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The characteristic molecular composition of the different glycosaminoglycans (GAGs) is related to their role as structural components and regulators of a multitude of functions of proteins, cells and tissues in the human body. Therefore, it is not surprising that GAGs are widely used as coating materials for implants, components of 3D-constructs such as tissue engineering scaffolds and hydrogels, but also as diagnostic devices such as biosensors and in controlled release applications. Beside a physisorption or encapsulation of GAGs, these applications often require their chemical modification to allow a stable covalent attachment on surfaces or cross-linking reactions with other molecules. Then, the preservation of the functionality of GAGs under maintenance of their biocompatibility is a challenging task and must be addressed in accordance with the designated field of application. Here, we will give a brief overview on structure and biological functions of GAGs, different methods of their activation and immobilization, the recent progress in GAG-related biomaterials development, as well as some examples of their application in the field of tissue engineering and regenerative medicine.

In cell cultures, HSV-1 replication is initiated by recruitment by virion protein 16 of transcriptional factors and histone-modifying enzymes to immediate early (α) gene promoters. HSV establishes latent infections characterized by suppression of viral gene expression except for latency-associated transcripts (LATs) and miRNAs. The latent virus reactivates in stressed neurons. A fundamental question is how reactivation initiates in the absence of virion protein 16. We report the following findings in the ganglion explant model. (i) Anti-nerve growth factor antibody accelerated the reactivation of latent virus. Viral mRNAs were detected as early as 9 h after explantation. (ii) After explantation the amounts of viral mRNAs increased whereas amounts of miRNAs and LATs decreased. The decrease in miRNAs and LATs required ongoing protein synthesis, raising the possibility that LAT and miRNAs were degraded by a viral gene product. (iii) The expression of viral genes in explanted ganglia was disordered rather than sequentially ordered as in infected cells in culture. These findings suggest that in reactivating ganglia gene expression is totally derepressed and challenge the current models in that establishment of or exit from latency could not be dependent on the suppression or activation of single or small clusters of viral genes. Finally, miRNAs and LATs reached peak levels 9-11 d after corneal inoculation, thus approximating the pattern of virus replication in these ganglia. These findings suggest that the patterns of accumulation of LATs and miRNAs reflect many different stages in the infection of neurons.T o initiate infection in cell culture and presumably also at the portal of entry into the body, the HSV-1 capsid delivers the DNA to the nucleus. Concurrently, virion protein 16 (VP16), a key viral protein packaged in the virion and delivered to the nucleus, recruits the cellular factors octamer-binding protein 1 (Oct1), host cell factor 1 (HCF1), lysine-specific demethylase 1 (LSD1), circadian locomotor output cycles kaput (CLOCK) histone acetyl transferase, and other transcriptional factors to initiate a cascade of viral gene expression that begins with immediate early (α) genes followed by early (β) and late (γ) genes (1-5). VP16 is encoded by a γ gene expressed late in infection (1). In all, the transcriptional program yields almost 100 different transcripts. In contrast, in latently infected neurons viral gene expression is limited to the latency-associated transcript (LAT) and approximately six or more miRNAs (6, 7). Given the requirement for VP16 to initiate viral replication in productively infected cells, the question arises as to how virus replication initiates in stressed neurons harboring latent virus. Among the many hypotheses, two stand out: That VP16 is expressed first or that in neurons α gene expression can ensue in the absence of VP16.Resolution of this problem requires analyses of the reactivation in ganglia under conditions that are physiologically similar to those that occur in vivo. In the st...

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