Activation of a chondrocyte volume-sensitive Cl − conductance prior to macroscopic cartilage lesion formation in the rabbit knee anterior cruciate ligament transection osteoarthritis model

Abstract

SummaryObjectiveThe anterior cruciate ligament transection (ACLT) rabbit osteoarthritis (OA) model confers permanent knee instability and induces joint degeneration. The degeneration process is complex, but includes chondrocyte apoptosis and OA-like loss of cartilage integrity. Previously, we reported that activation of a volume-sensitive Cl− current (ICl,vol) can mediate cell shrinkage and apoptosis in rabbit articular chondrocytes. Our objective was therefore to investigate whether ICl,vol was activated in the early stages of the rabbit ACLT OA model.DesignAdult Rabbits underwent unilateral ACLT and contralateral arthrotomy (sham) surgery. Rabbits were euthanized at 2 or 4 weeks. Samples were analyzed histologically and with assays of cell volume, apoptosis and electrophysiological characterization of ICl,vol.ResultsAt 2 and 4 weeks post ACLT cartilage appeared histologically normal, nevertheless cell swelling and caspase 3/7 activity were both significantly increased compared to sham controls. In cell-volume experiments, exposure of chondrocytes to hypotonic solution led to a greater increase in cell size in ACLT compared to controls. Caspase-3/7 activity, an indicator of apoptosis, was elevated in both ACLT 2wk and 4wk. Whole-cell currents were recorded with patch clamp of chondrocytes in iso-osmotic and hypo-osmotic external solutions under conditions where Na+, K+ and Ca2+ currents were minimized. ACLT treatment resulted in a large increase in hypotonic-activated chloride conductance.ConclusionChanges in chondrocyte ion channels take place prior to the onset of apparent cartilage loss in the ACLT rabbit model of OA. Further studies are needed to investigate if pharmacological inhibition of ICl,vol decreases progression of OA in animal models.

Acid- and Volume-Sensitive Chloride Currents in Human Chondrocytes

“…In detail, we investigated the mutual interdependence of the two currents and possible functional consequences of their interplay on chondrocyte CV regulation. Given their important role in CV homeostasis in chondrocytes on the one hand, and the relationship between deranged CV regulation, chondrocyte apoptosis, and OA on the other hand, Cl − channels have come into focus of OA research (Roach et al, 2004;Isoya et al, 2009;Lewis et al, 2011a,b;Perez-Hernandez et al, 2012;Ponce et al, 2012;Kumagai et al, 2016;Yamamura et al, 2018;Hall, 2019).…”

“…They contribute to the regulation of ion homeostasis, transepithelial transport, and electrical excitability, and are tightly linked to cell migration, phagocytosis, proliferation, and apoptosis (Jentsch et al, 2002;Jakab and Ritter, 2006;Okada et al, 2006;Hoffmann, 2011;Harl et al, 2013;Pedersen et al, 2016;Kittl et al, 2018). The function of the VSOR current in CV and membrane potential regulation has also been shown in chondrocytes (Wilkins et al, 2000;Isoya et al, 2009;Funabashi et al, 2010;Lewis et al, 2011a,b;Ponce et al, 2012;Kumagai et al, 2016), where the Cl − current might indirectly affect matrix protein synthesis by modulating intracellular Ca 2+ levels (Alford et al, 2003).…”

Effects of oral glucosamine hydrochloride and mucopolysaccharide protein in a rabbit model of osteoarthritis

“…Anterior cruciate ligament transection is the most widely acceptable treatment for OA . In animal ACLT models, the greatest OA severity occurs in the MFC and LFC . In our study, we transected only the cranial cruciate ligament instead of removing both ligaments to avoid instability and minimize the risk of disease.…”

Alterations in the chondrocyte surfaceome in response to pro-inflammatory cytokines

“…Note that some proteins appear in more than one category. Numbers in the pie chart represent the actual numbers of proteins in each subgroup macroscopic OA [21]. Despite these data, our current understanding of the surfaceome of primary articular chondrocytes, especially with regards to differentially regulated ion channels, receptors and transporters in OA, is currently lacking.…”