Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California 90033, United States.
Bioconjug Chem. 2021 May 19;32(5):916-927. doi: 10.1021/acs.bioconjchem.1c00036. Epub 2021 May 6.
We describe the design and synthesis of OFS-1, an Osteoadsorptive Fluorogenic Sentinel imaging probe that is adsorbed by hydroxyapatite (HAp) and bone mineral surfaces, where it generates an external fluorescent signal in response to osteoclast-secreted cathepsin K (Ctsk). The probe consists of a bone-anchoring bisphosphonate moiety connected to a Förster resonance energy transfer (FRET) internally quenched fluorescent (IQF) dye pair, linked by a Ctsk peptide substrate, GHPGGPQG. Key structural features contributing to the effectiveness of OFS-1 were defined by structure-activity relationship (SAR) and modeling studies comparing OFS-1 with two cognates, OFS-2 and OFS-3. In solution or when preadsorbed on HAp, OFS-1 exhibited strong fluorescence when exposed to Ctsk (2.5-20 nM). Time-lapse photomicrographs obtained after seeding human osteoclasts onto HAp-coated well plates containing preadsorbed OFS-1 revealed bright fluorescence at the periphery of resorbing cells. OFS-1 administered systemically detected early osteolysis colocalized with orthotopic engraftment of RPMI-8226-Luc human multiple myeloma cells at a metastatic skeletal site in a humanized mouse model. OFS-1 is thus a promising new imaging tool for detecting abnormal bone resorption.
我们描述了 OFS-1 的设计和合成，它是一种骨吸收荧光示踪成像探针，可被羟磷灰石（HAp）和骨矿物质表面吸附，在骨吸收细胞（破骨细胞）分泌的组织蛋白酶 K（Ctsk）的作用下，探针会产生外部荧光信号。该探针由一个与骨结合的双膦酸盐部分与一个 FRET 内部荧光猝灭（IQF）染料对连接而成，通过 Ctsk 肽底物 GHPGGPQG 连接。通过结构活性关系（SAR）和与两个同源物（OFS-2 和 OFS-3）进行建模研究，定义了导致 OFS-1 有效性的关键结构特征。在溶液中或在 HAp 上预吸附时，OFS-1 在暴露于 Ctsk（2.5-20 nM）时表现出强烈的荧光。在将人破骨细胞接种到含有预吸附 OFS-1 的 HAp 涂层孔板上后获得的延时显微照片显示，在吸收细胞的周边有明亮的荧光。全身性给予 OFS-1 可检测到早期溶骨性骨破坏，与 RPMI-8226-Luc 人多发性骨髓瘤细胞在人源化小鼠模型中骨转移部位的原位移植相吻合。因此，OFS-1 是一种很有前途的新的骨吸收检测成像工具。
