0391-3988/507-10$25.00/0 © Wichtig Editore, 2009 The International Journal of Artificial Organs / Vol. 32 / no. 8, 2009 / pp. 507-516 Biomaterials INTRODUCTION Tissue formation and cellular function in vivo are regu- lated by diverse biological factors, including cell-cell com- munication, cell-matrix interactions, and soluble factors. The ability to recreate such interactions in vitro may lead to advances in various fields, ranging from cell biology to tissue engineering. For example, tissue engineering con- structs that aim to restore and enhance natural tissue func- tion should ideally incorporate features of complex tissues, such as the integration of multiple cell types with appropri- ate extracellular matrices (1). The manipulation of the cell microenvironment by the modulation of cell-cell communi- cation and cell-matrix interaction is the first step towards creating such constructs for tissue replacement (2). It has been known that cells react to shape since 1911 (3) and the effects of micro-topography are well documented, includ- ing changes in cell adhesion, contact guidance, cytoskel- etal organization, apoptosis, macrophage activation and gene expression (4-7). Many approaches to the manipula- tion of the cell microenvironment have been conducted on micro-patterned surfaces and several studies have been carried out with the aim of realizing microstructures with different topographic domains (8-11). The presence of mi- cro- and nano-domains on a surface allows the manipula- tion of two fundamental external signals: cell-substrate and cell-cell interaction, in order to create a pattern of highly oriented cells capable of arranging themselves in tissue (12-16). The domain dimensions should be of the same size as the biological entities with which they interact. In fact, in the realization of microstructures, it is important to consider that the average dimension of a cell is in the range of 10 to 30 μm. Cell guidance also depends on the different chemical and/or topographic domains present on Heterotypic cell-cell interaction on micropatterned surfaces STEFANIA LAMPONI 1 , CLARA DI CANIO 1 *, ROLANDO BARBUCCI 1 * 1 Department of Pure and Applied Medicinal Chemistry, University of Siena, Siena - Italy CRISMA University of Siena, Siena - Italy ABSTRACT: Purpose: The aim of this paper was to study the influence of chemical and topographical signals on cell behavior and to obtain a heterotypic cell-cell interaction on microstructured domains. Methods: The polysaccharide hyaluronic acid (Hyal) was photoimmobilized on glass surfaces in order to obtain a pattern with squares and rectangles of different dimensions and chemistry. The microstructured sur- faces were characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The behavior of Human Coronary Artery Endothelial Cells (HCAEC) and human tumoral dermal fibroblasts (C54) was investigated on these micropatterned surfaces by adhesion studies. Moreover, heterotypic interaction among C54 and HCAEC adherent on patterned surfaces was evaluated by time-lapse video microscopy. Results: Surface analysis revealed the presence of a pattern consisting of alternating glass and Hyal microstructures whose dimensions decreased from the center to the edge of the sample. Neither HCAEC nor C54 adhered to the immobilized Hyal but both adapted their shape to the different sizes of the glass squares and rectangles. The number of adherent cells depended on the dimensions of both the glass domains and the nuclei of the cells. Co-cultured C54 on HCAEC patterned surfaces showed a heterotypic cell-cell interaction in the same chemical and topographic domain. Conclusions: A heterotypic cell-cell interaction occurred in the same chemical and topographic mi- cro-domains but in narrow areas only. Moreover, the number of cells adhering to the glass domains and cell morphology depended on the dimensions of both adhesive areas and cell nuclei. (Int J Artif Organs 2009; 32: 507-16) KEY WORDS: Co-cultures, Endothelial cells, Fibroblasts, Micropatterned surfaces, Hyaluronic acid