Clinical pathologies of bone fracture modelled in zebrafish

Abstract

Reduced bone quality or mineral density predict susceptibility to fracture and also attenuate subsequent repair. Bone regrowth is also compromised by bacterial infection, which exacerbates fracture site inflammation. Because of the cellular complexity of fracture repair, as well as genetic and environmental influences, there is a need for models that permit visualisation of the fracture repair process under clinically relevant conditions. To characterise the process of fracture repair in zebrafish, we employed a crush fracture of fin rays, coupled with histological and transgenic labelling of cellular responses; the results demonstrate a strong similarity to the phased response in humans. We applied our analysis to a zebrafish model of osteogenesis imperfecta (OI), which shows reduced bone quality, spontaneous fractures and propensity for non-unions. We found deficiencies in the formation of a bone callus during fracture repair in our OI model and showed that clinically employed antiresorptive bisphosphonates can reduce spontaneous fractures in OI fish and also measurably reduce fracture callus remodelling in wild-type fish. The csf1ra mutant, which has reduced osteoclast numbers, also showed reduced callus remodelling. Exposure to excessive bisphosphonate, however, disrupted callus repair. Intriguingly, neutrophils initially colonised the fracture site, but were later completely excluded. However, when fractures were infected with Staphylococcus aureus, neutrophils were retained and compromised repair. This work elevates the zebrafish bone fracture model and indicates its utility in assessing conditions of relevance to an orthopaedic setting with medium throughput.

Zebrafish as a model to study autophagy and its role in skeletal development and disease

“…Zebrafish are also a useful model for fracture repair studies as they show a fracture healing response with callus formation which is very similar to mammals (Sousa et al 2012 ; Tomecka et al 2019 ). Using the GFP-Map1Lc3 line and the live bone stain, Alizarin red, we were able to perform a fin fracture assay which showed that the expression of Map1Lc3 increases during the early stages of fracture repair (Fig.…”

Zebrafish: An Emerging Model for Orthopedic Research

“…Dedifferentiation of mature osteoblasts also occurs during repair of zebrafish fin fractures and skull injuries . While osteoblast dedifferentiation is more limited in mammals, fin repair after fracture exhibits some similarities to mammalian long bone fracture, including formation of a remodeling callus, and recruitment of osteoclasts . Recently, it was shown that neutrophils dynamically colonize the fracture site.…”

“…Recently, it was shown that neutrophils dynamically colonize the fracture site. When infected with Staphylococcus aureus , neutrophils were retained in the fracture site and repair was reduced . Further studies examining the utility of the fin fracture model to study the aspects of fracture biology are warranted.…”

Giantin is required for intracellular N-terminal processing of type I procollagen

“…and WT fish as has been previously described (Geurtzen et al, 2014;Tomecka et al, 2019). Injured fish 91 were stained with calcein at different timepoints to monitor calcification of newly formed bone matrix in 92 the callus.…”