Dental pulp inflammatory/immune response to a chitosan-enriched fibrin hydrogel in the pulpotomised rat incisor
1 Inserm, Université de Nantes, CHU Nantes, Centre de Recherche en Transplantation et Immunologie, UMR 1064, ITUN, F-44000 Nantes, France
2 Sarcomes Osseux et Remodelage des Tissus Calcifiés, INSERM UMR1238, Université de Nantes, Nantes, France
3 Université de Nantes, Faculté d’Odontologie, Nantes, France
4 CHU de Nantes, Service d’Odontologie Conservatrice et Pédiatrique, Nantes, France
5 CHU de Nantes, Service d’Odontologie Restauratrice et Chirurgicale, Nantes, France
6 Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Ingénierie des Matériaux Polymères UMR5223, F-69622, Villeurbanne, France
7 Laboratoire de Biologie Tissulaire et Ingénierie thérapeutique, UMR5305 CNRS/Université Lyon 1, UMS3444 BioSciences Gerland-Lyon Sud, Lyon, France
8 Université de Lyon, Université Lyon 1, Faculté d’Odontologie, Lyon, France
9 Hospices Civils de Lyon, Service d’Odontologie, Lyon, France
10 Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, France
Abstract
Current pulpotomy is limited in its ability to induce regeneration of the dental-pulp (DP) complex. Hydrogels are reported to be well-suited for tissue engineering and are unlikely to induce an inflammatory response that might damage the remaining tissue. The present study investigated the molecular and cellular actors in the early inflammatory/immune response and deciphered M1/M2 macrophage polarisation to a chitosan-enriched fibrin hydrogel in pulpotomised rat incisors. Both fibrin and fibrin-chitosan hydrogels induced a strong increase in interleukin-6 (IL-6) transcript in the DP when compared to the DP of untreated teeth. Gene expression of other inflammatory mediators was not significantly modified after 3 h. In the viable DP cell population, the percentage of leukocytes assessed by flow cytometry was similar to fibrin and fibrin-chitosan hydrogels after 1 d. In this leukocyte population, the proportion of granulocytes increased beneath both hydrogels whereas the antigen-presenting cell, myeloid dendritic cells, T cells and B cells decreased. The natural killer (NK) cell population was significantly decreased only in DPs from teeth treated with fibrin-chitosan hydrogel. Immunolabeling analysis of the DP/hydrogel interface showed accumulation of neutrophil granulocytes in contact with both hydrogels 1 d after treatment. The DP close to this granulocyte area contained M2 but no M1 macrophages. These data collectively demonstrated that fibrin-chitosan hydrogels induced an inflammatory/immune response similar to that of the fibrin hydrogel. The results confirmed the potential clinical use of fibrin-chitosan hydrogel as a new scaffold for vital-pulp therapies.
Graphical Abstract

Keywords
- Chitosan
- fibrin
- hydrogel
- inflammatory cells
- M1 macrophage
- M2 macrophage
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