Identification of the calcitonin receptor in osteoarthritic chondrocytes

Abstract

BackgroundPreclinical and clinical studies have shown that salmon calcitonin has cartilage protective effects in joint degenerative diseases, such as osteoarthritis (OA). However, the presence of the calcitonin receptor (CTR) in articular cartilage chondrocytes is yet to be identified. In this study, we sought to further investigate the expression of the CTR in naïve human OA articular chondrocytes to gain further confirmation of the existents of the CTR in articular cartilage.MethodsTotal RNA was purified from primary chondrocytes from articular cartilage biopsies from four OA patients undergoing total knee replacement. High quality cDNA was produced using a dedicated reverse transcription polymerase chain reaction (RT-PCR) protocol. From this a nested PCR assay amplifying the full coding region of the CTR mRNA was completed. Western blotting and immunohistochemistry were used to characterize CTR protein on protein level in chondrocytes.ResultsThe full coding transcript of the CTR isoform 2 was identified in all four individuals. DNA sequencing revealed a number of allelic variants of the gene including two potentially novel polymorphisms: a frame shift mutation, +473del, producing a shorter form of the receptor protein, and a single nucleotide polymorphism in the 3' non coding region of the transcript, +1443 C>T. A 53 kDa protein band, consistent with non-glycosylated CTR isoform 2, was detected in chondrocytes with a similar size to that expressed in osteoclasts. Moreover the CTR was identified in the plasma membrane and the chondrocyte lacuna of both primary chondrocytes and OA cartilage section.ConclusionsHuman OA articular cartilage chondrocytes do indeed express the CTR, which makes the articular a pharmacological target of salmon calcitonin. In addition, the results support previous findings suggesting that calcitonin has a direct anabolic effect on articular cartilage.

Calcitonin delays the progress of early-stage mechanically induced osteoarthritis. In vivo, prospective study

“…Given its safety record, it seems that the early administration of Calcitonin in humans may contribute in delaying the progression of OA. Nevertheless, and since the expression 53 or not 54 of Calcitonin receptor in the human cartilage and chondrocyte has not been clarified yet, prospective clinical studies are certainly needed in order to confirm the results of this experimental paper, especially when taking into account the fact that orally administered Calcitonin as well may have a promising role in the treatment of OA in the near future 55À57 .…”

Calcitonin suppresses intervertebral disk degeneration and preserves lumbar vertebral bone mineral density and bone strength in ovariectomized rats

“…MMP-1-and MMP-13-positive staining in the annulus fibrosis was stronger in the OVX+V group than in the sham and OVX+CT groups reduced as rodents age, the CT-receptor (CTR) was identified in bone-matrix-embedded osteocytes [25,26]. Moreover, articular cartilage chondrocytes from osteoarthritis (OA) patients do indeed express CTR, which makes articular cartilage a pharmacological target for salmon CT [27]. CT treatment increases proteoglycan and collagen synthesis in human osteoarthritic cartilage in vitro [28].…”

Circulating Protein Fragments of Cartilage and Connective Tissue Degradation Are Diagnostic and Prognostic Markers of Rheumatoid Arthritis and Ankylosing Spondylitis

“…These protein degradation fragments may be specific for the tissue of origin and for the involved enzymes, and may consequently be used for the identification of molecular biochemical markers [6]. Recently, neo-epitope-based biochemical markers measured in serum have received increased attention for their diagnostic and prognostic potential in rheumatic diseases [7]. In slowly progressing diseases, such as osteoporosis and osteoarthritis (OA), bone resorption and cartilage degradation markers have been studied extensively [8].…”