The role of tnfα in zebrafish skeletal regeneration

Abstract

TNF-α is a pro-inflammatory cytokine that is implicated in many chronic inflammatory and autoimmune disorders, including Rheumatoid Arthritis where it is associated with increased bone resorption. However, despite the use of anti-TNFα therapies routinely as clinical treatment, the effect of TNF-α on bone repair and regeneration has not been fully elucidated. Bone is constantly remodelled through a fine balance of anabolic osteoblast and catabolic osteoclast activity and the effect of tnfα on the proliferation and differentiation of these cells is paradoxical. In this study, employing zebrafish as a model, I investigate the involvement of tnfα in bone regeneration by genetically and pharmacologically inhibiting its function and assessing bone regeneration through a zebrafish caudal fin regeneration model. Bone mineralisation post caudal fin regeneration in tnfα^-/- mutants was comparable to WT when assessing the regrowth of bone length, width, and total fin area. At 4 days post amputation (dpa), the tnfα^-/- mutants exhibited subtly increased osx reporter expression, which was consistent with higher levels of osx mRNA expression. However, there was no significant difference in the mRNA expression levels of runx2a and tcf7. Moreover, no difference in TRAP staining was observed in the mutants at uninjured or 7dpa timepoints. In the tnfα^-/- mutants, the compensatory upregulation of il1b and tnfb were investigated and showed no difference compared to WT at uninjured or 4dpa timepoints. Together these results show that genetic ablation of tnfα has no gross effects on bone regeneration, however investigation into the biomechanical stability of the regenerated bone in these fish would further elucidate this finding. These results implicate that tnfα inhibition has a positive effect on osteoblastogenesis, suggesting that tnfα may act as a break on osteoblast proliferation, nonetheless a larger sample size is needed to confirm this trend.

Date of Award	5 Dec 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Chrissy L Hammond (Supervisor) & Beck J Richardson (Supervisor)