Review of 2D and 3D cell cultures

Review of 2D and 3D cell cultures
Shermin Lak,^1,*
1. University of Tehran
Introduction: Cell culture is an important in vitro tool to use in different studies such as cell behaviors, drug screening and gene expression.2D cell cultures are used because they are an economical and convenient method. However, they cannot accurately reflect tumor microenvironment. To overcome these limitations, three-dimensional spheroid culture models have developed. In this review article ٫we compare 2D and 3D culture methods.
Methods: A targeted search has been performed on 3 websites: PubMed, science direct and goggle scholar. Article information has collected from English articles.
Results: In2D culture, cells grow as monolayer in a rigid plate and cells adhere to surface of plate only one side. Thus, there is defect of interconnections between cells and extra cellular matrix (ECM) surrounding them. Gradients of Oxygen, nutrients and waste do not exist and all cells have access oxygen and nutrients. These changes affect the phenotype and behavior of cells. Thus, they cannot simulate the function of living tissues.in 3D cultures ,E-cadherin, actin, microtubules, and FAK are important elements in formation of spheroids. Spheroids due to oxygen, nutrient and waste gradients are divided 3 zones: Necrotic zone, Quiescent viable cell zone and proliferating zone. Proliferating zone is outer layer and has more access to oxygen and nutrients while inside layer has less access to nutrients and oxygen. This structure mimics the physical features of a solid tumor mass .The structure of spheroids has an effect on drug resistance because cells in medium zone have decreased access to drug .Also Because of oxygen gradient in spheroids , inadequate diffusion of oxygen produces hypoxia.in hypoxia up-regulation of VEGF is observed and it can lead to drug resistance. Another reason of drug resistance is up regulation of Cluster of differentiation 44(CD44) in spheroids .Spheroids interact with ECM. Hyaluronan is a main ligand for CD44 and actives It. CD44 regulates some signaling pathways such as PI3/AKT and Ras-MAPK pathways. It has been proven that knocking-out of CD44 by the CRISPR-Cas9 system can inhibit tumor progression, metastasis and ameliorate drug resistance.
Conclusion: There are Differences in morphology, gene expression ,hypoxia and drug resistance in 2D and 3D cultures and resemblance between 3D cultures and living tissues .failures of 2D culture models in drug screening in pre-clinical in vivo tests or clinical trials indicate that It is better to replace two-dimensional culture models with three-dimensional culture models.
Keywords: 2D cultures , 3D cultures,living tissues