Mechanical guidance to self-organization and pattern formation of stem cells.

The self-organization of stem cells (SCs) constitutes the fundamental basis of the development of biological organs and structures. SC-driven patterns are essential for tissue engineering, yet unguided SCs tend to form chaotic patterns, impeding progress in biomedical engineering. Here, we show that simple geometric constraints can be used as an effective mechanical modulation approach that promotes the development of controlled self-organization and pattern formation of SCs. Using the applied SC guidance with geometric constraints, we experimentally uncover a remarkable deviation in cell aggregate orientation from a random direction to a specific orientation. Subsequently, we propose a dynamic mechanical framework, including cells, the extracellular matrix (ECM), and the culture environment, to characterize the specific orientation deflection of guided cell aggregates relative to initial geometric constraints, which agrees well with experimental observation. Based on this framework, we further devise various theoretical strategies to realize complex biological patterns, such as radial and concentric structures. Our study highlights the key role of mechanical factors and geometric constraints in governing SCs' self-organization. These findings yield critical insights into the regulation of SC-driven pattern formation and hold great promise for advancements in tissue engineering and bioactive material design for regenerative application.

Effects of repetitive transcranial magnetic stimulation combined with functional electrical stimulation on hand function of stroke: A randomized controlled trial.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique that has been widely used for hand function recovery in patients with subacute and chronic stroke. OBJECTIVE: To observe the effect of low-frequency repetitive transcranial magnetic stimulation (rTMS) combined with functional electrical stimulation (FES) on hand function recovery during convalescence of stroke. METHODS: Patients were divided into3 groups of 20 patients in each. All patients received routine training. rTMS group was treated with low-frequency repetitive transcranial magnetic stimulation (rTMS). FES group received functional electrical stimulation (FES) therapy. Observation group was treated with low-frequency rTMS and FES. The changes of TMS-MEP in the 3 groups were observed at the time of enrollment and after 2 courses of treatment, respectively, and the total active activity of fingers (TAM) and Fugl-Meyer assessment (FMA) rating scale were evaluated in wrist and hand parts. RESULTS: The amplitude of TMS-MEP was significantly higher than that of FES group. FMA score and TAM score in the observation group were significantly better than that of rTMS group and FES group. CONCLUSION: Low-frequency rTMS combined with FES treatment can effectively improve the range of motion of fingers, and significantly improve the grasp, pinching and other functions of hands.