Essential amino acid starvation induces cell cycle arrest, autophagy, and inhibits osteogenic differentiation in murine osteoblast

RTN4IP1 Contributes to ESCC via Regulation of Amino Acid Transporters

Esophageal squamous cell carcinoma (ESCC) accounts for about 90% of esophageal cancer cases. The lack of effective therapeutic targets makes it difficult to improve the overall survival of patients with ESCC. Reticulon 4 Interacting Protein 1 (RTN4IP1) is a novel mitochondrial oxidoreductase. Here, a notable upregulation of RTN4IP1 is demonstrated, which is associated with poor survival in patients with ESCC. RTN4IP1 depletion impairs cell proliferation and induces apoptosis of ESCC cells. Furthermore, c-Myc regulates RTN4IP1 expression via iron regulatory protein 2 (IRP2) at the post-transcriptional level. Mechanistically, RTN4IP1 mRNA harbors functional iron-responsive elements (IREs) in the 3' UTR, which can be targeted by IRP2, resulting in increased mRNA stability. Finally, RTN4IP1 depletion abrogates amino acid uptake and induces amino acid starvation via downregulation of the amino acid transporters SLC1A5, SLC3A2, and SLC7A5, indicating a possible pathway through which RTN4IP1 contributes to ESCC carcinogenesis and progression. In vivo studies using cell-derived xenograft and patient-derived xenograft mouse models as well as a 4-nitroquinoline 1-oxide-induced ESCC model in esophageal-specific Rtn4ip1 knockout mice demonstrate the essential role of RTN4IP1 in ESCC development. Thus, RTN4IP1 emerges as a key cancer-promoting protein in ESCC, suggesting therapeutic RTN4IP1 suppression as a promising strategy for ESCC treatment.

SNHG1 knockdown promotes osteogenic differentiation of hDFSCs through anti-oxidative stress mediated by autophagy

The long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) plays a crucial role in tumorigenesis and is frequently employed as a prognostic biomarker. However, its involvement in the osteogenic differentiation of oral stem cells, particularly human dental follicle stem cells (hDFSCs), remains unclear. Our investigation revealed that the absence of SNHG1 enhances the osteogenic differentiation of hDFSCs. Furthermore, the downregulation of SNHG1 induces autophagy in hDFSCs, leading to a reduction in intracellular oxidative stress levels. Notably, this effect is orchestrated through the epigenetic regulation of EZH2. Our study unveils a novel function of SNHG1 in governing the osteogenic differentiation of hDFSCs, offering fresh insights for an in-depth exploration of the molecular mechanisms underlying dental follicle development. These findings not only provide a foundation for advancing the understanding of SNHG1 but also present innovative perspectives for promoting the repair and regeneration of periodontal supporting tissue, ultimately contributing to the restoration of periodontal health and tooth function.

3D stem cell spheroids with urchin-like hydroxyapatite microparticles enhance osteogenesis of stem cells

Cell therapy (also known as cell transplantation) has been considered promising as a next-generation living-cell therapy strategy to surpass the effects of traditional drugs. However, their practical clinical uses and product conversion are hampered by the unsatisfied viability and efficacy of the transplanted cells. Herein, we propose a synergistic enhancement strategy to address these issues by constructing 3D stem cell spheroids integrated with urchin-like hydroxyapatite microparticles (uHA). Specifically, cell-sized uHA microparticles were synthesized via a simple hydrothermal method using glutamic acid (Glu, E) as the co-template with good biocompatibility and structural antimicrobial performance (denoted as E-uHA). Combining with a hanging drop method, stem cell spheroids integrated with E-uHA were successfully obtained by culturing bone marrow mesenchymal stem cells (BMSCs) with a low concentration of the E-uHA suspensions (10 μg mL-1). The resulting composite spheroids of BMSCs/E-uHA deliver a high cellular viability, migration activity, and a superior osteogenic property compared to the 2D cultured counterpart or other BMSC spheroids. This work provides an effective strategy for integrating a secondary bio-functional component into stem cell spheroids for designing more cell therapy options with boosted cellular viability and therapeutic effect.

Essential Amino Acid Starvation-Induced Oxidative Stress Causes DNA Damage and Apoptosis in Murine Osteoblast-like Cells

Intracellular nutrient metabolism, particularly the metabolism of essential amino acids (EAAs), is crucial for cellular functions, including energy production and redox homeostasis. An EAA deficiency can lead to cellular dysfunction and oxidative stress. This study explores the mechanisms underlying cellular responses to EAA starvation, focusing on ROS-induced DNA damage and apoptosis. MC3T3-E1 cells were subjected to EAA starvation, and various assays were conducted to assess cell proliferation, survival, DNA damage, and apoptosis. The antioxidant N-acetylcysteine (NAC) was employed to block ROS formation and mitigate cellular damage. Gene expression and Western blot analyses were performed to elucidate molecular pathways. EAA starvation-induced ROS generation, DNA damage, and apoptosis in MC3T3-E1 cells. NAC administration effectively reduced DNA damage and apoptosis, highlighting the pivotal role of ROS in mediating these cellular responses during EAA deficiency. This study demonstrates that EAA starvation triggers ROS-mediated DNA damage and apoptosis, offering insights into the intricate interplay between nutrient deficiency, oxidative stress, and programmed cell death. NAC emerges as a potential therapeutic intervention to counteract these adverse effects.