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The tremendous personal and economic burden worldwide caused by low back pain (LBP) has been surging in recent years. While intervertebral disc degeneration (IVDD) is the leading cause of LBP and vast efforts have been made to develop effective therapies, this problem is far from being resolved, as most treatments, such as painkillers and surgeries, mainly focus on relieving the symptoms rather than reversing the cause of IVDD. However, as stem/progenitor cells possess the potential to regenerate IVD, a deeper understanding of the early development and role of these cells could help to improve the effectiveness of stem/progenitor cell therapy in treating LBP. Single-cell RNA sequencing results provide fresh insights into the heterogeneity and development patterns of IVD progenitors; additionally, we compare mesenchymal stromal cells and IVD progenitors to provide a clearer view of the optimal cell source proposed for IVD regeneration. [ABSTRACT FROM AUTHOR]

In recent years, 4D printing has gained increasing attention in the tissue engineering field since this advanced manufacturing platform can create stimulus-responsive structures, which can change their shapes, functions, and/or properties when appropriate external stimulus/stimuli is/are applied. A number of hydrogels with swellable/shrinkable abilities have been explored for 4D printing to fabricate different shape-morphing structures for tissue engineering. Among them, gelatin methacryloyl (GelMA) has been 4D printed, which can self-fold into microtubular structures. Currently, the self-folding ability of 4D printed GelMA hydrogels is mainly based on the different cross-linking degrees (which control and govern the swelling degrees) across the thickness of hydrogels. However, this strategy alone can only form self-folding GelMA tubes with diameters at the micrometer level and cannot create self-folding GelMA tubes with diameters at the millimeter level, which is mainly due to the insufficient internal force generated in 4D printed GelMA hydrogels when they are exposed to water. To overcome this limitation, this study has investigated a new strategy to fabricate self-folding GelMA tubes with large diameters at the millimeter level for tissue engineering applications. The new strategy introduced a cross-linking degree gradient across the GelMA plane in addition to its thickness by printing a second layer of strips on the first 4D printed GelMA film. In the aqueous environment, under the current fabrication condition, such bilayer GelMA hydrogels could self-fold into tubes of larger diameters up to 6 mm. The in vitro release behavior of heparin incorporated into the 4D printed GelMA was also studied. It was shown that heparin release could be controlled by the GelMA concentration and heparin content in 4D printed GelMA. The 4D printed GelMA hydrogels with the improved self-folding ability and controlled release of a drug are promising for targeted tissue engineering applications. [ABSTRACT FROM AUTHOR]

Textile‐based generators that can convert low‐grade energy from the human body or environment into sustainable electricity have generated immense scientific interest in self‐powered wearable applications. However, their low power density and environmental suitability have extremely restricted their portable applications in complex and mutable environments. Herein, an asymmetric sandwich structure between molybdenum disulfide (MoS2)‐carbonized silks (MCs) and MoS2/MXene–Cottons (MMCs) to construct efficient thermo–hydroelectric generators (THEGs) that synergistically harvest heat‐moisture energy to generate considerable electricity is rationally designed. Notably, the large surface area of MoS2/MXene van der Waals heterojunctions (vdWhs) enables efficient charge collection, and the vertical MoS2 nanosheet arrays supply abundant nanochannels for a highly efficient hydration effect, generating an output power density of 32.26 µW cm−2 after wetting with deionized water. Combined with the sensitive temperature recognition ability with a Seebeck coefficient of 23.5 µV K−1, the application possibilities of these prepared THEGs in the mutual conversion of fingertip temperature/language, and the monitoring of the human physiological state is foresee. [ABSTRACT FROM AUTHOR]