Micropatterned porous membranes for combinatorial cell-based assays.

Here, we describe a protocol for producing micropatterned porous membranes which can be used for combinatorial cell-based assays. We use contact printing to pattern the surface of a porous filter membrane with a thin layer of polydimethylsiloxane (PDMS). This allows the porosity of the filter membrane to be altered at selected locations.

Micro-patterned porous substrates for cell-based assays.

In the search for new therapeutic chemicals, lab-on-a-chip systems have recently emerged as innovative and efficient tools for cell-based assays and high throughput screening. Here, we describe a novel, versatile and simple device for cell-based assays at the bench-top. We created spatial variations of porosity on the surface of a membrane filter by microcontact printing with a biocompatible polymer (PDMS).

Gas-permeable membranes and co-culture with fibroblasts enable high-density hepatocyte culture as multilayered liver tissues.

To engineer reliable in vitro liver tissue equivalents expressing differentiated hepatic functions at a high level and over a long period of time, it appears necessary to have liver cells organized into a three-dimensional (3D) multicellular structure closely resembling in vivo liver cytoarchitecture and promoting both homotypic and heterotypic cell-cell contacts. In addition, such high density 3D hepatocyte cultures should be adequately supplied with nutrients and particularly with oxygen since it is one of the most limiting nutrients in hepatocyte cultures. Here we propose a novel but simple hepatocyte culture system in a microplate-based format, enabling high density hepatocyte culture as a stable 3D-multilayer.

Microfibrillated cellulose sheets coating oxygen-permeable PDMS membranes induce rat hepatocytes 3D aggregation into stably-attached 3D hemispheroids.

Here we report the use of natural, chemically-unmodified, microfibrillated cellulose (MFC) as a matrix for hepatocyte culture. We developed an original cell-culture design composed of a thin 3D-microstructured fibrous substrate consisting of a MFC sheet coating a highly O(2)-permeable polydimethylsiloxane (PDMS) membrane. The MFC-coated PDMS membranes were obtained according to a simple process where cellulose fibres were deposited from an aqueous suspension on the PDMS surfaces and the films were dried under mild conditions.

Spontaneous formation of stably-attached and 3D-organized hepatocyte aggregates on oxygen-permeable polydimethylsiloxane membranes having 3D microstructures.

In order to enhance the viability and the differentiated functions of primary hepatocytes in cultures, it appears important to have them organized within a three-dimensional (3D) structure which promotes extensive cell-cell contacts, but also to be adequately supplied with oxygen. Here, we report a simple methodology satisfying these two fundamental but sometimes conflicting issues: primary rat hepatocytes were cultured on polydimethylsiloxane (PDMS) membranes with 3D-pillared microstructures with various dimensions, so that the cells could organize themselves around the pillars into various kinds of 3D multicellular aggregates, while being continuously supplied with oxygen by diffusion through the PDMS membrane. As expected, under such conditions, hepatocyte cultures exhibited higher albumin secretion and urea synthesis rates.

Spontaneous formation of highly functional three-dimensional multilayer from human hepatoma Hep G2 cells cultured on an oxygen-permeable polydimethylsiloxane membrane.

When considering high-density liver cell cultures, adequate delivery of oxygen to the cells appears particularly crucial since it is one of the most limiting parameters of hepatocytes' functions. Here we report on the effects of direct oxygenation through a gas-permeable polydimethylsiloxane membrane on liver-derived cell culture. We used highly proliferative human hepatoma Hep G2 cells to assess the growth-related limitation of such direct oxygen supply.

Vitamin A/retinoids signalling in the human lung.

Vitamin A is used as a generic term for all vitamin A derivatives with retinol-like biological activity. Retinol is the main parent compound for vitamin A. It derives from carotenoids (provitamin A) and also directly from the pre-formed vitamin A contained in the diet.