Lamin A/C-Dependent Translocation of Megakaryoblastic Leukemia-1 and β-Catenin in Cyclic Strain-Induced Osteogenesis

Lamins are intermediate filaments that play a crucial role in sensing mechanical strain in the nucleus of cells. β-catenin and megakaryoblastic leukemia-1 (MKL1) are critical signaling molecules that need to be translocated to the nucleus for their transcription in response to mechanical strain that induces osteogenesis. However, the exact molecular mechanism behind the translocation of these molecules has not been fully investigated. This study used 10% cyclic strain to induce osteogenesis in the murine osteoblast precursor cell line (MC3T3). The translocation of β-catenin and MKL1 was studied by performing knockdown and overexpression of lamin A/C (LMNA). Cyclic strain increased the expression of osteogenic markers such as alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and enhanced ALP staining after seven days of incubation. Resultantly, MKL1 and β-catenin were translocated in the nucleus from the cytoplasm during the stress-induced osteogenic process. Knockdown of LMNA decreased the accumulation of MKL1 and β-catenin in the nucleus, whereas overexpression of LMNA increased the translocation of these molecules. In conclusion, our study indicates that both MKL1 and β-catenin molecules are dependent on the expression of LMNA during strain-induced osteogenesis.

Oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination via Wnt/β-catenin pathway in a mouse model of middle cerebral artery occlusion

White matter injury is a critical pathological characteristic during ischemic stroke. Oligodendrocyte precursor cells participate in white matter repairing and remodeling during ischemic brain injury. Since oligodendrocyte precursor cells could promote Wnt-dependent angiogenesis and migrate along vasculature for the myelination during the development in the central nervous system, we explore whether exogenous oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination after middle cerebral artery occlusion in mice. Here, oligodendrocyte precursor cell transplantation improved motor and cognitive function, and alleviated brain atrophy. Furthermore, oligodendrocyte precursor cell transplantation promoted functional angiogenesis, and increased myelin basic protein expression after ischemic stroke. The further study suggested that white matter repairing after oligodendrocyte precursor cell transplantation depended on angiogenesis induced by Wnt/β-catenin signal pathway. Our results demonstrated a novel pathway that Wnt7a from oligodendrocyte precursor cells acting on endothelial β-catenin promoted angiogenesis and improved neurobehavioral outcomes, which facilitated white matter repair and remodeling during ischemic stroke.

Long-Term Effects of Neural Precursor Cell Transplantation on Secondary Injury Processes and Functional Recovery after Severe Cervical Contusion-Compression Spinal Cord Injury

Cervical spinal cord injury (SCI) remains a devastating event without adequate treatment options despite decades of research. In this context, the usefulness of common preclinical SCI models has been criticized. We, therefore, aimed to use a clinically relevant animal model of severe cervical SCI to assess the long-term effects of neural precursor cell (NPC) transplantation on secondary injury processes and functional recovery. To this end, we performed a clip contusion-compression injury at the C6 level in 40 female Wistar rats and a sham surgery in 10 female Wistar rats. NPCs, isolated from the subventricular zone of green fluorescent protein (GFP) expressing transgenic rat embryos, were transplanted ten days after the injury. Functional recovery was assessed weekly, and FluoroGold (FG) retrograde fiber-labeling, as well as manganese-enhanced magnetic resonance imaging (MEMRI), were performed prior to the sacrifice of the animals eight weeks after SCI. After cryosectioning of the spinal cords, immunofluorescence staining was conducted. Results were compared between the treatment groups (NPC, Vehicle, Sham) and statistically analyzed (p < 0.05 was considered significant). Despite the severity of the injury, leading to substantial morbidity and mortality during the experiment, long-term survival of the engrafted NPCs with a predominant differentiation into oligodendrocytes could be observed after eight weeks. While myelination of the injured spinal cord was not significantly improved, NPC treated animals showed a significant increase of intact perilesional motor neurons and preserved spinal tracts compared to untreated Vehicle animals. These findings were associated with enhanced preservation of intact spinal cord tissue. However, reactive astrogliosis and inflammation where not significantly reduced by the NPC-treatment. While differences in the Basso–Beattie–Bresnahan (BBB) score and the Gridwalk test remained insignificant, animals in the NPC group performed significantly better in the more objective CatWalk XT gait analysis, suggesting some beneficial effects of the engrafted NPCs on the functional recovery after severe cervical SCI.

