Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Department of Nephrology and Hypertension, University Medical Center Utrecht, F03.227, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
J Control Release. 2014 Jun 28;184:58-66. doi: 10.1016/j.jconrel.2014.04.007. Epub 2014 Apr 13.
Timely vascularization is essential for optimal performance of bone regenerative constructs. Vascularization is efficiently stimulated by vascular endothelial growth factor (VEGF), a substance with a short half-life time. This study investigates the controlled release of VEGF from gelatin microparticles (GMPs) as a means to prolong VEGF activity at the preferred location within 3D bioprinted scaffolds, and the effects on subsequent vascularization. The release of VEGF from GMPs was continuous for 3 weeks during in vitro studies, and bioactivity was confirmed using human endothelial progenitor cells (EPCs) in migration assays. Traditional and real-time migration assays showed immediate and efficient EPC migration in the presence of GMP-released VEGF, indistinguishable from VEGF-solution that was added to the medium. Matrigel scaffolds containing EPCs and VEGF, which was released either in a fast or sustained fashion by application of GMPs, were investigated for their in vivo vasculogenic capacity. Implantation in subcutaneous pockets in nude mice for one week demonstrated that vessel formation was significantly higher in the VEGF sustained-release group compared to the fast release group. In addition, regional differences with respect to VEGF release were introduced in 3D bioprinted EPC-laden scaffolds and their influence on vasculogenesis was investigated in vivo. The different regions were retained and vessel formation occurred analogous with the results seen in the Matrigel plugs. We conclude that GMPs are suitable to generate sustained release profiles of bioactive VEGF, and that they can be used to create defined differentiation regions in 3D bioprinted heterogeneous constructs, allowing a new generation of smart scaffold design. The prolonged presence of VEGF led to a significant increase in scaffold vascularization when applied in vivo.
血管化对于骨再生构建体的最佳性能至关重要。血管内皮生长因子（VEGF）可有效刺激血管生成，但其半衰期较短。本研究探讨了将 VEGF 从明胶微球（GMP）中控制释放，以延长 3D 生物打印支架内首选位置的 VEGF 活性，并研究其对随后血管生成的影响。在体外研究中，GMP 持续释放 VEGF 长达 3 周，通过迁移实验用人内皮祖细胞（EPC）证实了其生物活性。传统和实时迁移实验表明，在存在 GMP 释放的 VEGF 时，EPC 能够立即且高效地迁移，与添加到培养基中的 VEGF 溶液一样。研究了含有 EPC 和 VEGF 的 Matrigel 支架，VEGF 通过 GMP 的快速或持续释放方式释放，以研究其体内血管生成能力。将其植入裸鼠的皮下囊中一周后，结果表明，与快速释放组相比，VEGF 持续释放组的血管形成明显更高。此外，在 3D 生物打印的负载 EPC 的支架中引入了关于 VEGF 释放的区域差异，并研究了其对血管生成的体内影响。不同区域被保留，并且类似于在 Matrigel 塞中观察到的结果，发生了血管形成。我们得出结论，GMP 适合生成生物活性 VEGF 的持续释放曲线，并且可以用于在 3D 生物打印的异质构建体中创建定义的分化区域，从而实现新一代智能支架设计。当在体内应用时，VEGF 的持续存在导致支架血管化显著增加。
