Knockdown of LAP2α inhibits osteogenic differentiation of human adipose-derived stem cells by activating NF-κB

Knockdown of LAP2α inhibits adipogenesis of human adipose-derived stem cells and ameliorates high-fat diet-induced obesity

Adipogenesis, a pivotal cellular process involving the differentiation of mesenchymal stem cells (MSCs) to mature adipocytes, plays a significant role in various physiological functions. Dysregulation of adipogenesis is implicated in conditions such as obesity. However, the complete molecular understanding of adipogenesis remains elusive. This study aimed to uncover the novel role of lamina-associated polypeptide 2 alpha (LAP2α) in human adipose-derived stem cells (hASCs) adipogenesis and its impact on high-fat diet (HFD)-induced obesity and associated metabolic disturbances. LAP2α expression was assessed during the adipogenic differentiation of hASCs using RT-qPCR and western blotting. The functional role of LAP2α in adipogenesis was explored both in vitro and in vivo through loss- and gain-of-function studies. Moreover, mice with HFD-induced obesity received lentivirus injection to assess the effect of LAP2α knockdown on fat accumulation. Molecular mechanisms underlying LAP2α in adipogenic differentiation were investigated using RT-qPCR, Western blotting, immunofluorescence staining, and Oil Red O staining. LAP2α expression was upregulated during hASCs adipogenic differentiation. LAP2α knockdown hindered adipogenesis, while LAP2α overexpression promoted adipogenic differentiation. Notably, LAP2α deficiency resisted HFD-induced obesity, improved glucose intolerance, mitigated insulin resistance, and prevented fatty liver development. Mechanistically, LAP2α knockdown attenuated signal transducer and activator of transcription 3 (STAT3) activation by reducing the protein level of phosphorylated STAT3. A STAT3 activator (Colivelin) counteracted the negative impact of LAP2α deficiency on hASCs adipogenic differentiation. Taken together, our current study established LAP2α as a crucial regulator of hASCs adipogenic differentiation, unveiling a new therapeutic target for obesity prevention.

c-Fos regulated by TMPO/ERK axis promotes 5-FU resistance via inducing NANOG transcription in colon cancer

Acquired drug resistance is one of the most common limitations for the clinical response of colon cancer to 5-Fluorouracil (5-FU)-based chemotherapy. The relevant molecular mechanisms might be diversity, but still not be elucidated clearly. In this study, we aimed to investigate the potential mechanisms of c-Fos, a subfamily of activator protein-1, in 5-FU chemoresistance. We determined that phosphorylated c-Fos promoted colon cancer cells resistance to 5-FU by facilitating the cancer stemness. Mechanically, 5-FU treatment induced autolysosome-dependent degradation of TMPO, which subsequently triggered ERK-mediated phosphorylation of c-Fos. Additionally, c-Fos was found to bind to the promoter of NANOG and phosphorylation of c-Fos at Ser 374 was required for its regulation of NANOG expression. NANOG ablation impaired c-Fos/p-c-Fos induced 5-FU resistance and stemness. Taken together, these findings revealed that TMPO-mediated phosphorylation of c-Fos conferred 5-FU resistance by regulating NANOG expression and promoting cell stemness in colon cancer cells. c-Fos could be as a therapeutic target for colon cancer.

Functions and regulatory mechanisms of resting hematopoietic stem cells: a promising targeted therapeutic strategy

Hematopoietic stem cells (HSCs) are the common and essential precursors of all blood cells, including immune cells, and they are responsible for the lifelong maintenance and damage repair of blood tissue homeostasis. The vast majority (> 95%) of HSCs are in a resting state under physiological conditions and are only activated to play a functional role under stress conditions. This resting state affects their long-term survival and is also closely related to the lifelong maintenance of hematopoietic function; however, abnormal changes may also be an important factor leading to the decline of immune function in the body and the occurrence of diseases in various systems. While the importance of resting HSCs has attracted increasing research attention, our current understanding of this topic remains insufficient, and the direction of clinical targeted treatments is unclear. Here, we describe the functions of HSCs, analyze the regulatory mechanisms that affect their resting state, and discuss the relationship between resting HSCs and different diseases, with a view to providing guidance for the future clinical implementation of related targeted treatments.

Transcription Factor Lmx1b Negatively Regulates Osteoblast Differentiation and Bone Formation

The LIM-homeodomain transcription factor Lmx1b plays a key role in body pattern formation during development. Although Lmx1b is essential for the normal development of multiple tissues, its regulatory mechanism in bone cells remains unclear. Here, we demonstrated that Lmx1b negatively regulates bone morphogenic protein 2 (BMP2)-induced osteoblast differentiation. Overexpressed Lmx1b in the osteoblast precursor cells inhibited alkaline phosphatase (ALP) activity and nodule formation, as well as the expression of osteoblast maker genes, including runt-related transcription factor 2 (Runx2), alkaline phosphatase (Alpl), bone sialoprotein (Ibsp), and osteocalcin (Bglap). Conversely, the knockdown of Lmx1b in the osteoblast precursors enhanced the osteoblast differentiation and function. Lmx1b physically interacted with and repressed the transcriptional activity of Runx2 by reducing the recruitment of Runx2 to the promoter region of its target genes. In vivo analysis of BMP2-induced ectopic bone formation revealed that the knockdown of Lmx1b promoted osteogenic differentiation and bone regeneration. Our data demonstrate that Lmx1b negatively regulates osteoblast differentiation and function through regulation of Runx2 and provides a molecular basis for therapeutic targets for bone diseases.

