Targeting TRPC6 as a mechanosensitive signalling hub linking inflammation and structural damage in osteoarthritis.

• Applicant: Dr. Joanna Sherwood, Ph.D.
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery ; Rheumatology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437750125

In order to maintain healthy load bearing cartilage matrix, chondrocytes are supported within a homeostatic equilibrium by a number of mechanical and biochemical signals. Forces exceeding physiological limits, disruption to the cartilage extracellular matrix and modulation of chondrocyte intracellular signalling pathways, particularly in combination with inflammatory events, lead to disruption of this equilibrium and initiation of a severe cascade of tissue degeneration, resulting in loss of joint function and consequent disability in osteoarthritis patients.Chondrocyte intracellular calcium levels are involved in the signal transduction of numerous homeostatic and inflammatory pathways, as well as being regulated via mechanical stimulation. I have previously demonstrated that CXCR2 signalling is required for cartilage homeostasis, while preliminary work for this project shows that transient receptor potential cation channel (TRPC6) is required for the transmission of CXCR2 signalling and that TRPC6 itself is required to protect against cartilage degradation. This study aims to determine whether specific modulation of TRPC6 activity is a suitable strategy in the development of novel osteoarthritis therapeutics. Firstly, we will examine the impact of conditional TRPC6 deletion in superficial, articular and preosteoblastic chondrocytes to determine which cell subset requires TRPC6 expression for cartilage homeostasis. Next, we will utilise two new genetically modified mouse strains developed in our group, that express either a phosphoresistant constitutively open form of TRPC6 or a phosphomimetic permenantly closed form of TRPC6, to examine the specific role of TRPC6 activity in cartilage homeostasis. We will investigate whether forced channel opening or closure affects the response of both wild type and CXCR2-deficient mice to destabilisation of the medial meniscus (DMM) and measure whether this regulated activity of TRPC6 alters chondrocyte phenotypic behaviour and response to mechanical and biochemical stimuli. By analysing at single cell level, this project will establish new paradigms on how control of intracellular calcium levels in chondrocytes contributes to osteoarthritis disease progression.

• DFG Programme: Research Grants