This study was designed to investigate how the strength of the interaction between octacalcium phosphate (OCP) and modified chondroitin-A sulfate (CS-A), a glycosaminoglycan, regulates the adsorption–desorption of cytokines and subsequently affects the osteoblastic differentiation of mesenchymal stem cells (MSCs) in vitro. The utilization of cytokines produced by cells, such as macrophages, stimulated by the hydrolysis of OCP, is expected to enhance the bone regeneration capacity of the OCP. CS-Na was used to modify CS-A on the OCP immobilized with the amino group through electrostatic interactions. On the other hand, N-hydroxysuccinimide (NHS)-esterified CS-A was used to form the covalent bond between CS-A and the amino group on the surface of OCP. X-ray diffraction and Raman spectroscopy indicated that the CS-A-modified OCP maintained its structure, regardless of the modification process. The remaining ratio of the modified CS-A in the buffer suggests that increasing the immobilized density of the amino group and the modification using NHS ester may enhance interaction strength between OCP and CS-A. The adsorption amount and retention rate of recombinant human bone morphological protein-2 (rhBMP-2, an endogenous cytokine model) increased onto CS-A-modified OCP under physiological conditions when the interaction strength between OCP and the protein was stronger. The higher interaction strength between the OCP and CS-A could be associated with the enhanced adsorption affinity for the lower-molecular-weight basic protein. The alkaline phosphatase activity of MSCs increased depending on the remaining rate of rhBMP-2 adsorption on the CS-A-modified-OCP. Fourier transform infrared spectroscopy and chemical analysis indicated that the hydrolysis of the OCP progressed regardless of CS-A modification after MSC incubation. The present study suggests that stronger interactions between the OCP and glycosaminoglycans could contribute to the capture and retention of endogenous cytokines on the surface to further promote osteoblastic differentiation under the chemical environment induced by the hydrolysis of the OCP.

中文翻译：

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通过相互作用控制的糖胺聚糖修饰增强磷酸八钙的细胞因子吸附能力以促进成骨细胞分化


本研究旨在探讨磷酸八钙 （OCP） 和糖胺聚糖硫酸软骨素 A （CS-A） 之间相互作用的强度如何调节细胞因子的吸附-解吸，并随后影响体外间充质干细胞 （MSC） 的成骨细胞分化。利用细胞产生的细胞因子，如巨噬细胞，在 OCP 水解的刺激下，有望增强 OCP 的骨再生能力。CS-Na 用于通过静电相互作用修饰与氨基固定的 OCP 上的 CS-A。另一方面，N-羟基琥珀酰亚胺 （NHS） 酯化 CS-A 用于在 CS-A 与 OCP 表面的氨基之间形成共价键。X 射线衍射和拉曼光谱表明，无论改性过程如何，CS-A 改性的 OCP 都保持其结构。缓冲液中修饰的 CS-A 的剩余比例表明，增加氨基的固定化密度和使用NHS酯的修饰可能会增强OCP和CS-A之间的相互作用强度。当 OCP 与蛋白质之间的相互作用强度较强时，在生理条件下，重组人骨形态蛋白-2 （rhBMP-2，一种内源性细胞因子模型） 对 CS-A 修饰的 OCP 的吸附量和保留率增加。OCP 和 CS-A 之间较高的相互作用强度可能与对低分子量碱性蛋白的吸附亲和力增强有关。MSC 的碱性磷酸酶活性增加取决于 rhBMP-2 在 CS-A 修饰的 OCP 上的剩余吸附速率。 傅里叶变换红外光谱和化学分析表明，MSC 孵育后，无论 CS-A 修饰如何，OCP 的水解都进行。本研究表明，OCP 和糖胺聚糖之间更强的相互作用有助于在 OCP 水解诱导的化学环境下捕获和保留表面的内源性细胞因子，从而进一步促进成骨细胞分化。