Electrospinning and Cell Fibers in Biomedical Applications

Human body tissues such as muscle, blood vessels, tendon/ligaments, and nerves have fiber-like fascicle morphologies, where ordered organization of cells and extracellular matrix (ECM) within the bundles in specific 3D manners orchestrates cells and ECM to provide tissue functions. Through engineering cell fibers (which are fibers containing living cells) as living building blocks with the help of emerging "bottom-up" biomanufacturing technologies, it is now possible to reconstitute/recreate the fiber-like fascicle morphologies and their spatiotemporally specific cell-cell/cell-ECM interactions in vitro, thereby enabling the modeling, therapy, or repair of these fibrous tissues. In this article, a concise review is provided of the "bottom-up" biomanufacturing technologies and materials usable for fabricating cell fibers, with an emphasis on electrospinning that can effectively and efficiently produce thin cell fibers and with properly designed processes, 3D cell-laden structures that mimic those of native fibrous tissues. The importance and applications of cell fibers as models, therapeutic platforms, or analogs/replacements for tissues for areas such as drug testing, cell therapy, and tissue engineering are highlighted. Challenges, in terms of biomimicry of high-order hierarchical structures and complex dynamic cellular microenvironments of native tissues, as well as opportunities for cell fibers in a myriad of biomedical applications, are discussed.

3D Tissue Formation of Unilocular Adipocytes in Hydrogel Microfibers

Adipose tissue, an active metabolic and endocrine organ mainly composed of unilocular adipocytes, is implicated in various obesity related diseases. Developing morphologically and functionally accurate in vitro models of the adipose tissue is therefore critically important for basic biological studies, drug screening/testing, and clinical implants to advance the understanding and treatment of these diseases. However, current adipose tissue engineering technologies either cannot replicate the unilocular morphologies of mature adipocytes, or lack the ease of monitoring, handling, and scaling up required in the above mentioned applications. This paper presents the differentiation of adipose derived stem cells (ADSCs) to mature adipocytes in highly observable and highly handleable 3D fiber shaped constructs exhibiting morphologies and functions of native adipose tissues. Using the cell fiber technology, ADSCs were encapsulated in hydrogel microfibers, allowed to form into fiber shaped constructs, and differentiated to mature unilocular adipocytes. These adipocyte fibers are observed and maintained for up to 91 d, and secretion of adipose tissue-specific factor, adiponectin, is further confirmed. The handleability of the adipocyte fibers is demonstrated by assembling the adipocyte fibers into doll shaped constructs. Such highly observable, highly handleable, and scalable characteristics of the adipocyte fibers make them suitable for biological studies, high-throughput drug screening/testing, and clinical applications.