Nanoengineered Red Blood Cells Loaded with TMPRSS2 and Cathepsin L Inhibitors Block SARS-CoV-2 Pseudovirus Entry into Lung ACE2+ Cells.

The enzymatic activities of Furin, Transmembrane serine proteinase 2 (TMPRSS2), Cathepsin L (CTSL), and Angiotensin-converting enzyme 2 (ACE2) receptor binding are necessary for the entry of coronaviruses into host cells. Precise inhibition of these key proteases in ACE2+ lung cells during a viral infection cycle shall prevent viral Spike (S) protein activation and its fusion with a host cell membrane, consequently averting virus entry to the cells. In this study, dual-drug-combined (TMPRSS2 inhibitor Camostat and CTSL inhibitor E-64d) nanocarriers (NCs) are constructed conjugated with an anti-human ACE2 (hACE2) antibody and employ Red Blood Cell (RBC)-hitchhiking, termed "Nanoengineered RBCs," for targeting lung cells. The significant therapeutic efficacy of the dual-drug-loaded nanoengineered RBCs in pseudovirus-infected K18-hACE2 transgenic mice is reported. Notably, the modular nanoengineered RBCs (anti-receptor antibody+NCs+RBCs) precisely target key proteases of host cells in the lungs to block the entry of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), regardless of virus variations. These findings are anticipated to benefit the development of a series of novel and safe host-cell-protecting antiviral therapies.

Influence of hypoxia on retinal progenitor and ganglion cells in human induced pluripotent stem cell-derived retinal organoids.

AIM: To observe the effect of low oxygen concentration on the neural retina in human induced pluripotent stem cell (hiPSC)-derived retinal organoids (ROs). METHODS: The hiPSC and a three-dimensional culture method were used for the experiments. Generated embryoid bodies (EBs) were randomly and equally divided into hypoxic and normoxic groups. Photographs of the EBs were taken on days 38, 45, and 52, and the corresponding volume of EBs was calculated. Simultaneously, samples were collected at these three timepoints, followed by fixation, sectioning, and immunofluorescence. RESULTS: The proportion of Ki67-positive proliferating cells increased steadily on day 38; this proliferation-promoting effect tended to increase tissue density rather than tissue volume. On days 45 and 52, the two groups had relatively similar ratios of Ki67-positive cells. Further immunofluorescence analysis showed that the ratio of SOX2-positive cells significantly increased within the neural retina on day 52 (P<0.05). In contrast, the percentage of PAX6- and CHX10-positive cells significantly decreased following hypoxia treatment at all three timepoints (P<0.01), except for CHX10 at day 45 (P>0.05). Moreover, the proportion of PAX6-/TUJ1+ cells within the neural retinas increased considerably (P<0.01, <0.05, <0.05 respectively). CONCLUSION: Low oxygen promotes stemness and proliferation of neural retinas, suggesting that hypoxic conditions can enlarge the retinal progenitor cell pool in hiPSC-derived ROs.

A Functional Screening Identifies a New Organic Selenium Compound Targeting Cancer Stem Cells: Role of c-Myc Transcription Activity Inhibition in Liver Cancer.

Cancer stem cells (CSCs) are reported to play essential roles in chemoresistance and metastasis. Pathways regulating CSC self-renewal and proliferation, such as Hedgehog, Notch, Wnt/ß-catenin, TGF-ß, and Myc, may be potential therapeutic targets. Here, a functional screening from the focused library with 365 compounds is performed by a step-by-step strategy. Among these candidate molecules, phenyl-2-pyrimidinyl ketone 4-allyl-3-amino selenourea (CU27) is chosen for further identification because it proves to be the most effective compound over others on CSC inhibition. Through ingenuity pathway analysis, it is shown CU27 may inhibit CSC through a well-known stemness-related transcription factor c-Myc. Gene set enrichment analysis, dual-luciferase reporter assays, expression levels of typical c-Myc targets, molecular docking, surface plasmon resonance, immunoprecipitation, and chromatin immunoprecipitation are conducted. These results together suggest CU27 binds c-Myc bHLH/LZ domains, inhibits c-Myc-Max complex formation, and prevents its occupancy on target gene promoters. In mouse models, CU27 significantly sensitizes sorafenib-resistant tumor to sorafenib, reduces the primary tumor size, and inhibits CSC generation, showing a dramatic anti-metastasis potential. Taken together, CU27 exerts inhibitory effects on CSC and CSC-associated traits in hepatocellular carcinoma (HCC) via c-Myc transcription activity inhibition. CU27 may be a promising therapeutic to treat sorafenib-resistant HCC.

