Tmbj.hkbu.edu.hk

Does aberrantly overexpressed casein kinase-2 interacting protein-1
contribute to failure of osteoblast-mediated repair for bone erosion
in rheumatoid arthritis?
Abstract
Rheumatoid arthritis (RA) is a severe, aggressive and debilitating disease, characterized by pain, swelling and progressive destruction of synovial joints. Consequently, patients with severe disease face significant disability, deformity, and irreversible joint damage. Bone erosion is the main reason leading to joint dysfunction, which is due to excessive osteoclast-mediated bone resorption and inadequate osteoblast-mediated bone formation. However, osteoblast-mediated repair of bone erosion in RA seems limited or occurs only infrequently during current combination It has been reported that mid- to late-stage differentiation of osteoblast toward maturation and capability of functional mineralization is compromised at sites of focal bone erosion in inflammatory arthritis. However, the molecular mechanism remains largely unknown. Thus, it is necessary to investigate the molecular mechanism responsible for osteoblast function to identify a target for developing a novel therapeutic strategy. Recently, the applicants have reported a newly discovered intracellular negative regulator casein kinase-2 interacting protein-1 (CKIP-1) for controlling osteoblast lineage cells from mid- to late-stage differentiation toward functional mineralization, which interacts Smurf1 and enhances its ligase activity for promoting proteasomal degradation of anabolic bone morphogenetic protein (BMP) signaling proteins, e.g. Smad1 (Lu K, et al. Nature Cell Biology 2008; Zhang G, et al.
Nature Medicine 2012). Further, the applicants found that CKIP-1 protein level was sharply higher
whereas Smad1 protein and osteocalcin mRNA levels were significantly lower in eroded bone specimen from RA patients when compared to that from age-matched non-RA subjects (Songlin
Peng 2012). Consistently, our recently available data suggested the increased CKIP-1 expression
within osteoblast well correlated with both reduced bone formation and progressive bone erosion in rodents with adjuvant-induced arthritis or collagen-induced arthritis (Xiaojuan He 2012A, 2012B).
Thereafter, the applicants demonstrated that proinflammatory cytokines involved in RA (TNF-, IL-1 and IL-6) could up-regulate CKIP-1 protein expression in dose-dependent manner in osteoblast-like cells in vitro (Chao Liang 2012A). Moreover, the above data not only advanced our
previous findings that CKIP-1 could be involved in cytokine signaling response, but also provided potential explanation for the reduced BMP signaling activity and subsequent decrease in bone formation within RA-like lesion in TNF transgenic mice. Taken together, the applicants have the following hypothesis that aberrantly overexpressed CKIP-1 could play an important role in failure of osteoblast-mediated repair for articular bone erosion in RA. To test the hypothesis, the applicants have generated osteoblast-specific CKIP-1 conditional ) based on the Cre-loxP strategy (Chao Liang 2012B) and
osteoblast-targeted delivery of CKIP-1 small interference RNA ((DSS)6-liposome-CKIP-1 siRNA) (Zhang G 2012). Our established induction protocol (Liu DY 2012; Xiao C 2011; Li J 2011) for
collagen-induced arthritis and K/BxN serum-transfer arthritis will be introduced in adult CKIP-1 and control littermate males, respectively, to achieve the following four specific aims: (1) To detect mice after induction with type II bovine collagen for inflammatory arthritis; (2) To detect bone phenotypes in CKIP-1 mice after induction with K/BxN serum for inflammatory arthritis; (3) To evaluate rescues in articular bone erosion by (DSS)6-liposome-CKIP-1 siRNA in inflammatory arthritic mice induced by type II bovine collagen; (4) To evaluate rescues in articular bone erosion by (DSS)6-liposome-CKIP-1 siRNA in inflammatory arthritic mice induced by The current proposal would help provide a potential target CKIP-1 and a novel therapeutic strategy to augment osteoblast- mediated bone formation toward repairing articular bone erosion in

Source: http://tmbj.hkbu.edu.hk/images/20130802/13754231352995.pdf