Advances in the construction of a scaffold for cardiac tissue engineering containing homogeneous and stable carbon nanotubes / 中国组织工程研究

BACKGROUND: How to efficiently and uniformly disperse carbon nanotubes (CNTs) into a tissue-engineered scaffold is crucial to construct an ideal CNTs-Polymer composite scaffold and it is also a hotspot of research in the tissue engineering. OBJECTIVE: To review the advances in the methodology progress of constructing a scaffold for cardiac tissue engineering, which contains uniformly and stably dispersed CNTs. METHODS: The Web of Science Core Collection and PubMed were searched by the first author for related papers about CNTs dispersion in the cardiac tissue engineering published from October 2004 to January 2017. The key words were "carbon nanotubes, dispersion, cardiac tissue engineering" in English. Original research papers were searched, which were screened through titles, abstracts and contents, and then reviewed. RESULTS AND CONCLUSION: CNTs are easy to aggregate because of high surface area, high aspect ratio and rough surface. Thus, it is one of the key points to construct an ideal CNTs-Polymer composite scaffold that whether CNTs could be uniformly and stably dispersed in polymer scaffolds. In the cardiac tissue engineering, covalent or non-covalent surface modification of CNTs significantly enhances the uniformity and stability of CNTs in the polymer scaffolds, which is conducive to construct the uniformly and stably CNTs-dispersed scaffold for cardiac tissue engineering, leading to notable improvement in mechanical and electrical properties of engineered cardiac tissues.

Progress on PI3K/Akt signaling pathway regulating self-renewal and pluripotency of embryonic stem cells / 生理学报

The phosphatidylinositol 3-kinase (PI3K) and its downstream target protein kinase B (Akt/PKB) can be activated by a variety of extracellular and intracellular signals. They are important signaling molecules and key survival factors involved in cell proliferation, differentiation, apoptosis and other cellular processes. Recently, many reports demonstrate that type I PI3K/Akt signaling pathway plays an important role in maintenance of self-renewal and pluripotency of embryonic stem (ES) cells. Further studies with regard to the self-renewal and pluripotency of ES cells and underlying molecular mechanisms are crucial to its application in cell replacement therapy, regenerative medicine and tissue engineering. The present review focuses on the recent progress on the mediation of PI3K/Akt signaling pathway on the maintenance of self-renewal and pluripotency of ES cells.

Acquirement and evaluation of murine ventricular extracellular matrix / 生理学报

Cardiac extracellular matrix (ECM), generated from the process of decellularization, has been widely considered as an ideal source of biological scaffolds. However, current ECM preparations are generally difficult to be applied to generate cardiac tissue. Our research was aimed to improve decellularization protocols to prepare cardiac ECM slices. Adult murine ventricular tissues were embedded in low melting agarose and cut into 300 μm slices, and then were divided randomly into three groups: normal cardiac tissue, SDS treated group (0.1% SDS) and SDS+Triton X-100 treated group (0.1% SDS+0.5% Triton X-100). Total RNA content and protein content quantification, HE staining and immunostaining were used to evaluate the removal of cell components and preservation of vital ECM components. Furthermore, murine embryonic stem cell-derived cardiomyocytes (mES-CMs) and mouse embryonic fibroblasts (MEFs) were co-cultured with ECM slices to evaluate biocompatibility. The relative residual RNA and protein contents of ECM slices significantly decreased after decellularization. HE staining showed that SDS+Triton X-100 treatment better destroyed cellular structure and removed nuclei of ECM slices, compared with SDS treatment. Immunostaining showed that collagen IV and laminin were better preserved and presented better similarity to original cardiac tissue in ECM slices acquired by SDS+Triton X-100 treatment. However, collagen IV and laminin were significantly decreased and arranged disorderly in SDS treated group. We observed effective survival (≥ 12 days) of MEFs and mES-CMs on ECM slices acquired by SDS+Triton X-100 treatment, and signs of integration, whereas those signs were not found in SDS treated group. We concluded that, compared with traditional SDS method, new combined protocol (SDS+Triton X-100) generated ECM slices with better component and structural preservation, as well as better biocompatibility.

Different signal molecules involved in the muscarinic modulation of pacemaker current I(f) on the heart of mouse embryo in different developmental stages / 生理学报

We isolated mouse embryonic cardiomyocytes derived from timed-pregnant females at different periods and used patch-clamp technique to investigate the muscarinic cholinergic modulation of pacemaker current I(f) in different developmental stages. In early development stage (EDS), muscarinic agonist carbachol (CCh) significantly decreased the magnitude of the pacemaker current I(f) but had no effect in late development stage (LDS). Forskolin (a direct adenylate cyclase activator) and IBMX (a non-selective phosphodiesterase inhibitor) increased I(f) in both EDS and LDS cells. Interestingly, although both forskolin and IBMX increased basal I(f), their effects on CCh-inhibited I(f) were different. Forskolin did not reverse the inhibitory action of CCh until intermediate development stage (IDS). In contrast, IBMX reversed the inhibitory action of CCh on I(f) in EDS but not in IDS. It is suggested that a decrease in intracellular cAMP is a possible mechanism for CCh to modulate I(f). During the EDS and IDS CCh controls the cytoplasmic cAMP level by different pathways: In EDS, CCh modulates I(f) possibly by activating PDE which accelerates the breakdown of cAMP, but in IDS possibly by inhibiting adenylate cyclase (AC) which then reduces the synthesis of cAMP.

Chronic intermittent hypoxia decreases acute hypoxic inhibition of voltage-gated potassium channel in rat pulmonary arterial smooth muscle cells / 生理学报

For determination the ionic mechanisms of the hypoxic acclimatization at the level of channels, male Spradue-Dawley rats were divided into two groups: control normoxic group and chronic intermittent hypoxic group [O2 concentration: (10 +/-0.5)%, hypoxia 8 h a day]. Using whole cell patch-clamp technique, voltage-gated potassium channel currents (IK(V)) were recorded in freshly isolated pulmonary arterial smooth muscle cells (PASMCs) of rat with acute isolated method. The effect of acute hypoxia on IK(V) of PASMCs from chronic intermittent hypoxia group was investigated to offer some basic data for clarifying the ionic mechanisms of the hypoxic acclimatization. The results showed: (1) In control normoxic group, after acute hypoxia free-Ca(2+) solution, the resting membrane potential (Em) of PASMCs was depolarized significantly from -47.2+/-2.6 mV to -26.7+/-1.2 mV, and the IK(V) of PASMCs was decreased significantly from 153.4+/-9.5 pA/pF to 70.1+/-0.6 pA/pF, the peak current percent inhibition was up to (57.6+/-3.3)% at +60 mV, and current-voltage relationship curve shifted to the right. (2) In chronic intermittent hypoxic group, the IK(V) of PASMCs was decreased significantly by exposure to intermittent hypoxia in a time-dependent manner, appeared to start on day 10 and continued to day 30 (the longest time tested) of hypoxia, and current-voltage relationship curve shifted to the right in a time-dependent manner. (3) Compared with the control normoxic group, the percent IK(V) inhibition by acute hypoxia was significantly attenuated in the chronic intermittent hypoxia group and this inhibition effect declined with time exposure to hypoxia. The results suggest that K(V) inhibition was significantly attenuated by chronic intermittent hypoxia, and this effect may be a critical mechanism of the body hypoxic acclimatization.