Biochemical Regulation of Regenerative Processes by Growth Factors and Cytokines: Basic Mechanisms and Relevance for Regenerative Medicine.

Regenerative medicine that had emerged as a scientific and medical discipline at end of 20th century uses cultured cells and tissue-engineered structures for transplantation into human body to restore lost or damaged organs. However, practical achievements in this field are far from the promising results obtained in laboratory experiments. Searching for new directions has made apparent that successful solution of practical problems is impossible without understanding the fundamental principles of the regulation of development, renewal, and regeneration of human tissues. These aspects have been extensively investigated by cell biologists, physiologists, and biochemists working in a specific research area often referred to as regenerative biology. It is known that during regeneration, growth factors, cytokines, and hormones act beyond the regulation of individual cell functions, but rather activate specific receptor systems and control pivotal tissue repair processes, including cell proliferation and differentiation. These events require numerous coordinated stimuli and, therefore, are practically irreproducible using single proteins or low-molecular-weight compounds, i.e., cannot be directed by applying classical pharmacological approaches. Our review summarizes current concepts on the regulatory mechanisms of renewal and regeneration of human tissues with special attention to certain general biological and evolutionary aspects. We focus on the biochemical regulatory mechanisms of regeneration, in particular, the role of growth factors and cytokines and their receptor systems. In a separate section, we discussed practical approaches for activating regeneration using small molecules and stem cell secretome containing a broad repertoire of growth factors, cytokines, peptides, and extracellular vesicles.

Cell Sheets of Mesenchymal Stromal Cells Effectively Stimulate Healing of Deep Soft Tissue Defects.

We used rat model of splinted defect of the skin and soft tissues to compare the efficiency f mesenchymal stromal cells applied in sheets or in suspension for the treatment of these injuries. Transplantation of mesenchymal stromal cells significantly accelerated wound healing in comparison with the control. In the group treated by application of mesenchymal stromal cell sheets, the defect was closed by day 28, in the group treated with cell suspension by day 35, and in the control group after 49 days. According to histological analysis of the tissue samples, the formation of the granulation tissue and fibrosis occurred earlier after application of mesenchymal stromal cells. Application of mesenchymal stromal cells in the form of cell sheets demonstrated high efficiency, which allowed us to consider this approach as a promising method of healing of skin and soft tissue injuries.

Endothelial and smooth muscle cells derived from human cardiac explants demonstrate angiogenic potential and suitable for design of cell-containing vascular grafts.

BACKGROUND: Endothelial and smooth muscle cells are considered promising resources for regenerative medicine and cell replacement therapy. It has been shown that both types of cells are heterogeneous depending on the type of vessels and organs in which they are located. Therefore, isolation of endothelial and smooth muscle cells from tissues relevant to the area of research is necessary for the adequate study of specific pathologies. However, sources of specialized human endothelial and smooth muscle cells are limited, and the search for new sources is still relevant. The main goal of our study is to demonstrate that functional endothelial and smooth muscle cells can be obtained from an available source-post-surgically discarded cardiac tissue from the right atrial appendage and right ventricular myocardium. METHODS: Heterogeneous primary cell cultures were enzymatically isolated from cardiac explants and then grown in specific endothelial and smooth muscle growth media on collagen IV-coated surfaces. The population of endothelial cells was further enriched by immunomagnetic sorting for CD31, and the culture thus obtained was characterized by immunocytochemistry, ultrastructural analysis and in vitro functional tests. The angiogenic potency of the cells was examined by injecting them, along with Matrigel, into immunodeficient mice. Cells were also seeded on characterized polycaprolactone/chitosan membranes with subsequent analysis of cell proliferation and function. RESULTS: Endothelial cells isolated from cardiac explants expressed CD31, VE-cadherin and VEGFR2 and showed typical properties, namely, cytoplasmic Weibel-Palade bodies, metabolism of acetylated low-density lipoproteins, formation of capillary-like structures in Matrigel, and production of extracellular matrix and angiogenic cytokines. Isolated smooth muscle cells expressed extracellular matrix components as well as α-actin and myosin heavy chain. Vascular cells derived from cardiac explants demonstrated the ability to stimulate angiogenesis in vivo. Endothelial cells proliferated most effectively on membranes made of polycaprolactone and chitosan blended in a 25:75 ratio, neutralized by a mixture of alkaline and ethanol. Endothelial and smooth muscle cells retained their functional properties when seeded on the blended membranes. CONCLUSIONS: We established endothelial and smooth muscle cell cultures from human right atrial appendage and right ventricle post-operative explants. The isolated cells revealed angiogenic potential and may be a promising source of patient-specific cells for regenerative medicine.

