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A. Nakao, M. Afrakhte, A. Moren, T. Nakayama, J. L. Christian, R. Heuchel, S. Itoh, M. Kawabata, N. E. Heldin, C. H. Heldin and P. T. Dijke, “Identification of Smad 7, a TGFβ-Inducible Antagonist of TGF-β Signaling,” Nature, Vol. 389, No. 6651, 1997, pp. 631-635.

has been cited by the following article:

• TITLE: Biological Evaluation of Tissue-Engineered Cartilage Using Thermoresponsive Poly(N-isopropylacrylamide)-Grafted Hyaluronan

  AUTHORS: Kazuaki Muramatsu, Mika Ide, Fujio Miyawaki

  KEYWORDS: Cartilage Tissue Engineering; Hyaluronan; Self-Assembly; Thermally Responsive Material

  JOURNAL NAME: Journal of Biomaterials and Nanobiotechnology, Vol.3 No.1, December 31, 2011

  ABSTRACT: In order to contribute to the development of minimally invasive surgery techniques for autologous chondrocyte implantation, a novel self-assembling biomaterial consisting of thermoresponsive poly(N-isopropylacrylamide)-grafted hyaluronan (PNIPAAm-g-HA) has been synthesized as an injectable scaffold for cartilage tissue engineering. The aim of this study was to investigate the efficacy and cytocompatibility of PNIPAAm-g-HA to normal chondrocytes by using reverse transcription-polymerase chain reaction (RT-PCR) analysis and histochemical staining in preliminary in vitro and in vitro experiments. Hematoxylin and eosin staining showed homogeneous distribution of cells in the PNIPAAm-g-HA hydrogel in 3-dimensional in vitro cultivation. Alcian blue staining also indicated that abundant extracellular matrix formation, including acidic glycosaminoglycans, occurred in tissue-engineered cartilage over time in vitro. Cartilage-related gene expression patterns, which were tested in rabbit normal chondrocytes embedded in the hydrogel, were almost maintained for 4 weeks. Transforming growth factor-β1 (TGF-β1) stimulation enhanced the expression of SRY-related HMG box-containing gene 9 (Sox9) and type X collagen genes suggesting promotion of chondrogenic differentiation. Histochemical evaluation showed neocartilage formation following subcutaneous implantation of the chondrocyte-gel mixture in nude mice. Furthermore, TGF-β1 stimulation promoted production and maturation of the extracellular matrix of the in situ tissue engineered hyaline cartilage. These data suggested that PNIPAAm-g-HA could be a promising biomaterial, i.e., a self-assembling and injectable scaffold for cartilage tissue engineering.