Department of Biomaterials and Tissue Engineering, Eastman Dental Institute, University College London, 256 Grays Inn Rd, London WC1X8LD, United Kingdom; UCL Centre for Nerve Engineering, University College London, London, United Kingdom; Department of Pharmacology, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, Bloomsbury, London WC1N 1AX, United Kingdom.
UCL Centre for Nerve Engineering, University College London, London, United Kingdom; Department of Pharmacology, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, Bloomsbury, London WC1N 1AX, United Kingdom.
Acta Biomater. 2021 May;126:224-237. doi: 10.1016/j.actbio.2021.03.039. Epub 2021 Mar 22.
Vascularisation is important in nerve tissue engineering to provide blood supply and nutrients for long-term survival of implanted cells. Furthermore, blood vessels in regenerating nerves have been shown to serve as tracks for Schwann cells to migrate along and thus form Bands of Büngner which promote axonal regeneration. In this study, we have developed tissue-engineered constructs containing aligned endothelial cells, or co-cultures of both endothelial cells and Schwann cells to test whether these structures could promote regeneration across peripheral nerve gaps. Type I rat tail collagen gels containing HUVECs (Human Umbilical Vein Endothelial Cells, 4 × 10 cells/ml) were cast in perforated tethering silicone conduits to facilitate cellular self-alignment and tube formation for 4 days of culture. For co-culture constructs, optimal tube formation and cellular alignment was achieved with a ratio of 4:0.5 × 10 cells/ml (HUVECs:Schwann cells). An in vivo test of the engineered constructs to bridge a 10 mm gap in rat sciatic nerves for 4 weeks revealed that constructs containing only HUVECs significantly promoted axonal regeneration and vascularisation across the gap, as compared to conventional aligned Schwann cell constructs and those containing co-cultured HUVECs and Schwann cells. Our results suggest that tissue-engineered constructs containing aligned endothelial cells within collagen matrix could be good candidates to treat peripheral nerve injury. STATEMENT OF SIGNIFICANCE: Nerve tissue engineering provides a potential way to overcome the limitations associated with current clinical grafting techniques for the repair of severe peripheral nerve injuries. However, the therapeutic cells within engineered nerve tissue require effective vascularisation in order to survive. This work therefore aimed to develop engineered nerve constructs containing aligned tube-like structures made from endothelial cells. Not only did this provide a method to improve vascularisation, it demonstrated for the first time that aligned endothelial cells can outperform Schwann cells in promoting nerve regeneration in the rat sciatic nerve model. This has introduced the concept of developing pre-vascularised engineered nerve tissues, and indicated the potential usefulness of endothelial cell structures in tissue engineering for peripheral nerve repair.
血管化对于神经组织工程学很重要，它为植入细胞的长期存活提供血液供应和营养。此外，研究表明，再生神经中的血管可以作为施万细胞迁移的轨道，从而形成邦纳带，促进轴突再生。在这项研究中，我们开发了含有排列的内皮细胞的组织工程构建体，或内皮细胞和施万细胞的共培养物，以测试这些结构是否可以促进周围神经间隙的再生。含有 HUVEC（人脐静脉内皮细胞，4×10 个细胞/ml）的 I 型大鼠尾巴胶原凝胶被浇铸在穿孔的拴系硅酮导管中，以促进细胞的自我排列和管形成，培养 4 天。对于共培养构建体，以 4:0.5×10 个细胞/ml（HUVEC：施万细胞）的比例可实现最佳的管形成和细胞排列。在体内测试这些工程构建体以桥接大鼠坐骨神经 10mm 的间隙 4 周的结果表明，与传统的排列良好的施万细胞构建体和含有共培养的 HUVEC 和施万细胞的构建体相比，仅含有 HUVEC 的构建体显著促进了轴突再生和血管生成穿过间隙。我们的结果表明，在胶原基质中含有排列的内皮细胞的组织工程构建体可能是治疗周围神经损伤的良好候选物。
神经组织工程学为克服当前用于修复严重周围神经损伤的临床移植技术相关的局限性提供了一种潜在的方法。然而，工程神经组织内的治疗细胞需要有效的血管化才能存活。因此，这项工作旨在开发含有由内皮细胞制成的排列管状结构的工程神经构建体。这不仅提供了一种改善血管化的方法，而且首次证明了排列的内皮细胞在促进大鼠坐骨神经模型中的神经再生方面优于施万细胞。这引入了开发预血管化工程神经组织的概念，并表明内皮细胞结构在周围神经修复的组织工程中的潜在有用性。