Insights Into the Biological Role of NEDD4L E3 Ubiquitin Ligase in Human Cancers

Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is an E3 ubiquitin ligase that has been reported to participate in multiple cellular procedures by regulating of substrate ubiquitination and subsequent protein degradation. A great amount of evidence has demonstrated that NEDD4L mainly functions as a tumor suppressor in most cancer types, while it also acts as an oncogene in a few cancers. In this review, we summarize the potential role of NEDD4L in carcinogenesis and the related underlying molecular mechanism to improve our understanding of its functions in the tumorigenesis of human malignancies. Developing clinical drugs targeting NEDD4L could be a potential therapeutic strategy for cancer therapy in the future.

SORLA is required for insulin-induced expansion of the adipocyte precursor pool in visceral fat

Visceral adipose tissue shows remarkable plasticity, constantly replacing mature adipocytes from an inherent pool of adipocyte precursors. The number of precursors is set in the juvenile organism and remains constant in adult life. Which signals drive precursor pool expansion in juveniles and why they operate in visceral but not in subcutaneous white adipose tissue (WAT) are unclear. Using mouse models, we identified the insulin-sensitizing receptor SORLA as a molecular factor explaining the distinct proliferative capacity of visceral WAT. High levels of SORLA activity in precursors of juvenile visceral WAT prime these cells for nutritional stimuli provided through insulin, promoting mitotic expansion of the visceral precursor cell pool in overfed juvenile mice. SORLA activity is low in subcutaneous precursors, blunting their response to insulin and preventing diet-induced proliferation of this cell type. Our findings provide a molecular explanation for the unique proliferative properties of juvenile visceral WAT, and for the genetic association of SORLA with visceral obesity in humans.

A Novel Three-Dimensional Culture Device Favors a Myelinating Morphology of Neural Stem Cell-Derived Oligodendrocytes

The complexity of the central nervous system (CNS) requires researchers to consider all the variables linked to the interaction between the different cell inhabitants. On this basis, any in vitro study of the physiological and pathological processes regarding the CNS should consider the balance between the standardization of the assay and the complexity of the cellular system which mimics the in vivo microenvironment. One of the main structural and functional components of the CNS is the oligodendrocyte precursor cell (OPC), responsible for developmental myelination and myelin turnover and repair during adulthood following differentiation into mature oligodendrocytes. In the present brief research report, we describe a 3D culture tool (VITVO) based on an inert and biocompatible synthetic polymer material scaffold, functionalized with laminin coating, and tested as a new culture microenvironment for neural stem/precursor cell (NSPC) differentiation compared to standard 2D cultures. NSPCs spontaneously differentiate in the three neural lineages (neurons, astrocytes and OPCs), identified by specific markers, along the fibers in the 3D structure. Analysis of the mRNA levels for lineage differentiation markers reveals a higher expression compared to those seeded on a 2D surface, suggesting an acceleration of the differentiation process. We then focused on the oligodendroglial lineage, showing that in VITVO, mature oligodendrocytes exhibit a myelinating morphology, proven by 3D image elaboration, linked to a higher expression of mature oligodendrocyte markers. This preliminary study on an innovative 3D culture system is the first robust step in producing new microenvironment-based strategies to investigate in vitro OPC and oligodendrocyte biology.

Wnt Signaling Induces Asymmetric Dynamics in the Actomyosin Cortex of the C. elegans Endomesodermal Precursor Cell

During asymmetrical division of the endomesodermal precursor cell EMS, a cortical flow arises, and the daughter cells, endodermal precursor E and mesodermal precursor MS, have an enduring difference in the levels of F-actin and non-muscular myosin. Ablation of the cell cortex suggests that these observed differences lead to differences in cortical tension. The higher F-actin and myosin levels in the MS daughter coincide with cell shape changes and relatively lower tension, indicating a soft, actively moving cell, whereas the lower signal in the E daughter cell is associated with higher tension and a more rigid, spherical shape. The cortical flow is under control of the Wnt signaling pathway. Perturbing the pathway removes the asymmetry arising during EMS division and induces subtle defects in the cellular movements at the eight-cell stage. The perturbed cellular movement appears to be associated with an asymmetric distribution of E-cadherin across the EMS cytokinesis groove. ABpl forms a lamellipodium which preferentially adheres to MS by the E-cadherin HMR-1. The HMR-1 asymmetry across the groove is complete just at the moment cytokinesis completes. Perturbing Wnt signaling equalizes the HMR-1 distribution across the lamellipodium. We conclude that Wnt signaling induces a cortical flow during EMS division, which results in a transition in the cortical contractile network for the daughter cells, as well as an asymmetric distribution of E-cadherin.