Engineered scaffolds for tissue-engineering should be designed to match the stiffness and strength of healthy tissues while maintaining an interconnected pore network and a reasonable porosity. In this work, we have used 3D-plotting technique to produce poly-L-Lactide macroporous scaffolds with two different pore sizes. The ability of these macroporous scaffolds to support chondrocyte attachment and viability were compared under static and dynamic loading in vitro. Moreover, the 3D-plotting technique was combined with porogen-leaching, leading to macro/microporous scaffolds, so as to examine the effect of microporosity on the level of cell attachment and viability under similar loading condition. Canine chondrocytes’ cells were seeded onto the scaffolds with different topologies, and the constructs were cultured for up to 2 weeks under static conditions or in a bioreactor under dynamic compressive strain of 10% strain, at a frequency of 1 Hz. The attachment and cell growth of chondrocytes were examined by scanning electron microscopy and by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. A significant difference in cell attachment was observed in macroporous scaffolds with different pore sizes after 1, 7, and 14 days. Cell viability in the scaffolds was enhanced with decreasing pore size and increasing microporosity level throughout the culture period. Chondrocyte viability in the scaffolds cultured under dynamic loading was significantly higher (p<0.05) than the scaffolds cultured statically. Dynamic cell culture of the scaffolds improved cell viability and decreased the time of in vitro culture when compared to statically cultured constructs. Optimizing the culture conditions and scaffold properties could generate optimal tissue/constructs combination for cartilage repair.

Little mechanical data is available on human arteries because of the difficulty of testing artery samples often obtained from autopsy, while arteries are still considered “fresh”. Various solutions mimicking the physiological environment have been used to preserve artery samples from harvesting to testing. Cryopreservation might provide a means to preserve the mechanical properties of arteries for days or weeks after harvesting. The objective of this study is to investigate the effect of several preservation methods, including simplified cryopreservation methods, on the passive mechanical properties of arteries. Eighteen fresh cruciform samples were mechanically tested. Samples were divided in three groups based on preservation medium and freezing method: isotonic saline solution, Krebs-Henseleit buffer solution with dimethyl sulfoxide (DMSO), and dipped in liquid nitrogen. In each group, half of the samples were stored at -20℃ and the other half at -80℃. Two months later, all the tissues were thawed at 4℃ and mechanical tests were repeated. Preservation of arteries for two months in Krebs solution with DMSO (at -20℃ or at -80℃) or in isotonic saline solution at -20℃ were the methods that least changed the mechanical properties of the arteries

Background Cell reprogramming is a promising avenue for cell-based therapies as it allows for the generation of multipotent, unipotent, or mature somatic cells without going through a pluripotent state. While the use of autologous cells is considered ideal, key challenges for their clinical translation include the ability to reproducibly generate sufficient quantities of cells within a therapeutically relevant time window. Methods We performed transfection of three distinct human somatic starting populations of cells with a non-integrating synthetic plasmid expressing Musashi 1 ( MSI1 ), Neurogenin 2 ( NGN2 ), and Methyl-CpG-Binding Domain 2 ( MBD2 ). The resulting directly reprogrammed neural precursor cells (drNPCs) were examined in vitro using RT-qPCR, karyotype analysis, immunohistochemistry, and FACS at early and late time post-transfection. Electrophysiology (patch clamp) was performed on drNPC-derived neurons to determine their capacity to generate action potentials. In vivo characterization was performed following transplantation of drNPCs into two animal models (Shiverer and SCID/Beige mice), and the numbers, location, and differentiation profile of the transplanted cells were examined using immunohistochemistry. Results Human somatic cells can be directly reprogrammed within two weeks to neural precursor cells (drNPCs) by transient exposure to Msi1, Ngn2, and MBD2 using non-viral constructs. The drNPCs generate all three neural cell types (astrocytes, oligodendrocytes, and neurons) and can be passaged in vitro to generate large numbers of cells within four weeks. drNPCs can respond to in vivo differentiation and migration cues as demonstrated by their migration to the olfactory bulb and contribution to neurogenesis in vivo. Differentiation profiles of transplanted cells onto the corpus callosum of myelin-deficient mice reveal the production of oligodendrocytes and astrocytes. Conclusions Human drNPCs can be efficiently and rapidly produced from donor somatic cells and possess all the important characteristics of native neural multipotent cells including differentiation into neurons, astrocytes, and oligodendrocytes, and in vivo neurogenesis and myelination. Electronic supplementary material The online version of this article (10.1186/s13287-019-1255-4) contains supplementary material, which is available to authorized users.

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