Bone de novo deposition in ASC protein-dependent

Abstract

Event Abstract Back to Event Bone de novo deposition in ASC protein-dependent Monica Calasans-Maia1, Suelen C. Sartoretto1, Sara Gemini-Piperni2, Thais P. Santos3, Inaya C. Lima3, Alexandre M. Rossi4, Gutemberg G. Alves5, Jose M. Granjeiro1, 2, Willian F. Zambuzzi6, Anna M. Teti7 and Nadia Rucci7 1 Fluminense Federal University, Dentistry School, Brazil 2 INMETRO, Bioengineering Programme, Brazil 3 COPPE - UFRJ, Nuclear Instrumentation Department, Brazil 4 Brazilian Center for Physics Research, LABIOMAT, Brazil 5 Fluminense Federal University, Clinical Research Unit, Italy 6 UNESP - Botucatu, Chemistry and Biochemistry, Brazil 7 University of L'Aquila, Department of Biotechnological and Applied Clinical Sciences, Italy One of the most important strategies in regenerative medicine is to fill bone defects with biocompatible materials in order to support functional bone healing. In particular, properties such as osteoconductivity and bio-absorption are improved by partial substitution of CO3 and PO3- in Hydroxyapatite (HA). However, biomaterial implantation also has adverse effects, mainly inflammatory reactions at the early stages. Recent studies demonstrate the role of ASC protein as a mediator of the inflammatory response due to the recruitment and formation of the inflammasome complex. Thus, it has been shown that ASC KO mice present resistance to inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis, but the contributions of the inflammasome component of ASC in the biological response to inorganic biomaterials for implanting have not been yet investigated. In order to address the function of ASC in the bone de novo deposition, we subjected wild type/C57BL/6 and ASC KO mice to three inorganic biomaterials, taking particular note of tibia defect healing. First, primary osteoprogenitor cells from both genotypes were collected. Positive staining for the activity of the osteoblast marker alkaline phosphatase (ALP) and the osteoclast marker tartrate resistant acid phosphatase (TRAcP) were detected histochemically. Thereafter, in order to validate our hypothesis that the ASC protein regulated osteoblast differentiation and bone de novo deposition, we evaluate the healing process of tibia defects on both wild type and ASC KO mice genotypes. Histological and histomorfometric analysis was performed. X-ray micro-computed tomography (μCT) analysis was used in order to confirm the data. Our results showed that primary osteoblast-like cells from ASC KO mice presented a lower level of ALP staining when compared to the same condition osteoblast-like cells from wild type mice, regardless of indirect exposure to the different inorganic biomaterials, suggesting ASC as a novel dependent protein involved in osteoblast differentiation in vitro, independent of inorganic biomaterial influence. Furthermore, our set of in vivo results showed that ASC KO mice were not able to fully heal tibia defects until after 28 days, independent of the inorganic biomaterial used as a scaffold, while wild type tibia defects presented a higher bone de novo volume. Altogether, our results strongly suggest that bone de novo deposition is a biological ASC-dependent event, which should be explored within the field of bone bioengineering. FAPESP; FAPERJ; CNPq; Marie Curie International Research Staff Exchange Scheme Fellowship to SGP within the 7th European Community Framework Programme.