PMC:4996398 / 45130-50271 JSONTXT

{"project":"2_test","denotations":[{"id":"27600217-2337892-69475977","span":{"begin":1057,"end":1060},"obj":"2337892"},{"id":"27600217-23349734-69475978","span":{"begin":1427,"end":1430},"obj":"23349734"},{"id":"27600217-24129782-69475979","span":{"begin":3078,"end":3081},"obj":"24129782"},{"id":"27600217-20564616-69475980","span":{"begin":3229,"end":3232},"obj":"20564616"},{"id":"27600217-24626259-69475981","span":{"begin":4002,"end":4005},"obj":"24626259"},{"id":"27600217-22776769-69475982","span":{"begin":4632,"end":4635},"obj":"22776769"},{"id":"27600217-24113327-69475983","span":{"begin":4877,"end":4880},"obj":"24113327"}],"text":"4. Future\nDeveloping 3D cell culture technology will lead to more physiologically relevant and likely more predictive approaches to organogenesis, tissue morphology, the importance of hypoxia, drug discovery, cell-based assays, and reduced animal use. The ability of 3D cell culture systems to mimic tissue structures, either from single cells or co-cultures, is a great advance from 2D monolayer cultures. Cell–cell communication and differentiated cellular function are more relevant in 3D and the impact of 3D cultures on predicting efficacy of drug treatments to actual in vivo response is great.\n\n4.1. Drug Discovery\nAllowing cells to acquire a more natural phenotype when grown in 3D as opposed to 2D is a great advantage. This is especially true for the field of drug discovery where countless examples have been shown of the mismatch between in vitro drug effect and in vivo drug efficacy.\n\n4.1.1. Cancer\nAlready in 1990 an alginate culture method was used to test the effects of vincristine and 5‑fluorouracil on HT-29 human colon carcinoma cells [130]. Creating a more clinically relevant model of tumor biology has been a prime impetus for developing 3D culture systems. Burdett et al. [131] described the superiority of 3D over 2D cell culture where mimicking tumor behavior and drug resistance often seen in vivo is important. AlgiMatrix® is a commercial alginate-based product for 3D cell culture. Godugu et al. [110] demonstrate the possibility of using this culture system as an in vitro tumor model for anticancer drug screening. They treated several human non-small cell lung cancer cell lines (A549, H460, and H1650) with several anticancer drugs used in the clinic.\n\n4.1.2. Safety and Toxicology\nHepG2 liver cells have been encapsulated in sterile alginate hydrogels and used to demonstrate their capability to metabolize a coumarin pro-drug in a manner similar to in vivo hepatic metabolic activity [132]. Another hepatic cell line, Huh-7, cultured in an alginate hydrogel showed cellular organization and hepatocyte architecture with respect to cell polarity, cell junctions and the appearance of bile canaliculi. The alginate-encapsulated Huh-7 cells also expressed specific hepatitis C virus receptors indicating that this 3D culture system may be useful in viral studied and liver tissue engineering [133]. Alginate encapsulation of hepatocytes provides protection from shear stress for hepatocyte aggregates in a 3D bioreactor cultures system [134]. In addition, the alginate hydrogel seems to provide the cells with a good support for extracellular matrix deposition.\n\n4.2. Tissue Engineering and Regenerative Medicine\n\n4.2.1. Skin\nEstablishing normal physiology and function in a traditional 2D in vitro cell culture of skin is almost impossible. The advent of organotypic culture systems does allow approximation of skin complexity. 3D culture of skin allows dermatological studies which would otherwise be unsafe for animals and humans such as validating the mechanisms of skin diseases and testing the therapeutic potential of experimental drugs [135]. Developing a 3D in vitro human skin co-culture model has shown promise for detecting skin irritants as an alternative to in vivo animal testing [136].\n\n4.2.2. Cartilage\nSpecific signature gene cluster regulation was seen during in vitro chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells which were immobilized in a self-gelling alginate hydrogel. Upregulation of transcription factor genes as well as a signature cluster of extracellular matrix genes occurred during chondrogenesis while gene clusters involved in immune response, blood vessel development, and cell adhesion were downregulated [95]. Marker genes identified in this study show that stem cells can be directed to produce hyaline cartilage when immobilized in 3D alginate hydrogels.\nImmobilizing cells with chondrogenic potential in an alginate hydrogel has shown that neocartilage can be formed by mesenchymal stem cells [137]. Here, production of not only type II collagen but also assembled fibrils was dependent on cell seeding density. When cells were seeded at a high density, fibril assembly and procollagen processing occurred at a distance from the cell surface.\n\n4.2.3. Cardiac\nCardiac tissue engineering may involve the regeneration of myocardial tissue by first immobilizing stem cells in a scaffold or matrix in vitro and then placing such a scaffold on, or within, the damaged cardiac tissue. Immobilizing myocardial stem cells within a scaffold ensures that they will remain within the cardiac tissue after implantation. Ceccaldi et al. [138] has studied the influence of alginate composition on mesenchymal stem cells in alginate scaffolds. Their conclusion was the G-rich alginate hydrogels provided the most appropriate milieu for MSCs intended for cardiac therapy. Levit et al. [139] have shown similar results where alginate-encapsulated human mesenchymal stem cells were placed onto a rat heart as a hydrogel patch. The alginate hydrogel retained the MSCs and led to an improvement of cardiac function following induced myocardial infarct.\n\n"}