Spermatogenesis is a highly unique and intricate process, finely regulated at multiple levels, including post-transcriptional regulation. N6-methyladenosine (m6A), the most prevalent internal modification in eukaryotic mRNA, plays a significant role in transcriptional regulation during spermatogenesis. Previous research indicated extensive m6A modification at each stage of spermatogenesis, but depletion of Mettl3 and/or Mettl14 in spermatogenic cells with Stra8-Cre did not reveal any detectable abnormalities up to the stage of elongating spermatids. This suggests the involvement of other methyltransferases in the regulation of m6A modification during spermatogonial differentiation and meiosis. As a METTL3/14-independent m6A methyltransferase, METTL16 remains insufficiently studied in its roles during spermatogenesis. We report that male mice with Mettl16^vasa-cre exhibited significantly smaller testes, accompanied by a progressive loss of spermatogonia after birth. Additionally, the deletion of Mettl16 in A1 spermatogonia using Stra8-Cre results in a blockade in spermatogonial differentiation. Given YTHDC1's specific recognition for METTL16 target genes, we further investigated the role of YTHDC1 using Ythdc1-sKO mouse model. Our results indicate that Ythdc1^Stra8-cre also impairs spermatogonial differentiation, similar to the effects observed in Mettl16^Stra8-cre mice. RNA-seq and m6A-seq analyses revealed that deletion of either Mettl6 or Ythdc1 disrupted the gene expression related to chromosome organisation and segregation, ultimately leading to male infertility. Collectively, this study underscores the essential roles of the m6A writer METTL16 and its reader YTHDC1 in the differentiation of spermatogonia.

Human induced pluripotent stem cells (hiPSCs) represent a promising cell source for generating functional cells suitable for clinical therapeutic applications, particularly in the context of autologous cell therapies. However, the production of hiPSCs through genetic manipulation, especially involving oncogenes, may raise safety concerns. Furthermore, the complexity and high costs associated with hiPSCs generation have hindered their broad clinical use. In this study, we utilised a recently developed chemical reprogramming method in conjunction with a guided differentiation protocol, introducing a chemically defined strategy for generating functional human retinal pigment epithelium (RPE) cells from adipose tissue, bypassing conventional hiPSCs generation challenges. By utilising small molecule-based chemical cocktails, we reprogrammed somatic adipose cells into human chemically induced pluripotent stem cells (hCiPSCs) in a safer and more streamlined manner, entirely free from gene manipulation. Subsequent differentiation of hCiPSCs into functional RPE cells demonstrated their capability for secretion and phagocytosis, emphasising their vital role in maintaining retinal homeostasis and underscoring their therapeutic potential. Our findings highlight the transformative potential of hCiPSCs as a safer, more efficient option for personalised cell therapies, with applications extending beyond ocular disease to a wide range of medical conditions.

The de-ubiquitinase USP33 has been shown to possess either tumour-promoting or inhibitory effect on human cancer cells. However, all these findings are mainly based on in vitro cell culture models, and the in vivo evidence, which is more plausible to digest the functional role of USP33 in carcinogenic process, is still lacking. Here, we demonstrate that USP33 modulates DNA damage responses including cell cycle arrest and apoptosis induction through associating with p53. It directly interacts with p53 to mediate its de-ubiquitination and further stabilisation under DNA damage condition. Depletion of USP33 induces an enhanced level of p53 ubiquitination, which de-stabilises p53 protein leading to impaired DNA damage responses. Furthermore, USP33 silencing shows either promoted or inhibited effect on cell proliferation in human cancer cells with p53 WT and mutant background, respectively. Consistently, mice with hepatocyte-specific USP33 knockout are more sensitive to nitrosodiethylamine (DEN)-induced hepatocarcinogenesis compared to wild type mice. Thus, our in vitro and in vivo evidences illustrate that USP33 possesses anti-tumour activity via regulating p53 stability and activity.

