The mechanical impact ofcol11a2loss on joints;col11a2mutant zebrafish show changes to joint development and function, which leads to early-onset osteoarthritis

Abstract

Collagen is the major structural component of cartilage, and mutations in the genes encoding type XI collagen are associated with severe skeletal dysplasias (fibrochondrogenesis and Stickler syndrome) and early-onset osteoarthritis (OA). The impact of the lack of type XI collagen on cell behaviour and mechanical performance during skeleton development is unknown. We studied a zebrafish mutant for col11a2 and evaluated cartilage, bone development and mechanical properties to address this. We show that in col11a2 mutants, type II collagen is made but is prematurely degraded in maturing cartilage and ectopically expressed in the joint. These changes are correlated with increased stiffness of both bone and cartilage; quantified using atomic force microscopy. In the mutants, the skeletal rudiment terminal region in the jaw joint is broader and the interzone smaller. These differences in shape and material properties impact on joint function and mechanical performance, which we modelled using finite element analyses. Finally, we show that col11a2 heterozygous carriers reach adulthood but show signs of severe early-onset OA. Taken together, our data demonstrate a key role for type XI collagen in maintaining the properties of cartilage matrix; which when lost leads to alterations to cell behaviour that give rise to joint pathologies.This article is part of the Theo Murphy meeting issue ‘Mechanics of development’.

Exposure to hypergravity during zebrafish development alters cartilage material properties and strain distribution

“…Atomic Force Microscopy (AFM) was conducted utilizing a Multi-mode VIII microscope with Nanoscope V controller, operating in a PeakForce control regime [Bruker, CA, USA]. Larval cartilage was investigated in a hydrated state in an ambient environment (Elizabeth A. Lawrence et al , 2018). Prior to AFM investigation, larvae were fixed in 4% formaldehyde, stained with Alcian blue and Alizarin red (as above), and the lower jaw was dissected in 1% glycerol in PBS to prevent structural changes induced by drying.…”

“…Confocal image stacks of the lower jaw immunostained for type II collagen were loaded in to Fiji (Schindelin et al , 2012) and the line tool, followed by the measure command, were used to take length and width measurements (Figure 1 A). 3D jaw renders and joint measurements were executed as previously described in (Elizabeth A. Lawrence et al , 2018) (Figure 1 D) using Amira 6.0 [FEI].…”

“…The same cartilage morphology and muscle forces were used for both conditions’ models in the absence of significant differences in cartilage and muscle morphology between 1g static and 6g specimens (Figure 1A-C, H, H’). The FE meshes were developed and modelled for jaw opening and closing movements as previously published (E.A. Lawrence et al , 2018).…”

Potential of zebrafish as a model to characterise MicroRNA profiles in mechanically mediated joint degeneration

“…FEA can be used to visualise patterns of strain by displaying them with colours to show areas of high and low strain, or degree of tissue deformation. Finite element models for the developing zebrafish jaw have been published for wild-type fish (Brunt et al 2016;Brunt et al 2016), mutants (Lawrence et al 2018) and larvae exposed to different gravitational fields (Lawrence et al 2020). Cartilage material properties change during development, in response to mutations to chondrocyte genes or changes to gravitational force, and can be tested ex vivo by atomic force microscopy (AFM) or nanoindentation (Lawrence et al 2018(Lawrence et al , 2020, to provide further information and accuracy to FE models.…”

Mechanics of development

“…Research groups across the world are investigating how mechanical forces affect the development of every major organ in the body, including the cardiovascular and lymphatic systems [2][3][4][5][6][7], the musculoskeletal system [3,[8][9][10][11][12][13], the brain [14,15], the eye [16], the neural tube [17,18], the skin [19], the gut [20 -23] and the lung and mammary gland [24][25][26], in addition to the processes that shape the very early embryo, such as gastrulation [27], and mechanotransduction at the cellular or sub-cellular levels during development [28][29][30][31]. A range of animal models are being used, including chick [8][9][10], mouse [8,11] fly [28,[32][33][34] and zebrafish [12 -35] in addition to-or alongside-computational models [2,12,13,36,37]. Researchers in the field come from a range of backgrounds including developmental biology, biomechanics, bioengineering, cell signalling, anatomy, computational sciences and biophysics and therefore use a range of techniques.…”