In the paper we investigated how frequency and duration of loading affect cartilage and bone development. We used an in vitro explant culture system to culture embryonic chick limb explants under a range of loading regimes in which the amount of loading and the frequency were systematically varied. We found that increasing the duration (amount) of loading promoted cartilage growth, shape development and mineralisation of the femur and tibiotarsus. However, varying frequency only had significant effects on mineralisation, and not on cartilage growth or shape. Increased glycosaminoglycan deposition and cell proliferation may have contributed to the accelerated cartilage growth and shape change under increasing loading duration. The results demonstrated that frequencies and durations of applied biomechanical stimulation differentially promoted cartilage and bone formation, with implications for developmentally inspired tissue engineering strategies aiming to modulate tissue construct properties.
The work described in this paper was funded by an ERC Starting Grant. Congratulations Nidal and Cristian!
In previous papers by Aurélie, Rebecca and others, we demonstrated that muscle loading is needed for normal development of the spine, including spinal curvature, vertebral shape and vertebral segmentation in the chick embryo. However, the chick embryo does not have the same type of discs as humans (or mammals in general) as it lacks a nucleus pulposus. Therefore, we needed to switch to the mouse to look at the influence of muscles on development of the discs. Our usual mouse line of choice (splotch delayed) wasn’t suitable due to the fact that spine development and vertebral segmentation is known to be abnormal in this line. Therefore we used the “mdg” or muscular dysgenesis line (with grateful thanks to Prof Eli Zelzer, Weizmann Institute) in which skeletal muscles form but do not contract.
In this paper, we investigated how muscle forces affect (1) notochord involution and vertebral segmentation, and (2) intravertebral disc (IVD) development including the mechanical properties and morphology, as well as collagen fibre alignment in the annulus fibrosus. We looked at three different stages of development; Theiler Stage (TS)22 when notochord involution starts, at TS24 when involution is complete, and at TS27 when the IVD is formed. Vertebral and IVD development were characterised using histology, immunofluorescence, and indentation testing. We found that notochord involution and vertebral segmentation occurred independently of muscle contractions between TS22 and TS24. However, in the absence of muscle contractions, we found vertebral fusion in the cervical region at TS27, along with (i) a displacement of the nucleus pulposus towards the dorsal side, (ii) a disruption of the structural arrangement of collagen in the annulus fibrosus, and (iii) an increase in viscous behaviour of the annulus fibrosus. Therefore, mechanical loading due to muscle contractions are important for the later stages of disc development, particularly for annulus fibrosus formation. We believe our results suggest a need for mechanical loading in the creation of fibre-reinforced tissue engineering replacement IVDs as a therapy for IVD degeneration.
The research described in this paper was funded by the Leverhulme Trust and by an ERC Starting Grant.
See @NTAurelie‘s nice twitter thread here! Congratulations Aurélie and all the team!
Congratulations to Devi (together with collaborators Rebecca and Colin Boyle) on publication of her paper entitled “Quantifying the tolerance of chick hip joint development to temporary paralysis and the potential for recovery” in Developmental Dynamics.
In this paper, we wanted to discover when- and for how long- fetal movements are most important for development of the hip joint, in order to better understand conditions affecting the skeletons of babies who may have had restricted or reduced movements in utero, including developmental dysplasia of the hip (where the hip joint is unstable) and arthrogryposis (multiple joint contractures). We also wanted to know if joint development can be “rescued” by external manipulation even when immobilised.
We varied the initiation and duration of drug-induced paralysis in the chick embryo, and found that a three day period between 4 and 7 embryonic days was most important for hip joint shape. In terms of hip joint development, this timeline is equivalent to roughly 10 to 12 gestational weeks in humans, and means that the end of the first trimester would be a useful time for targeted screening for arthrogryposis and hip dysplasia. We found that cavitation was more dependent on duration of paralysis, rather than timing.