Cellular mechanotransduction is a complex physiological process that integrates alterations in the external environment with cellular behaviours. In recent years, the role of the nucleus in mechanotransduction has gathered increased attention. Our research investigated the involvement of lamin A/C, a component of the nuclear envelope, in the mechanotransduction of macrophages under compressive force. We discovered that hydrostatic compressive force induces heterochromatin formation, decreases SUN1/SUN2 levels, and transiently downregulates lamin A/C. Notably, downregulated lamin A/C increased nuclear permeability to yes-associated protein 1 (YAP1), thereby amplifying certain effects of force, such as inflammation induction and proliferation inhibition. Additionally, lamin A/C deficiency detached the linker of nucleoskeleton and cytoskeleton (LINC) complex from nuclear envelope, consequently reducing force-induced DNA damage and IRF4 expression. In summary, lamin A/C exerted dual effects on macrophage responses to mechanical compression, promoting certain outcomes while inhibiting others. It operated through two distinct mechanisms: enhancing nuclear permeability and impairing intracellular mechanotransmission. The results of this study support the understanding of the mechanisms of intracellular mechanotransduction and may assist in identifying potential therapeutic targets for mechanotransduction-related diseases.

The global increase in the aging population has led to a concurrent rise in the incidence of age-related diseases, posing substantial challenges to healthcare systems and affecting the well-being of the elderly. Identifying and securing effective treatments has become an urgent priority. In this context, mesenchymal stem cell-derived exosomes (MSC-Exos) have emerged as a promising and innovative modality in the field of anti-aging medicine, offering a multifaceted therapeutic approach. MSC-Exos demonstrate significant potential due to their immunomodulatory and anti-inflammatory properties, their ability to inhibit oxidative stress, and their reparative effects on senescent tissues. These attributes make them valuable in combating a range of conditions associated with aging, such as cardiovascular diseases, neurodegeneration, skin aging, and osteoarthritis. The integration of exosomes with membrane-penetrating peptides introduces a novel strategy for the delivery of biomolecules, surmounting traditional cellular barriers and enhancing therapeutic efficacy. This review provides a comprehensive synthesis of the current understanding of MSC-Exos, underscoring their role as a novel and potent therapeutic strategy against the intricate challenges of age-related diseases.

Mitochondria perform multiple functions within the cell, including the production of ATP and a great deal of metabolic intermediates, while also contributing to the cellular stress response. The majority of mitochondrial proteins are encoded by nuclear genomes, highlighting the importance of mitonuclear communication for sustaining mitochondrial homeostasis and functional. As a crucial part of the intracellular signalling network, mitochondria can impact stem cell fate determinations. Considering the essential function of stem cells in tissue maintenance, regeneration and aging, it is important to understand how mitochondria influence stem cell fate. This review explores the significant roles of mitonuclear communication and mitochondrial proteostasis, highlighting their influence on stem cells. We also examine how mitonuclear interactions contribute to cellular homeostasis, stem cell therapies, and the potential for extending lifespan.

Testicular ageing is accompanied by a series of morphological changes, while the features of mitochondrial dysfunction remain largely unknown. Herein, we observed a range of age-related modifications in testicular morphology and spermatogenic cells, and conducted single-cell RNA sequencing on young and old testes in Drosophila. Pseudotime trajectory revealed significant changes in germline subpopulations during ageing. Our examination unveiled that genes showing bias in spermatids exhibited higher dN/dS than those in GSCs_Spermatogonia. Genes biased towards young GSCs_Spermatogonia displayed higher dN/dS than those in old GSCs_Spermatogonia. Interestingly, genes biased towards young spermatids demonstrated lower dN/dS in contrast to those in old spermatids, revealing the complexity of evolutionary adaptations during ageing. Furthermore, mitochondria associated events, including oxidative phosphorylation, TCA cycle and pyruvate metabolism, were significantly enriched in germline subpopulations. Specifically, mitochondrial function was significantly impaired during the process of testicular ageing, concurrently emphasising the role of several key nuclear genome-encoded mitochondrial regulatory genes, such as Hsp60B, fzo, Tim17b1 and mRpL12. Our data offer insights into testicular homeostasis regulated by mitochondrial function during the ageing process.

