Transformed notochordal cells trigger chronic wounds in zebrafish, destabilizing the vertebral column and bone homeostasis

Abstract

Notochordal cells play a pivotal role in vertebral column patterning, contributing to the formation of the inner architecture of intervertebral discs (IVDs). Their disappearance during development has been associated with reduced repair capacity and IVD degeneration. Notochord cells can give rise to chordomas, a highly invasive bone cancer associated with late diagnosis. Understanding the impact of neoplastic cells during development and on the surrounding vertebral column could open avenues for earlier intervention and therapeutics. We investigated the impact of transformed notochord cells in the zebrafish skeleton using a RAS expressing line in the notochord under the control of the Kita promoter, with the advantage of adulthood endurance. Transformed cells caused damage in the notochord and destabilised the sheath layer triggering a wound repair mechanism, with enrolment of sheath cells (col9a2+) and expression of wt1b, similar to induced notochord wounds. Moreover, increased recruitment of neutrophils and macrophages, displaying abnormal behaviour in proximity to the notochord sheath and transformed cells, supported parallels between chordomas, wound and inflammation. Cancerous notochordal cells interfere with differentiation of sheath cells to form chordacentra domains leading to fusions and vertebral clefts during development. Adults displayed IVD irregularities reminiscent of degeneration; reduced bone mineral density, increased osteoclast activity; while disorganised osteoblasts and collagen indicate impaired bone homeostasis. By depleting inflammatory cells, we abrogated chordoma development and rescued the skeletal features of the vertebral column. Therefore, we showed that transformed notochord cells alter the skeleton during life, causing a wound-like phenotype and activating chronic wound response, suggesting parallels between chordoma, wound, IVD degeneration and inflammation, highlighting inflammation as a promising target for future therapeutics.

Histopathology of the Intervertebral Disc of Nothobranchius furzeri, a Fish Model of Accelerated Aging

“…This, afterwards, can lead to spinal malformations, as notochord abnormalities are associated with vertebral defects. Furthermore, it is described that the notochord, in particular the notochordal cells, plays a crucial part in vertebrae development and intervertebral disc formation, as their disappearance is linked to reduced repair capacity and intervertebral disc degeneration [26][27][28][29][30]. We expected to see similarities between old and deformed N. furzeri, as in human degenerative spine diseases and mammalian aging, a degradation of the intervertebral discs can be observed.…”

Functional Validation of Osteoporosis Genetic Findings Using Small Fish Models

“…Examples include live images of reporter lines labeling osteoblasts, live staining with Alizarin Red to label the bones. ( B ) Images of volume rendering from micro-computed tomography (uCT) of adult WT and mutant (chordoma model [ 90 ]), as an example of skeletal abnormalities in mutants (vertebral fusion and lower TMD). Variations of TMD are shown color-coded.…”

Understanding and drugging RAS: 40 years to break the tip of the iceberg

“…In the four decades since the discovery of RAS mutations in cancer, researchers have made significant advances in understanding their mechanistic underpinnings. For example, work previously published in DMM has shown that dysregulated RAS signaling affects phenotypic plasticity ( Bangs et al, 2020 ; López-Cuevas et al, 2021 ), an emerging hallmark of cancer ( Hanahan, 2022 ). Several such interdisciplinary studies focus on the oncogenic output of dysregulated RAS signaling and provide essential bases for identifying actionable therapeutics.…”