Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_980_Библиотеки_им_академика_М_И_Перельмана

Mechanical stimuli allow culture medium streaming within scaffolds, further contributing to the role of dynamicity in tissue engineering. Hence, restricted expression of osteogenic markers, inhibited stem cell differentiation, and limited nutrient diffusion to the scaffold core are among the drawbacks of static cultural settings that inherently tend to disregard the role of dynamicity in tissue generation and growth. Constraints of static culturing have led to an ongoing endeavors for incorporating mechanical stimuli [6, 23], using bioreactors. Bioreactors are housing devices that provide controlled conditions that allow enactment of physiologic, bio­logic, and biochemical phenomena within articial tissue constructs. Initial objec­tive of bioreactors was to test biomaterials, but afterward, various modalities were developed aiming for extracorporeal tissue growth. Incorporation of bioreactors in terms of tissue engineering has led to the recent emergence of the term “Tissue Engineering Quadriad” as for the combination of cells, carrier constructs, signaling factors, and bioreactor systems, which formerly only consisted of rst three compo­nents, the so-called tissue engineering triad [6]. Bioreactors have helped with addressing the static culturing-associated limitations and culminated in a paradigm shift regarding extracorporeal fabrication of viable tissue fragments. Osteogenic­based bioreactors are designed to promote osteogenic capabilities of bio-scaffolds and “in vitro bone tissue morphogenesis,” namely, the generation of bone-like struc­tures and ECM [24]. Bioreactors are used for facilitation, monitoring, and control­ling the inherent biological or biochemical phenomena that occur within natural tissue. Complex bioreactors allow tuning of certain physiologic parameters,

The spinner ask bioreactors create a turbulent ow leading to a promoted diffusion of biotic substances [29]. These bioreactors are relatively simple and inexpensive systems. Spinner asks consisted of a glass reservoir, side arms, and porous ltering covers. The reservoir holds the media, and the side arms are unlocked to reach the reservoir’s internal space. While scaffolds are attached to the lid of unit ask with needles, an assembled mixer starts convective forces and medium ow at the ask center unit. Mixer’s stirring speed is set based on the aimed for shear stress that is to be applied on scaffolds. The porous ltering covers allow the gas by-products to exchange within the system. Once prepared, the whole ask is retained in incuba­tors with pre-controlled temperature and oxygen-delivery content [6, 23, 30].

Spinner ask bioreactors were primarily designed to be used in BTE [31]. Spinner ask systems have been known as facile and low-cost setups, capable of promoting proliferation and differentiation of cultured cells [6, 29, 31, 32]. They are capable of more efciently enhancing nutrient mass transport when compared to rotating wall vessels [6, 29]. Moreover, spinner asks can impart higher stress val­ues upon cells. Spinner ask bioreactors can house multiple small scaffolds and culture clinically relevant engineered tissue fragments concomitantly. This can put spinner ask bioreactor at use when reconstruction of segmental skeletal defects is planned [6]. With regard to development of thin bone substitutes that are used as bone patches in restorative interventions or at bone reconstructions, spinner asks and rotating wall vessels are both rational choices [6]. In addition to their differen­tial and proliferative impacts, spinner ask systems have the advantage of low acquisition costs [29].