Correction: Exploration of biomimetic poly(γ-benzyl-L-glutamate) fibrous scaffolds for corneal nerve regeneration.

Correction for 'Exploration of biomimetic poly(γ-benzyl-L-glutamate) fibrous scaffolds for corneal nerve regeneration' by Tien-Li Ma et al., J. Mater. Chem. B, 2022, 10, 6372-6379, https://doi.org/10.1039/D2TB01250B.

Dual-Function Fibrous Co-Polypeptide Scaffolds for Neural Tissue Engineering.

This paper reports dual-function (high cell attachment and cell viability) fibrous scaffolds featuring aligned fibers, displaying good biocompatibility and no cytotoxicity. These scaffolds are fabricated through the electrospinning of a co-polypeptide comprising molar equivalents of N6 -carbobenzyloxy-l-lysine and γ-benzyl-l-glutamate, with the lysine moieties enhancing cell adhesion and the neural-stimulating glutamate moieties improving cell viability. These new scaffolds allow neural cells to attach and grow effectively without any special surface treatment or coating. Pheochromocytoma (PC-12) cells grown on these scaffolds exhibit better neuronal activity and longer neurite length, relative to those grown on scaffolds prepared from their respective homo-polypeptides. When the scaffolds are partially hydrolyzed such that they present net positive charge and increased hydrophilicity, the cell viability and neurite growth both increase further. Accordingly, these novel co-polypeptide fibrous scaffolds have potential applications in neural tissue engineering.

Podocalyxin-Like Protein 1 Regulates Pluripotency through the Cholesterol Biosynthesis Pathway.

Deciphering signaling mechanisms critical for the extended pluripotent stem cell (EPSC) state and primed pluripotency is necessary for understanding embryonic development. Here, a membrane protein, podocalyxin-like protein 1 (PODXL) as being essential for extended and primed pluripotency, is identified. Alteration of PODXL expression levels affects self-renewal, protein expression of c-MYC and telomerase, and induced pluripotent stem cell (iPSC) and EPSC colony formation. PODXL is the first membrane protein reported to regulate de novo cholesterol biosynthesis, and human pluripotent stem cells (hPSCs) are more sensitive to cholesterol depletion than fibroblasts. The addition of exogenous cholesterol fully restores PODXL knockdown-mediated loss of pluripotency. PODXL affects lipid raft dynamics via the regulation of cholesterol. PODXL recruits the RAC1/CDC42/actin network to regulate SREBP1 and SREBP2 maturation and lipid raft dynamics. Single-cell RNA sequencing reveals PODXL overexpression enhanced chimerism between human cells in mouse host embryos (hEPSCs 57%). Interestingly, in the human-mouse chimeras, laminin and collagen signaling-related pathways are dominant in PODXL overexpressing cells. It is concluded that cholesterol regulation via PODXL signaling is critical for ESC/EPSC.

Exploration of biomimetic poly(γ-benzyl-L-glutamate) fibrous scaffolds for corneal nerve regeneration.

Poly(γ-benzyl-L-glutamate) (PBG) made biomimetic scaffolds are explored as candidate materials for corneal nerve regeneration and neurotrophic keratopathy treatment. The PBG with built-in neurotransmitter glutamate was synthesized and fabricated into 3D fibrous scaffolds containing aligned fibers using electrospinning. In in vitro experiments, primary mouse trigeminal ganglia (TG) cells were used. Immunohistochemistry (IHC) analysis shows that TG cells cultured on PBG have no cytotoxic response for 21 days. Without any nerve growth factor, TG cells have the longest neurite length of 225.3 µm in the PBG group and 1.3 times the average length as compared with the polycaprolactone and no scaffold groups. Also, aligned fibers guide the neurite growth and extension unidirectionally. In vivo assays were carried out by intracorneal implantation of PBG on clinical New Zealand rabbits. The external eye photos and in vivo confocal microscopy (IVCM) show a low immune response. The corneal neural markers (ßIII tubulin and SMI312) in the IHC analysis are consistent with the position stained by glutamate of implanted scaffolds, indicating that PBG induces neurogenesis. PBG exhibits mechanical stiffness to resist material deformation possibly caused by surgical operations. The results of this study demonstrate that PBG is suitable for corneal nerve regeneration and the treatment of neurotrophic keratopathy.

