A P19 and P19CL6 cell-based complementary approach to determine paracrine effects in cardiac tissue engineering.

The negligible self-repair potential of the myocardium has led to cell-based tissue engineering approaches to restore heart function. There is more and more consensus that, in addition to cell development, paracrine effects in particular play a pivotal role in the repair of heart tissue. Here, we present two complementary murine P19 and P19CL6 embryonic carcinoma cell-based in vitro test approaches to study the potential of repair cells and the factors secreted by these cells to induce cardiomyogenesis. P19 cells were 3-dimensionally cultured in hanging drops and P19CL6 cells in a monolayer. Both systems, capable of inducible differentiation towards the cardiomyogenic lineage shown by the appearance of beating cells, the expression of connexin 43 and cardiac troponins T and I, were used to test the cardiomyogenesis-inducing potential of human cardiac-derived adherent proliferating (CardAP) cells, which are candidates for heart repair. CardAP cells in coculture as well as CardAP cell-conditioned medium initiated beating in P19 cells, depending on the cell composition and concentration of the medium. CardAP cell-dependent beating was not observed in P19CL6 cultures, but connexin 43 and cardiac troponin formation as well as expression of GATA-binding protein 4 indicated the dose-dependent stimulatory cardiomyogenic effect of human CardAP cells. In summary, in different ways, P19 and P19CL6 cells have shown their capability to detect paracrine effects of human CardAP cells. In a complementary approach, they could be beneficial for determining the stimulatory cardiomyogenic potential of candidate cardiac-repair cells in vitro.

N-truncation and pyroglutaminylation enhances the opsonizing capacity of Aß-peptides and facilitates phagocytosis by macrophages and microglia.

Abnormal accumulations of amyloid-ß (Aß)-peptides are one of the pathological hallmarks of Alzheimer's disease (AD). The precursor of the Aß-peptides, the amyloid precursor protein (APP), is also found in peripheral blood cells, but its function in these cells remains elusive. We previously observed that mononuclear phagocytes release Aß-peptides during activation and phagocytosis, suggesting a physiologic role in inflammatory processes. Here, we show that supplementing the media with soluble N-terminally truncated Aß(2-40) and Aß(2-42) as well as Aß(1-42) induced the phagocytosis of polystyrene particles (PSPs) by primary human monocytes. If the PSPs were pre-incubated with Aß-peptides, phagocytosis was induced by all tested Aß-peptide species. N-terminally truncated Aß(x-42) induced the phagocytosis of PSPs significantly more effectively than did Aß(x-40). Similarly, the phagocytosis of Escherichia coli by GM-CSF- and M-CSF-elicited macrophages as well as microglia was particularly facilitated by pre-incubation with N-terminally truncated Aß(x-42). The proinflammatory polarization of monocytes was indicated by the reduced MSRI expression and IL-10 secretion after phagocytosis of PSPs coated with Aß(1-42), Aß(2-42) and Aß(3p-42). Polarization of the macrophages by GM-CSF reduced the phagocytic activity, but it did not affect the capabilities of Aß-peptides to opsonize prey. Taken together, Aß-peptides support phagocytosis as soluble factors and act as opsonins. Differential effects among the Aß-peptide variants point to distinct mechanisms of interaction among monocytes/macrophages, prey and Aß-peptides. A proinflammatory polarization induced by the phagocytosis of Aß-peptide coated particles may provide a model for the chronic inflammatory reaction and sustained plaque deposition in AD.