ISOLATION AND CHARACTERIZATION OF CARDIAC PROGENITOR CELLS OBTAINING FROM MYOCARDIAL RIGHT ATRIAL APPENDAGE TISSUE.

Resident stem cells of the heart are denoted as heterogeneous population of immature cells, which reside in the myocardium and characterized by their ability to self-renewal and are multipotent differentiation capacity into cardiomyocyte-like and vascular like cells. CSCs were originally isolated directly by long enzymatic digestion of heart tissue and selection using stem cell markers. However, long exposure to enzymatic digestion and small myocardial sample size can affect the possibility of obtaining a significant amount of viable cells. To avoid these problems, we developed a method consisting of growing of the CPC in explant culture and subsequent immunomagnetic selection.

[Urinary bladder substitution using combined membrane based on secretions of human mesenchymal stem cells and type I collagen].

AIM: Despite the widespread use of intestinal cystoplasty, urinary bladder substitution remains a challenging problem due to the complexity of operations and the potentially high risk of complications. A promising alternative may be bio-engineered collagen-based matrices containing stem cells or their secretions. MATERIAL AND METHODS: To evaluate the effectiveness of this bladder substitution modality, an experiment was conducted on 14 male rabbits. The animals underwent resection of urinary bladder, and the formed defect was substituted with a membrane of type I collagen (series 1, 5 rabbits) or a membrane of the same composition containing a conditioned medium with secretion of mesenchymal stem/stromal cells derived from human adipose tissue (series 2, 5 rabbits). In the comparison group (4 rabbits) resection of the bladder and the closure of the defect was carried out without bladder substitution (series 3). RESULTS: At 1 month after surgery, there was a complete epithelization of the inner surface of the implant, and body tissues replaced the collagen matrix. In series 1, the collagen implant was replaced mainly by connective tissue ingrown with occasional solitary smooth muscle cells. In series 2, the newly formed bladder wall contained numerous smooth muscle cells, growing into the collagen matrix and forming the muscular coat. In series 3, the muscular layer regeneration at the scar site was also noted, but it was less intense, which was confirmed by morphometry. In series 2, more active vascularization of the collagen implant occurred due to neo-angiogenesis, which was more intense than that in series 3, and especially in series 1. Functional studies revealed a reduced bladder functional capacity in series 1 and 3, while in series 2 it was close to normal. During filling cystometry, changes in intra-vesical pressure profile in series 2 were close to normal, while in series 1 and 3 infusion of a small volume of saline resulted in a marked increase in intra-vesical pressure, showing a reduced compliance of the reconstructed bladder. Discussion The study findings show that implants based on type I collagen can be effectively used to substitute a part of the urinary bladder wall, but bio-engineered collagen matrix grafts containing cell regeneration stimulants secreted by stem cells in their culture medium seem to be more promising.

[UROKINASE SYSTEM INVOLVES IN VASCULAR CELLS MIGRATION AND REGULATES THE GROWTH AND BRANCHING OF CAPILLARIES].

Urokinase system representing urokinase-type plasminogen activator (urokinase, uPA) and urokinase re- ceptor (uPAR) plays an important regulatory role in the vascular wall and has the ability to run a proteolytic cascade, degradation of extracellular matrix and activate intracellular signaling in vascular cells. In this work, we have firstly shown a fundamental mechanism of urokinase system-dependent regulation of the trajectory of growth and branching of blood vessels what may be of particular importance in the growth of blood vessels in early embryogenesis and in adults during the repair/regeneration of tissues.

[Therapeutic Angiogenesis Using Growth Factors: Current State and Prospects for Development].

Therapeutic angiogenesis has been in use for treatment of ischemic diseases for about 15 years. During this period of successes and failures this field has accumulated a significant amount of published and ongoing surveys giving insights and raising new questions and problems. One of the most utilized methods for therapeutic angiogenesis suggests introduction of angiogenic growth factors (VEGF, bFGF, angiopoietin-1 etc.) into ischemic tissues. Still, there is a whole range of problems regarding the efficacy of therapeutic angiogenesis. These can be potentially circumvented by use of new delivery methods, development of combined approaches and use of more relevant pre-clinical animal models. Present review gives a brief analysis of crucial achievements and issues that has been recently raised in experimental and clinical studies focusing on therapeutic angiogenesis. Final part brings some possible directions for development that can give an opportunity to circumvent current obstacles and provide further development.

[Recombinant human alpha-fetoprotein as a regulator of adipose tissue stromal cell activity].