CXCL14 Maintains hESC Self-Renewal through Binding to IGF-1R and Activation of the IGF-1R Pathway.

Human embryonic stem cells (hESCs) have important roles in regenerative medicine, but only a few studies have investigated the cytokines secreted by hESCs. We screened and identified chemokine (C-X-C motif) ligand 14 (CXCL14), which plays crucial roles in hESC renewal. CXCL14, a C-X-C motif chemokine, is also named as breast and kidney-expressed chemokine (BRAK), B cell and monocyte-activated chemokine (BMAC), and macrophage inflammatory protein-2γ (MIP-2γ). Knockdown of CXCL14 disrupted the hESC self-renewal, changed cell cycle distribution, and further increased the expression levels of mesoderm and endoderm differentiated markers. Interestingly, we demonstrated that CXCL14 is the ligand for the insulin-like growth factor 1 receptor (IGF-1R), and it can activate IGF-1R signal transduction to support hESC renewal. Currently published literature indicates that all receptors in the CXCL family are G protein-coupled receptors (GPCRs). This report is the first to demonstrate that a CXCL protein can bind to and activate a receptor tyrosine kinase (RTK), and also the first to show that IGF-1R has another ligand in addition to IGFs. These findings broaden our understanding of stem cell biology and signal transduction.

Down-regulation of ATF1 leads to early neuroectoderm differentiation of human embryonic stem cells by increasing the expression level of SOX2.

We reveal by high-throughput screening that activating transcription factor 1 (ATF1) is a novel pluripotent regulator in human embryonic stem cells (hESCs). The knockdown of ATF1 expression significantly up-regulated neuroectoderm (NE) genes but not mesoderm, endoderm, and trophectoderm genes. Of note, down-regulation or knockout of ATF1 with short hairpin RNA (shRNA), small interfering RNA (siRNA), or clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) was sufficient to up-regulate sex-determining region Y-box (SOX)2 and paired box 6 (PAX6) expression under the undifferentiated or differentiated conditions, whereas overexpression of ATF1 suppressed NE differentiation. Endogenous ATF1 was spontaneously down-regulated after d 1-3 of neural induction. By double-knockdown experiments, up-regulation of SOX2 was critical for the increase of PAX6 and SOX1 expression in shRNA targeting Atf1 hESCs. Using the luciferase reporter assay, we identified ATF1 as a negative transcriptional regulator of Sox2 gene expression. A novel function of ATF1 was discovered, and these findings contribute to a broader understanding of the very first steps in regulating NE differentiation in hESCs.-Yang, S.-C., Liu, J.-J., Wang, C.-K., Lin, Y.-T., Tsai, S.-Y., Chen, W.-J., Huang, W.-K., Tu, P.-W. A., Lin, Y.-C., Chang, C.-F., Cheng, C.-L., Lin, H., Lai, C.-Y., Lin, C.-Y., Lee, Y.-H., Chiu, Y.-C., Hsu, C.-C., Hsu, S.-C., Hsiao, M., Schuyler, S. C., Lu, F. L., Lu, J. Down-regulation of ATF1 leads to early neuroectoderm differentiation of human embryonic stem cells by increasing the expression level of SOX2.

CHAC2 is essential for self-renewal and glutathione maintenance in human embryonic stem cells.

