31 research outputs found
Engineered Heart Tissue: A Novel Tool to Study the Ischemic Changes of the Heart In Vitro
Background: Understanding the basic mechanisms and prevention of any disease pattern lies mainly on development of a successful experimental model. Recently, engineered heart tissue (EHT) has been demonstrated to be a useful tool in experimental transplantation. Here, we demonstrate a novel function for the spontaneously contracting EHT as an experimental model in studying the acute ischemia-induced changes in vitro. Methodology/Principal Findings: EHT was constructed by mixing cardiomyocytes isolated from the neonatal rats and cultured in a ring-shaped scaffold for five days. This was followed by mechanical stretching of the EHT for another one week under incubation. Fully developed EHT was subjected to hypoxia with 1 % O2 for 6 hours after treating them with cell protective agents such as cyclosporine A (CsA) and acetylcholine (ACh). During culture, EHT started to show spontaneous contractions that became more synchronous following mechanical stretching. This was confirmed by the increased expression of gap junctional protein connexin 43 and improved action potential recordings using an optical mapping system after mechanical stretching. When subjected to hypoxia, EHT demonstrated conduction defects, dephosphorylation of connexin-43, and down-regulation of cell survival proteins identical to the adult heart. These effects were inhibited by treating the EHT with cell protective agents. Conclusions/Significance: Under hypoxic conditions, the EHT responds similarly to the adult myocardium, thus making EHT a promising material for the study of cardiac functions in vitro
Perivascular-like cells contribute to the stability of the vascular network of osteogenic tissue formed from cell sheet-based constructs
In recent years several studies have been supporting the existence of a close relationship in terms of function and progeny
between Mesenchymal Stem Cells (MSCs) and Pericytes. This concept has opened new perspectives for the application of
MSCs in Tissue Engineering (TE), with special interest for the pre-vascularization of cell dense constructs. In this work, cell
sheet technology was used to create a scaffold-free construct composed of osteogenic, endothelial and perivascular-like
(CD146+) cells for improved in vivo vessel formation, maturation and stability. The CD146 pericyte-associated phenotype
was induced from human bone marrow mesenchymal stem cells (hBMSCs) by the supplementation of standard culture
medium with TGF-b1. Co-cultured cell sheets were obtained by culturing perivascular-like (CD146+) cells and human
umbilical vein endothelial cells (HUVECs) on an hBMSCs monolayer maintained in osteogenic medium for 7 days. The
perivascular-like (CD146+) cells and the HUVECs migrated and organized over the collagen-rich osteogenic cell sheet,
suggesting the existence of cross-talk involving the co-cultured cell types. Furthermore the presence of that particular ECM
produced by the osteoblastic cells was shown to be the key regulator for the singular observed organization. The
osteogenic and angiogenic character of the proposed constructs was assessed in vivo. Immunohistochemistry analysis of
the explants revealed the integration of HUVECs with the host vasculature as well as the osteogenic potential of the created
construct, by the expression of osteocalcin. Additionally, the analysis of the diameter of human CD146 positive blood
vessels showed a higher mean vessel diameter for the co-cultured cell sheet condition, reinforcing the advantage of the
proposed model regarding blood vessels maturation and stability and for the in vitro pre-vascularization of TE constructs.Funding provided by Fundacao para a Ciencia e a Tecnologia project Skingineering (PTDC/SAU-OSM/099422/2008). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Biofabrication: an overview of the approaches used for printing of living cells
The development of cell printing is vital for establishing biofabrication approaches as clinically relevant tools. Achieving this requires bio-inks which must not only be easily printable, but also allow controllable and reproducible printing of cells. This review outlines the general principles and current progress and compares the advantages and challenges for the most widely used biofabrication techniques for printing cells: extrusion, laser, microvalve, inkjet and tissue fragment printing. It is expected that significant advances in cell printing will result from synergistic combinations of these techniques and lead to optimised resolution, throughput and the overall complexity of printed constructs
Effect of reactive and nonreactive surface modifications and compatibilizer use on mechanical and flame-retardant properties of linear low-density polyethylene filled with huntite and hydromagnesite mineral
In the current study, huntite and hydromagnesite (HH) was used as
flame-retardant additive in linear low-density polyethylene (LLDPE). The
effect of HH amount on the flame-retardant and mechanical properties of
the composites was investigated. The compatibilizer (ethylene butyl
acrylate) use and the surface modifications with stearic acid and silane
coupling agent were used in order to improve the mechanical properties
of the composites. The mechanical properties of the composites were
studied using tensile test and dynamic mechanical analysis. The
fire-retardant properties of the composites were investigated using
limiting oxygen index (LOI), mass loss calorimeter, vertical (UL 94V)
and horizontal (UL 94 HB) burning tests. According to the flammability
test results, LOI value increased, horizontal burning rate reduced as
the added amount of HH increased, whereas UL 94V rating remained burn to
clamp. According to the mechanical test results, the addition of HH
reduced the tensile strength and elongation at break values and
increased the elastic modulus and the transition temperature of the
LLDPE as the added amount increased. Only the compatibilizer use
improved the flammability properties of the composites with improved
tensile strength. Both stearic acid and silane modification merely
increased the toughness of the composites