AUTHOR=El Khassawna Thaqif , Serra Alessandro , Bucher Christian H. , Petersen Ansgar , Schlundt Claudia , Könnecke Ireen , Malhan Deeksha , Wendler Sebastian , Schell Hanna , Volk Hans-Dieter , Schmidt-Bleek Katharina , Duda Georg N. TITLE=T Lymphocytes Influence the Mineralization Process of Bone JOURNAL=Frontiers in Immunology VOLUME=8 YEAR=2017 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2017.00562 DOI=10.3389/fimmu.2017.00562 ISSN=1664-3224 ABSTRACT=

Bone is a unique organ able to regenerate itself after injuries. This regeneration requires the local interplay between different biological systems such as inflammation and matrix formation. Structural reconstitution is initiated by an inflammatory response orchestrated by the host immune system. However, the individual role of T cells and B cells in regeneration and their relationship to bone tissue reconstitution remain unknown. Comparing bone and fracture healing in animals with and without mature T and B cells revealed the essential role of these immune cells in determining the tissue mineralization and thus the bone quality. Bone without mature T and B cells is stiffer when compared to wild-type bone thus lacking the elasticity that helps to absorb forces, thus preventing fractures. In-depth analysis showed dysregulations in collagen deposition and osteoblast distribution upon lack of mature T and B cells. These changes in matrix deposition have been correlated with T cells rather than B cells within this study. This work presents, for the first time, a direct link between immune cells and matrix formation during bone healing after fracture. It illustrates specifically the role of T cells in the collagen organization process and the lack thereof in the absence of T cells.