Glutathione (GSH), the major non-enzymatic antioxidant, plays a critical role in cellular reactive oxygen species (ROS) neutralization. Moreover, GSH is required for the self-renewal maintenance of human embryonic stem cells (hESCs), and is highly accumulated in undifferentiated cells. Among 8 GSH biosynthesis-related enzymes, we found CHAC2 is highly enriched in undifferentiated hESCs. CHAC2 downregulation in hESCs efficiently decreased the levels of GSH and blocked self-renewal. The self-renewal of sh-CHAC2 cells can be rescued by GSH supplement. CHAC2 downregulation promoted mesoderm differentiation and hampered both teratoma formation and the expression of Nrf2 and glutamate-cysteine ligase (GCL). Notably, CHAC1 knockdown restored the self-renewability of CHAC2-downregulated cells. Although both CHAC1 and CHAC2 purified protein alone showed the catalytic activities to GSH, our data extraordinarily revealed that CHAC2 prevented CHAC1-mediated GSH degradation, which suggests that CHAC2 competes with CHAC1 to maintain GSH homeostasis. This is the first report to demonstrate that CHAC2 is critical for GSH maintenance and the novel roles of the CHAC family in hESC renewal.

Elimination of undifferentiated human embryonic stem cells by cardiac glycosides.

An important safety concern in the use of human pluripotent stem cells (hPSCs) is tumorigenic risk, because these cells can form teratomas after an in vivo injection at ectopic sites. Several thousands of undifferentiated hPSCs are sufficient to induce teratomas in a mouse model. Thus, it is critical to remove all residue-undifferentiated hPSCs that have teratoma potential before the clinical application of hPSC-derived cells. In this study, our data demonstrated the cytotoxic effects of cardiac glycosides, such as digoxin, lanatoside C, bufalin, and proscillaridin A, in human embryonic stem cells (hESCs). This phenomenon was not observed in human bone marrow mesenchymal stem cells (hBMMSCs). Most importantly, digoxin and lanatoside C did not affect the stem cells' differentiation ability. Consistently, the viability of the hESC-derived MSCs, neurons, and endothelium cells was not affected by the digoxin and lanatoside C treatment. Furthermore, the in vivo experiments demonstrated that digoxin and lanatoside C prevented teratoma formation. To the best of our knowledge, this study is the first to describe the cytotoxicity and tumor prevention effects of cardiac glycosides in hESCs. Digoxin and lanatoside C are also the first FDA-approved drugs that demonstrated cytotoxicity in undifferentiated hESCs.

Efficient Generation of Chemically Induced Mesenchymal Stem Cells from Human Dermal Fibroblasts.

Human mesenchymal stromal/stem cells (MSCs) are multipotent and currently undergoing hundreds of clinical trials for disease treatments. To date, no studies have generated induced MSCs from skin fibroblasts with chemicals or growth factors. Here, we established the first chemical method to convert primary human dermal fibroblasts into multipotent, induced MSC-like cells (iMSCs). The conversion method uses a defined cocktail of small molecules and growth factors, and it can achieve efficient conversion with an average rate of 38% in 6 days. The iMSCs have much higher clonogenicity than fibroblasts, and they can be maintained and expanded in regular MSC medium for at least 8 passages and further differentiated into osteoblasts, adipocytes, and chondrocytes. Moreover, the iMSCs can suppress LPS-mediated acute lung injury as effectively as bone marrow-derived mesenchymal stem cells. This finding may greatly benefit stem cell biology, cell therapy, and regenerative medicine.

EpEX/EpCAM and Oct4 or Klf4 alone are sufficient to generate induced pluripotent stem cells through STAT3 and HIF2α.

Epithelial cell adhesion molecule (EpCAM) was reported to be cleaved into extracellular domain of EpCAM (EpEX) and intracellular domain of EpCAM (EpICD). We previously reported that EpCAM serves as a potent stem cell marker which is highly and selectively expressed by undifferentiated rather than differentiated hESC. However, the functional role of EpCAM remains elusive. Here, we found that EpEX and EpCAM enhance the efficiency of OSKM reprogramming. Interestingly, Oct4 or Klf4 alone, but not Sox2, can successfully reprogram fibroblasts into iPSCs with EpEX and EpCAM. Moreover, EpEX and EpCAM trigger reprogramming via activation of STAT3, which leads to the nuclear-translocation of HIF2α. This study reveals the importance of a novel EpEX/EpCAM-STAT3-HIF2α signal in the reprogramming process, and uncovers a new means of triggering reprogramming by delivery of soluble and transmembrane proteins.

