Many works focus on the use of polyesters like poly(lactic acid) (PLA) to produce nanofibrous scaffolds for cardiac tissue engineering. However, such scaffolds are hydrophobic and difficult to functionalize. Here, we show that adding 30% of poly(glycerol sebacate) (PGS) elastomer within PLA leads to PLA:PGS scaffolds with improved biological properties, depending on the processing parameters. Two categories of fibers were produced by blend electrospinning, with diameters of 600 and 1300 nm. The resulting fibers were cured at 90°C or 120°C in order to achieve two different crosslinking densities. The designed scaffolds were considered for cytocompatibility, biocompatibility, biodegradability, chemical and mechanical properties. Our results demonstrated that the presence of PGS increases the hydrophilicity of the material and thus improves surface functionalization by Matrigel and laminin coating, a commonly used cell culture matrix. PLA:PGS scaffolds associated with Matrigel and laminin allow an increased material-cell interaction. Moreover, the cardiomyocytes seeded on such scaffolds acquire a morphology similar to that observed in native tissue, this result being more remarkable on fibers having the smallest diameter and the highest PGS crosslinking density. In addition, these scaffolds induce neovascularization without inflammatory response and foreign body giant cell response after grafting on mice's heart. Hence, the improved biocompatibility and the ability to support cardiomyocytes development suggest that thin PLA:PGS scaffolds could be promising biomaterials for cardiac application.

We examined the relationship between somatic Ca 2ϩ signals and spiking activity of cerebellar molecular layer interneurons (MLIs) in adult mice. Using two-photon microscopy in conjunction with cell-attached recordings in slices, we show that in tonically firing MLIs loaded with high-affinity Ca 2ϩ probes, Ca 2ϩ -dependent fluorescence transients are absent. Spike-triggered averages of fluorescence traces for MLIs spiking at low rates revealed that the fluorescence change associated with an action potential is small (1% of the basal fluorescence ] i is not a direct readout of the firing activity, but rather reflects the time integral of this activity. MATERIALS AND METHODSAll experimental procedures were designed in accordance with the animal care guidelines of our host institution, which have been approved by the "Prefecture de Police" (approval number A-750607) following inspection by Veterinary Services of the City of Paris and by representatives of the French Ministry of Research and the Ministry for Health, in agreement with European Directive 86/609/EEC regarding the protection of animals used for experimental and other scientific purposes. In Vitro Patch-Clamp Recording and ImagingSlice preparation. Sagittal cerebellar slices (200 m thick) were prepared from C57BL/6J mice and from PVϪ/Ϫ mice. The PVϪ/Ϫ animals are congenic with C57BL/6J, after 10 matings of heterozygous (PVϩ/Ϫ) mice with wild-type C57BL/6J animals (Moreno et al 2011). Mice aged 22-33 days were decapitated after cervical dislocation. Slices were cut at 4°C in a saline solution of the following composition (in mM): 87 NaCl, 2.5 KCl, 1.25 NaH 2 PO 4 , 25 NaHCO 3 ,