Recombinant human alpha-fetoprotein (rhAFP) expressed in yeast system as a glycoprotein, was isolated and purified to 98% by multistep method. The testing of the rhAFP in the culture of adipose tissue stromal cells (hASC) has revealed its ability to enhance hASC proliferation and migration as well as vascular endothelial growth factor production, with no significant influence on cell invasion and matrix metalloproteinase-2 and -9 secretion. It has been also estimated that rhAFP is internalized in hASC via clathrin-dependent mechanism. A study in the murine experimental model of hindlimb ischemia has shown the capability of rhAFP to enhance blood flow recovery. These data suggest that rhAFP is a promising agent for enhancement of the hASC regenerative ability.

European Biomedical Research Infrastructures and the Fight against COVID-19 Pandemic.

The study aims to assess the role of EU biomedical research infrastructures in the fight against the COVID-19 pandemic and to analyze their response to the challenges associated with the spread of the new pathogen. Materials and Methods: We analyzed the materials of the Seventh Framework Program for Research and Technological Development (FP7, 2007-2013) of the EU and the Eighth Framework Program "Horizon 2020" (FP8, 2014-2020), official reports of the European Strategic Forum on Research Infrastructures, expert reports, as well as documents of the European Commission, the COVID-19 Data Portal, and other relevant sources of information. Results: The analysis revealed that the mechanisms created within the united European research community provided for a flexible response to the emerging threat of COVID-19 as soon as January-May 2020. In particular, information channels were established to timely analyze the research results and coordinate the efforts in the fight against COVID-19. The biomedical infrastructures created in the EU and proved successful earlier have now been mobilized to search for ways of preventing and treating COVID-19. These mechanisms facilitated communication and data exchange between various research institutions and thus laid the ground for new achievements in this area. Conclusion: The decisions taken to combat the COVID-19 pandemic have convincingly illustrated that the EU research infrastructures, integrated into a united ecosystem, are highly adaptable and flexible, which allows to realign priorities in a short time and to create instruments that enable scientists to respond to new challenges.

[Influence of polymorphism's of endothelial nitric oxide synthase gene and polymorphism of NADPH oxidase gene on development of complications of arterial hypertension].

The aim of the study was to analyze the prevalence of polymorphism Glu298Asp of endothelial nitric oxide synthase gene and C242T p22 phox polymorphism of NADPH oxidase gene in patients with arterial hypertension (AH) and their influence on AH complications. The study included 272 AH patients, average age 50,7 years. The following analyses were performed: clinical analysis of the blood, general analysis of the urine, lipid spectrum, plasma electrolytes, creatinine, glucose, electrocardiography, echocardioscopy, examination of eye vessels, ultrasound examination of the carotid arteries, determination of microalbuminuria. The polymorphism Glu298Asp of endothelial nitric oxide synthase gene and C242T p22 phox polymorphism of NADPH oxidase gene were detected with two methods: polymerase chain reaction and restrictase reaction. The control group for Glu298Asp polymorphism detection included 102 healthy Russian donors aged 18 to 50 years. Genotypes prevalence in AH patients was as follows: GG 58,8%, GA 32,3%, AA 8,9%, and CC 48,2%, CT 44,9%, TT 6.9%. In the control group: GG 53%, GA 36%, AA 11% and CC 42%, CT 54%, TT 4%. These polymorphisms did not affect the incidence of complications, such as obliterating atherosclerosis of the lower extremity vessels, ischemic heart disease, and acute insufficiency of cerebral circulation, chronic heart failure, left ventricular hypertrophy, microalbuminuria, carotid arteries atherosclerosis.

Plasmid-based gene therapy with hepatocyte growth factor stimulates peripheral nerve regeneration after traumatic injury.

Peripheral nerve injury remains a common clinical problem with no satisfactory treatment options. Numerous studies have shown that hepatocyte growth factor (HGF) exerts neurotrophic effect in motor, sensory, and parasympathetic neurons in addition to mitogenic, morphogenic, angiogenic, antiapoptotic, antifibrotic, and anti-inflammatory effect on various tissues and cells. In our study we examined efficacy of gene therapy with HGF-bearing plasmid (pC4W-hHGF) to improve consequences of traumatic nerve injury in mice. Treatment by pC4W-hHGF led to restoration of nerve structure and functional recovery compared to similar parameters in control animals. Compound action potentials (CAP) in experimental groups treated with 100 or 200 µg of pC4W-hHGF demonstrated increased amplitude and latency decrease compared to spontaneous recovery control group. In HGF-treated mice histological analysis showed a three-fold increase in axon number in nerve portion located distal to the lesion site compared to control. Moreover, significant functional recovery of n. peroneus communis triggered by pC4W-hHGF gene therapy was observed using the footprints analysis. Obtained results provide evidence for plasmid-based HGF gene therapy as a potential treatment for traumatic injury of peripheral nerve.