One-Step Fabrication of Porous Membrane-Based Scaffolds by Air-Water Interfacial Phase Separation: Opportunities for Engineered Tissues.

Common methods for fabricating membrane-based scaffolds for tissue engineering with (hydrophobic) polymers include thermal or liquid-phase inversion, sintering, particle leaching, electrospinning and stereolithography. However, these methods have limitations, such as low resolution and pore interconnectivity and may often require the application of high temperatures and/or toxic porogens, additives or solvents. In this work, we aim to overcome some of these limitations and propose a one-step method to produce large porous membrane-based scaffolds formed by air-water interfacial phase separation using water as a pore-forming agent and casting substrate. Here, we provide proof of concept using poly (trimethylene carbonate), a flexible and biocompatible hydrophobic polymer. Membrane-based scaffolds were prepared by dropwise addition of the polymer solution to water. Upon contact, rapid solvent-non-solvent phase separation took place on the air-water interface, after which the scaffold was cured by UV irradiation. We can tune and control the morphology of these scaffolds, including pore size and porosity, by changing various parameters, including polymer concentration, solvent type and temperature. Importantly, human hepatic stellate cells cultured on these membrane-based scaffolds remained viable and showed no signs of pro-inflammatory stress. These results indicate that the proposed air-water interfacial phase separation represents a versatile method for creating porous membrane-based scaffolds for tissue engineering applications.

The horse as a natural model to study reproductive aging-induced aneuploidy and weakened centromeric cohesion in oocytes.

Aneuploidy of meiotic origin is a major contributor to age-related subfertility and an increased risk of miscarriage in women. Although age-related aneuploidy has been studied in rodents, the mare may be a more appropriate animal model to study reproductive aging. Similar to women, aged mares show reduced fertility and an increased incidence of early pregnancy loss; however, it is not known whether aging predisposes to aneuploidy in equine oocytes. We evaluated the effect of advanced mare age on (1) gene expression for cohesin components, (2) incidence of aneuploidy and (3) chromosome centromere cohesion (measured as the distance between sister kinetochores) in oocytes matured in vitro. Oocytes from aged mares showed reduced gene expression for the centromere cohesion stabilizing protein, Shugoshin 1. Moreover, in vitro matured oocytes from aged mares showed a higher incidence of aneuploidy and premature sister chromatid separation, and weakened centromeric cohesion. We therefore propose the mare as a valid model for studying effects of aging on centromeric cohesion; cohesion loss predisposes to disintegration of bivalents and premature separation of sister chromatids during the first meiotic division, leading to embryonic aneuploidy; this probably contributes to the reduced fertility and increased incidence of pregnancy loss observed in aged mares.