone marrow-derived multipotent mesenchymal stromal cells was measured by multiplex analysis. In most cases, the concentrations of bioactive factors in the culture medium conditioned by umbilical cord-derived cells was ten- to hundred-times higher than in the medium conditioned by bone marrow-derived cells. These results suggest that both multipotent mesenchymal stromal cells from the umbilical cord and cell-free products can have more pronounced therapeutic effect in comparison with mesenchymal stromal cells obtained from "adult" sources.

Human Umbilical Cord Mesenchymal Stromal Cell-Derived Microvesicles Express Surface Markers Identical to the Phenotype of Parental Cells.

Production of microvesicles in culture of human umbilical cord multipotent mesenchymal stromal cells was studied and comparative analysis of the expression of some surface molecules (clusters of differentiation, CD) was performed. It was found that the mesenchymal stromal cells produce microvesicles in the amount sufficient for their detection by flow cytometry. Parallel analysis of the phenotypes of maternal mesenchymal stromal cells and secreted microvesicles revealed identical expression of surface molecules CD13, CD29, CD44, CD54, CD71, CD73, CD90, CD105, CD106, and HLA-I. The concentration of microvesicles in the conditioned medium was 17.9±4.6×106/ml; i.e. one cell produced ~40-50 (44.7±11.5) microvesicles over 2 days in culture.

Human Umbilical Cord Mesenchymal Stromal Cells Support Viability of Umbilical Cord Blood Hematopoietic Stem Cells but not the "Stemness" of Their Progeny in Co-Culture.

Cell-cell interactions and the ability of mesenchymal stromal cells to support the expansion of hematopoietic progenitor cells were studied in co-culture of human umbilical cord tissue-derived mesenchymal stromal cells and nucleated umbilical cord blood cells. It was found that hematopoietic stem cells from the umbilical cord blood are capable to adhere to mesenchymal stromal cells and proliferate during 3-4 weeks in co-culture. However, despite the formation of hematopoietic foci and accumulation of CD34+ and CD133+ cells in the adherent cell fraction, the ability of newly generated blood cells to form colonies in semi-solid culture medium was appreciably reduced. These findings suggest that human umbilical cord tissue-derived mesenchymal stromal cells display a weak capability to support the "stemness" of hematopoietic stem cell progeny despite long-term maintenance of their viability and proliferation.

Human Umbilical Cord Blood Serum: Effective Substitute of Fetal Bovine Serum for Culturing of Human Multipotent Mesenchymal Stromal Cells.

Optimal conditions for culturing of multipotent mesenchymal stromal cells in the presence of pooled umbilical cord blood serum were determined. It was found that umbilical cord blood serum in a concentration range of 1-10% effectively supported high viability and proliferative activity of cells with unaltered phenotype and preserved multilineage differentiation capacity. The proposed approach allows avoiding the use of xenogenic animal sera for culturing of multipotent mesenchymal stromal cells and creates prerequisites for designing and manufacturing safe cellular and/or acellular products for medical purposes.

Expression of Surface Molecules in Human Mesenchymal Stromal Cells Co-Cultured with Nucleated Umbilical Cord Blood Cells.

We studied the expression of different classes of surface molecules (CD13, CD29, CD40, CD44, CD54, CD71, CD73, CD80, CD86, CD90, CD105, CD106, CD146, HLA-I, and HLA-DR) in mesenchymal stromal cells from human umbilical cord and bone marrow during co-culturing with nucleated umbilical cord blood cells. Expression of the majority of surface markers in both types of mesenchymal stromal cells was stable and did not depend on the presence of the blood cells. Significant differences were found only for cell adhesion molecules CD54 (ICAM-1) and CD106 (VCAM-1) responsible for direct cell-cell contacts with leukocytes and only for bone marrow derived cells.

Changes in Cell Composition of Umbilical Cord Blood and Functional Activity of Hematopoietic Stem Cells during Cryogenic Storage and Repeated Freezing/Thawing Cycles.

We analyzed changes in cell composition of umbilical cord blood and functional activity of hematopoietic stem cells during cryogenic storage and after repeated freezing/thawing cycles. It was found that repeated freezing/thawing cycles performed according to the optimal programmable freezing protocol did not significantly affect viability and functional activity of hematopoietic stem cells. When fast freezing program was used, the cells completely lost their capacity to form colonies in semisolid medium, despite high viability parameters in the test with 7-AAD.

Isolation of Multipotent Mesenchymal Stromal Cells from Cryopreserved Human Umbilical Cord Tissue.

Umbilical cord stroma is an easily available, convenient, and promising source of multipotent mesenchymal stromal cells for regenerative medicine. Cryogenic storage of umbilical cord tissue provides more possibilities for further isolation of multipotent mesenchymal stromal cells for autologous transplantation or scientific purposes. Here we developed a protocol for preparation of the whole umbilical cord tissue for cryogenic storage that in combination with the previously described modified method of isolation of multipotent mesenchymal stromal cells allowed us to isolate cells with high proliferative potential, typical phenotype, and preserved differentiation potencies.

Optimized Protocol for Isolation of Multipotent Mesenchymal Stromal Cells from Human Umbilical Cord.

