Circadian production of melatonin in cartilage modifies rhythmic gene expression

Abstract

Endochondral ossification, including bone growth and other metabolic events, is regulated by circadian rhythms. Herein, we provide evidence that melatonin has a direct effect on the circadian rhythm of chondrocytes. We detected mRNA expression of the genes which encode the melatonin-synthesizing enzymes AANAT (arylalkylamine N-acetyltransferase) and HIOMT (hydroxyindole O-methyltransferase), as well as the melatonin receptors MT1 and MT2 in mouse primary chondrocytes and cartilage. Production of melatonin was confirmed by mass spectrometric analysis of primary rat and chick chondrocytes. Addition of melatonin to primary mouse chondrocytes caused enhanced cell growth and increased expression of Col2a1, Aggrecan, and Sox9, but inhibited Col10a1 expression in primary BALB/c mouse chondrocytes. Addition of luzindole, an MT1 and MT2 antagonist, abolished these effects. These data indicate that chondrocytes produce melatonin, which regulates cartilage growth and maturation via the MT1 and MT2 receptors. Kinetic analysis showed that melatonin caused rapid upregulation of Aanat, Mt1, Mt2, and Pthrp expression, followed by Sox9 and Ihh. Furthermore, expression of the clock gene Bmal1 was induced, while that of Per1 was downregulated. Chronobiological analysis of synchronized C3H mouse chondrocytes revealed that melatonin induced the cyclic expression of Aanat and modified the cyclic rhythm of Bmal1, Mt1, and Mt2. In contrast, Mt1 and Mt2 showed different rhythms from Bmal1 and Aanat, indicating the existence of different regulatory genes.Our results indicate that exogenous and endogenous melatonin work in synergy in chondrocytes to adjust rhythmic expression to the central suprachiasmatic nucleus clock.

The Effect of Orally Supplemented Melatonin on Larval Performance and Skeletal Deformities in Farmed Gilthead Seabream (Sparus aurata)

“…The dose-response relationship between PTHrP expression level and melatonin concentration registered at least during the treatment period (MEL1 and MEL2) contradicts the negative correlation of those two parameters stipulated by Abbink et al [49]. Indeed, another study on primary BALB/c mouse chondrocytes [50] supports our finding about melatonin's capacity to upregulate PTHrP expression. Additionally, an association between abnormally developing bones and a high expression of PTHrP on Sparus aurata was already described [51].…”

Changes in the intra- and peri-cellular sclerostin distribution in lacuno-canalicular system induced by mechanical unloading

“…Mechanical unloading (reduced mechanical stress on the bone) induces significant bone loss, as evidenced by disuse osteoporosis, which is a critical issue for bedridden patients and astronauts [1,2]. Mechanical loading is a crucial factor controlling bone mass [2].…”

Prospects of circadian clock in joint cartilage development

“…And several studies have demonstrated the regulation of integrin acting on retina 157,158 . The addition of melatonin results in increased growth of chondrocytes and promotes expression of typical cartilage components, such as COL2A1, aggrecan, and SOX9 159 …”