Summary. Local progenitor cells are present in all tissues, including the myocardium. Stimulation of these cells can significantly improve the efficiency of the regeneration process. Biodegradation products of Alloplant biomaterials (ABM) are an inhibitor of fibrosis and serve as an inducer of stem cells in various body tissues including smooth and skeletal muscles, as well as connective tissue.Aim. To determine the cell regenerative potential of progenitorial c-kit and committed GATA-4 cells in ischemic myocardium on the background of ABM application in chronic experiment.Materials and methods. 100 Wistar rats weighing 180-200g were used, that underwent ligation of coronary artery. In the experimental group (n = 50), 600 μl of a physiological solution containing 12 mg of ABM was administered simultaneously with coronary occlusion. General histological studies (hematoxylin and eosin staining, and staining as per Mallory), immunohistochemical (c-kit, GATA-4) and morphometric studies (determination of the index of the scar's area, counting of stained cells) were carried out. The statistical processing of the results was carried out using the rank methods - single factor dispersion analysis as per Kruskalou-Wallace and the comparison of uncorrelated data by the Mann-Whitney method.Results. When using ABM during coronary occlusion, myocardium was characterized by a statistically significant (p <0.0001) prevalence of c-kit⁺ / GATA-4⁺ cells numbers throughout the follow-up period (3-45 days). These cells were localized mainly in the granulation tissue of the peri-cicatricial area, bordering on the preserved cardiac muscle tissue. In the peri-cicatricial area, cardiac cells had a different degree of maturity - from poorly differentiated forms (without clear ultrastructural signs of cardiomyogenic orientation) to young cardiomyocytes. In the presence of ABM, coronary occlusion was characterized by statistically significantly smaller values of the index of the scar's area (p <0,05 ÷ <0,0001).Conclusion. ABM degradation products are chemoattractants for c-kit cells and promote their differentiation into cardiomyogenic GATA-4 cells, which contributes to more successful myocardium repair.

Aim. To assess the expression of ММР-9 and TIMP-2 after intramyocardial injection of the allogenic biomaterial (AB) into ischemized myocardium in rodents.Material and methods.One hundred Wistar rodents were used, who underwent ligation of coronary artery. The experiment group (n=50), together with coronary occlusion, received the suspension of AB 12 mg. General histology was applied: hematoxyline and eosine, by Mallori; immune histochemistry (ММP-9, TIMP-2, CD68); morphometry: index of the scar area (ISA), amount of ММP-9, TIMP-2, CD68-positive cells.Results.It was shown that in the experimental group, after implantation of AB there were lesser than in controls values of ISA (2,74 times, p<0,05 . <0,0001), numbers of MMP9+ cells (p<0,001) and macrophages CD68+ (p<0,05), as the manifestation of proteolysis and area of lesion. On the contrary, amount of Timp-2+ cells in the experimental group was higher than in the control (p<0,0004).Conclusion.Resorption of allogenic material (Alloplant) products does influence the balance of metalloproteinases and their inhibitors in the myocardium after ischemic lesion. This effect might influence the processes of myocardial remodelling and scar formation.

Макрофаги как регуляторы гомеостаза миокарда после его ишемического повреждения в условиях применения аллогенного биоматериала

Injectable allogeneic decellularized biomaterials are being developed both as scaffolds for delivery of cellular products and as independent pharmacological agents that affect the cascade of tissue reactions during the period of post-ischemic myocardial remodeling. Biomaterial degradation products can affect cellular processes and modulate cytokine effects, thus determining the healing strategy of damaged tissue. In this work, the influence of biomaterial on the expression of key fibrogenic factors by the cells of tissue bed was demonstrated, and the degree of damage to the myocardium during its ischemic damage was experimentally determined. The aim of our study was to determine the area of myocardial scar degeneration and detection of key fibrogenic factors (bFGF-1, TGFb1, MMP-9), as well as TIMP-2 (MMP-9 antagonist) at the acute and subacute stages of myocardial infarction after implantation of allogeneic powder-like biomaterial in an experimental model.In the course of experiments, the left ventricular coronary artery was ligated in male Wistar rats (experimental group). All animals were divided into 3 groups: experimental group I (n = 50), experimental group II (n = 50), and controls (n = 50). In experimental group I, the artery ligation was simultaneously accompanied by intramyocardial administration of powder-like biomaterial suspension (2 mg). In experimental group II, the allogeneic powder-like biomaterial was administered 5 days after coronary occlusion, and only physiological saline was administered in the control group. The animals were withdrawn from experiment on days +3, +7, +14, +30, and +45. Standard histological assessment (hematoxylin and eosin staining, according to Mallory) and immunohistochemical examination (MMP-9, TGFb1, bFGF-1, TIMP-2) were made, and statistical evaluation was performed. The cells with positive staining were counted, and the scar area index was calculated.We have found that administration of dispersed allogeneic biomaterial was followed by a five-fold decrease in the degree of scar degeneration in both experimental groups at the acute and subacute stages of ischemic myocardial damage as compared to the control group. A significantly decreased expression of fibrogenic factors (MMP-9, TGFb1, bFGF-1) by the local cells was found, along with increased activity of metalloproteinase inhibitor (TIMP-2) in connective tissue cells.Decellularized allogeneic powder-like biomaterial serves as a fibrosis inhibitor and promotes cardioprotection during myocardial remodeling at the initial stages after ischemic injury.

Introduction. The question of the possibility of recovery of postischemic myocardium remains relevant.Aim. The aim of the study was to study the effect of dispersed decellularized allogeneic extracellular matrix (allogeneic biomaterial, DAB) on the developed fibrous degeneration of the myocardium, as well as to reveal the possible mechanisms of cellular regeneration.Materials and methods. The muscular wall of the heart of rats was subjected to cryodestruction. After 45 days, the rats of the main group were intramyocardially injected with a suspension of allogeneic biomaterialinto the area of the affected myocardium, and the rats of the control group were injected with saline.Results and discussions. In the experimental group, there was a regression of the formed fibrous connective tissue, chemoattraction of progenitor cells, their differentiation and integration into the myocardium. The thickness of the muscular part of the wall of the left ventricle was three orders of magnitude higher than in the control group.Conclusion. Analysis of the results of the study indicates that the heart in adult mammals has a powerful regenerative reserve. It is likely that, based on the use of DAB, a protocol can be developed that allows the restoration of the heart muscle even in conditions of already developed fibrous degeneration.

Aim. To identify the features of myocardial remodeling after implantation of a dispersed allogenic biomaterial (DAB) in the subacute stage of experimental infarction and determine the role of decay products in the formation of regenerate.Material and methods. Male rats in the control group (n=30) 5 days after coronary occlusion received physiological saline (intramyocardially), in the experimental group (n=30) — 3 mg of DAB. Myocardial tissues were examined after 7 14, 50 days from the beginning of the experiment using histological, immunohistochemical and statistical methods.Results. In the experimental group, the cicatrix area was reduced by 1,66 times. The products of DAB biodegradation were collagen, sulfated (dermatan- and keratan sulfate), as well as non-sulfated (hyaluronic acid) glycosaminoglycans. Used DAB served as a promoter of the early proliferative phase of inflammation and had an anti-inflammatory effect. DAB particles were a chemoattractant of stem and progenitor myocardial cells in the subacute stage of myocardial infarction. It contributed to their differentiation and integration into the tissue.Conclusion. The products of biodegradation of allogeneic biomaterial, administered intramyocardially in the subacute stage of infarction, contribute to the formation of muscular-connective tissue regenerate and effectively prevent its cicatricial devolution.