RESUMO
OBJECTIVES: The circadian clocks are internal timing mechanisms that drive â¼24-hour rhythms in a tissue-specific manner. Many aspects of the physiology of the intervertebral disc (IVD) show clear diurnal rhythms. However, it is unknown whether IVD tissue contains functional circadian clocks and if so, how their dysregulation is implicated in IVD degeneration. METHODS: Clock gene dynamics in ex vivo IVD explants (from PER2:: luciferase (LUC) reporter mice) and human disc cells (transduced with lentivirus containing Per2::luc reporters) were monitored in real time by bioluminescence photon counting and imaging. Temporal gene expression changes were studied by RNAseq and quantitative reverse transcription (qRT)-PCR. IVD pathology was evaluated by histology in a mouse model with tissue-specific deletion of the core clock gene Bmal1. RESULTS: Here we show the existence of the circadian rhythm in mouse IVD tissue and human disc cells. This rhythm is dampened with ageing in mice and can be abolished by treatment with interleukin-1ß but not tumour necrosis factor α. Time-series RNAseq revealed 607 genes with 24-hour patterns of expression representing several essential pathways in IVD physiology. Mice with conditional knockout of Bmal1 in their disc cells demonstrated age-related degeneration of IVDs. CONCLUSIONS: We have established autonomous circadian clocks in mouse and human IVD cells which respond to age and cytokines, and control key pathways involved in the homeostasis of IVDs. Genetic disruption to the mouse IVD molecular clock predisposes to IVD degeneration. These results support the concept that disruptions to circadian rhythms may be a risk factor for degenerative IVD disease and low back pain.
Assuntos
Fatores de Transcrição ARNTL/genética , Envelhecimento/fisiologia , Relógios Circadianos/fisiologia , Degeneração do Disco Intervertebral/fisiopatologia , Disco Intervertebral/fisiologia , Proteínas Circadianas Period/genética , Fatores de Transcrição ARNTL/análise , Fatores Etários , Animais , Proteínas CLOCK/análise , Células Cultivadas , Relógios Circadianos/efeitos dos fármacos , Relógios Circadianos/genética , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/genética , Humanos , Interleucina-1beta/farmacologia , Disco Intervertebral/química , Disco Intervertebral/citologia , Degeneração do Disco Intervertebral/genética , Camundongos , Camundongos Knockout , NF-kappa B/antagonistas & inibidores , NF-kappa B/metabolismo , Núcleo Pulposo/química , Núcleo Pulposo/citologia , Núcleo Pulposo/fisiologia , Transdução de Sinais , Temperatura , Técnicas de Cultura de Tecidos , Transcriptoma , Transfecção , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
Mucopolysaccharidoses (MPS) are inherited metabolic disorders, caused by mutations leading to dysfunction of one of enzymes involved in degradation of glycosaminoglycans (GAGs) in lysosomes. Due to their impaired degradation, GAGs accumulate in cells of patients, which results in dysfunction of tissues and organs, including the heart, respiratory system, bones, joints and central nervous system. Depending on the kind of deficient enzyme, 11 types and subtypes of MPS are currently recognized. Although enzyme replacement therapy has been developed for 3 types of MPS (types I, II and VI), this treatment was found to be effective only in management of somatic symptoms. Since all MPS types except IVA, IVB and VI are characterized by various problems with functioning of the central nervous system (CNS), a search for effective treatment of this system is highly desirable. Recent discoveries suggested that substrate reduction therapy may be an efficient method for treatment of MPS patients, including their CNS. In this review, different variants of this therapy will be discussed in the light of recently published reports.