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Aldehyde dehydrogenases (ALDHs) defend intracellular homeostasis by catalyzing the conversion of toxic aldehydes into non-toxic carboxylic acids, which is of particular importance to the self-renewal of stem cells and cancer stem cells. The widely used ALDEFLUOR assay was initially designed to indicate the activity of ALDH1A1 in leukemia and has been demonstrated to detect the enzyme activity of several other ALDH isoforms in various cancer types in recent years. However, it is still elusive which isoforms, among the 19 ALDH isoforms in human genome, are the potential contributors in catalyzing ALDEFLUOR assay in different cancers. In the current study, we performed a screening via overexpressing each ALDH isoform to assess their ability of catalyzing ALDEFLUOR assay. Our results demonstrate that nine isoforms are active in ALDEFLUOR assay, whose overexpression significantly increases ALDH-positive (ALDH) population. Further analysis of the expression of these active isoforms in various cancers reveals cancer-type specific expression patterns, suggesting that different cancer types may exhibit ALDEFLUOR activity through expression of specific active ALDH isoforms. This study strongly indicates that a detailed elucidation of the functions for each active ALDH isoform in CSCs is necessary and important for a profound understanding of the underlying mechanisms of ALDH-associated stemness.

BackgroundTendon/ligament injuries are common sports injuries. Clinically, the repair of a ruptured tendon or ligament to its bony insertion is needed, but the enthesis structure is not well reestablished following surgical repair. Herein, we fabricated dual-layer aligned-random scaffold (ARS) by electrospinning and aimed to investigate the effect of the scaffold on tendon-to-bone healing in vivo.Materials and methodsThe random and dual-layer aligned-random silk fbroin poly(L-lactic acid-co-e-caprolactone) (P(LLA-CL)) nanofibrous scaffolds were successfully fabricated by electrospinning methods. Ninety New Zealand white rabbits were randomly divided into three groups (random scaffold [RS], ARS, and control groups), and they were subjected to surgery to establish an extra-articular tendon-to-bone healing model with autologous Achilles tendon.ResultsHistological assessment showed that the ARS significantly increased the area of metachromasia, decreased the interface width, and improved collagen maturation and organization at the tendon–bone interface compared with the RS and control groups. Microcomputed tomography analysis showed that the bone tunnel area of RS and ARS groups was significantly smaller than those of the control group. Real-time polymerase chain reaction showed that BMP-2 and osteopontin expression levels of the tissue at the interface between the bone and graft in the RS and ARS groups were higher than those of the control group at 6 weeks. Collagen I expression level of the ARS group was significantly higher than those of the RS and control groups at 6 and 12 weeks. Moreover, the ARS groups had a better ultimate load-to-failure and stiffness than the RS and control groups.ConclusionARS could effectively augment the tendon-to-bone integration and improve gradient microstructure in a rabbit extra-articular model by inducing the new bone formation, increasing the area of fibrocartilage, and improving collagen organization and maturation. The dual-layer aligned-random silk fibroin/P(LLA-CL) nanofibrous scaffold is proved to be a promising biomaterial for tendon-to-bone healing.

Tendon regeneration is still a great challenge due to its avascular structure and low self-renewal capability. The nitric oxide (NO) therapy emerges as a promising treatment for inducing the regeneration of injured tendon by angiogenesis. Here, in this study, a system that NO-loaded metal–organic frameworks (MOFs) encapsulated in polycaprolactone (PCL)/gelatin (Gel) aligned coaxial scaffolds (NMPGA) is designed and prepared for tendon repair. In this system, NO is able to be released in vitro at a slow and stable average speed of 1.67 nM h−1 as long as 15 d without a burst release stage in the initial 48 h. Furthermore, NMPGA can not only improve the tubular formation capability of endothelial cells in vitro but also obviously increase the blood perfusion near the injured tendon in vivo, leading to accelerating the maturity of collagen and recovery of biomechanical strength of the regenerated tendon tissue. As a NO-loaded MOFs therapeutic system, NMPGA can promote tendon regeneration in a shorter healing period with better biomechanical properties in comparison with control group by angiogenesis. Therefore, this study not only provides a promising scaffold for tendon regeneration, but also paves a new way to develop a NO-based therapy for biomedical application in the future.