Research

Many of the research results obtained in RUBICON secondments cannot be yet disclosed as they must first be published in peer reviewed journals. Several publications are in preparation and participating researchers have presented results at conferences including the annual congresses of European Calcified Tissues Society, American Society of Bone and Mineral Research, American Society of Matrix Biology, and the European College of Sports Science.

Results which are already published, or that can otherwise be disclosed are as follows:

Circadian clock biology

• Several secondments in RUBICON have investigated the effects of the circadian clock on connective tissues, especially cartilage and intravertebral disc.

• Results are already available from the secondment of Manchester researcher Michal Dudek to Murdoch Children’s Research Institute. He conducted the first known study of circadian proteomics in articular cartilage, which covers the end of bones at the joints and is damaged by diseases such as osteoarthritis or by injury. This analysis showed that 12% of extractable proteins have a daily rhythm of expression controlled by the circadian clock, revealing that articular cartilage is a much more dynamic tissue than previously thought (DOI: 10.1101/654855).

Genetics and treatment of musculoskeletal soft tissue injuries

• Mathijs Suijkerbuijk from Erasmus Medical Centre studied variations in our DNA predisposing to anterior crucial ligament (ACL) injury, a common sports injury. Based on his findings at the University of Cape Town he postulated that DNA variations in some genes involved in inflammation may alter the protein structure in extracellular matrix, and contribute to a higher risk of ACL injury. (DOI: 10.1016/j.jsams.2019.07.012.)

• Region Hovedstaden has completed a clinical study evaluating whether treatment with IGF-1 can improve recovery from tendinopathy in combination with strength training (manuscript in preparation).

• Senanile Dlamini from South Africa set up a database of human tendon tissues of patients at Erasmus Medical Centre, and was also able to culture tendon cells from these tissues to generate a biobank. In this way we will be able to couple the tendon disease not only with genetic variations in the DNA but also the behaviour of tendon cells from the specific patients. This obtained knowledge will help us to better understand the relation between a tendon disease, its cellular behaviour and the genetic makeup involved.

Rare diseases

RUBICON secondments have obtained new insights into the biological mechanisms and pathology of several rare diseases, and have tested potential therapeutic drugs:

• Studies of a mouse model of autosomal dominant osteopetrosis type 2 (ADO2) investigated the mechanism of the mutation in bone cells, identifying how the affected cell components alter the function of bone osteoclasts. Also, extra-skeletal alterations of ADO2 have been characterised in a mouse model, especially in lung, kidney and muscle, all affected by perivascular fibrosis. (DOI: 10.1038/s41413-019-0055-x)

• Rapamycin, an autophagy inducing compound, has been tested in a mouse model for mild-to-moderate osteogenesis imperfecta in a study involving RUBICON researchers. Results show some improvement in bone structure but impaired bone growth, so rapamycin is not considered a suitable therapy for OI in this case (DOI: 10.1111/jcmm.14072).

• Danish researchers Peter Tran and Tanja Skrba investigated the effects of fibrillin-1 and physical activity on mouse tendon tissue, to understand how exercise could benefit patients with Marfan Syndrome and potentially obtain a new mouse model for tendinopathy. This study was performed in the fibrillin-1 knockout mouse model of Marfan syndrome at Icahn School of Medicine at Mount Sinai, using a specially designed exercise wheel system to record data from voluntary exercise. Analysis found these mice found had smaller tendons compared to normal mice, but their functioning was not significantly different with no evidence of overload or damage due to exercise, hence the model is not suited to study of tendinopathy. (DOI: 10.14814/phy2.14267)

• In her secondment at Hong Kong University, Newcastle researcher Beth Gibson performed an in-depth analysis of the spinal pathologies of mouse models of rare skeletal diseases osteochondritis dissecans (OCD) and spondyloepimetaphyseal dysplasia (SEMD). Both the OCD and SEMD mouse models exhibit reduced vertebral body height and morphological changes associated with intervertebral disc degeneration. These results will now be compared to clinical data obtained from patients with these OCD and SEMD aggrecan mutations in order to better understand human pathology and potentially develop better diagnostic and prognostic markers.

Interactions between connective tissues

• University of L’Aquila has led studies on the effects of lipocalin 2 (Lcn2) in bone and tendon in WP3. Firstly, building on results obtained in the previous INTERBONE project, it has been confirmed that Lcn2 is involved in interactions between bone osteoblasts and endothelial cells under unloading conditions, giving us new information on interactions between bone cells and blood vessels during osteoporosis (DOI:10.1007/s00223-018-0496-z). Other investigations of how Lcn2 transports within osteoblast cells are in progress.

• Studies of potential interactions between bone and tendon involving Lcn2 confirmed there is no expression of Lcn2 in human tenocytes under either normal or unloading conditions, but its receptor is expressed. This raised the possibility that increased Lcn2 from bone under unloading conditions may affect the nearby tendons. However, experiments with mice have observed no alteration of the mouse tendon under unloading conditions. Furthermore, it was confirmed that Lcn2 expression is not affected by the circadian clock.

• In his secondment to Erasmus Medical Centre, Indian researcher Pavitra Kumar was able to show that alterations in the matrix of proteins surrounding our cells has a great influence on their behaviour. He studied the function of bone forming cells, osteoblasts, and endothelial cells that make blood vessels. Failure of these cells to interact closely leads to so-called non-unions, bone fractures that do not heal. With his obtained knowledge, we will be able to better anticipate on the role the extracellular matrix plays in controlling cell behaviour and thereby potentially shorten the fracture healing time and increase the success rate.