Biomaterials 21 (2000) 2315}2322 Vascular cell responses to polysaccharide materials: in vitro and in vivo evaluations Janeen M. Chupa, Angela M. Foster, Stephanie R. Sumner, Sundararajan V. Madihally, Howard W.T. Matthew* Department of Chemical Engineering & Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202, USA Abstract Chitosan has shown promise as a structural material for a number of tissue engineering applications. Similarly the glycosamino- glycans (GAGs) and their analogs have been known to exert a variety of biological activities. In this study we evaluated the potential of GAG}chitosan and dextran sulfate (DS)}chitosan complex materials for controlling the proliferation of vascular endothelial (EC) and smooth muscle cells (SMC). GAG}chitosan complex membranes were generated in vitro and seeded with human ECs or SMCs for culture up to 9 d. In addition, porous chitosan and GAG}chitosan complex sca!olds were implanted subcutaneously in rats to evaluate the in vivo response to these materials. The results indicated that while chitosan alone supported cell attachment and growth, GAG}chitosan materials inhibited spreading and proliferation of ECs and SMCs in vitro. In contrast, DS}chitosan surfaces supported proliferation of both cell types. In vivo, heparin}chitosan and DS}chitosan sca!olds stimulated cell proliferation and the formation of a thick layer of dense granulation tissue. In the case of heparin sca!olds the granulation layer was highly vascularized. These results indicate that the GAG}chitosan materials can be used to modulate the proliferation of vascular cells both in vitro and in vivo.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Chitosan; Glycosaminoglycans; Heparin; Dextran sulfate; Endothelial cells; Smooth muscle; Sca!old; Tissue response 1. Introduction The expanding "eld of Tissue Engineering has acceler- ated the demand for materials which are tissue compat- ible, biodegradable, and with mechanical properties closely matched to the target tissues [1}4]. Molecular level control of biological activity is also a highly de- sirable feature. For many such materials, porous microstructures are also required to either allow tissue ingrowth in vivo or to provide a template for directed tissue assembly in vitro. The matrix polysaccharides termed glycosaminoglycans (GAGs) and composite ma- terials derived from them are of interest for such applica- tions since carbohydrate moieties interact with or are integral components of many cell adhesion molecules and matrix glycoproteins [5]. In this work, bioactive polysaccharide-based materials are being investigated as * Corresponding author. Tel.: #1-313-577-5238; fax: #1-313-577- 3810. E-mail address: h.matthew@wayne.edu (H.W.T. Matthew). potential solutions to a long-standing biomaterials prob- lem, namely, the design of an e!ective small-diameter vascular graft. Incomplete endothelialization and smooth muscle cell hyperplasia are two of the problems contributing to the poor performance of existing small-diameter vas- cular grafts [6}8]. Improvements in long-term perfor- mance of these devices might be attained through the use of structural materials with speci"c biological activities. In one scenario, the bioactive sca!old would both enhance the rate of endothelialization and speci"cally inhibit the migration of smooth muscle to the graft lu- men. GAG-based materials hold promise for this system because of their growth inhibitory e!ects on vascular smooth muscle cells and their anticoagulant activity. Furthermore, these molecules readily form complexes with the structural polysaccharide derivative chitosan [9]. In this study, the morphological and growth re- sponses of vascular cells to polysaccharide complex sur- faces were evaluated. In addition, porous bioactive materials were prepared by complexation of GAGs with porous chitosan sca!olds and the tissue response to these implants was examined. 0142-9612/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 1 4 2 - 9 6 1 2 ( 0 0 ) 0 0 1 5 8 - 7