The influence of fibrin based hydrogels on the chondrogenic differentiation of human bone marrow stromal cells Saey T.B. Ho a, b,1 , Simon M. Cool c, 2 , James H. Hui a, 1 , Dietmar W. Hutmacher d, * a Department of Orthopaedic Surgery, Yong Loo Lin School of Medical, National University of Singapore, Singapore 119074, Singapore b Graduate Programme in Bioengineering, Yong Loo Lin School of Medical, National University of Singapore, Singapore 119260, Singapore c Stem Cells and Tissue Repair Group, Institute of Medical Biology, A*STAR, 8A Biomedical Grove, # 06 – 06 Immunos, Singapore 138648, Singapore d Regenerative Medicine, Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove QLD 4059, Australia article info Article history: Received 10 July 2009 Accepted 7 September 2009 Available online 3 October 2009 Keywords: Cartilage tissue engineering MSC Fibrin and alginate abstract Mesenchymal Stem Cells (MSC) are frequently incorporated into osteochondral implants and cell seeding is often facilitated with hydrogels which exert a profound influence on the chondrogenic differentiation of MSC. An attempt was made to elucidate this effect by comparing the chondrogenic differentiation of Bone Marrow Stromal Cells (BMSC) in fibrin and fibrin alginate composites. A biphasic osteochondral model which simulated the native in vivo environment was employed in the study. In the first stage of the experiment, BMSC was encapsulated in fibrin, Fibrin Alginate 0.3% (FA0.3) and 0.6% (FA0.6). Chondrogenic differentiation within these cell-hydrogel pellets was compared against that of standard cell pellets under inductive conditions and the matrices which supported chondrogenesis were used in the cartilage phase of biphasic constructs. Neo-cartilage growth was monitored in these cocultures. It was observed that hydrogel encapsulation influenced mesenchymal condensation which preceded chondrogenic differen- tiation. Early cell agglomeration was observed in fibrin as compared to fibrin alginate composites. These fibrin encapsulated cells differentiated into chondrocytes which secreted aggrecan and collagen II. When the alginate content rose from 0.3 to 0.6%, chondrogenic differentiation declined with a reduction in the expression of collagen II and aggrecan. Fibrin and FA0.3 were tested in the cartilage phase of the biphasic osteochondral constructs and the former supported superior cartilage growth with higher cellularity, total Glycosaminoglycan (GAG) and collagen II levels. The FA0.3 cartilage phase was found to be fragmented and partially calcified. The use of fibrin for cartilage repair was advocated as it facilitated BMSC chondrogenesis and cartilaginous growth in an osteochondral environment. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Scaffolds perform a vital role in tissue engineered osteochondral implants because they serve as a temporary supportive stratum, carriers for cells and growth factors. A porous matrix supports tissue in growth and molecular transport. This is crucial for the cartilage phase as the avascular tissue is solely dependent on diffusion for survivability. However cell retention is poor for such highly porous scaffold hence it has to be assisted by hydrogel encapsulation. This constitutes ‘‘a micro matrix within a macro scaffold’’ system as the macro scaffold provides the necessary physical support and protection from the excessive stresses expe- rienced at osteochondral site while the hydrogel facilitates cell retention and biomimetic interactions [1,2]. Hydrogel selection is critical as it affects tissue development. Hydrogels are crosslinked polymeric matrices that have a 0.5–20% dry mass relative to the total mass. The low dry mass minimizes foreign body reaction, while the high water content promotes the diffusion of nutrients and metabolites necessary for cellular viability [3]. Hydrogels can be derived from synthetic and natural sources but the former has to be enhanced with additives because it is usually bioert [4]. Natural hydrogels would include fibrin and alginate. Fibrin contains factor XIII which enhances MSC proliferation and migration [5]. Sams et al. advocated the use of fibrin for the encapsulation of chondrocytes as it promoted collagen II expression [6]. Besides cartilaginous constructs, fibrin was also used in the seeding of MSC in calvarial bone implants [7]. Alginate is widely used in chondrocyte * Corresponding author. Fax: þ61 7 31386030. E-mail addresses: g0201956@nus.edu.sg (S.T.B. Ho), simon.cool@imb.a-star.edu.sg (S.M. Cool), doshuij@nus.edu.sg (J.H. Hui), dietmar.hutmacher@qut.edu.au (D.W. Hutmacher). 1 National University of Singapore, DSO Building (Kent Ridge), NUS Tissue Engi- neering Program (NUSTEP), Level 4, 27 Medicine Drive, Singapore 117510, Singapore. Fax: þ65 67744082. 2 Fax: þ65 64789477. Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2009.09.021 Biomaterials 31 (2010) 38–47