The splicing regulatory factor hnRNPU is a novel transcriptional target of c-Myc in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most common liver cancer with high mortality. Here, we found that hnRNPU is overexpressed in HCC tissues and is correlated with the poor prognosis of HCC patients. Besides, hnRNPU is of high significance in regulating the proliferation, apoptosis, self-renewal, and tumorigenic potential of HCC cells. Mechanismly, c-Myc regulates hnRNPU expression at the transcriptional level, and meanwhile, hnRNPU stabilizes the mRNA of c-MYC. We found that the hnRNPU and c-Myc regulatory loop exerts a synergistic effect on the proliferation and self-renewal of HCC, and promotes the HCC progression. Taken together, hnRNPU functions as a novel transcriptional target of c-Myc and promotes HCC progression, which may become a promising target for the treatment of c-Myc-driven HCC.

A new protocol for long-term culture of a specific subpopulation of liver cancer stem cells enriched by cell surface markers.

Liver cancer stem cells (L-CSCs) are considered to be an important therapeutic target for hepatocellular carcinoma (HCC). This study provides a new in vitro long-term culture model for a specific subpopulation of L-CSCs enriched by cell surface markers. We combined CD13, CD133 and EpCAM to selectively enrich L-CSCs, which we then cultured in modified chemically defined medium. The enriched L-CSCs exhibited enhanced proliferation, self-renewal and long-term clonal maintenance ability as compared with non-CSCs. Compared with wild-type hepatocellular carcinoma, the expression of stemness surface markers, oncogenes, drug resistance and tumorigenicity in enriched L-CSCs was significantly increased. In summary, the subpopulation of L-CSCs still maintains cancer stem cell-related phenotypes after 14 days of culture.

Arsenic trioxide inhibits liver cancer stem cells and metastasis by targeting SRF/MCM7 complex.

Hepatocellular carcinoma (HCC) has a high mortality rate due to the lack of effective treatments and drugs. Arsenic trioxide (ATO), which has been proved to successfully treat acute promyelocytic leukemia (APL), was recently reported to show therapeutic potential in solid tumors including HCC. However, its anticancer mechanisms in HCC still need further investigation. In this study, we demonstrated that ATO inhibits tumorigenesis and distant metastasis in mouse models, corresponding with a prolonged mice survival time. Also, ATO was found to significantly decrease the cancer stem cell (CSC)-associated traits. Minichromosome maintenance protein (MCM) 7 was further identified to be a potential target suppressed dramatically by ATO, of which protein expression is increased in patients and significantly correlated with tumor size, cellular differentiation, portal venous emboli, and poor patient survival. Moreover, MCM7 knockdown recapitulates the effects of ATO on CSCs and metastasis, while ectopic expression of MCM7 abolishes them. Mechanistically, our results suggested that ATO suppresses MCM7 transcription by targeting serum response factor (SRF)/MCM7 complex, which functions as an important transcriptional regulator modulating MCM7 expression. Taken together, our findings highlight the importance of ATO in the treatment of solid tumors. The identification of SRF/MCM7 complex as a target of ATO provides new insights into ATO's mechanism, which may benefit the appropriate use of this agent in the treatment of HCC.

Human fetal liver stromal cells expressing erythropoietin promote hematopoietic development from human embryonic stem cells.

