Chondrocytes From Osteoarthritic and Chondrocalcinosis Cartilage Represent Different Phenotypes

Abstract

Basic calcium phosphate (BCP)-based calcification of cartilage is a common finding during osteoarthritis (OA) and is directly linked to the severity of the disease and hypertrophic differentiation of chondrocytes. Chondrocalcinosis (CC) is associated with calcium pyrophosphate dihydrate (CPPD) deposition disease in the joint inducing OA-like symptoms. There is only little knowledge about the effect of CPPD crystals on chondrocytes and the signaling pathways involved in their generation. The aim of this study was to investigate the chondrocyte phenotype in CC cartilage and the effect of CPPD crystals on chondrocytes. Cartilage samples of patients with CC, patients with severe OA, and healthy donors were included in this study. The presence of CC was evaluated using standard X-ray pictures, as well as von Kossa staining of cartilage sections. OA severity was evaluated using the Chambers Score on cartilage sections, as well as the radiological Kellgren–Lawrence Score. Patients with radiologically detectable CC presented calcification mainly on the cartilage surface, whereas OA patients showed calcification mainly in the pericellular matrix of hypertrophic chondrocytes. OA cartilage exhibited increased levels of collagen X and matrix metalloproteinase 13 (MMP13) compared with CC and healthy cartilage. This observation was confirmed by qRT-PCR using cartilage samples. No relevant influence of CPPD crystals on hypertrophic marker genes was observed in vitro, whereas BCP crystals significantly induced hypertrophic differentiation of chondrocytes. Interestingly, we observed an increased expression of p16 and p21 in cartilage samples of CC patients compared with OA patients and healthy controls, indicating cellular senescence. To investigate whether CPPD crystals were sufficient to induce senescence, we incubated chondrocytes with BCP and CPPD crystals and quantified senescence using β-gal staining. No significant difference was observed for the staining, but an increase of p16 expression was observed after 10 days of culture. Primary chondrocytes from CC patients produced CPPD crystals in culture. This phenotype was stabilized by mitomycin C-induced senescence. Healthy and OA chondrocytes did not exhibit this phenotype. BCP and CPPD crystals seem to be associated with two different chondrocyte phenotypes. Whereas BCP deposition is associated with chondrocyte hypertrophy, CPPD deposition is associated with cellular senescence.

mtDNA variability determines spontaneous joint aging damage in a conplastic mouse model

“…To study the senescence activity, we measured the cartilage expression of MMP13, β-Galactosidase, and p16, markers involved in the senescence process, and Ki67, an indicator of proliferation activity. Increased production of MMPs, in particular MMP13 and MMP3, was detected in cartilage with aging [28], while β-Galactosidase and p16 are widely used markers for cellular senescence [29][30][31]. In mice at 90 weeks of age, we found less cartilage expression of MMP13, β-Galactosidase, and p16 in joints from conplastic (BL/6 NZB ) mice than in the original strain, whereas proliferation activity measured as Ki67 expression was increased in BL/6 NZB strain (Figure 3).…”

A new perspective on intervertebral disc calcification—from bench to bedside

“…45 , 46 In osteoarthritic menisci, calcification shows a different extracellular matrix composition and higher content of calcium phosphate in comparison to primary chondrocalcinosis, characterized by calcium pyrophosphate dehydrate deposits. 47 Although the trigger for joint calcification is unknown, there are some well-established hallmarks of the disease: hypertrophic chondrocytes, presenting the high expression of COL10; 39 , 48 TNAP, ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), and progressive ankylosis gene (ANK) upregulation; 49 , 50 and local inflammation. 51 Despite the prevalence of cartilage calcification and its close link to OA and cartilage trauma, the pathophysiology in the knee, similar to the intervertebral disc, is still poorly understood, which hinders the development of disease-modifying drugs.…”

Structural and Molecular Changes of Human Chondrocytes Exposed to the Rotating Wall Vessel Bioreactor

“…Sections were covered with ROTI-Mount FluorCare DAPI (Carl Roth GmbH u. Co. KG, Karlsruhe, Germany) and microscopically investigated (Axio Observer, Axiocam 702 mono, HXP 120 V, Carl Zeiss, Jena, Germany). All sections were controlled for unspecific binding by incubation with an iso-rabbit antibody (Invitrogen, Waltham, MA, USA) [35].…”