Direct bone formation during distraction osteogenesis does not require TNFα receptors and elevated serum TNFα fails to inhibit bone formation in TNFR1 deficient mice

Abstract

Distraction Osteogenesis (DO) is a process which induces direct new bone formation as a result of mechanical distraction. Tumor necrosis factor-α (TNF) is a cytokine that can modulate osteoblastogenesis. The direct effects of TNF on direct bone formation in rodents are hypothetically mediated through TNF receptor 1 and/or 2 (TNFR1/2) signaling. We utilized a unique model of mouse DO to assess the effects of 1) TNFR homozygous null gene alterations on direct bone formation and 2) rmTNF on wild type (WT), TNFR1 -/-(R1KO), and TNR2 -/-(R2KO) mice. Radiological and histological analyses of direct bone formation in the distraction gaps demonstrated no significant differences between the WT, R1KO, R2KO, or TNFR1 -/-& R2 -/-(R1&2KO) mice. R1&2KO mice had elevated levels of serum TNF but demonstrated no inhibition of new bone formation. Systemic administration by osmotic pump of rmTNF during DO (10 ug/ kg/day) resulted in significant inhibition of gap bone formation measures in WT and R2KO mice, but not in R1KO mice. We conclude that exogenous rmTNF and/or endogenous TNF act to inhibit new bone formation during DO by signaling primarily through TNFR1.

Cisplatin inhibits bone healing during distraction osteogenesis

“…Based on previous studies which suggest that TNFR1 mediates the negative effects of exogenous TNF, we performed a study identical to that above except we used nine week old male TNFR1 deficient mice (n=6: saline & n=6 CDP) 22 . Serum TNF levels were measured.…”

“…Distraction was performed as we have previously described 14, 22, 25 . Following acclimation and under Nembutal anesthesia, each mouse underwent placement of an external fixator and osteotomy to the left tibia 22 .…”

“…Five to seven micron longitudinal sections were cut on a microtome (Leitz 1512, Wetzlar, Germany) for hematoxylin and eosin staining (H&E). Sections were selected to represent a central or near central gap location as we have described 14, 22, 25 . To be included in both radiographic and histologic analyses the DO samples had to 1) be well aligned, 2) have no broken pin sites, 3) have few bone chips within the DO gap, 4) have an intact ankle, and 5) have had no significant weight loss or health problems during the distraction period as we have described previously 14, 22, 25 .…”

Honokiol stimulates osteoblastogenesis by suppressing NF-κB activation

“…By contrast, activation of NF-κB signaling by inflammatory cytokines such as TNFα potently inhibits osteoblast differentiation and function in vitro (5,(10)(11)(12)(13) and in vivo (10,14,15). By contrast, suppression of NF-κB promotes osteoblast differentiation and mineralization in vitro (10) and bone formation at baseline (16) and in in vivo models of estrogen deficiency (16,17) and of fracture repair (18,19).…”

Suppression of NF-κB Activation By Gentian Violet Promotes Osteoblastogenesis and Suppresses Osteoclastogenesis

“…Indeed, TNFαneutralization in mice is effective in mitigating bone loss associated with estrogen deficiency in ovariectomized mice [3]. TNFα antagonists are further able to reverse compromised bone regeneration potential associated with aging in an animal fracture repair model [4] through association of TNFα with its type I receptor [5]. …”