Differential effects of tyrosine-rich amelogenin peptide on chondrogenic and osteogenic differentiation of adult chondrocytes

• Type of Material: Article
• Authors: H.D. Amin, Imperial College London; Christopher Ethier, Emory University
• Language: English
• Date: 2015-09-25
• Publisher: Springer Verlag (Germany)
• Publication Version: Final Published Version
• Copyright Statement: © 2015 The Author(s)
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1007/s00441-015-2292-7
• Title of Journal or Parent Work: Cell and Tissue Research
• ISSN: 0302-766X
• Volume: 364
• Issue: 1
• Start Page: 219
• End Page: 224
• Grant/Funding Information: Financial support was provided by the Medical Engineering Solutions in the Osteoarthritis Centre of Excellence funded by the Wellcome Trust and the EPSRC (088844/Z/09/Z).; C Ross Ethier is a recipient of the Royal Society Wolfson Research Merit Award.
• Keywords: Stem cells; Chondrogenesis; Cartilage repair; Amelogenin; ACI
• Research Categories: Health Sciences, General; Health Sciences, Opthamology

Abstract

Current approaches to treat osteoarthritis (OA) are insufficient. Autologous chondrocyte implantation (ACI) has been used for the past decade to treat patients with OA or focal cartilage defects. However, a number of complications have been reported post-ACI, including athrofibrosis and symptomatic hypertrophy. Thus, a long-term ACI strategy should ideally incorporate methods to ‘prime’ autologous chondrocytes to form a cartilage-specific matrix and suppress hypertrophic mineralization. The objective of this study is to examine the effects of tyrosine-rich amelogenin peptide (TRAP; an isoform of the developmental protein amelogenin) on human articular cartilage cell (HAC) chondrogenic differentiation and hypertrophic mineralization in vitro. Effects of chemically synthesized TRAP on HAC chondrogenic differentiation were determined by assessing: (1) sGAG production; (2) Alcian blue staining for proteoglycans; (3) collagen type II immunostaining; and (4) expression of the chondrogenic genes SOX9, ACAN and COL2A1. Hypertrophic mineralization was assayed by: (1) ALP expression; (2) Alizarin red staining for Ca+2-rich bone nodules; (3) OC immunostaining; and (4) expression of the osteogenic/hypertrophic genes Ihh and BSP. Chemically synthesized TRAP was found to suppress terminal osteogenic differentiation of HACs cultured in hypertrophic mineralization-like conditions, an effect mediated via down-regulation of the Ihh gene. Moreover, TRAP was found to augment chondrogenic differentiation of HACs via induction of SOX9 gene expression when cells were cultured in pro-chondrogenic media. The results obtained from this proof-of-concept study motivate further studies on the use of TRAP as part of a preconditioning regimen in autologous chondrocyte implantation procedures for OA patients and patients suffering from focal cartilage defects.