Secretome profiles of mesenchymal stem cells (MSCs) are reflective of their local microenvironments. These biologically active factors exert an impact on the surrounding cells, eliciting regenerative responses that create an opportunity for exploiting MSCs towards a cell-free therapy for cartilage regeneration. The conventional method of culturing MSCs on a tissue culture plate (TCP) does not provide the physiological microenvironment for optimum secretome production. In this study, we explored the potential of electrospun fiber sheets with specific orientation in influencing the MSC secretome production and its therapeutic value in repairing cartilage. Conditioned media (CM) were generated from MSCs cultured either on TCP or electrospun fiber sheets of distinct aligned or random fiber orientation. The paracrine potential of CM in affecting chondrogenic differentiation, migration, proliferation, inflammatory modulation, and survival of MSCs and chondrocytes was assessed. The involvement of FAK and ERK mechanotransduction pathways in modulating MSC secretome were also investigated. We showed that conditioned media of MSCs cultured on electrospun fiber sheets compared to that generated from TCP have improved secretome yield and profile, which enhanced the migration and proliferation of MSCs and chondrocytes, promoted MSC chondrogenesis, mitigated inflammation in both MSCs and chondrocytes, as well as protected chondrocytes from apoptosis. Amongst the fiber sheet-generated CM, aligned fiber-generated CM (ACM) was better at promoting cell proliferation and augmenting MSC chondrogenesis, while randomly oriented fiber-generated CM (RCM) was more efficient in mitigating the inflammation assault. FAK and ERK signalings were shown to participate in the modulation of MSC morphology and its secretome production. This study demonstrates topographical-dependent MSC paracrine activities and the potential of employing electrospun fiber sheets to improve the MSC secretome for cartilage regeneration.

中文翻译：

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电纺纤维增强了间充质干细胞的旁分泌信号传导软骨再生

间充质干细胞（MSCs）的分泌组图谱反映了它们的局部微环境。这些生物活性因子对周围细胞产生影响，引发再生反应，从而为利用MSC进行无细胞软骨再生治疗创造了机会。在组织培养板（TCP）上培养MSC的常规方法不能提供最佳分泌组产生的生理微环境。在这项研究中，我们探索了特定方向的电纺纤维片在影响MSC分泌组产生中的潜力及其在修复软骨中的治疗价值。条件培养基（CM）由在TCP或电纺纤维片上培养的MSC产生，这些纤维具有不同的排列方向或随机纤维方向。评估了CM的旁分泌潜力对软骨分化，迁移，增殖，炎症调节以及MSC和软骨细胞存活的影响。还研究了FAK和ERK机械转导途径在调节MSC分泌组中的作用。我们发现，与电纺丝相比，在电纺纤维片上培养的MSC的条件培养基具有更高的分泌组产量和特性，可增强MSC和软骨细胞的迁移和增殖，促进MSC软骨形成，减轻MSC和软骨细胞的炎症。作为保护软骨细胞免于凋亡。在纤维片生成的CM中，排列的纤维生成的CM（ACM）在促进细胞增殖和增强MSC软骨形成方面表现更好，而随机定向的纤维生成CM（RCM）在减轻炎症侵袭方面更为有效。FAK和ERK信号显示参与MSC形态的调节及其分泌组的产生。这项研究证明了地形依赖的MSC旁分泌活性以及采用电纺纤维片改善MSC分泌组用于软骨再生的潜力。