Bone-Conditioned Medium Inhibits Osteogenic and Adipogenic Differentiation of Mesenchymal Cells In Vitro.
OBJECTIVE
Autografts are used for bone reconstruction in regenerative medicine including oral and maxillofacial surgery. Bone grafts release paracrine signals that can reach mesenchymal cells at defect sites. The impact of the paracrine signals on osteogenic, adipogenic, and chondrogenic differentiation of mesenchymal cells has remained unclear.


METHODS
Osteogenesis, adipogenesis, and chondrogenesis were studied with murine ST2 osteoblast progenitors, 3T3-L1 preadipocytes, and ATDC5 prechondrogenic cells, respectively. Primary periodontal fibroblasts from the gingiva, from the periodontal ligament, and from bone were also included in the analysis. Cells were exposed to bone-conditioned medium (BCM) that was prepared from porcine cortical bone chips.


RESULTS
BCM inhibited osteogenic and adipogenic differentiation of ST2 and 3T3-L1 cells, respectively, as shown by histological staining and gene expression. No substantial changes in the expression of chondrogenic genes were observed in ATDC5 cells. Primary periodontal fibroblasts also showed a robust decrease in alkaline phosphatase and peroxisome proliferator-activated receptor gamma (PPARγ) expression when exposed to BCM. BCM also increased collagen type 10 expression. Pharmacologic blocking of transforming growth factor (TGF)-β receptor type I kinase with SB431542 and the smad-3 inhibitor SIS3 at least partially reversed the effect of BCM on PPARγ and collagen type 10 expression. In support of BCM having TGF-β activity, the respective target genes were increasingly expressed in periodontal fibroblasts.


CONCLUSIONS
The present work is a pioneer study on the paracrine activity of bone grafts. The findings suggest that cortical bone chips release soluble signals that can modulate differentiation of mesenchymal cells in vitro at least partially involving TGF-β signaling.
Department of Cranio-Maxillofacial Surgery, Inselspital, University of Bern, Bern, Switzerland.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.|College of Stomatology, GuangXi Medical University, GuangXi, China.
Jianbo
J
Peng
Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Michael
M
Nemec
Department of Cranio-Maxillofacial Surgery, Inselspital, University of Bern, Bern, Switzerland.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Eliane
E
Brolese
Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Robert K. Schenk Laboratory of Oral Histology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Dieter D
DD
Bosshardt
Department of Cranio-Maxillofacial Surgery, Inselspital, University of Bern, Bern, Switzerland.
Benoit
B
Schaller
Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Daniel
D
Buser
Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Reinhard
R
Gruber
D050156:Adipogenesis; D000818:Animals; D016025:Bone Transplantation; D001842:Bone and Bones / Q000166:cytology*; D020219:Chondrogenesis; D017077:Culture Media, Conditioned / Q000494:pharmacology*; D005347:Fibroblasts / Q000166:cytology; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology; D010012:Osteogenesis; D010513:Periodontal Ligament / Q000166:cytology; D013552:Swine
D017077:Culture Media, Conditioned
ADAM19; ALPL; COL10; IL-11; MAPK; PPARγ; Sema7a; TGF-β; adipocytes; adipogenic differentiation; autografts; autologous bone grafts; bone regeneration; chondrogenic differentiation; conditioned medium; differentiation; graft consolidation; mesenchymal cells; osteoblasts; osteocytes; osteogenic differentiation; paracrine; periodontal fibroblasts; smad-3; supernatant