Engineering vascularised tissues in vitro

Tissue engineering aims at replacing or regenerating tissues lost due to diseases or traumas (Langer and Vacanti, 1993). However, mimicking in vitro the physiological complexity of vascularized tissue is a major obstacle, which possibly contributes to impaired healing in vivo. In higher organisms, native features including the vascular network, the lymphatic networks and interstitial flow promote both mass transport and organ development. Attempts to mimic those features in engineered tissues will lead to more clinically relevant cell-based therapies. Aside from current strategies promoting angiogenesis from the host, an alternative concept termed prevascularization is emerging. It aims at creating a biological vasculature inside an engineered tissue prior to implantation. This vasculature can rapidly anastamose with the host and enhances tissue survival and differentiation. Interestingly, growing evidence supports a role of the vasculature in regulating pattern formation and tissue differentiation. Thus, prevascularized tissues also benefit from an intrinsic contribution of their vascular system to their development. From those early attempts are emerging a body of principles and strategies to grow and maintain, in vitro, those self-assembled biological vascular networks. This could lead to the generation of engineered tissues of more physiologically relevant complexity and improved regenerative potential

Arrangement of Type IV Collagen and Laminin on Substrates with Controlled Density of ¿OH Groups

This is a copy of an article published in the Diabetes Technology and Therapeutics © 2011 [copyright Mary Ann Liebert, Inc.]; Diabetes Technology and Therapeutics is available online at: http://online.liebertpub.com.Collagen IV (Col IV) and laminin (Lam) are the main structural components of the basement membrane where they form two overlapping polymeric networks. We studied the adsorption pattern of these proteins on five model surfaces with tailored density of-OH groups obtained by copolymerization of different ratios ethyl acrylate (EA) and hydroxyl EA (HEA): X OH=0, X OH=0.3, X OH=0.5, X OH=0.7, and X OH=1 (where X refers the ratio of HEA). Atomic force microscopy revealed substratum-specific adsorption patterns of Col IV and Lam, ranging from single molecules deposition on more hydrophilic substrata to the formation of complex networks on hydrophobic ones. Human umbilical endothelial cells were used to study the biological performance of adsorbed proteins, following the overall cell morphology, the quantities for cell adhesion and spreading, and the development of focal adhesion complexes and actin cytoskeleton. Surprisingly, two optima in the cellular interaction were observed-one on the most hydrophilic X OH=1 and other on the relatively hydrophobic X OH=0.3 substrate-valid for both Col IV and Lam. When the proteins were adsorbed consecutively, a hydrophobic shift to X OH=0 substratum was obtained. Collectively, these data suggest that varying with the density of-OH groups one can tailor the conformation and the functional activity of adsorbed basement membrane proteins. © 2011, Mary Ann Liebert, Inc.AFM was performed under the technical guidance of the Microscopy Service at the Universidad Politecnica de Valencia, whose advice is greatly appreciated. The work was supported by the Spanish Ministry of Science and Innovation through project nos. MAT2009-14440-C02-0 and MAT2009-14440-C02-02.Coelho, NM.; González García, C.; Salmerón Sánchez, M.; Altankov, G. (2011). Arrangement of Type IV Collagen and Laminin on Substrates with Controlled Density of ¿OH Groups. Tissue Engineering Part A. 17:2245-2257. doi:10.1089/ten.tea.2010.0713S224522571

Observaciones sobre las algas corticicolas del nordeste y sudeste de EspaÑa

Se presentan los resultados de un estudio sobre la flora algal corticícola realizado en el nordeste y sudeste de España. Se citan treinta y siete táxones, dieciséis de los cuales constituyen nuevas citas para España. Se comentan los datos referentes a las principales características morfológicas y se ilustran las especies más relevantes

Micro-aggregates do not influence bone marrow stromal cell chondrogenesis

Although bone marrow stromal cells (BMSCs) appear promising for cartilage repair, current clinical results are suboptimal and the success of BMSC-based therapies relies on a number of methodological improvements, among which is better understanding and control of their differentiation pathways. We investigated here the role of the cellular environment (paracrine vs juxtacrine signalling) in the chondrogenic differentiation of BMSCs. Bovine BMSCs were encapsulated in alginate beads, as dispersed cells or as small micro-aggregates, to create different paracrine and juxtacrine signalling conditions. BMSCs were then cultured for 21 days with TGFβ3 added for 0, 7 or 21 days. Chondrogenic differentiation was assessed at the gene (type II and X collagens, aggrecan, TGFβ, sp7) and matrix (biochemical assays and histology) levels. The results showed that micro-aggregates had no beneficial effects over dispersed cells: matrix production was similar, whereas chondrogenic marker gene expression was lower for the micro-aggregates, under all TGFβ conditions tested. This weakened chondrogenic differentiation might be explained by a different cytoskeleton organization at day 0 in the micro-aggregates

Cellular microtissues spontaneously formed in a microfabricated device for angiongenesis

We report here on a microdevice for the spontaneous and simultaneous formation of microtissues-or microscale spheroids- in a fast, controlled and reproducible way. Spheroids are relevant constructs for tissue engineering applications, and notably for studying the process of angiogenesis which is of crucial importance for both tissue regeneration and understanding/manipulating tumor vascularization. Our microde-vices consist of PDMS microwell arrays whose surface properties are optimized (PDMS composition and applied coating agent) for both promoting cellular aggrega-tion into spheroids and facilitating spheroid removal out of the device