Blood cells transfusion and hematopoietic stem cells (HSCs) transplantation are important methods for cell therapy. They are widely used in the treatment of incurable hematological disorder, infectious diseases, genetic diseases, and immunologic deficiency. However, their availability is limited by quantity, capacity of proliferation and the risk of blood transfusion complications. Recently, human embryonic stem cells (hESCs) have been shown to be an alternative resource for the generation of hematopoietic cells. In the current study, we describe a novel method for the efficient production of hematopoietic cells from hESCs. The stable human fetal liver stromal cell lines (hFLSCs) expressing erythropoietin (EPO) were established using the lentiviral system. We observed that the supernatant from the EPO transfected hFLSCs could induce the hESCs differentiation into hematopoietic cells, especially erythroid cells. They not only expressed fetal and embryonic globins but also expressed the adult-globin chain on further maturation. In addition, these hESCs-derived erythroid cells possess oxygen-transporting capacity, which indicated hESCs could generate terminally mature progenies. This should be useful for ultimately developing an animal-free culture system to generate large numbers of erythroid cells from hESCs and provide an experimental model to study early human erythropoiesis.

[Erythropoietin gene-modified conditioned medium of human mesenchymal cells promotes hematopoietic development from human embryonic stem cells].

The study was aimed to investigate the effect of deriving hematopoietic cells from human embryonic stem cells (hESCs) by the erythropoietin gene-modified conditioned medium of human mesenchymal cells. The mesenchymal stem cells (MSCs) steadily expressing EPO were established by lentiviral system. The expression of exogenous EPO was detected by RT-PCR and Western blot. After suspension culture, hESCs developed into embryonic bodies (EBs). Then the EB cells were cultured in conditional medium. The hESCs-derived hematopoietic cells were analyzed by immunofluorescence, CFU assay and RT-PCR. The results indicated that the exogenous EPO successfully expressed in the EPO transfected MSCs (EPO/MSCs). The supernatant from EPO/MSCs increased CD34(+) cell population and the expression of globin, and enhanced colony forming unit incidence. These effects were obviously higher than that of control. It is concluded that the EPO gene-modified conditioned medium of human mesenchymal cells can induce the hESCs to differentiate into hematopoietic cells.

Self-renewal and pluripotency is maintained in human embryonic stem cells by co-culture with human fetal liver stromal cells expressing hypoxia inducible factor 1alpha.

Human embryonic stem (hES) cells are typically maintained on mouse embryonic fibroblast (MEF) feeders or with MEF-conditioned medium. However, these xenosupport systems greatly limit the therapeutic applications of hES cells because of the risk of cross-transfer of animal pathogens. The stem cell niche is a unique tissue microenvironment that regulates the self-renewal and differentiation of stem cells. Recent evidence suggests that stem cells are localized in the microenvironment of low oxygen. We hypothesized that hypoxia could maintain the undifferentiated phenotype of embryonic stem cells. We have co-cultured a human embryonic cell line with human fetal liver stromal cells (hFLSCs) feeder cells stably expressing hypoxia-inducible factor-1 alpha (HIF-1alpha), which is known as the key transcription factor in hypoxia. The results suggested HIF-1alpha was critical for preventing differentiation of hES cells in culture. Consistent with this observation, hypoxia upregulated the expression of Nanog and Oct-4, the key factors expressed in undifferentiated stem cells. We further demonstrated that HIF-1alpha could upregulate the expression of some soluble factors including bFGF and SDF-1alpha, which are released into the microenvironment to maintain the undifferentiated status of hES cells. This suggests that the targets of HIF-1alpha are secreted soluble factors rather than a cell-cell contact mechanism, and defines an important mechanism for the inhibition of hESCs differentiation by hypoxia. Our findings developed a transgene feeder co-culture system and will provide a more reliable alternative for future therapeutic applications of hES cells.

Cells extract from fetal liver promotes the hematopoietic differentiation of human embryonic stem cells.