Tooth root development is a complex process essential for tooth function, yet the role of root dentin development in tooth morphogenesis is not fully understood. Optineurin (OPTN), linked to bone disorders like Paget's disease of bone (PDB), may affect tooth root development. In this study, we used single-cell sequencing of embryonic day 16.5 (E16.5), postnatal day 1 (P1), and P7 mouse teeth, as well as embryonic and adult human teeth, to show that OPTN is vital for odontoblastic differentiation. In Optn^−/− mice, we observed short root deformities and defective dentin, with impaired apical papilla differentiation and increased apoptosis. In vitro OPTN downregulation in stem cells of the apical papilla (SCAPs) exacerbated apoptosis and hindered odontoblastic differentiation. RNA-seq analysis revealed significant differences in mitochondrial dynamics between control and OPTN knockout SCAPs. We discovered that OPTN influences mitochondrial dynamics primarily by promoting fission, leading to odontoblastic differentiation and mineralisation. Mechanistically, OPTN cooperates with NRF2 to regulate mitochondrial fission via DRP1 phosphorylation and affects the transcription of BCL2. Rescue experiments using an activator of NRF2 in ex vivo organ cultures and local gingival injection experiments confirmed these findings. Therefore, we concluded that OPTN, interacting with NRF2, acts as a key regulator of SCAPs mitochondrial dynamics, mineralisation and apoptosis during tooth development. These findings provide fresh insights into the mechanisms underlying tooth root development.

This study aimed to clarify the role and mechanism of tetrahedral framework nucleic acids (tFNAs) in regulating M2 macrophages to reduce intestinal injury. An intestinal injury model was established by intraperitoneal injection of lipopolysaccharides (LPS) in mice to explore the alleviating effects of tFNAs on intestinal injury. Inflammatory factors were detected by quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA). The intestinal barrier and permeability were assessed using western blotting and immunohistochemistry. Macrophages in the gut were localised and quantified using immunofluorescence. Western blotting was used to investigate the role and mechanism of tFNAs in regulating macrophages and alleviating inflammation in the injured intestines. These results show that tFNAs attenuated sepsis-induced intestinal injury. tFNAs can also promote the intestinal barrier reconstruction and reduce intestinal permeability. In vivo, tFNAs accelerated the aggregation of M2 macrophages at an early stage of injury and reduced the number of M1 macrophages in the intestine. In addition, tFNAs enhanced the clearance ability of intestinal macrophages. They activated the signalling and transcription activating factor 1(STAT1) and cytokine signalling inhibitory factor 1/3 (SOCS1/3) pathways by increasing the expression of the phagocytic receptor Mertk. These findings indicated that tFNAs can alleviate sepsis-induced intestinal injury by regulating M2 macrophages, providing a new option for treating intestinal injury.

The pathogenesis of stress urinary incontinence (SUI), a condition common in women, remains to be fully elucidated. This study revealed that the incidence of SUI is associated with mitochondrial homeostasis dysregulation following oxidative stress in the fibrous connective tissue of the pelvic floor. SIRT1 is an essential factor for maintaining mitochondrial homeostasis; however, its potential role and mechanism of action in SUI pathogenesis remain unclear. Both in vitro and in vivo, we observed that oxidative stress reduced SIRT1 expression to inhibit the PGC-1α/NRF1/TFAM and PINK1/Parkin signalling pathways, eliciting impairment of mitochondrial biogenesis and mitophagy in L929 cells and SUI mice. Decreased SIRT1 levels induced endoplasmic reticulum (ER) stress and altered the structure of mitochondria-associated membranes (MAMs), disrupting ER-mitochondrial calcium homeostasis and exacerbting ROS accumulation. SIRT1 activation can restore mitochondrial function and the structure of MAMs and alleviate ER stress in fibroblasts, promoting anterior vaginal wall repair and improving urodynamic parameters in the SUI model. Our findings provide novel insights into the role and associated mechanism of SIRT1 in ameliorating oxidative stress-induced mitochondrial dysfunction in fibroblasts of the anterior vaginal wall and propose SIRT1 as a potential therapeutic target for SUI.

Somatic mutations accumulation and subsequent malignant clonal selection are the processes that lead to cancer. The intricacy includes exposure to carcinogens as well as the ways in which these exposures interact with genetic, polygenic, or epigenetic predispositions. It is worthwhile to investigate how environmental factors influence the initial transformation of healthy cells into malignant ones, or their effects on promoting growth, invasion, immune evasion, inflammation and drug resistance of onset cancerous cells.