Program of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, 240 Pasteur Dr., Biomedical Innovation Building 1200, Palo Alto, CA 94304, United States of America.
Departments of Orthopaedic Surgery and Bioengineering Stanford University, 240 Pasteur Dr., Biomedical Innovation Building 1200, Palo Alto, CA 94304, United States of America.
Biomater Adv. 2022 Sep;140:213050. doi: 10.1016/j.bioadv.2022.213050. Epub 2022 Jul 28.
Hydroxyapatite (HA) has a composition similar to mineral bone and has been used for coating macroporous scaffolds to enhance bone formation. However, previous macroporous scaffolds did not support minimally invasive delivery. Our lab has reported on gelatin-based microribbon (μRB) shaped hydrogels, which combine injectability with macroporosity and support cranial bone formation in an immunocompromised mouse model. However, gelatin alone was not sufficient to support cranial bone formation in immunocompetent animals. To overcome this challenge, here we evaluated two methods to incorporate HA into gelatin μRB scaffolds using either modified simulated body fluid (mSBF) or commercially available HA nanoparticles (HAnp). HA incorporation and distribution were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. While both methods enhanced MSC osteogenesis and mineralization, the mSBF method led to undesirable reduction in mechanical properties. HAnp-coated μRB scaffolds were further evaluated in an immunocompetent mouse cranial defect model. Acellular HAnp-coated gelatin μRB scaffolds induced rapid and robust endogenous cranial bone regeneration as shown by MicroCT imaging and histology. Co-delivery with exogenous MSCs led to later bone resorption accompanied by increased osteoclast activity. In summary, our results demonstrate the promise of gelatin μRBs with HAnps as a promising therapy for cranial bone regeneration without the need for exogenous cells or growth factors.
羟基磷灰石（HA）的组成与矿物质骨骼相似，已被用于涂覆大孔支架以增强成骨作用。然而，以前的大孔支架不支持微创输送。我们的实验室已经报道了基于明胶的微带（μRB）形状水凝胶，它将可注射性与大孔率结合在一起，并在免疫功能低下的小鼠模型中支持颅盖骨形成。然而，单独的明胶不足以在免疫功能正常的动物中支持颅盖骨形成。为了克服这一挑战，我们在这里评估了两种将 HA 掺入明胶 μRB 支架中的方法，一种是使用改良的模拟体液（mSBF），另一种是使用市售的 HA 纳米颗粒（HAnp）。使用扫描电子显微镜和能谱分析对 HA 的掺入和分布进行了表征。虽然这两种方法都增强了 MSC 的成骨作用和矿化作用，但 mSBF 方法导致机械性能的不可取降低。进一步在免疫功能正常的小鼠颅缺损模型中评估了 HAnp 涂层的 μRB 支架。无细胞 HAnp 涂层的明胶 μRB 支架通过 MicroCT 成像和组织学显示出快速而强大的内源性颅盖骨再生。与外源性 MSC 共递送导致后期骨吸收，同时伴有破骨细胞活性增加。总之，我们的结果表明，含有 HAnp 的明胶 μRB 作为一种有前途的颅盖骨再生疗法具有很大的潜力，无需外源性细胞或生长因子。
