Juvenile zebrafish (Danio rerio) are able to recover from lordosis

Abstract

Haemal lordosis, a frequent skeletal deformity in teleost fish, has long been correlated with increased mechanical loads induced by swimming activity. In the present study, we examine whether juvenile zebrafish can recover from haemal lordosis and explore the musculoskeletal mechanisms involved. Juveniles were subjected to a swimming challenge test (SCT) that induced severe haemal lordosis in 49% of the animals and then immediately transferred them to 0.0 total body lengths (TL) per second of water velocity for a week. The recovery from lordosis was examined by means of whole mount staining, histology and gene expression analysis. Results demonstrate that 80% of the lordotic zebrafish are capable of internal and external recovery within a week after the SCT. Recovered individuals presented normal shape of the vertebral centra, maintaining though distorted internal tissue organization. Through the transcriptomic analysis of the affected haemal regions, several processes related to chromosome organization, DNA replication, circadian clock and transcription regulation were enriched within genes significantly regulated behind this musculoskeletal recovery procedure. Genes especially involved in adipogenesis, bone remodeling and muscular regeneration were regulated. A remodeling tissue-repair hypothesis behind haemal lordosis recovery is raised. Limitations and future possibilities for zebrafish as a model organism to clarify mechanically driven musculoskeletal changes are discussed.

Effect of Early Peptide Diets on Zebrafish Skeletal Development

“…This preference could potentially trigger a differential musculoskeletal response during the SCT ( spp1 and tnni2 increased expression in P6 and P12 diets, respectively, after the SCT in ADF regime), explaining the increased lordosis counts in this regime. Additionally, since lordosis induction requires muscular adaptations of the haemal region [ 34 , 57 ], future research should focus on the effect of early nutrition on larval and post-larval musculoskeletal development.…”

“…Given this background, the differences in methionine, leucine and lysine between the peptide diets and our control one could potentially induce an altered muscle developmental pattern from early stages. Based on the musculoskeletal nature of the haemal lordosis [ 34 ], a potential either enforcement or myopathy induced by the peptides could explain the differential response and/or ability to adapt under increased swimming conditions.…”

“…Similarly, after SCT, 4–8 individuals of each external phenotype (S, N), experimental diet, replicate and feeding regime were randomly sampled for RNA analysis. A dissection of the haemal parts of the SCT fish was applied according to Printzi et al 2022 [ 34 ]. SCT samples were pooled in two individuals per sample within each phenotype, diet, replicate and regime to meet the extraction requirements (two individuals/sample [ 10 ]).…”

“…Following the mammalian pattern of osteoblast differentiation, zebrafish express several differentiation markers such as bglap , sparc , collagens and other bone matrix genes during bone development [ 33 ]. Simultaneously, several key genes (e.g., tgfb , foxo1 , tnni2 , pparγ ) have been highlighted as differentially regulated behind a musculoskeletal remodeling of normally developed post-larvae bones on the species [ 34 ]. Although the digestive enzymatic activity (e.g., amy2a , prss1 , [ 35 ]) and nutrient transport (e.g., pept1, [ 36 ]) during zebrafish ontogenetic development have been described, the precise nutritional needs remain unrevealed.…”

Deformity or variation? Phenotypic diversity in the zebrafish vertebral column

“…Atavism or retention of an ancestral character, zebrafish show the inherent potential to develop variant morphologies under husbandry conditions, without them reflecting certain gene defects. These variants could be more frequently expressed under sub‐optimal husbandry conditions, such as rearing density (Martini et al, 2021), tank size (Di Biagio et al, 2022), water current (Printzi et al, 2022) or temperature (Ytteborg et al, 2010). These are important points when assessing mutated zebrafish models for skeletal diseases.…”