CD34+cells augment endothelial cell differentiation of CD14+endothelial progenitor cells in vitro

Neovascularization by endothelial progenitor cells (EPC) for the treatment of ischaemic diseases has been a topic of intense research. The CD34+ cell is often designated as EPC, because it contributes to repair of ischaemic injuries through neovascularization. However, incorporation of CD34+ cells into the neovasculature is limited, suggesting another role which could be paracrine. CD14+ cells can also differentiate into endothelial cells and contribute to neovascularization. However, the low proliferative capacity of CD14+ cell-derived endothelial cells hampers their use as therapeutic cells. We made the assumption that an interaction between CD34+ and CD14+ cells augments endothelial differentiation of the CD14+ cells. In vitro, the influence of CD34+ cells on the endothelial differentiation capacity of CD14+ cells was investigated. Endothelial differentiation was analysed by expression of endothelial cell markers CD31, CD144, von Willebrand Factor and endothelial Nitric Oxide Synthase. Furthermore, we assessed proliferative capacity and endothelial cell function of the cells in culture. In monocultures, 63% of the CD14+-derived cells adopted an endothelial cell phenotype, whereas in CD34+/CD14+ co-cultures 95% of the cells showed endothelial cell differentiation. Proliferation increased up to 12% in the CD34+/CD14+ co-cultures compared to both monocultures. CD34-conditioned medium also increased endothelial differentiation of CD14+ cells. This effect was abrogated by hepatocyte growth factor neutralizing antibodies, but not by interleukin-8 and monocyte chemoattractant protein-1 neutralizing antibodies. We show that co-culturing of CD34+ and CD14+ cells results in a proliferating population of functional endothelial cells, which may be suitable for treatment of ischaemic diseases such as myocardial infarction

Preparation of Degradable Porous Structures Based on 1,3-Trimethylene Carbonate and D,L-Lactide (Co)polymers for Heart Tissue Engineering

Biodegradable porous scaffolds for heart tissue engineering were prepared from amorphous elastomeric (co)polymers of 1,3-trimethylene carbonate (TMC) and D,L-lactide (DLLA). Leaching of salt from compression-molded polymer-salt composites allowed the preparation of highly porous structures in a reproducible fashion. By adjusting the salt particle size and the polymer-to-particle weight ratio in the polymer-salt composite preparation the pore size and porosity of the scaffolds could be precisely controlled. The thermal properties of the polymers used for scaffold preparation had a strong effect on the morphology, mechanical properties and dimensional stability of the scaffolds under physiological conditions. Interconnected highly porous structures (porosity, 94%; average pore size, 100 μm) based on a TMC-DLLA copolymer (19:81, mol%) had suitable mechanical properties and displayed adequate cell-material interactions to serve as scaffolds for cardiac cells. This copolymer is noncytotoxic and allows the adhesion and proliferation of cardiomyocytes. During incubation in phosphate-buffered saline at 37°C, these scaffolds were dimensionally stable and the number average molecular weight (Mn) of the polymer decreased gradually from 2.0 × 105 to 0.3 × 105 in a period up to 4 months. The first signs of mass loss (5%) were detected after 4 months of incubation. The degradation behavior of the porous structures was similar to that of nonporous films with similar composition and can be described by autocatalyzed bulk hydrolysis