Hydroxyapatite (HA)-based materials are widely used as bone substitutes due to their inherent biocompatibility, osteoconductivity, and bio-absorption properties. However, HA scaffolds lack compressive strength when compared to autograft bone. It has been shown that the fluoridated form of HA, fluorapatite (FA), can be sintered to obtain this desired strength as well as slower degradation properties. Also, FA surfaces have been previously shown to promote stem cell differentiation toward an osteogenic lineage. Thus, it was hypothesized that FA, with and without stromal vascular fraction (SVF), would guide bone healing to an equal or better extent than the clinical gold standard. The regenerative potentials of these scaffolds were tested in 32 Lewis rats in a femoral condylar defect model with untreated (negative), isograft (positive), and commercial HA as controls. Animals were survived for 12 weeks post-implantation. A semi-quantitative micro-CT analysis was developed to quantify the percent new bone formation within the defects. Our model showed significantly higher (p < .05) new bone depositions in all apatite groups compared to the autograft group. Overall, the FA group had the most significant new bone deposition, while the differences between HA, FA, and FA + SVF were insignificant (p > .05). Histological observations supported the micro-CT findings and highlighted the presence of healthy bone tissues without interposing capsules or intense immune responses for FA groups. Most importantly, the regenerating bone tissue within the FA + SVF scaffolds resembled the architecture of the surrounding trabecular bone, showing intertrabecular spaces, while the FA group presented a denser cortical bone-like architecture. Also, a lower density of cells was observed near FA granules compared to HA surfaces, suggesting a reduced immune response. This first in vivo rat study supported the tested hypothesis, illustrating the utility of FA as a bone scaffold material.

中文翻译：

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烧结氟磷灰石支架作为自体移植样工程骨移植物

羟基磷灰石（HA）基材料由于其固有的生物相容性、骨传导性和生物吸收特性而被广泛用作骨替代品。然而，与自体移植骨相比，HA 支架缺乏抗压强度。研究表明，HA 的氟化形式氟磷灰石 (FA) 可以通过烧结来获得所需的强度以及较慢的降解特性。此外，FA 表面先前已被证明可以促进干细胞向成骨谱系分化。因此，假设 FA，无论有无基质血管分数 (SVF)，都将指导骨愈合达到与临床金标准相同或更好的程度。这些支架的再生潜力在 32 只 Lewis 大鼠的股骨髁缺损模型中进行了测试，并以未经治疗的（阴性）、同种移植物（阳性）和商业 HA 作为对照。动物在植入后存活12周。开发了半定量显微 CT 分析来量化缺损内新骨形成的百分比。 我们的模型显示，与自体移植组相比，所有磷灰石组的新骨沉积明显更高 ( p < .05)。总体而言，FA 组的新骨沉积最显着，而 HA、FA 和 FA + SVF 之间的差异不显着 ( p  > .05)。组织学观察结果支持了微型 CT 的发现，并强调了健康骨组织的存在，而没有插入胶囊或 FA 组的强烈免疫反应。最重要的是，FA + SVF 支架内的再生骨组织类似于周围小梁骨的结构，显示出小梁间空间，而 FA 组则呈现出更致密的皮质骨样结构。此外，与 HA 表面相比，在 FA 颗粒附近观察到的细胞密度较低，表明免疫反应减弱。第一项大鼠体内研究支持了所测试的假设，说明了 FA 作为骨支架材料的效用。