Celik Cenk, Franco-Obregón Alfredo, Lee Eng Hin, Hui James Hp, Yang Zheng
Department of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228.
Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228; BioIonic Currents Electromagnetic Pulsing Systems Laboratory, BICEPS, National University of Singapore, Singapore, 117599; Institute for Health Innovation & Technology, iHealthtech, National University of Singapore, Singapore, 117599; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, DSO (Kent Ridge) Building, #04-01, 27 Medical Drive, Singapore, 117593.
Acta Biomater. 2021 Jan 1;119:169-183. doi: 10.1016/j.actbio.2020.10.039. Epub 2020 Oct 29.
Mesenchymal stem cell (MSC) chondrogenesis is modulated by diverse biophysical cues. We have previously shown that brief, low-amplitude pulsed electromagnetic fields (PEMFs) differentially enhance MSC chondrogenesis in scaffold-free pellet cultures versus conventional tissue culture plastic (TCP), indicating an interplay between magnetism and micromechanical environment. Here, we examined the influence of PEMF directionality over the chondrogenic differentiation of MSCs laden on electrospun fibrous scaffolds of either random (RND) or aligned (ALN) orientations. Correlating MSCs' chondrogenic outcome to pFAK activation and YAP localisation, MSCs on the RND scaffolds experienced the least amount of resting mechanical stress and underwent greatest chondrogenic differentiation in response to brief PEMF exposure (10 min at 1 mT) perpendicular to the dominant plane of the scaffolds (Z-directed). By contrast, in MSC-impregnated RND scaffolds, greatest mitochondrial respiration resulted from X-directed PEMF exposure (parallel to the scaffold plane), and was associated with curtailed chondrogenesis. MSCs on TCP or the ALN scaffolds exhibited greater resting mechanical stress and accordingly, were unresponsive, or negatively responsive, to PEMF exposure from all directions. The efficacy of PEMF-induced MSC chondrogenesis is hence regulated in a multifaceted manner involving focal adhesion dynamics, as well as mitochondrial responses, culminating in a final cellular response. The combined contributions of micromechanical environment and magnetic field orientation hence will need to be considered when designing magnetic exposure paradigms.
间充质干细胞(MSC)的软骨形成受到多种生物物理信号的调节。我们之前已经表明,短暂的低振幅脉冲电磁场(PEMF)在无支架微球培养中与传统组织培养塑料(TCP)相比,对MSC软骨形成有不同程度的增强作用,这表明磁性和微机械环境之间存在相互作用。在此,我们研究了PEMF方向性对负载于随机(RND)或定向(ALN)取向的电纺纤维支架上的MSC软骨分化的影响。将MSC的软骨形成结果与pFAK激活和YAP定位相关联,RND支架上的MSC承受的静息机械应力最小,并且在垂直于支架主平面(Z方向)的短暂PEMF暴露(1 mT下10分钟)后经历最大程度的软骨分化。相比之下,在MSC浸渍的RND支架中,X方向的PEMF暴露(平行于支架平面)导致最大的线粒体呼吸作用,并与软骨形成减少相关。TCP或ALN支架上的MSC表现出更大的静息机械应力,因此对来自所有方向的PEMF暴露无反应或产生负反应。因此,PEMF诱导的MSC软骨形成的功效以多方面的方式受到调节,涉及粘着斑动力学以及线粒体反应,最终导致最终的细胞反应。因此,在设计磁暴露模式时,需要考虑微机械环境和磁场方向的综合作用。
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