BMP Receptor Signaling Is Required for Postnatal Maintenance of Articular Cartilage

Department of Developmental Biology and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California, USA.
PLoS Biology (Impact Factor: 9.34). 12/2004; 2(11):e355. DOI: 10.1371/journal.pbio.0020355
Source: PubMed


Articular cartilage plays an essential role in health and mobility, but is frequently damaged or lost in millions of people that develop arthritis. The molecular mechanisms that create and maintain this thin layer of cartilage that covers the surface of bones in joint regions are poorly understood, in part because tools to manipulate gene expression specifically in this tissue have not been available. Here we use regulatory information from the mouse Gdf5 gene (a bone morphogenetic protein [BMP] family member) to develop new mouse lines that can be used to either activate or inactivate genes specifically in developing joints. Expression of Cre recombinase from Gdf5 bacterial artificial chromosome clones leads to specific activation or inactivation of floxed target genes in developing joints, including early joint interzones, adult articular cartilage, and the joint capsule. We have used this system to test the role of BMP receptor signaling in joint development. Mice with null mutations in Bmpr1a are known to die early in embryogenesis with multiple defects. However, combining a floxed Bmpr1a allele with the Gdf5-Cre driver bypasses this embryonic lethality, and leads to birth and postnatal development of mice missing the Bmpr1a gene in articular regions. Most joints in the body form normally in the absence of Bmpr1a receptor function. However, articular cartilage within the joints gradually wears away in receptor-deficient mice after birth in a process resembling human osteoarthritis. Gdf5-Cre mice provide a general system that can be used to test the role of genes in articular regions. BMP receptor signaling is required not only for early development and creation of multiple tissues, but also for ongoing maintenance of articular cartilage after birth. Genetic variation in the strength of BMP receptor signaling may be an important risk factor in human osteoarthritis, and treatments that mimic or augment BMP receptor signaling should be investigated as a possible therapeutic strategy for maintaining the health of joint linings.

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Available from: Vincent Harley, Oct 09, 2014
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    • "(1) GDF5Cre-Confetti. In order to measure the clonal expansion of enthesis progenitors, constitutive GDF5Cre mice generously provided by Dr. David Kingsley (Rountree et al., 2004; Dyment et al., 2014 "
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    ABSTRACT: The sequence of events that leads to the formation of a functionally graded enthesis is not clearly defined. The current study demonstrates that clonal expansion of Gdf5 progenitors contributes to linear growth of the enthesis. Prior to mineralization, Col1+ cells in the enthesis appose Col2+ cells of the underlying primary cartilage. At the onset of enthesis mineralization, cells at the base of the enthesis express alkaline phosphatase, Indian hedgehog, and ColX as they mineralize. The mineralization front then extends towards the tendon midsubstance as cells above the front become encapsulated in mineralized fibrocartilage over time. The hedgehog (Hh) pathway regulates this process, as Hh-responsive Gli1+ cells within the developing enthesis mature from unmineralized to mineralized fibrochondrocytes in response to activated signaling. Hh signaling is required for mineralization, as tissue-specific deletion of its obligate transducer Smoothened in the developing tendon and enthesis cells leads to significant reductions in the apposition of mineralized fibrocartilage. Together, these findings provide a spatiotemporal map of events-from expansion of the embryonic progenitor pool to synthesis of the collagen template and finally mineralization of this template-that leads to the formation of the mature zonal enthesis. These results can inform future tendon-to-bone repair strategies to create a mechanically functional enthesis in which tendon collagen fibers are anchored to bone through mineralized fibrocartilage. Copyright © 2015. Published by Elsevier Inc.
    Developmental Biology 06/2015; 405(1). DOI:10.1016/j.ydbio.2015.06.020 · 3.55 Impact Factor
    • "We have demonstrated that a band of Nog-expressing cells (Fig. 5) serves this purpose. Thus, the absence of joint structures upon ectopic activation of BMP signaling should not be interpreted as fusion of cartilage elements (Duprez et al., 1996; Zou et al., 1997; Guo et al., 2004; Rountree et al., 2004). Rather, it should be interpreted as failure of articular cartilage formation and consequent failure to segment the cartilage anlagen. "
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    ABSTRACT: The articular cartilage, which lines the joints of the limb skeleton, is distinct from the adjoining transient cartilage, and yet, it differentiates as a unique population within a contiguous cartilage element. Current literature suggests that articular cartilage and transient cartilage originate from different cell populations. Using a combination of lineage tracing and pulse-chase of actively proliferating chondrocytes, we here demonstrate that, similar to transient cartilage, embryonic articular cartilage cells also originate from the proliferating chondrocytes situated near the distal ends of skeletal anlagen. We show that nascent cartilage cells are capable of differentiating as articular or transient cartilage, depending on exposure to Wnt or BMP signaling, respectively. The spatial organization of the articular cartilage results from a band of Nog-expressing cells, which insulates these proliferating chondrocytes from BMP signaling and allows them to differentiate as articular cartilage under the influence of Wnt signaling emanating from the interzone. Through experiments conducted in both chick and mouse embryos we have developed a model explaining simultaneous growth and differentiation of transient and articular cartilage in juxtaposed domains. © 2015. Published by The Company of Biologists Ltd.
    Development 03/2015; 142(6):1169-79. DOI:10.1242/dev.110940 · 6.46 Impact Factor
    • "GDF5 is known as BMP14 or Cartilage-Derived Morphogenetic Protein 1 (CDMP1). It is a central modulator of early cartilage formation and plays an important role in the development of bones, joints, tendons and ligaments in the axial and appendicular skeleton [3] [4] [5] [6]. As a therapeutic agent, the regeneration-supporting activities of wild type GDF5 (GDF5 wt ) have been investigated in various preclinical studies and clinical trials including craniofacial, peri-implant [7] [8] and calvarial [9] [10] bone formation, spine [11] [12] [13] and long bone surgery [14] [15] as well as cartilage [16], tendon and ligament [17] [18] [19] formation and repair [20]. "
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    ABSTRACT: Multiple synostoses syndrome 2 (SYNS2) is a rare genetic disease characterized by multiple fusions of the joints of the extremities, like phalangeal joints, carpal and tarsal joints or the knee and elbows. SYNS2 is caused by point mutations in the Growth- and Differentiation Factor 5 (GDF5), which plays an essential role during skeletal development and regeneration. We selected one of the SYNS2-causing GDF5 mutations, p.N445T, which is known to destabilize the interaction with the Bone Morphogenetic Protein (BMP) antagonist NOGGIN (NOG), in order to generate the superagonistic GDF5 variant GDF5(N445T). In this study, we tested its capacity to support regeneration in a rat critical-sized defect model in vivo. MicroCT and histological analyses indicate that GDF5(N445T)-treated defects show faster and more efficient healing compared to GDF5 wild type (GDF5(wt))-treated defects. Microarray-based gene expression and quantitative PCR analyses from callus tissue point to a specific acceleration of the early phases of bone healing, comprising the inflammation and chondrogenesis phase. These results support the concept that disease-deduced growth factor variants are promising lead structures for novel therapeutics with improved clinical activities. Copyright © 2014. Published by Elsevier Inc.
    Bone 12/2014; 73. DOI:10.1016/j.bone.2014.12.017 · 3.97 Impact Factor
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