Impact of REDV peptide density and its linker structure on the capture, movement, and adhesion of flowing endothelial progenitor cells in microfluidic devices.

Ligand-immobilization to stents and vascular grafts is expected to promote endothelialization by capturing flowing endothelial progenitor cells (EPCs). However, the optimized ligand density and linker structure have not been fully elucidated. Here, we report that flowing EPCs were selectively captured by the REDV peptide conjugated with a short linker. The microchannel surface was modified with the REDV peptide via Gly-Gly-Gly (G3), (Gly-Gly-Gly)3 (G9), and diethylene glycol (diEG) linkers, and the moving velocity and captured ratio were evaluated. On the unmodified microchannels, the moving velocity of the cells exhibited a unimodal distribution similar to the liquid flow. The velocity of the endothelial cells and EPCs on the peptide-immobilized surface indicated a bimodal distribution, and approximately 20 to 30% of cells moved slower than the liquid flow, suggesting that the cells were captured and rolled on the surface. When the immobilized ligand density was lower than 1 molecule/nm2, selective cell capture was observed only in REDV with G3 and diEG linkers, but not in G9 linkers. An in silico study revealed that the G9 linker tends to form a bent structure, and the REDV peptide is oriented to the substrate side. These results indicated that REDV captured the flowing EPC in a sequence-specific manner, and that the short linker was more adequate.

Enhanced ß2-microglobulin binding of a "navigator" molecule bearing a single-chain variable fragment antibody for artificial switching of metabolic processing pathways.

Kidney dysfunction increases the blood levels of ß2-microglobulin (ß2-m), triggering dialysis-related amyloidosis. Previously, we developed a navigator molecule, consisting of a fusion protein of the N-terminal domain of apolipoprotein E (ApoE NTD) and the α3 domain of the major histocompatibility complex class I (MHC α3), for switching the metabolic processing pathway of ß2-m from the kidneys to the liver. However, the ß2-m binding of ApoE NTD-MHC α3 was impaired in the blood. In the current study, we replaced the ß2-m binding part of the navigator protein (MHC α3) with an anti-ß2-m single-chain variable fragment (scFv) antibody. The resultant ApoE NTD-scFv exhibited better ß2-m binding than ApoE NTD-MHC α3 in buffer, and even in serum. Similar to ApoE NTD-MHC α3, in the mice model ApoE NTD-scFv bound to the liver cells' surfaces in vitro and accumulated mainly in the liver, when complexed with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Both ApoE NTD-MHC α3 + DMPC and ApoE NTD-scFv + DMPC significantly switched the ß2-m accumulation in mice from the kidneys to the liver, but only the ApoE NTD-scFv + DMPC group showed a significantly higher ratio of ß2-m accumulation in the liver versus the kidneys, compared with the control group. These results suggest that the enhanced ß2-m binding activity of the navigator molecule increased the efficiency of switching the metabolic processing pathway of the etiologic factor.

Label-Free Separation of Induced Pluripotent Stem Cells with Anti-SSEA-1 Antibody Immobilized Microfluidic Channel.

When induced pluripotent stem cells (iPSCs) are routinely cultured, the obtained cells are a heterogeneous mixture, including feeder cells and partially differentiated cells. Therefore, a purification process is required to use them in a clinical stage. We described a label-free separation of iPSCs using a microfluidic channel. Antibodies against stage-specific embryonic antigen 1 (SSEA-1) was covalently immobilized on the channel coated with a phospholipid polymer. After injection of the heterogeneous cell suspension containing iPSCs, the velocity of cell movement under a liquid flow condition was measured. The mean velocity of the cell movement was 2.1 mm/sec in the unmodified channel, while that in the channel with the immobilized-antibody was 0.4 mm/sec. The eluted cells were fractionated by eluting time. As a result, the SSEA-1 positive iPSCs were mainly contained in later fractions, and the proportion of iPSCs was increased from 43% to 82% as a comparison with the initial cell suspension. These results indicated that iPSCs were selectively separated by the microfluidic channel. This channel is a promising device for label-free separation of iPSCs based on their pluripotent state.

Individual evaluation of cardiac marker expression and self-beating during cardiac differentiation of P19CL6 cells on different culture substrates.

Cell-based therapies using self-beating cardiomyocytes have been attracting great attention for use in cardiac regeneration, although an effective procedure to improve cardiac differentiation and self-beating induction is required. The purpose of this study is to clarify the effect of the culture substrate on cardiac maturation by separately evaluating the cardiac differentiation step and the beating induction step in vitro. To this end, the well-studied cardiomyocyte-like progenitor cell line P19CL6 and neonatal cardiomyocytes (NCMs) were selected and cultured on substrates coated with collagen type I (Col-I), gelatin (Gel), fibronectin (FN), or poly-l-lysine (PLL). It was found that the cardiac differentiation step, which was assessed using cardiac marker gene expression (GATA-binding protein 4 (GATA4), myocyte-specific enhancer factor 2D (MEF2D), and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4)) in the P19CL6 embryonal carcinoma cells, was greatly enhanced on Col-I, Gel, and PLL. In contrast, the spontaneous beating step, which was directly assessed by counting the beating colonies and measuring contractile protein gene expression (α-myosin heavy chain (α-MHC), troponin C type 1 (TnC1), and troponin T type 2 (TnT2)) in the rat NCMs, was enhanced on the FN and PLL surfaces. In the present study, for the first time, it was found that PLL enhances both the cardiac differentiation and the beating induction steps of cardiac maturation, which can aid in preparing beating cardiomyocytes for regenerative medicine. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1166-1174, 2017.