Vol.:(0123456789) 1 3 Histochemistry and Cell Biology https://doi.org/10.1007/s00418-019-01789-1 ORIGINAL PAPER Cellular and collagen reference values of gingival and periodontal ligament tissues in rats: a pilot study Antoine Alves 1,2  · Nina Attik 2,3  · Carine Wirth 1  · Yves Bayon 4  · Alexis Piat 5  · Brigitte Grosgogeat 2,3,6  · Kerstin Gritsch 2,3,6 Accepted: 4 May 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Reference data are lacking on the periodontal ligament and the gingival tissue of the rat model, which would be useful for studies of new medical or biomaterial periodontal treatments. The objective of the current study was to propose cellular and collagen reference values of gingival and periodontal ligament tissues in rat, using a simple and reliable quantitative method after decalcification. Mandibular samples of ten adult Sprague–Dawley rats were used. Mild decalcification was carried out using ethylenediaminetetraacetic acid (EDTA) to preserve the morphology of tissues. Half of the samples were decalcified and the other half were not. The gingiva and the periodontal ligament were analyzed. Descriptive histology and computer- assisted image analysis were performed. The data showed that qualitatively, cellular and extracellular matrix morphologies were well preserved compared to non-decalcified periodontal soft tissue biopsies. Histomorphometrically, constitutive cellularity and the total amount of native collagen, collagen directionality and collagen anisotropy in both experimental conditions did not significantly differ. Taken together, these results suggested that EDTA decalcification did not negatively affect the studied endpoints. Moreover, this mild decalcification method allowed in situ maintenance of the periodontal soft and hard tissue integrity. The structural and compositional computerized assessment performed in the healthy periodontal soft tissue could provide reference values that will be required for future assessment on the effects of pathological, reparative and regenerative processes in rat periodontal soft tissues. Keywords Periodontal soft tissue · Histomorphometric analysis · Cellularity · Collagen · EDTA decalcification · Anisotropy · Directionality Introduction In the study of periodontal diseases and treatments, there is a continuous need for a simple, predictive and inexpen- sive preclinical model for testing therapeutic agents, and medical devices. A suitable animal model should allow evaluation of key parameters involved in the pathology or in the healing process. Jacob and Nath reported that the development and the resolution of inflammation as well as the gingival wound healing in rats are remarkably similar to humans (Bourgeois et al. 2007; Kim et al. 2012; Jacob and Nath 2013; Takamori et al. 2016; Elburki et al. 2016). Furthermore, the rat model is simple as it is easily avail- able, reliable, and cheaper compared to other inflamma- tory models and can be mainly extrapolated to humans (Jacob and Nath 2013). Rat models have been frequently used for preclinical investigations of periodontitis, peri- implantitis and their therapy (Castania et al. 2015; Pamuk * Nina Attik nina.attik@univ-lyon1.fr 1 NAMSA, 115 chemin de l’Islon, 38670 Chasse-sur-Rhône, France 2 Laboratoire des Multimatériaux et Interfaces, Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5615, 69622 Villeurbanne, France 3 Faculté d’Odontologie, Université de Lyon, Université Claude Bernard Lyon 1, 69008 Lyon, France 4 Medtronic—Sofradim Production, 116 Avenue du Formans, 01600 Trévoux, France 5 Département Biosciences, INSA, Bâtiment Louis Pasteur, 69621 Villeurbanne, France 6 Service de Consultations et de Traitements Dentaires, Hospices Civils de Lyon, 69007 Lyon, France