RETRACTED: TRAF2 gene silencing induces proliferation and represses apoptosis of nucleus pulposus cells in rats with intervertebral disc degeneration

Metformin Promotes Proliferation of Mouse Female Germline Stem Cells by Histone Acetylation Modification of Traf2

Female germline stem cells (FGSCs) are adult stem cells that can both self-renew and differentiate into mature oocytes. Although small-molecule compounds are capable of regulating the development of FGSCs, the effects and mechanisms of action of metformin, a commonly used drug for diabetes, on FGSCs are largely unknown. Here, we found that metformin promoted the viability and proliferation of FGSCs through H3K27ac modification. To elucidate the mechanism by which metformin promoted FGSCs proliferation, Chromatin Immunoprecipitation Sequencing of histone 3 lysine 27 acetylation (H3K27ac) in FGSCs was performed with or without metformin-treatment. The results indicate that metformin modulates FGSCs via the mitogen-activated protein kinase (MAPK) signaling pathway, and tumor necrosis factor receptor associated factor 2 (Traf2) was identified as an important target gene for H3K27ac modification during FGSCs proliferation. Subsequent experiments showed metformin promoted FGSCs proliferation by H3K27ac modification of Traf2 to regulate MAPK signaling. Our findings deepen understanding of how H3K27ac modifications regulate FGSCs development and provide a theoretical basis for the prevention and treatment of premature ovarian failure, polycystic ovary syndrome, infertility, and related diseases.

Immune exposure: how macrophages interact with the nucleus pulposus

Intervertebral disc degeneration (IDD) is a primary contributor to low back pain. Immune cells play an extremely important role in modulating the progression of IDD by interacting with disc nucleus pulposus (NP) cells and extracellular matrix (ECM). Encased within the annulus fibrosus, healthy NP is an avascular and immune-privileged tissue that does not normally interact with macrophages. However, under pathological conditions in which neovascularization is established in the damaged disc, NP establishes extensive crosstalk with macrophages, leading to different outcomes depending on the different microenvironmental stimuli. M1 macrophages are a class of immune cells that are predominantly pro-inflammatory and promote inflammation and ECM degradation in the NP, creating a vicious cycle of matrix catabolism that drives IDD. In contrast, NP cells interacting with M2 macrophages promote disc tissue ECM remodeling and repair as M2 macrophages are primarily involved in anti-inflammatory cellular responses. Hence, depending on the crosstalk between NP and the type of immune cells (M1 vs. M2), the overall effects on IDD could be detrimental or regenerative. Drug or surgical treatment of IDD can modulate this crosstalk and hence the different treatment outcomes. This review comprehensively summarizes the interaction between macrophages and NP, aiming to highlight the important role of immunology in disc degeneration.

Integrins, cadherins and channels in cartilage mechanotransduction: perspectives for future regeneration strategies

Articular cartilage consists of hyaline cartilage, is a major constituent of the human musculoskeletal system and has critical functions in frictionless joint movement and articular homoeostasis. Osteoarthritis (OA) is an inflammatory disease of articular cartilage, which promotes joint degeneration. Although it affects millions of people, there are no satisfying therapies that address this disease at the molecular level. Therefore, tissue regeneration approaches aim at modifying chondrocyte biology to mitigate the consequences of OA. This requires appropriate biochemical and biophysical stimulation of cells. Regarding the latter, mechanotransduction of chondrocytes and their precursor cells has become increasingly important over the last few decades. Mechanotransduction is the transformation of external biophysical stimuli into intracellular biochemical signals, involving sensor molecules at the cell surface and intracellular signalling molecules, so-called mechano-sensors and -transducers. These signalling events determine cell behaviour. Mechanotransducing ion channels and gap junctions additionally govern chondrocyte physiology. It is of great scientific and medical interest to induce a specific cell behaviour by controlling these mechanotransduction pathways and to translate this knowledge into regenerative clinical therapies. This review therefore focuses on the mechanotransduction properties of integrins, cadherins and ion channels in cartilaginous tissues to provide perspectives for cartilage regeneration.