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Hydroxyapatite (HAp) is critical to health both as the main structural material of the skeleton and storage material of calcium and phosphate. Nanosized HAp (nHAp) is naturally produced by mineralizing cells during bone formation and remodeling and is the main constituent of the skeleton. As such, HAp is currently being investigated as a therapeutic biomaterial for orthopedic and dental purposes. Recent studies have suggested that extracellular nHAp can influence osteoblast lineage commitment and cell function through changes in gene expression; however, the mechanisms remain to be elucidated. Here, the cellular and molecular mechanism by which rod-shaped nHAp (10 × 100 nm) stimulates gene expression in preosteoblast bone marrow stromal cells was investigated. Electron microscopy detected a rapid and stable interaction of nHAp with the cell membrane, which correlated with a strong stimulation of the Erk1/2 signaling pathway. Results also identified the requirement of the Fgf receptor signaling and phosphate-transporters for nHAp regulated gene expression whereas a calcium-sensing receptor inhibitor had no effect. Collectively, the study uncovers novel signaling pathways and cellular events specifically stimulated by and required for the cellular response to free extracellular HAp. The results provide insight into the osteoblastic response to HAp relevant to functional mineralization and pathological calcification and could be used in the development of biomaterials for orthopedic purposes.

Objective: To review the pharmacology, efficacy, and safety of the selective transthyretin inhibitor tafamidis for transthyretin amyloid cardiomyopathy (ATTR-CM). Data Sources: A PubMed (1966 to October 2019) and ClinicalTrials. gov search was conducted using the keywords tafamidis, Fx-1006A, Vyndaqel, and Vyndamax. Additional articles were identified from references. Study Selection and Data Extraction: We included English-language clinical studies evaluating the pharmacology, efficacy, or safety of tafamidis in humans for ATTR-CM. Data Synthesis: Tafamidis binds to the thyroxine-binding sites of the transthyretin tetramer and inhibits its dissociation into monomers, which is the rate-limiting step in the amyloidogenic process. Treatment with tafamidis was significantly associated with a significant reduction in mortality, lowered cardiovascular-related hospitalizations, less functional decline, and improved transthyretin stabilization compared with placebo. Additionally, tafamidis was found to have fewer adverse events, with no difference found compared with placebo. Relevance to Patient Care and Clinical Practice: Historically, symptomatic management for ATTR-CM was the only option, and the treatment of the underlying disease was limited to liver or heart transplantation. Tafamidis is the first medication approved for the treatment of ATTR-CM and the only medication that showed a reduction in all-cause mortality and cardiovascular-related hospitalizations in patients with amyloidosis. However, the role of tafamidis in patients with the New York Heart Association class III/IV heart failure or mutated transthyretin remains unclear. Conclusion: Tafamidis is an effective and safe oral medication for the treatment of the cardiomyopathy of transthyretin-mediated amyloidosis in adults to reduce cardiovascular mortality and cardiovascular-related hospitalization.