Absence of substance P and the sympathetic nervous system impact on bone structure and chondrocyte differentiation in an adult model of endochondral ossification

• DOI: 10.1016/j.matbio.2014.06.007
• Publication Date: 2014-07-22T03:46:51Z
• Authors: Tanja Niedermair; Volker Kuhn; Fatemeh Doranehgard; Richard Stange; Britta Wieskötter; Johannes Beckmann; Philipp Salmen; Hans-Robert Sprin...; Rainer H. Straub; Andreas Zimmer; Joachim Grifka; Susanne Grässel
• Keywords: Endochondral ossification; Callus; Intramembranous ossification

Sensory and sympathetic nerve fibers (SNF) innervate bone epiphyseal growth plate. The role of neuronal signals for proper endochondral ossification during skeletal is mostly unknown. Here, we investigated the impact absence sensory neurotransmitter substance P (SP) removal SNF on callus differentiation, a model in adult animals, formation. In order to generate callus, tibia fractures were set left hind leg wild type (WT), tachykinin 1-deficient (Tac1 −/−) mice (no SP) animals without SNF. Locomotion was tested healthy touch sensibility determined early after fracture. Callus tissue prepared immunofluorescence staining SP, neurokinin1-receptor (NK1R), tyrosine-hydroxylase (TH) adrenergic receptors α1, α2 β2. At fracture site, osteoclasts stained TRAP, osteoblasts RUNX2, histomorphometric analysis composition performed. Primary murine marrow derived macrophages (BMM), osteoclasts, activity, proliferation apoptosis vitro. Femoral all three groups mechanical testing μCT-analysis. cells positive NK1R, α1d- α2b adrenoceptors remained β2-adrenoceptor TH-negative. Absence SP did not change general locomotion but reduces sensitivity SNF, detected more mesenchymal less cartilaginous 5 days day 13 past fracture, observed decrease area covered by hypertrophic chondrocytes Tac1 −/− lower number an increase mineralized Apoptosis rate activity isolated from sympathectomized partly altered Mechanical fractured- contralateral legs 21 revealed overall reduced quality μCT-analysis clear structural alteration fractured proximal site with respect trabecular parameters, mass connectivity density. Notably, parameters are when related unfractured WT pain stability general. micro-architecture profoundly impaired intact drastic effect SP-deficient mice. Both neurotransmitters indispensable differentiation. Importantly, formation whereas induces resorption rate. produce its receptor NK1 α-adrenoceptors indicating endogenous signaling loop. We propose that have crucial trophic effects which essential addition their classical neurological actions.