Lamina-associated polypeptide 2α is required for intranuclear MRTF-A activity

Myocardin-related transcription factor A (MRTF-A), a coactivator of serum response factor (SRF), regulates the expression of many cytoskeletal genes in response to cytoplasmic and nuclear actin dynamics. Here we describe a novel mechanism to regulate MRTF-A activity within the nucleus by showing that lamina-associated polypeptide 2α (Lap2α), the nucleoplasmic isoform of Lap2, is a direct binding partner of MRTF-A, and required for the efficient expression of MRTF-A/SRF target genes. Mechanistically, Lap2α is not required for MRTF-A nuclear localization, unlike most other MRTF-A regulators, but is required for efficient recruitment of MRTF-A to its target genes. This regulatory step takes place prior to MRTF-A chromatin binding, because Lap2α neither interacts with, nor specifically influences active histone marks on MRTF-A/SRF target genes. Phenotypically, Lap2α is required for serum-induced cell migration, and deregulated MRTF-A activity may also contribute to muscle and proliferation phenotypes associated with loss of Lap2α. Our studies therefore add another regulatory layer to the control of MRTF-A-SRF-mediated gene expression, and broaden the role of Lap2α in transcriptional regulation.

NOD2 is involved in regulating odontogenic differentiation of DPSCs suppressed by MDP through NF-κB/p65 signaling

Dental pulp stem cells (DPSCs) are well known for their capable of both self-renewal and multilineage differentiation. Dental tissue diseases, include caries, are often accompanied by inflammatory microenvironment, and muramyl dipeptide (MDP) is involved in the inflammatory stimuli to influence the differentiation of DPSCs. Nucleotide-binding oligomerization domain 2 (NOD2), a member of the cytosolic Nod-like receptor (NLR) family, plays a key role in inflammatory homeostasis regulation, but the role of NOD2 in DPSCs differentiation under inflammatory is still unclear. In this study, we identified that MDP suppressed odontogenic differentiation of DPSCs via NOD2/ NF-κB/p65 signaling pathway. Alizarin red staining and ALP activity showed the odontogenic differentiation was suppressed by MDP in a concentration-dependent manner, and the expression of dentin differentiation marker protein dentin matrix protein 1 (DMP-1) and dentin Sialophosphoprotein (DSPP) also indicated the same results. The expression of NOD2 increased gradually with the concentration of MDP as well as the phosphorylation and nuclear translocation of p65, which meant NF-κB signaling pathway was activated. Further, the interference of NOD2 inhibited the phosphorylation and nuclear translocation of p65 and reversed the MDP-mediated decrease of odontoblast differentiation of DPSCs. Our study showed that MDP can inhibit the odontoblast differentiation of DPSCs in a concentration-dependent manner. The NF-κB signaling pathway was activated by increasing expression of NOD2. Interference of NOD2 reversed the negative ability odontoblast differentiation of DPSCs in the inflammatory environment. Our study might provide a theoretical basis for the clinical treatment for dentinogenesis of DPSCs.

Classical isoforms of protein kinase C (PKC) and Akt regulate the osteogenic differentiation of human dental follicle cells via both β-catenin and NF-κB

BACKGROUND

Human dental follicle cells (DFCs) are the precursor cells of the periodontium with a high potential for regenerative therapies of (alveolar) bone. However, the molecular mechanisms of osteogenic differentiation are inadequately understood. Classical isoforms of protein kinase C (PKC) are reported to inhibit osteogenesis of stem/precursor cells. This study evaluated the role of classical PKCs and potential downstream targets on the osteogenic differentiation of DFCs.

METHODS

DFCs were osteogenic differentiated with dexamethasone or bone morphogenetic protein 2 (BMP2). Expression of PKC and potential upstream/downstream regulators was manipulated using activators, inhibitors, and small interfering ribonucleic acid (siRNA). Expression of proteins was examined by Western blot analysis, while the activation levels of enzymes and transcription factors were examined by their phosphorylation states or by specific activation assays. Expression levels of osteogenic markers were examined by RT-qPCR (reverse transcription-quantitative polymerase chain reaction) analysis. Activity of alkaline phosphatase (ALP) and accumulation of calcium nodules by Alizarin Red staining were measured as indicators of mineralization.

RESULTS

Classical PKCs like PKCα inhibit the osteogenic differentiation of DFCs, but do not interfere with the induction of differentiation. Inhibition of classical PKCs by Gö6976 enhanced activity of Akt after osteogenic induction. Akt was also regulated during differentiation and especially disturbed BMP2-induced mineralization. The PKC/Akt axis was further shown to regulate the canonical Wnt signaling pathway and eventually nuclear expression of active β-catenin during dexamethasone-induced osteogenesis. Moreover, the nuclear factor "kappa-light-chain-enhancer" of activated B cells (NF-κB) pathway is regulated during osteogenic differentiation of DFCs and via the PKC/Akt axis and disturbs the mineralization. Upstream, parathyroid hormone-related protein (PTHrP) sustained the activity of PKC, while Wnt5a inhibited it.

CONCLUSIONS

Our results demonstrate that classical PKCs like PKCα and Akt regulate the osteogenic differentiation of DFCs partly via both β-catenin and NF-κB.