Control of Dkk-1 ameliorates chondrocyte apoptosis, cartilage destruction, and subchondral bone deterioration in osteoarthritic knees.
OBJECTIVE
Perturbation of Wnt signaling components reportedly regulates chondrocyte fate and joint disorders. The Wnt inhibitor Dkk-1 mediates remodeling of various tissue types. We undertook this study to examine whether control of Dkk-1 expression prevents joint deterioration in osteoarthritic (OA) knees.


METHODS
Anterior cruciate ligament transection-and collagenase-induced OA in rat knees was treated with end-capped phosphorothioate Dkk-1 antisense oligonucleotide (Dkk-1-AS). Articular cartilage destruction, cartilage degradation markers, bone mineral density (BMD), and subchondral trabecular bone volume of injured knee joints were measured using Mankin scoring, enzyme-linked immunosorbent assay, dual x-ray absorptiometry, and histomorphometry. Dkk-1-responsive molecule expression and apoptotic cells in knee tissue were detected by quantitative reverse transcriptase-polymerase chain reaction, immunoblotting, and TUNEL staining.


RESULTS
Up-regulated Dkk-1 expression was associated with increased Mankin score and with increased serum levels of cartilage oligomeric matrix protein and C-telopeptide of type II collagen (CTX-II) during OA development. Dkk-1-AS treatment alleviated OA-associated increases in Dkk-1 expression, Mankin score, cartilage fibrillation, and serum cartilage degradation markers. Dkk-1-AS also alleviated epiphyseal BMD loss and subchondral bone exposure associated with altered serum levels of osteocalcin and CTX-I. The treatment abrogated chondrocyte/osteoblast apoptosis and subchondral trabecular bone remodeling in OA. Dkk-1 knockdown increased levels of nuclear beta-catenin and phosphorylated Ser(473)-Akt but attenuated expression of inflammatory factors (Toll-like receptor 4 [TLR-4], TLR-9, interleukin-1beta, and tumor necrosis factor alpha), the apoptosis regulator Bax, matrix metalloproteinase 3, and RANKL in OA knee joints.


CONCLUSIONS
Interference with the cartilage- and bone-deleterious actions of Dkk-1 provides therapeutic potential for alleviating cartilage destruction and subchondral bone damage in OA knee joints.
Chang Gung Memorial Hospital-Kaohsiung Medical Center and Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Lin-Hsiu
LH
Weng
Ching-Jen
CJ
Wang
Jih-Yang
JY
Ko
Yi-Chih
YC
Sun
Feng-Sheng
FS
Wang
D000818:Animals; D016118:Anterior Cruciate Ligament / Q000473:pathology; D000070598:Anterior Cruciate Ligament Injuries; D017209:Apoptosis / Q000502:physiology*; D030161:Avian Proteins / Q000378:metabolism; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology*; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology*; D016207:Cytokines / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods*; D006132:Growth Plate / Q000473:pathology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D007719:Knee Joint / Q000473:pathology; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D020370:Osteoarthritis, Knee / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology; D053245:RANK Ligand / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D013977:Tibia / Q000473:pathology; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
D030161:Avian Proteins; D016207:Cytokines; C531384:Dkk1 protein, rat; C071280:EMF-1 protein, Gallus gallus; D036341:Intercellular Signaling Peptides and Proteins; D016376:Oligonucleotides, Antisense; D053245:RANK Ligand; D051153:Wnt Proteins; D051176:beta Catenin; D019278:Matrix Metalloproteinase 3