sirolimus and Osteoarthritis--Knee

A decline in skeletal muscle mitochondrial function is associated with the loss of skeletal muscle size and function during knee osteoarthritis (OA). We have recently reported that 12-weeks of dietary rapamycin (Rap, 14 ppm), with or without metformin (Met, 1000 ppm), increased plasma glucose and OA severity in male Dunkin Hartley (DH) guinea pigs, a model of naturally occurring, age-related OA. The purpose of the current study was to determine if increased OA severity after dietary Rap and Rap+Met was accompanied by impaired skeletal muscle mitochondrial function. Mitochondrial respiration and hydrogen peroxide (H

Topics: Animals; Cell Respiration; Guinea Pigs; Humans; Hydrogen Peroxide; Male; Mitochondria; Mitochondria, Muscle; Muscle, Skeletal; Osteoarthritis, Knee; Respiration; Sirolimus

Autophagy is a cellular homeostasis mechanism that facilitates normal cell function and survival. Objectives of this study were to determine associations between autophagic responses with meniscus injury, joint aging, and osteoarthritis (OA), and to establish the temporal relationship with structural changes in menisci and cartilage.. Constitutive activation of autophagy during aging was measured in GFP-LC3 transgenic reporter mice between 6 and 30 months. Meniscus injury was created by surgically destabilizing the medial meniscus (DMM) to induce posttraumatic OA in C57BL/6J mice. Levels of autophagy proteins and activation were analyzed by confocal microscopy and immunohistochemistry. Associated histopathological changes, such as cellularity, matrix staining, and structural damage, were graded in the meniscus and compared to changes in articular cartilage.. In C57BL/6J mice, basal autophagy was lower in the meniscus than in articular cartilage. With increasing age, expression of the autophagy proteins ATG5 and LC3 was significantly reduced by 24 months. Age-related changes included abnormal Safranin-O staining and reduced cellularity, which preceded structural damage in the meniscus and articular cartilage. In mice with DMM, autophagy was induced in the meniscus while it was suppressed in cartilage. Articular cartilage exhibited the most profound changes in autophagy and structure that preceded meniscus degeneration. Systemic administration of rapamycin to mice with DMM induced autophagy activation in cartilage and reduced degenerative changes in both meniscus and cartilage.. Autophagy is significantly affected in the meniscus during aging and injury and precedes structural damage. Maintenance of autophagic activity appears critical for meniscus and cartilage integrity.

Topics: Aging; Animals; Autophagy; Autophagy-Related Protein 5; Cartilage, Articular; Green Fluorescent Proteins; Immunosuppressive Agents; Menisci, Tibial; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microscopy, Confocal; Microtubule-Associated Proteins; Osteoarthritis, Knee; Sirolimus; Tibial Meniscus Injuries

Articular chondrocyte activation, involving aberrant proliferation and prehypertrophic differentiation, is essential for osteoarthritis (OA) initiation and progression. Disruption of mechanistic target of rapamycin complex 1 (mTORC1) promotes chondrocyte autophagy and survival, and decreases the severity of experimental OA. However, the role of cartilage mTORC1 activation in OA initiation is unknown. In this study, we elucidated the specific role of mTORC1 activation in OA initiation, and identify the underlying mechanisms.. Expression of mTORC1 in articular cartilage of OA patients and OA mice was assessed by immunostaining. Cartilage-specific tuberous sclerosis complex 1 (Tsc1, mTORC1 upstream inhibitor) knockout (TSC1CKO) and inducible Tsc1 KO (TSC1CKO. mTORC1 activation stimulates articular chondrocyte proliferation and differentiation to initiate OA, in part by downregulating FGFR3 and PPR.

Topics: Adult; Aged; Animals; Butylamines; Cartilage, Articular; Cell Proliferation; Chondrocytes; Down-Regulation; Female; Humans; Hypertrophy; Immunosuppressive Agents; Knee Joint; Male; Mechanistic Target of Rapamycin Complex 1; Menisci, Tibial; Mice; Mice, Knockout; Middle Aged; Osteoarthritis; Osteoarthritis, Knee; Receptor, Fibroblast Growth Factor, Type 3; Receptor, Parathyroid Hormone, Type 1; Reverse Transcriptase Polymerase Chain Reaction; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 1 Protein; Tumor Suppressor Proteins; Young Adult

Autophagy, an evolutionarily conserved process for the bulk degradation of cytoplasmic components, serves as a cell survival mechanism. The purpose of this study was to elucidate the role of autophagy in human chondrocytes and pathophysiology of osteoarthritis (OA).. Autophagy in articular cartilage and primary chondrocytes was assessed using antibodies for the autophagy markers light chain 3 and beclin 1. The states of autophagy under catabolic and nutritional stresses were examined. We also examined the effects of inhibition or induction of autophagy under stimulation with interleukin-1β. Autophagy was inhibited by small interfering RNA targeting ATG5, and autophagy was induced by rapamycin. The effects of inhibition or induction of autophagy were examined by real-time polymerase chain reaction for aggrecan, COL2A1, MMP13, and ADAMTS5 messenger RNA. To further examine the mechanism of autophagy regulation in OA human chondrocytes, we investigated whether autophagy modulates apoptosis and reactive oxygen species (ROS).. Autophagy was increased in OA chondrocytes and cartilage. Catabolic and nutritional stresses increased autophagy. In addition, the inhibition of autophagy caused OA-like gene expression changes, while the induction of autophagy prevented them. Furthermore, the inhibition of autophagy increased the amount of cleaved poly(ADP-ribose) polymerase and cleaved caspase 9, while the induction of autophagy inhibited these increases. ROS activity was also decreased by induction of autophagy.. These observations suggested that increased autophagy is an adaptive response to protect cells from stresses, and that autophagy regulates OA-like gene expression changes through the modulation of apoptosis and ROS. Further studies about autophagy in chondrocytes will provide novel insights into the pathophysiology of OA.

Topics: Aged; Apoptosis Regulatory Proteins; Autophagy; Beclin-1; Cartilage, Articular; Cells, Cultured; Chondrocytes; Female; Gene Expression; Humans; Male; Membrane Proteins; Microtubule-Associated Proteins; Osteoarthritis, Knee; RNA, Small Interfering; Sirolimus