An injectable heparin-conjugated hyaluronan scaffold for local delivery of transforming growth factor β1 promotes successful chondrogenesis

• Published in: Acta biomaterialia 2019-11, Vol.99, p.168-180
• Main Authors: Levinson, Clara, Lee, Mihyun, Applegate, Lee Ann, Zenobi-Wong, Marcy
• Format: Article
• Language: English
• Subjects: Biomaterials; Biomedical materials; Cartilage; Cell culture; Cell proliferation; Cell viability; Chondrogenesis; Chondroprogenitors; Controlled release; Deposition; Growth factors; Heparin; Homeostasis; Hyaluronan; Hyaluronic acid; Hydrogels; Repair; Scaffolds; Surgical implants; Sustained release; TGF-β1; Tissue engineering; Transforming growth factor-b1
• ISSN: 1742-7061; 1878-7568
• DOI: 10.1016/j.actbio.2019.09.017

[Display omitted] Cartilage lacks basic repair mechanisms and thus surgical interventions are necessary to treat lesions. Minimally-invasive arthroscopic procedures require the development of injectable biomaterials to support chondrogenesis of implanted cells. However, most cartilage tissue engineering approaches rely on pre-culture of scaffolds in media containing growth factors (GFs) such as transforming growth factor (TGF)-β1, which are crucial for cartilage formation and homeostasis. GFs media-supplementation is incompatible with injectable approaches and has led to a knowledge gap about optimal dose of GFs and release profiles needed to achieve chondrogenesis. This study aims to determine the optimal loading and release kinetics of TGF-β1 bound to an engineered GAG hydrogel to promote optimal cartilaginous matrix production in absence of TGF-β1 media-supplementation. We show that heparin, a GAG known to bind a wide range of GFs, covalently conjugated to a hyaluronan hydrogel, leads to a sustained release of TGF-β1. Using this heparin-conjugated hyaluronan hydrogel, 0.25 to 50 ng TGF-β1 per scaffold was loaded and cell viability, proliferation and cartilaginous matrix deposition of the encapsulated chondroprogenitor cells were measured. Excellent chondrogenesis was found when 5 ng TGF-β1 per scaffold and higher were used. We also demonstrate the necessity of a sustained release of TGF-β1, as no matrix deposition is observed upon a burst release. In conclusion, our biomaterial loaded with an optimal initial dose of 5 ng/scaffold TGF-β1 is a promising injectable material for cartilage repair, with potentially increased safety due to the low, locally administered GF dose. Cartilage cell-based products are dependent on exogenous growth factor supplementation in order for proper tissue maturation. However, for a one-step repair of defects without need for expensive tissue maturation, an injectable, growth factor loaded formulation is required. Here we show development of an injectable hyaluronan hydrogel, which achieves a sustained release of TGF-β1 due to covalent conjugation of heparin. These grafts matured into cartilaginous tissue in the absence of growth factor supplementation. Additionally, this system allowed us to screen TGF-β1 concentrations to determine the mimimum amount of growth factor required for chondrogenesis. This study represents a critical step towards development of a minimally-invasive, arthroscopic treatment for cartilage lesions.