Diagnostic value of serum complement C3 and C4 levels in Chinese patients with systemic lupus erythematosus.

In 2009, hypocomplementemia involving C3, C4, and total hemolytic complement (CH50) was proposed as an immunologic criterion to enhance the sensitivity of systemic lupus erythematosus (SLE) classification criteria. This study evaluated the diagnostic value of low serum complement C3 and C4 levels in Chinese patients with SLE. In total, 2452 patients were enrolled in this study (158 with SLE and 2294 with other diseases). Receiver operating characteristic analysis showed that the optimal C3 and C4 cut-off levels for a diagnosis of SLE were 0.785 g/L (sensitivity, 77.9%; specificity, 81.5%) and 0.145 g/L (sensitivity, 80.1%; specificity, 83.2%), respectively. The prevalence of a low C3 or C4 level alone was similar between patients with SLE and those with other diseases, while the prevalence of simultaneously low C3 and C4 levels was higher in patients with SLE (73.42%). Antinuclear antibody had a high sensitivity (96.64%) and low negative likelihood ratio (0.04). Hypocomplementemia with positive antinuclear antibody had a high positive likelihood ratio. Inclusion of hypocomplementemia as a classification criterion for SLE resulted in a 16.18% increase in the number of patients assigned to the SLE group (from 136 to 158 patients). Hypocomplementemia was highly prevalent in patients with hematological disease (41.94%). These results suggest that hypocomplementemia has important diagnostic value for SLE by improving the sensitivity of the diagnosis of SLE. C3 and C4 should be tested simultaneously because a low C3 or C4 level alone is not a suitable immunological criterion.

Enhancement of anti-murine colon cancer immunity by fusion of a SARS fragment to a low-immunogenic carcinoembryonic antigen.

BACKGROUND: It is widely understood that tumor cells express tumor-associated antigens (TAAs), of which many are usually in low immunogenicity; for example, carcinoembryonic antigen (CEA) is specifically expressed on human colon cancer cells and is viewed as a low-immunogenic TAA. How to activate host immunity against specific TAAs and to suppress tumor growth therefore becomes important in cancer therapy development. RESULTS: To enhance the immune efficiency of CEA in mice that received, we fused a partial CEA gene with exogenous SARS-CoV fragments. Oral vaccination of an attenuated Salmonella typhimurium strain transformed with plasmids encoding CEA-SARS-CoV fusion gene into BALB/c mice elicited significant increases in TNF-α and IL-10 in the serum. In addition, a smaller tumor volume was observed in CT26/CEA-bearing mice who received CEA-SARS-CoV gene therapy in comparison with those administered CEA alone. CONCLUSION: The administration of fusing CEA-SARS-CoV fragments may provide a promising strategy for strengthening the anti-tumor efficacy against low-immunogenic endogenous tumor antigens.

A potential role for Helicobacter pylori heat shock protein 60 in gastric tumorigenesis.

Helicobacter pylori has been found to promote the malignant process leading to gastric cancer. Heat shock protein 60 of H. pylori (HpHSP60) was previously been identified as a potent immunogene. This study investigates the role of HpHSP60 in gastric cancer carcinogenesis. The effect of HpHSP60 on cell proliferation, anti-death activity, angiogenesis and cell migration were explored. The results showed that HpHSP60 enhanced migration by gastric cancer cells and promoted tube formation by umbilical vein endothelial cells (HUVECs); however, HpHSP60 did not increase cell proliferation nor was this protein able to rescue gastric cancer cells from death. Moreover, the results also indicated HpHSP60 had different effects on AGS gastric cancer cells or THP-1 monocytic cells in terms of their expression of pro-inflammatory cytokines, which are known to be important to cancer development. We propose that HpHSP60 may trigger the initiation of carcinogenesis by inducing pro-inflammatory cytokine release and by promoting angiogenesis and metastasis. Thus, this extracellular pathogen-derived HSP60 is potentially a vigorous virulence factor that can act as a carcinogen during gastric tumorigenesis.