Here, we have now developed a new inducing system to promote the differentiation of human stem cells (hESCs) toward hematopoietic lineages by the treatment with cells extract of human fetal liver tissue (hFLT). The embryoid bodies (EBs) obtained from human H1 embryonic stem cells were exposed to buffer, hFLT cells extract, heated hFLT cell extract, and cell extract of human liver cells lines-LO2. Then, the feature of EBs in different groups was characterized by real-time RT-PCR and colony-forming assays. The results showed the treatment by hFLT cells extract could activate the hematopoietic genes expression and improve the capacity for hematopoietic progenitor development of hEBs. After that, we cocultured hFLT extract treated hEBs on the hFLSCs (human fetal liver stromal cells) feeder to differentiate them into hematopoietic cells. As a control, untreated hEBs were cocultured on hFLSCs feeder with cytokines. The feature of induced cells from hEBs was characterized by flow cytometry, Wright-Giemsa staining, and colony-forming assays. The results demonstrated that hFLT cells extract was capable of inducing hEBs into hematopoietic cells and combing it with hFLSCs feeder could largely promote hematopoietic differentiation of hESCs. This method may supply a new way to substitute the cytokines required in hematopoietic induction of hESCs.

[Construction of the plant expression vectors containing the multiepitope gene of Toxoplasma gondii].

OBJECTIVE: To construct the plant expression vectors containing the multiepitope gene of Toxoplasma gondii (TGMG). METHODS: 1. TGMG was subcloned into pBAC55 vector to construct the intermediate plasmid pB35MG. The E35S/TGMG/NOS3' fragment was cleaved from pB35MG and ligated into the plant binary vector pCAMBIA2300 to construct the plant expression vector pC35MG. 2. Tomato fruit-specific E81. 1 promoter was introduced to pB35MG to construct pB35E1MG vector. The E35SE81. 1/TGMG/NOS3' fragment was subcloned into pCAMBIA2300 to construct the plant expression vector pC35E1MG. 3. Tomato fruit-specific E82.2 promoter was inserted to pB35MG to construct pBE2MG vector. The E82.2/TGMG/NOS3' fragment was subcloned into pCAMBIA2300 to construct the plant expression vector pCE2MG. The insert gene TGMG in the vectors pB35MG, pC35E1MG and pCE2MG were confirmed by sequencing. 4. pC35MG, pC35E1MG and pCE2MG were introduced into Agrobacterium tumefaciens strain LBA4404 competent cell. RESULTS: Digestion with restriction enzymes proved that all recombinant vectors had the inserts with expected length of the target fragments. And the sequencing results were confirmed correct. CONCLUSION: The TGMG intermediate vectors pB35MG, pB35E1MG and pBE2MG and the plant expression vectors pC35MG, pC35E1MG and pCE2MG were constructed successfully, and the three plant expression vectors were introduced into Agrobacterium tumefaciens.

[Cloning and sequence analysis of tomato fruit-specific E8 promoter from Lycopersicon esculentum (Zhongshu No.5)].

OBJECTIVE: To obtain the gene encoding tomato fruit-specific E8 promoter therefore to prepare for exogenous gene transcription and expression in transgenic tomato fruit. METHODS: The cotyledons of tomato Lycopersicon esculentum (Zhongshu No.5) were collected for extracting the genomic DNA of this plant. The fruit-specific E81.1 and E82.2 promoter DNA were then amplified by PCR, the product of which was subcloned into pGEM-T vector. After identification by restriction enzymes, the recombinant T-vectors were subjected to sequence analysis. RESULTS: The fragments of the promoter as amplified by PCR were of predicted length. Digestion with Xba I and Hind III /BamH I proved correct insertion of the target fragments with expected length into the recombinant T vectors. As indicated by homology analysis, the resultant tomato fruit-specific E8 promoter was highly conservative, and E82.2 promoter of Zhongshu No.5, with GenBank submission number of AF515784, proved to share 99% homology with E82.2 promoter of Zhongshu No.5 Cherry as reported by Deikman J. CONCLUSION: Tomato fruit-specific E8 promoter of Zhongshu No.5 has been successfully cloned, thus making possible the subsequent research in oral vaccine of transgenic tomato.