Self-assembled cell aggregates for tissue engineering

组织工程学的目标是用实验室开发的功能结构来取代受损或丢失的组织或器官。细胞，最好来自患者自己，在被转移到三维聚合物支架之前，被分离并在培养瓶中生长。在这里，细胞的持续生长和发育成为功能性组织替代物得到支持，直到构建物准备好植入患者体内。当然，这是一种理想化的情况，如果要使常规的组织替代物制造成为现实，仍有许多技术障碍必须克服。在这一领域遇到的一个主要问题是细胞生长所在的3D支架的性质。虽然它们可以通过促进黏附和释放有助于细胞生长的因子为细胞提供合适的环境，但它们的内部规模和结构意味着细胞的行为就像在平面上生长一样。在自然组织中，细胞接收三维信号，不仅来自它们的邻居，还来自它们周围的蛋白质基质。这些信号对于维持正确的组织功能和细胞存活至关重要，因此在组织工程中，更广泛地说，在整个生物学研究中，需要开发新的方法来生长具有真正3D组织的细胞结构。这项研究提出了一种新的3D细胞培养方法，即细胞和细胞大小的聚合物微粒在悬浮液中快速交联在一起，以有效地在细胞周围自组装聚合物支架。这不仅将为细胞提供3D信号环境，还将受益于从颗粒中释放生长因子以帮助细胞和组织发育的能力。在这个系统中，颗粒是可生物降解的，随着时间的推移会消失，离开自然组织。研究方案将初步优化将细胞与聚合物微粒相连接的方法，并着手确定三维形成聚集体结构的最佳条件。为了证明其潜在的好处，来自骨髓的成体干细胞将被分离并与聚合物微粒聚集。根据培养条件的不同，这些细胞有可能发育成许多不同的组织。在这项工作中，细胞将与释放促进骨形成的生长因子的微粒聚集在一起。这种方法的成功将通过检查骨聚体中的骨特异性标记物与不含生长因子的骨聚体进行比较来确定。显然，这项技术在产生医疗应用的替代组织方面具有巨大的潜力。它不仅对骨工程有用，而且还可以应用于任何细胞或组织类型和相关的生长因子。因此，这可以在帮助克服伤害和疾病造成的巨大社会经济代价方面得到广泛应用。这项技术还可以用于开发更逼真的3D组织模型，用于基础生物学研究。例如，在实验室中构建真实的肿瘤模型的能力为更好地了解癌症和开发更有效的治疗方法提供了前景。此外，这项研究还可以应用于构建药物测试应用的组织，减少在动物身上测试药物产品的要求。

Tissue engineering aims to replace damaged or lost tissues or organs with functional constructs that have been developed in the laboratory. Cells, ideally from the patient themselves, are isolated and grown in culture flasks before being transferred to a three-dimensional polymer scaffold. Here, the continued growth and development of the cells into a functional tissue replacement is supported until the construct is ready for implantation into the patient. This, of course, is an idealized scenario and there are still many technical hurdles that must be overcome if routine fabrication of tissue replacements is to become a reality. One major problem encountered within this area is the nature of 3D scaffolds that cells are grown on. While they can provide a suitable environment for cells by promoting their adhesion and releasing factors that help their growth, their internal scale and structure means that cells behave as if grown on a flat surface. In natural tissues, cells receive signals in three dimensions, not only from their neighbours, but from the protein matrix that surrounds them. These signals are vital for the maintenance of correct tissue function and cell survival, so there is a need in tissue engineering and, more broadly, in biological research as a whole, to develop novel methods to grow cell structures with a true 3D organization. This research proposes a novel method of 3D cell culture where cells and cell-sized polymer microparticles are rapidly cross-linked together in suspension to effectively self-assemble a polymer scaffold around the cells. Not only will this provide the cells with a 3D signalling environment, but it also benefits from the ability to release growth factors from the particles to assist cell and tissue development. In this system, the particles are biodegradable and disappear over time to leave a natural tissue. The research programme will initially optimize methods to cross-link the cells with polymer microparticles and proceed to determine the best conditions for the 3D formation of aggregate structures. To demonstrate its potential benefits, adult stem cells from bone marrow will be isolated and aggregated with polymer microparticles. These cells have the potential to develop into a number of different tissues depending on the culture conditions used. For this work, the cells will be aggregated with microparticles that release a growth factor that promotes bone formation. The success of this approach will be determined by examining bone-specific markers within the aggregates in comparison to aggregates that contained no growth factor. It is apparent that this technique has huge potential for the generation of replacement tissue for medical applications. Not only is it useful for bone engineering, but can also be applied to any cell or tissue type and relevant growth factors. Therefore, this could find widespread use in helping to overcome the huge socio-economic cost caused by injury and disease. This technology could also be used to develop more realistic 3D tissue models for fundamental biological research. For example, the ability to construct realistic tumour models in the laboratory offers the prospect of a greater understanding of cancer and the development of more effective treatments. In addition, this research could be applied to construct tissues for drug testing applications, decreasing the requirement to test pharmaceutical products on animals.