The essence of biophysical cues in skeletal muscle tissue engineering

Skeletal muscle is an appealing topic for tissue engineering because of its variety in applications. Evidently, tissue engineered skeletal muscle can be used in the field of regenerative medicine to repair muscular defects or dystrophies. Engineered skeletal muscle constructs can also be used as a model system for drug-screening or to study muscle physiology and the etiology of pressure sores. Besides these well known applications, a new field of interest with high societal impact has arisen, being in vitro cultured meat. Contemporary large-scale farming and transportation of livestock brings along a high risk of infectious animal diseases and environmental burden through greenhouse gas emission. In vitro cultured meat can dramatically reduce these risks and improve animal welfare. Although major advances have been made so far in skeletal muscle tissue engineering, the maturation level of the engineered muscle constructs is still not satisfactory. The requirements of the engineered skeletal muscle constructs are similar for both regenerative medicine and in vitro meat production: mature functional skeletal muscle tissue is required that can produce force within the physiological range. To improve the maturation process of skeletal muscle progenitor cells we have focused on mimicking the native environment of these cells. In particular, we have focused on biophysical cues that play an essential role in the regeneration of skeletal muscle tissue in vivo. These cues were investigated in conventional 2D cultures, as well as in 3D model systems that are physiologically more relevant. An important biophysical cue that was investigated is electrical stimulation, since nerve stimulation is known to be a prerequisite for myotube formation in vivo. We have shown that electrical stimulation results in an acceleration of the formation of cross striations and increased expression levels of muscle maturation markers in 2D and 3D experiments. These effects were observed in cultures of the conventional C2C12 cell line and primary muscle progenitor cells (MPCs). More specifically, electrical stimulation of 3D cultures with MPCs resulted in a shift of myosin heavy chain (MHC) expression towards slower isoforms. Electrical stimulation can be implemented in skeletal muscle tissue engineering strategies to improve efficiency of the culture process and to tune MHC expression, which may be relevant for the final texture of the engineered constructs. Mechanical cues also play an important role in muscle development in vivo, both in the embryonic phase and in adults. Stretch can result in hypertrophy of skeletal muscle tissue and can therefore improve texture and force production of tissue engineered skeletal muscle constructs. However, our mechanical stimulation protocol, with applied strains within the physiological range, resulted in impaired muscle maturation in both C2C12 and primary MPCs and is therefore not useful for skeletal muscle tissue engineering. A major finding of the results presented in this thesis is that the 3D environment in which muscle progenitor cells are cultured is essential for myogenesis. Sarcomere formation was faster in a 3D hydrogel based environment, compared to conventional 2D cultures. In 2D, sarcomere formation is optimal on substrates with a stiffness similar to in vivo skeletal muscle tissue, between 3-12 kPa. However, the stiffness of our 3D hydrogel systems was considerably lower than this range and muscle formation still progressed rapidly. We concluded that not the substrate stiffness itself, but the ability of cells to develop tension is essential for the formation of cross striations. Both in 2D and 3D settings we demonstrated that the Rho-associated kinase plays a role in this process, since no cross striations were observed when this kinase was inhibited. Additionally, 3D culture methods that enable an increase in cellular tension result in acceleration of the maturation process. MPCs cultured in 3D resulted in more mature skeletal muscle tissue compared to C2C12 and are therefore the preferred cell source for tissue engineering applications. However, their proliferative capacity remains limited. We showed that the C2C12 cell line, which is readily accessible and easy to culture and differentiate, can be used as a model system to design 3D culture methods and biophysical stimulation regimes. In conclusion, we have shown that several biophysical cues are important for in vitro skeletal muscle maturation. The results presented in this thesis have contributed to the technology that can realize the in vitro production of meat

Parameterized Optimal Trajectory Generation for Target Localization

This paper presents an approach to near-optimal target localization for small and mi-cro uninhabited aerial vehicles using a family of pre-computed parameterized trajectories. These trajectories are pre-computed for a set of nominal target locations uniformly dis-tributed over the sensor field of view and stored off-line. Upon target detection the vehicle chooses the trajectory corresponding to the closest nominal target location. Adaptation is enabled with the ability to select new trajectories as the target state estimate is updated. Simulation results show the validity of this approach for both single target and sequential target localization missions. Further, results show that very coarse trajectory tables give the same or better target localization performance as finely discretized tables. I

Inverted Landing in a Small Aerial Robot via Deep Reinforcement Learning for Triggering and Control of Rotational Maneuvers

