Role of growth factors and oxygen to limit hypertrophy and impact of high magnetic nanoparticles dose during stem cell chondrogenesis

Aurore Van De Walle,Waïss Faissal,Claire Wilhelm,Nathalie Luciani

doi:10.1016/j.csbj.2018.10.014

Abstract

Due to an unmet clinical need of curative treatments for osteoarthritic patients, tissue engineering strategies that propose the development of cartilage tissue replacements from stem cells have emerged. Some of these strategies are based on the internalization of magnetic nanoparticles into stem cells to then initiate the chondrogenesis via magnetic compaction. A major difficulty is to drive the chondrogenic differentiation of the cells such as they produce an extracellular matrix free of hypertrophic collagen. An additional difficulty has to be overcome when nanoparticles are used, knowing that a high dose of nanoparticles can limit the chondrogenesis. We here propose a gene-based analysis of the effects of chemical factors (growth factors, hypoxia) on the chondrogenic differentiation of human mesenchymal stem cells both with and without nanoparticles. We focus on the synthesis of two of the most important constituents present in the cartilaginous extracellular matrix (Collagen II and Aggrecan) and on the expression of collagen X, the signature of hypertrophic cartilage, in order to provide a quantitative index of the type of cartilage produced (i.e. hyaline, hypertrophic). We demonstrate that by applying specific environmental conditions, gene expression can be directed toward the production of hyaline cartilage, with limited hypertrophy. Besides, a combination of the growth factors IGF-1, TGF-β3, with a hypoxic conditioning remarkably reduced the impact of high nanoparticles concentration.

Highlights

Articular cartilage is an avascular tissue with a rich extracellular matrix and a low cell density and turnover
It is demonstrated that a concentration at 1 ng/mL is too low to efficiently initiate chondrogenesis as collagen II is not expressed and aggrecan remains significantly lower than in all other conditions (Fig. 4 A, C). Under this low TGF-β3 concentration, collagen X expression is higher than collagen II leading to poor collagen II-to-collagen X ratios that are indicative of hypertrophy (Fig. 4 B)
Conditioned aggregates observed in transmission electron microscopy clearly demonstrated an extensive production of extracellular matrix (ECM) and the presence of an important amount of collagen type II, recognizable by the typical periodicity of the fibers, while no ECM production was observed in the negative control (Fig. S1 C and D)

Summary

Introduction

Articular (hyaline) cartilage is an avascular tissue with a rich extracellular matrix and a low cell density and turnover. Various options exist including autologous chondrocyte implantation (ACI), osteochondral grafts, and microfracture, which have all shown various degrees of success but typically prove unsatisfactory in the long term or are linked to donor site morbidity [1,2,3]. For this reason, tissue engineering strategies that propose the development of cartilage tissue replacements have emerged.

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