Open Access Research article

Neutrophils exhibit distinct phenotypes toward chitosans with different degrees of deacetylation: implications for cartilage repair

Pascale Simard12, Hugo Galarneau1, Sébastien Marois1, Daniel Rusu13, Caroline D Hoemann4, Patrice E Poubelle13, Hani El-Gabalawy5 and Maria JG Fernandes12*

Author Affiliations

1 Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ-CHUL, boul. Laurier, Québec, G1V 4G2, Canada

2 Department of Anatomy and Physiology, Université Laval, avenue de la Médecine, Québec, G1V 0A6, Canada

3 Department of Medicine, Université Laval, avenue de la Médecine, Québec, G1V 0A6, Canada

4 Department of Chemical Engineering, Institute of Biomedical Engineering, Ecole Polytechnique, boul. Édouard-Montpetit, Montréal, H3C 3A7, Canada

5 Arthritis Centre, University of Manitoba, Sherbrook Street, Winnipeg, R3A 1M4, Canada

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Arthritis Research & Therapy 2009, 11:R74  doi:10.1186/ar2703

Published: 21 May 2009

Abstract

Introduction

Osteoarthritis is characterized by the progressive destruction of cartilage in the articular joints. Novel therapies that promote resurfacing of exposed bone in focal areas are of interest in osteoarthritis because they may delay the progression of this disabling disease in patients who develop focal lesions. Recently, the addition of 80% deacetylated chitosan to cartilage microfractures was shown to promote the regeneration of hyaline cartilage. The molecular mechanisms by which chitosan promotes cartilage regeneration remain unknown. Because neutrophils are transiently recruited to the microfracture site, the effect of 80% deacetylated chitosan on the function of neutrophils was investigated. Most studies on neutrophils use preparations of chitosan with an uncertain degree of deacetylation. For therapeutic purposes, it is of interest to determine whether the degree of deacetylation influences the response of neutrophils to chitosan. The effect of 95% deacetylated chitosan on the function of neutrophils was therefore also investigated and compared with that of 80% deacetylated chitosan.

Methods

Human blood neutrophils from healthy donors were isolated by centrifugation on Ficoll-Paque. Chemotaxis was performed using the chemoTX system. Production of superoxide anions was evaluated using the cytochrome c reduction assay. Degranulation was determined by evaluating the release of myeloperoxidase and lactoferrin. The internalization of fluorescently labelled 80% deacetylated chitosan by neutrophils was studied by confocal microscopy.

Results

Neutrophils were dose dependently attracted to 80% deacetylated chitosan. In contrast, 95% deacetylated chitosan was not chemotactic for neutrophils. Moreover, the majority of the chemotactic effect of 80% deacetylated chitosan was mediated by phospholipase-A2-derived bioactive lipids. Contrary to the induction of chemotaxis, neither 80% nor 95% deacetylated chitosan activated the release of granule enzymes or the generation of active oxygen species. Despite the distinct response of neutrophils toward 80% and 95% deacetylated chitosan, both chitosans were internalized by neutrophils.

Conclusions

Eighty per cent deacetylated chitosan induces a phenotype in neutrophils that is distinct from the classical phenotype induced by pro-inflammatory agents. Our observations also indicate that the degree of deacetylation is an important factor to consider in the use of chitosan as an accelerator of repair because neutrophils do not respond to 95% deacetylated chitosan.