Differential effects of altered patterns of movement and strain on joint cell behaviour and skeletal morphogenesis

Abstract

SummaryObjectiveThere is increasing evidence that joint shape is a potent predictor of osteoarthritis (OA) risk; yet the cellular events underpinning joint morphogenesis remain unclear. We sought to develop a genetically tractable animal model to study the events controlling joint morphogenesis.DesignZebrafish larvae were subjected to periods of flaccid paralysis, rigid paralysis or hyperactivity. Immunohistochemistry and transgenic reporters were used to monitor changes to muscle and cartilage. Finite Element Models were generated to investigate the mechanical conditions of rigid paralysis. Principal component analysis was used to test variations in skeletal morphology and metrics for shape, orientation and size were applied to describe cell behaviour.ResultsWe show that flaccid and rigid paralysis and hypermobility affect cartilage element and joint shape. We describe differences between flaccid and rigid paralysis in regions showing high principal strain upon muscle contraction. We identify that altered shape and high strain occur in regions of cell differentiation and we show statistically significant changes to cell maturity occur in these regions in paralysed and hypermobile zebrafish.ConclusionWhile flaccid and rigid paralysis and hypermobility affect skeletal morphogenesis they do so in subtly different ways. We show that some cartilage regions are unaffected in conditions such as rigid paralysis where static force is applied, whereas joint morphogenesis is perturbed by both flaccid and rigid paralysis; suggesting that joints require dynamic movement for accurate morphogenesis. A better understanding of how biomechanics impacts skeletal cell behaviour will improve our understanding of how foetal mechanics shape the developing joint.

The mechanical impact of col11a2 loss on joints; col11a2 mutant zebrafish show changes to joint development and function, which leads to early onset osteoarthritis

“…We have previously modelled the biomechanics of zebrafish jaw opening and closure during early ontogeny using Finite Element Analysis (FEA) (39) and shown that paralysis and the accompanying changes to joint shape impact the strain pattern in the developing joint (29). Therefore, we used FEA to model how the changes to shape and material properties observed in col11a2 mutants would affect the biomechanical performance of the lower jaw.…”

“…The larvae are translucent which, twinned with fluorescent reporter transgenic lines, enables dynamic imaging of skeletal cells (23,24) and the development of the zebrafish craniofacial skeleton is well documented (25)(26)(27). The zebrafish jaw joint is synovial (28) and requires mechanical input to form normally (29,30).…”

A zebrafish model of developmental joint dysplasia: Manipulating the larval mechanical environment to drive the malformation and recovery of joint shape

“…The anaesthetic MS222 (tricaine) induces flaccid paralysis in zebrafish and has been shown to lead to malformation of the jaw joint and changes to joint cell behaviour [5,15,16]. To determine the capacity of these malformed joints to recover functionality larvae were treated with MS222 for 48hrs from 3-5dpf then allowed to resume movement.…”

“…At 7dpf immobilised and AM-ablated larvae were classified as “Subluxed” or “Recovered”. Outlines of the MC at 5dpf (Fig 2A) were analysed using npManova and between-groups Principal Component Analysis (bgPCA) [16] to quantify how MC shape differs between the groups. Each principal component (PC) describes a trend in how the shapes within the analysis vary.…”

“…Mechanoregulatory signals generated by muscle contraction are vital to the development of its characteristic 3D structure [5–9] and have been suggested as primary driver of DDH development [10]. Studies in the chick [6,11,12], mouse [13–15] and zebrafish [5,15,16] have shown that loss of muscle activity leads to malformed joints lacking features such as ligaments, articular cartilage, meniscus and articular processes. Gradients of shear, tension and compression are created during muscle contractions and cells are differentially responsive to these varying mechanical signals altering their cell behaviour or differentiation in response to the changing mechanical force [17–19].…”