Plasticity of Human THP-1 Cell Phagocytic Activity during Macrophagic Differentiation.

Studies of the role of macrophages in phagocytosis are of great theoretical and practical importance for understanding how these cells are involved in the organism's defense response and in the development of various pathologies. Here we investigated phagocytic plasticity of THP-1 (acute monocytic human leukemia) cells at different stages (days 1, 3, and 7) of phorbol ester (PMA)-induced macrophage differentiation. Analysis of cytokine profiles showed that PMA at a concentration of 100 nM induced development of the proinflammatory macrophage population. The functional activity of macrophages was assessed on days 3 and 7 of differentiation using unlabeled latex beads and latex beads conjugated with ligands (gelatin, mannan, and IgG Fc fragment) that bind to the corresponding specific receptors. The general phagocytic activity increased significantly (1.5-2.0-fold) in the course of differentiation; phagocytosis occurred mostly through the Fc receptors, as shown previously for M1 macrophages. On day 7, the levels of phagocytosis of gelatin- and Fc-covered beads were high; however, the intensity of ingestion of mannan-conjugated beads via mannose receptors increased 2.5-3.0-fold as well, which indicated formation of cells with an alternative phenotype similar to that of M2 macrophages. Thus, the type and the plasticity of phagocytic activity at certain stages of macrophage differentiation can be associated with the formation of functionally mature morphological phenotype. This allows macrophages to exhibit their phagocytic potential in response to specific ligands. These data are of fundamental importance and can be used to develop therapeutic methods for correcting the M1/M2 macrophage ratio in an organism.

[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.