Inverted landing in a rapid and robust manner is a challenging feat for aerial robots, especially while depending entirely on onboard sensing and computation. In spite of this, this feat is routinely performed by biological fliers such as bats, flies, and bees. Our previous work has identified a direct causal connection between a series of onboard visual cues and kinematic actions that allow for reliable execution of this challenging aerobatic maneuver in small aerial robots. In this work, we first utilized Deep Reinforcement Learning and a physics-based simulation to obtain a general, optimal control policy for robust inverted landing starting from any arbitrary approach condition. This optimized control policy provides a computationally-efficient mapping from the system's observational space to its motor command action space, including both triggering and control of rotational maneuvers. This was done by training the system over a large range of approach flight velocities that varied with magnitude and direction. Next, we performed a sim-to-real transfer and experimental validation of the learned policy via domain randomization, by varying the robot's inertial parameters in the simulation. Through experimental trials, we identified several dominant factors which greatly improved landing robustness and the primary mechanisms that determined inverted landing success. We expect the learning framework developed in this study can be generalized to solve more challenging tasks, such as utilizing noisy onboard sensory data, landing on surfaces of various orientations, or landing on dynamically-moving surfaces.Comment: 8 pages, 6 Figures, Submitted for ICRA 2023 Conference (Pending Review

Quality of life of visually impaired working age adults

Er bestaan verschillende vormen van revalidatie voor mensen met een visuele beperking. De meest intensieve vorm vindt plaats in het nationale revalidatiecentrum Visio Het Loo Erf te Apeldoorn. Deze vorm van revalidatie is bedoeld voor mensen met complexe problematiek en / of complexe hulpvragen. Onderdelen van het programma zijn onder andere het computertraining, acceptatie van visuele beperking en leren jezelf te redden in het dagelijks leven. Onderzoek naar het effect van revalidatie bij mensen met een visuele beperking is schaars, zeker in de leeftijdscategorie van 18 tot 65 jaar. De belangrijkste doelstelling van dit onderzoek was: inzicht verkrijgen in de prognostische factoren van kwaliteit van leven van volwassenen tussen 18 en 65 jaar met een visuele beperking die een intensief revalidatieprogramma volgen. Er werden op drie tijdstippen vragenlijsten afgenomen: voordat de revalidatie begon, 3 maanden en 1 jaar na afloop van het revalidatieprogramma. Uit de resultaten blijkt dat er een verschil in kwaliteit van leven is tussen de eerste meting (vóór de revalidatie) en de tweede en derde meting. Het volgen van een revalidatieprogramma resulteerde in een betere kwaliteit van leven. Bovendien kwam naar voren dat met name leeftijd, gezichtsscherpte en gezichtsveld een belangrijke rol spelen bij een verandering in kwaliteit van leven na revalidatie. Op dit moment wordt uitvoerig met de medewerkers van Visio Het Loo Erf overlegd hoe de zorg aan de hand van de resultaten mogelijk verbeterd kan worden. Overige doelstellingen waren tijdens dit onderzoek waren: - Overzicht geven van eerdere studies naar kwaliteit van leven bij volwassenen met een visuele beperking - valideren van de Functional Field Score (een maat om de totale visuele beperking te bepalen) zoals gepubliceerd in de “Guides to the evaluation of permanent impairment” van de American Medical Association. - Het vergelijken van de kwaliteit van leven van mensen met een visuele beperking met de kwaliteit van leven van mensen met andere chronische aandoeningen en gezonde mensen. - Valideren van een van de internationaal meest gebruikte vragenlijsten voor het meten van visus-gerelateerde kwaliteit van leven, de Visual Functioning Questionnaire. - Richtlijn maken voor de verwijzing van mensen met een visuele beperking naar diverse vormen van revalidatie in Nederland.Rens, G.H.M.B. van [Promotor]Ringens, P.J. [Promotor]Boer, M.R. de [Copromotor]Moll, A.C. [Copromotor

Обернені сингулярно збурені задачі типу «конвекція-дифузія» для двозв’язних областей

Побудовано асимптотичне розвинення розв’язків сингулярно збурених крайових задач типу «конвекція-дифузія» з невідомим коефіцієнтом дифузії, який залежить від координат двозв’язної області. При побудові алгоритму використано перехід від вихідної постановки конвективно-дифузійної задачі у криволінійній двозв’язній області до періодичної задачі стосовно відповідної області комплексного потенціалу. Наведено результати числових розрахунків.The asymptotic expansion is constructed for solving singular disturbed boundary-value «convection-diffusion» problems with the unknown coefficient of diffusion which depends on physical coordinates of a double-connected area. Transition from the initial formulation of «convectional-diffusion» problems in curvilinear double-connected area to periodic task at the corresponding area complex potential is used to algorithm construction. The results of numerical calculations are given.Построено асимптотическое развитие решений сингулярно возмущенных краевых задач типа «конвекция-диффузия» с неизвестным коэффициентом диффузии, зависящем от координат двухсвязной области. При построении алгоритма использовано переход от исходной постановки конвективно-диффузионной задачи в криволинейной двусвязной области к периодической задаче относительно соответствующей области комплексного потенциала. Приведены результаты численных расчетов