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[EN]Cardiosphere-derived cells (CDCs) encapsulated within alginate-poly-L-lysine-alginate (APA) microcapsules present a promising treatment alternative for myocardial infarction. However, clinical translatability of encapsulated CDCs requires robust long-term preservation of microcapsule and cell stability, since cell culture at 37 degrees C for long periods prior to patient implantation involve high resource, space and manpower costs, sometimes unaffordable for clinical facilities. Cryopreservation in liquid nitrogen is a well-established procedure to easily store cells with good recovery rate, but its effects on encapsulated cells are understudied. In this work, we assess both the biological response of CDCs and the mechanical stability of microcapsules after long-term (i.e., 60 days) cryopreservation and compare them to encapsulated CDCs cultured at 37 degrees C. We investigate for the first time the effects of cryopreservation on stiffness and topographical features of microcapsules for cell therapy. Our results show that functionality of encapsulated CDCs is optimum during 7 days at 37 degrees C, while cryopreservation seems to better guarantee the stability of both CDCs and APA microcapsules properties during longer storage than 15 days. These results point out cryopreservation as a suitable technique for long-term storage of encapsulated cells to be translated from the bench to the clinic. This work has been supported by the European Union's H2020 Framework Program (H2020/2014-2020) and National Authorities through the Electronic Components and Systems for European Leadership Joint Undertaking (ECSEL JU) program under grant agreement Ecsel-78132-Position-II-2017-IA. The regional Government of Aragon provided L.P. studentship. This research was partially funded by Instituto de Salud Carlos III (PI20/00247) and Agencia Estatal de Investigacion (PID2019-107329RA-C22), cofunded by European Regional Development Fund "A way to make Europe."

Microfluidic systems have emerged as a technique with the potential to recreate biomimetic microenvironments that permit in vitro modeling of several important organ functions (organ-on-chip) as well as to analyze cellular processes. This allows designing experiments for validating scientific hypotheses and better understand complex biological processes, and determine biological parameters in an unprecedented way. The crosstalk between this new experimental capacity and mathematical models within a general framework is extensively discussed in this chapter, reviewing the formulation of cell processes, together with their interaction with the surrounding environment. Also, its particularization to a particular problem of interest such as the analysis of tumor evolution, which can be modeled in organ-on-chip devices. One of the important cases of the solid tumors is glioblastoma (GBM), the most lethal primary brain tumor. One of the characteristics in such types of tumors is the appearance of hypercellularized regions, named as pseudopalisades. These structures have been hypothesized to be produced by oxygen and nutrient depletion caused by tumor-induced blood vessel occlusion. However, despite the important instrumental role of these pseudopalisades in GBM's spread and invasion, the recreation of these in vitro has remained challenging. To analyze this problem, we designed a microdevice that comprises a central microchamber flanked by two lateral microchannels, separated by a series of projections. GBM cells were then embedded within a collagen hydrogel in the central microchamber thereby mimicking the three-dimensional structure and distribution. The lateral microchannels were used to perfuse different media or drugs, so normoxic, hypoxic, and necrotic regions may be naturally generated. In this chapter, we detail the model itself and the fitting of the model parameters. We compare the experimental and numerical results and we discuss the experimental trends and the underlying hypotheses.

The development of macroporous biodegradable polymeric materials with three-dimensional pore structure is an important research field in tissue engineering. Structural scaffolds not only provide the cells with a mechanical support, but also perform an interactive physico-chemical role in tissue regeneration, thus it becomes important to be able to tune their mechanical properties to deliver appropriate mechanical signals to adhered cells for proper tissue regeneration. This work presents two series of poly(L-lactic acid) (PLLA) scaffolds in which we modulated the mechanical properties by systematically changing two synthesis parameters: polymer/solvent ratio and polymer-solution/porogen percentage. The peculiarity of the constructs is the presence of a double porosity: micropores generated by dioxane solvent using a freeze extraction technique and macropores produced by the leaching of macroporogen spheres. An increase in the PLLA/dioxane ratio decreases the micropores size and also influences to some extent the macropores size, due to the ability of dioxane to swell macroporogen particles. On the other hand, an increase in the amount of macroporogen increases the porosity by increasing the dimension of pore the throats connecting the macropores. Consequently, the increase in the PLLA/dioxane ratio produces a significant decrease in the permeability, and an increase in the apparent compression Young's modulus and aggregate modulus. When increasing the amount of macroporogen the permeability significantly increases and a decrease in the mechanical properties of the scaffolds is observed. Summarizing, with a systematic change of two fabrication parameters (amount of dioxane and macroporogen) the structural characteristics of the scaffolds were modulated and thereby their mechanical and transport properties were controlled., The authors gratefully acknowledge research support from the Spanish Ministry of Science and Innovation through research project DPI2010-20399-C04-00. CIBER-BBN is an initiative funded by the VI National R&D&D&i Plan 2008-2011, Iniciativa Ingenio 2010, and Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.