When we externally manipulated the immobilised chick limbs, the hip joints had more normal shapes, and more normal progression of cavitation, compared to the contralateral limbs of the same chicks. This implies that the developing limb has the potential to recover from periods of immobility, and external manipulation provides an innovative avenue for prevention and treatment of developmental joint pathologies.
The full paper is available open-access here. The research was funded by ERC Starting Grant #336306.
Saima‘s paper funded by the ERC characterising the collagens in the developing skeletal rudiment was published in eCM. We used immuno-fluorescence to look at the major and minor collagens in sections of the humerus at TS22 (e13.5, before formation of the primary ossification centre), TS25 (e15.5) and TS27 (e17.5).
Several collagens change substantially with the progression of the ossification centre, like for example Col V.
Some develop amazingly complex structures over the period of development studied, like Col II (green) and XI (grey).
Vivien‘s first first-author paper entitled “Effects of Abnormal Muscle Forces on Prenatal Joint Morphogenesis in Mice” has been published in the Journal of Orthopaedic Research. The paper characterises the effects of absent or reduced muscle on prenatal development of the major synovial joints. Vivien used image registration to qualitatively and quantitatively compare joint shapes between muscleless, reduced-muscle and normal mice. Different joints were affected more than others, and what we found most interesting is that a reduction in muscle often led to *more* severe effects than no muscle- like in the humeral distal condyles (blue: control, yellow: reduced-muscle, purple: muscleless)
Congratulations Vivien! You can access the final version of the paper here, or the submitted version here if you don’t have access to JOR.
Aurélie‘s paper (on which Yuming and Rebecca are also authors) entitled “Short-term foetal immobility temporally and progressively affects chick spinal curvature and anatomy and rib development” has been published in eCM (European Cells and Materials). The paper describes how a very short period of paralysis during prenatal development can have severe and lasting effects on development of the spine and ribs, as summarised in the graphical abstract. This work has consequences for understanding congenital scoliosis, for which a change or reduction in fetal movements could be an important factor. The project was funded by the Leverhulme Trust and was a collaboration with Prof James Iatridis in the Icahn School of Medicine at Mount Sinai, New York, USA. View the paper for free here.
Stefaan’s final and Perren Award winning paper from his postdoc in the Developmental Biomechanics has been published online in the Journal of Biomechanics. In the paper, the effects of different risk factors for hip dysplasia (such as fetal breech position, first born babies and oligohydramnios (reduced amniotic fluid)) on fetal kicks and the stresses and strains in their hip joints are quantified. Kick force, stress and strain were found to be significantly lower in cases of breech position and oligohydramnios. Similarly, firstborn fetuses were found to generate significantly lower kick forces than non-firstborns.
Congratulations to Stefaan and co-authors whose paper entitled “Altered Biomechanical Stimulation of the Developing Hip Joint in Presence of Hip Dysplasia Risk Factors” (soon to be published in the Journal of Biomechanics) has been awarded the 2018 S.M. Perren Award by the European Society of Biomechanics! Stefaan will present a plenary lecture of the World Congress of Biomechanics in Dublin, Ireland in July.
Our paper on developing a new type of sensor for fetal movements has been published in PLoS One! The paper describes how acoustic sensors are combined with accelerometers for the first time. The sensor was able to detect and identify the short, rigorous ‘startle’ movements of the fetus. Further development is ongoing, but this is an important first step! The work builds on a patent held by the several of the authors, including Niamh.
Citation: Lai J, Woodward R, Alexandrov Y, ain Munnee Q, Lees CC, Vaidyanathan R, Nowlan NC. Performance of a wearable acoustic system for fetal movement discrimination. PloS one. 2018 May 7;13(5):e0195728.
Stefaan‘s work on quantifying the stresses and strains induced by fetal kicks over gestation has been published in the Journal of the Royal Society Interface. The work attracted a lot of publicity, being featured by Nature, Science and Newsweek and on the Imperial College website. Congratulations Stefaan! See here for the online version of the paper, and access the pdf here.