Several members of the CCN family of matricellular proteins are required for chondrocyte proliferation, survival, and ECM production in the growth plate. However, the mechanisms by which CCNs mediate these activities are unknown. Similarly, although some CCN proteins are expressed in adult articular cartilage and intervertebral discs (IVDs), their functions in these tissues are unknown. Thus there is a large gap in knowledge regarding the roles of CCN proteins in healthy adult cartilage and IVDs, and their roles in degenerative diseases such as osteoarthritis (OA) and degenerative disc disease (DDD), for which there are currently no therapies. The studies in this proposal address these fundamental issues. The central hypothesis is that CCNs 1, 2, and 4 have overlapping functions in and are required for chondrogenesis and postnatal maintenance of articular cartilage and nucleus pulposus (NP), and that they mediate their effects in part through regulation of HIF1a and HIF2a, and in part by acting as escorts/chaperones for ECM proteins. This hypothesis will be tested in three specific aims.
In Aim 1, the roles of CCNs 1, 2, and 4 in growth plate chondrogenesis and articular cartilage will be determined. Mice carrying floxed alleles of Ccns 1 and 2 have been generated, as have Ccn4-/- mice, and will be used to excise Ccn genes prenatally and postnatally. Preliminary studies support the hypothesis that CCNs 1 and 2 have overlapping functions in postnatal cartilage. Other studies in this aim build on preliminary data showing that loss of Ccn2 leads to decreased nuclear localization of NFkB (RelA), and decreased levels of HIF1a, both of which have pro-survival functions in cartilage. The hypothesis that CCNs induce HIF1a and HIF2a by activating NFkB /RelA is tested.
In Aim 2, the roles of CCNs in the formation and maintenance of the nucleus pulposus (NP) of the IVD are tested by generating mice in which excision of CCNs is induced.
This aim i s based on preliminary data showing that Ccn2 mutants have primary defects in formation of the NP, and these are exacerbated in Ccn1/2 double mutants. Other experiments in this aim test the hypothesis that CCNs mediate their effects on ECM production and cell survival in part through maintaining levels of HIF1a and HIF2a, as in growth plate cartilage.
In Aim 3, the ability of CCNs 1 and 2 to act directly as """"""""chaperones"""""""" to facilitate ECM assembly is tested. Precedent for this mode of action comes from observations that other secreted proteins have this activity, and from the finding that CCN proteins contain CXXC motifs characteristic of such chaperones. The studies are innovative, because they utilize new mouse models to test two novel modes of action for CCNs: regulation of cell viability and matrix production by NFkB and HIFs, and direct roles in ECM assembly via chaperone-like activity. The proposed research is significant, because it is expected to demonstrate for the first time that CCNs are essential for the maintenance of articular cartilage and IVD. This knowledge has the potential to lead to new therapeutic approaches to the treatment of OA and DDD.
Osteoarthritis (OA) is the most common form of arthritis and the leading cause of long-term disability in the US. Degenerative disc disease (DDD) is the most common form of low back pain, and as with OA, there are no effective therapies. CCN proteins are key regulators of cartilage formation;however, their roles in adult articular cartilage and intervertebral discs are unknown. The studies in this proposal investigate these functions and could lead to the development of sorely needed therapies for the treatment of OA and DDD.
|Jiang, J; Leong, N L; Khalique, U et al. (2016) Connective tissue growth factor (CTGF/CCN2) in haemophilic arthropathy and arthrofibrosis: a histological analysis. Haemophilia 22:e527-e536|
|Maeda, Azusa; Ono, Mitsuaki; Holmbeck, Kenn et al. (2015) WNT1-induced Secreted Protein-1 (WISP1), a Novel Regulator of Bone Turnover and Wnt Signaling. J Biol Chem 290:14004-18|
|Cheung, Laurence C; Strickland, Deborah H; Howlett, Meegan et al. (2014) Connective tissue growth factor is expressed in bone marrow stromal cells and promotes interleukin-7-dependent B lymphopoiesis. Haematologica 99:1149-56|
|Maeda-Uematsu, Aya; Kubota, Satoshi; Kawaki, Harumi et al. (2014) CCN2 as a novel molecule supporting energy metabolism of chondrocytes. J Cell Biochem 115:854-65|
|Hall-Glenn, Faith; Aivazi, Armen; Akopyan, Lusi et al. (2013) CCN2/CTGF is required for matrix organization and to protect growth plate chondrocytes from cellular stress. J Cell Commun Signal 7:219-30|
|Tran, Cassie M; Fujita, Nobuyuki; Huang, Bau-Lin et al. (2013) Hypoxia-inducible factor (HIF)-1Ã½Ã½ and CCN2 form a regulatory circuit in hypoxic nucleus pulposus cells: CCN2 suppresses HIF-1Ã½Ã½ level and transcriptional activity. J Biol Chem 288:12654-66|
|Hall-Glenn, Faith; De Young, R Andrea; Huang, Bau-Lin et al. (2012) CCN2/connective tissue growth factor is essential for pericyte adhesion and endothelial basement membrane formation during angiogenesis. PLoS One 7:e30562|
|Chien, Wenwen; O'Kelly, James; Lu, Daning et al. (2011) Expression of connective tissue growth factor (CTGF/CCN2) in breast cancer cells is associated with increased migration and angiogenesis. Int J Oncol 38:1741-7|
|Nagashima, Takashi; Kim, Jaeyeon; Li, Qinglei et al. (2011) Connective tissue growth factor is required for normal follicle development and ovulation. Mol Endocrinol 25:1740-59|
|Nishida, Takashi; Emura, Kenji; Kubota, Satoshi et al. (2011) CCN family 2/connective tissue growth factor (CCN2/CTGF) promotes osteoclastogenesis via induction of and interaction with dendritic cell-specific transmembrane protein (DC-STAMP). J Bone Miner Res 26:351-63|
Showing the most recent 10 out of 18 publications