Extraembryonic tissues, in particular, umbilical cord stroma are promising sources of multipotent mesenchymal stromal cells for regenerative medicine. In recent years, methods for isolation of mesenchymal stromal cells from different compartments of the umbilical cords based on enzymatic disaggregation of the tissue or on tissue explants have been proposed. Here we propose a protocol of isolation of multipotent mesenchymal stromal cells from the whole umbilical cord that combines the advantages of each approach and ensures sufficient cell yield for further experimental and clinical applications. A combination of short-term incubation of tissue fragments on cold collagenase solution followed by their culturing in the form of explants significantly increased the yield of cells with high proliferative activity, typical pluripotent mesenchymal stromal cell phenotype, and preserved differentiation capacity.

[EFFECT OF STROMAL CELLS AND OXYGEN CONCENTRATION ON THE MAINTENANCE OF CORD BLOOD HEMATOPOIETIC PRECURSORS].

The paper analyses the morphological and functional features of cord blood cells (CBCs) in the co-culture with multipotent mesenchymal stromal cells (MMSCs) from human adipose tissue under tissue-related oxygen. We have established that MMSCs effectively maintained viability of CBCs at different oxygen concentrations (1, 5 and 20%). According to the data obtained, the oxygen concentration affected the number of colony-forming units (CFUs) formed by CBCs in selective medium. In particular, not co-cultured CBCs the 1 and 5% O2 than at 20% O2. After co-culture with MMSCs, the CFUs numbers were similar at 1 and 20% O2 and increased by 30 at 5% O2. Tissue related O2 concentrations had an impact on the proportion of lineage-resctricted CFCs among CBCs: the number of more committed progenitors--CFU-G and CFU-M, increased, and multi and bipotent--CFU-GEMM and CFU-GM, decreased at low oxygen concentrations. This effect was more pronounced after co-culture compared to that of initial CBCs. Thus, the presence of stromal cells and tissue-related oxygen jointly and severally influenced CBCs in vitro.

Umbilical cord blood for autologous transfusion in the early postnatal ontogeny: analysis of cell composition and viability during long-term culturing.

Changes in cell composition and viability as well as the content and functional activity of hemopoietic progenitor cells were analyzed during long-term (up to 1 month at 4°C) storage of human umbilical cord blood cells. No significant quantitative changes in erythrocytes were found during this period. The total content and viability of leukocytes changed, which resulted in the prevalence of mononuclear cells (lymphocytes and monocytes). Analysis of functional activity of hemopoietic stem cells in semisolid culture revealed a decrease in the relative content of CFU during the first week of storage [corrected] and inability of cells to colony formation after 2 weeks.

Enrichment of umbilical cord blood mononuclears with hemopoietic precursors in co-culture with mesenchymal stromal cells from human adipose tissue.

We demonstrated the possibility of enrichment of umbilical cord blood mononuclear fraction with early non-differentiated precursors under conditions of co-culturing with mesenchymal stromal cells from the human adipose tissue. It was established that umbilical cord blood mononuclear cells adhered to mesenchymal stromal cell feeder and then proliferate and differentiate into hemopoietic cells. In comparison with the initial umbilical cord blood mononuclear fraction, the cell population obtained after 7-day expansion contained 2-fold more CFU and 33.4 ± 9.5 and 24.2 ± 11.2% CD34(+) and CD133(+) cells, respectively, which corresponds to enrichment of precursor cell population by 148 ± 60. The proposed scheme of expansion of hemopoietic cells from umbilical cord blood is economically expedient and can widely used in biology and medicine.

Rhythms of cell division of different periodicity in small intestinal cryptic epithelium and their contribution to circadian rhythm formation.

We used an improved method of chronobiological information processing enabling not only to detect oscillations with different frequencies, but also to determine the significance of each harmonic. This has made it possible to identify significant high-power harmonics present in the majority of cell positions in the crypt. These harmonics make the major contribution to the formation of diurnal rhythm of cell division in the crypt and hence determine spatial and temporal organization of the proliferative system in the crypt.

Zener tunneling in semiconductor superlattices.

Characteristics of miniband tunneling and Wannier-Stark levels in semiconductor superlattices are studied as regards their dependence on the symmetry of the unit cells and the type of miniband structure. We modify the k ⋅ p method into a k ⋅ v form and on this basis generalize the Zener formula for the inter-band tunneling in homogeneous semiconductors to the case of inter-miniband tunneling in superlattices, account being taken of the inhomogeneity of the electron effective mass. The corresponding sum rule for the effective masses in such structures is obtained. We develop a unified matrix approach for the calculation of the inter-miniband tunneling and Wannier-Stark levels in the case of an arbitrary number of minibands. We study the electric field dependence of the probability of inter-miniband tunneling for an electron transferred through the Brillouin minizone only once. The peculiarities of the inter-miniband transitions for the case where this transfer is repeated are also examined for various unit cells and miniband structures of the superlattice. In addition, we discuss mechanisms and specific features of the resonant Zener tunneling and its manifestations in electron transport.

Relationship between proliferation of Ehrlich ascitic tumor cells and status of the chalone system under conditions of modified photoregimen.

The effects of permanent darkness on proliferation of Ehrlich ascitic tumor cells and status of the chalone system in the tumor were studied. Chalone-containing preparations from animals exposed to different light conditions exhibited different biological effects on cell proliferation in this tumor. A relationship between biological activity of chalone-containing preparations and sensitivity of tumor cells to these preparations under conditions of modified photoregimen was revealed.