Impaired osteoblast differentiation in annexin A2- and -A5-deficient cells

• Published in: PloS one 2014-09, Vol.9 (9), p.e107482
• Main Authors: Genetos, Damian C, Wong, Alice, Weber, Thomas J, Karin, Norman J, Yellowley, Clare E
• Format: Article
• Language: English
• Subjects: Alkaline phosphatase; Anatomy & physiology; Animals; Annexin A2 - genetics; Annexin A5 - genetics; Annexins; Biocompatibility; Biology; Biology and Life Sciences; Bone growth; Bone marrow; Calcium; Cbfa-1 protein; Cell culture; Cell cycle; Cell Differentiation - genetics; Cell proliferation; Cell Proliferation - genetics; Collagen (type I); Collagen Type I - biosynthesis; Control; Core Binding Factor Alpha 1 Subunit - biosynthesis; Cytokines; Deoxyribonucleic acid; Differentiation; DNA; Fibrinolysis; Gene expression; Gene Expression Regulation, Developmental; Gene Knockdown Techniques; Hypoxia; Integrin-Binding Sialoprotein - biosynthesis; Interleukins; Ion transport; Laboratories; Lipid rafts; Matrix vesicles; Medicine and Health Sciences; Metastasis; Mice; Mineralization; Osteoblastogenesis; Osteoblasts; Osteoblasts - metabolism; Osteogenesis; Osteogenesis - genetics; Osteoprogenitor cells; Physiology; Protein binding; Protein expression; Proteins; Rafts; Research and Analysis Methods; RNA, Small Interfering; Rodents; Signal Transduction - genetics; Signaling; Stat6 protein; STAT6 Transcription Factor - biosynthesis; STAT6 Transcription Factor - genetics; Toxicology; Transcription; Vesicles; Veterinary colleges; Veterinary medicine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0107482

Annexins are a class of calcium-binding proteins with diverse functions in the regulation of lipid rafts, inflammation, fibrinolysis, transcriptional programming and ion transport. Within bone, they are well-characterized as components of mineralizing matrix vesicles, although little else is known as to their function during osteogenesis. We employed shRNA to generate annexin A2 (AnxA2)- or annexin A5 (AnxA5)-knockdown pre-osteoblasts, and determined whether proliferation or osteogenic differentiation was altered in knockdown cells, compared to pSiren (Si) controls. We report that DNA content, a marker of proliferation, was significantly reduced in both AnxA2 and AnxA5 knockdown cells. Alkaline phosphatase expression and activity were also suppressed in AnxA2- or AnxA5-knockdown after 14 days of culture. The pattern of osteogenic gene expression was altered in knockdown cells, with Col1a1 expressed more rapidly in knock-down cells, compared to pSiren. In contrast, Runx2, Ibsp, and Bglap all revealed decreased expression after 14 days of culture. In both AnxA2- and AnxA5-knockdown, interleukin-induced STAT6 signaling was markedly attenuated compared to pSiren controls. These data suggest that AnxA2 and AnxA5 can influence bone formation via regulation of osteoprogenitor proliferation, differentiation, and responsiveness to cytokines in addition to their well-studied function in matrix vesicles.