Construction of Covalent Organic Frameworks via a Visible-Light-Activated Photocatalytic Multicomponent Reaction.

Multicomponent reactions (MCRs), as a powerful one-pot combinatorial synthesis tool, have been recently applied to the synthesis of covalent organic frameworks (COFs). Compared with the thermally driven MCRs, the photocatalytic MCR-based COF synthesis has not yet been investigated. Herein, we first report the construction of COFs by a photocatalytic multicomponent reaction. Upon visible-light irradiation, a series of COFs with excellent crystallinity, stability, and permanent porosity are successfully synthesized via photoredox-catalyzed multicomponent Petasis reaction under ambient conditions. Additionally, the obtained Cy-N3-COF exhibits excellent photoactivity and recyclability for the visible-light-driven oxidative hydroxylation of arylboronic acids. The concept of photocatalytic multicomponent polymerization not only enriches the methodology for COF synthesis but also opens a new avenue for the construction of COFs that might not be possible with the existing synthetic methods based on thermally driven MCRs.

In situ utilization of photogenerated hydrogen for hydrogenation reaction over a covalent organic framework.

A fully sp2-carbon conjugated COF (Py-FTP-COF) was designed and synthesized, exhibiting excellent hydrogen evolution rate of 5.22 mmol g-1 h-1. More importantly, in situ hydrogenation of nitroarenes under visible-light irradiation without any additional hydrogen source was successfully accomplished for the first time over COF-based materials.

[Advances about perineuronal nets in the repair of nerve function after spinal cord injury].

Perineuronal nets (PNNs) is a complex network composed of highly condensed extracellular matrix molecules surrounding neurons. It plays an important role in maintaining the performance of neurons and protecting them from harmful substances. However, after spinal cord injury, PNNs forms a physical barrier that surrounds the neuron and limits neuroplasticity, impedes axonal regeneration and myelin formation, and promotes local neuroinflammatory uptake. This paper mainly describes the composition and function of PNNs of neurons and its regulatory effects on axonal regeneration, myelin formation and neuroinflammation after spinal cord injury.

Impact of treatment modality on long-term survival of stage IA small-cell lung cancer patients: a cohort study of the U.S. SEER database.

BACKGROUND: The optimal treatment modality for patients with stage IA (T1N0M0) small-cell lung cancer (SCLC) is still unclear. METHODS: Patients who received surgical resection or chemo-radiotherapy (CRT) between January 2004 and December 2014 were identified from The Surveillance, Epidemiology and End Results (SEER) database. Surgical resection included lobectomy, wedge resection, segmentectomy with lymphadenectomy [examined lymph node (ELN) ≥1]. Propensity score match analysis was utilized to balance the baseline characteristics. RESULTS: A total of 686 stage IA SCLC cases were included: 337 patients underwent surgery and 349 patients were treated by CRT alone. Surgery achieved a better outcome than CRT alone, with an adjusted hazard ratio (HR) of 0.495. Patients who underwent lobectomy demonstrated a longer overall survival (OS), compared to those who received sublobectomy (crude cohort, median OS, 69 vs. 38 months; match cohort, median OS, 67 vs. 38 months). Patients with ELN >7 presented with longer OS than those with ELN ≤7 (crude cohort, median OS, 91 vs. 49 months; matched cohort, median OS, 91 vs. 54 months). The additional efficacy of chemotherapy or radiotherapy in patients receiving lobectomy was observed. The best prognosis was achieved in the lobectomy plus CRT cohort, with a 5-year survival rate of 73.5%. CONCLUSIONS: The prolonged survival associated with lobectomy and chemotherapy or radiotherapy presents a viable treatment option in the management of patients with stage IA SCLC.

MiR-26a-5p Serves as an Oncogenic MicroRNA in Non-Small Cell Lung Cancer by Targeting FAF1.

PURPOSE: Non-small cell lung cancer (NSCLC) accounts for approximately 80-85% of all lung cancers, with the FAS-associated factor 1 (FAF1) acting as a tumor suppressor. MicroRNAs (miRNAs) can influence cancer progression by targeting oncogenes or anti-oncogenes. In this study, we aimed to reveal the influence of miR-26a-5p on the regulation of FAF1 expression and NSCLC progression, with the motivation of identifying a potential therapeutic target for NSCLC treatment. METHODS: A dual-luciferase reporter assay was used to check for the direct targeting of FAF1 by miR-26a-3p. The miR-26a-5p inhibitor or FAF1 shRNA plasmid was transfected into A549 and H1299 cells to modulate FAF1 expression. Then, the effect of miR-26a-5p/FAF1 on cellular functions was investigated. MTT assay was used to evaluate cell viability. EdU proliferation assay and cell cycle assay were performed to analyze the effect of miR-26a-5p on cell replication and cell cycle. We used annexin V-FITC and PI to stain apoptotic cells, followed by flow cytometric analysis. Transwell and wound healing assays were performed to investigate metastasis. Moreover, the effect of miR-26a-5p/FAF1 on cancer progression was examined in vivo. Lastly, the underlying mechanism was uncovered using RT-qPCR, Western blotting, and TOP/FOP flash assay. RESULTS: miR-26a-5p was found to directly target FAF1 and downregulate its expression. Blocking miR-26a-5p inhibited the cell growth, migration, and invasion, but promoted cell apoptosis. In addition, this inhibited the growth of tumor in mice. FAF1 knockdown reversed the functions of miR-26a-5p. Further, miR-26a-5p/FAF1 was observed to play an important role in the Wnt signaling pathway, regulating the expression of genes such as AXIN, c-Myc, and cyclin-D1. CONCLUSION: Taken together, we show that miR-26a-5p functions as an oncogenic microRNA in NSCLC by targeting FAF1 and may serve as a potential target for NSCLC treatment.

[Effect of electroacupuncture at "Jiaji" (EX-B 2) points on the proliferation and differentiation of oligodendrocyte precursor cells in rats with acute spinal cord injury].

OBJECTIVE: To observe the effect of electroacupuncture (EA) at "Jiaji" (EX-B 2) points on the proliferation and differentiation of oligodendrocyte precursor cells in rats with acute incomplete spinal cord injury, and to explore the mechanism of EA on improving motor function of spinal cord injury. METHODS: A total of 72 male SPF SD rats were randomly divided into a sham operation group, a model group, an EA group and a medication group, 18 rats in each group. Each group was further divided into 1-day subgroup, 7-day subgroup and 14-day subgroup, 6 rats in each subgroup. The T10 acute incomplete spinal cord injury model was established by modified Allen's method in the model group, EA group and medication group. The rats in each group received intraperitoneal injection of 5-bromodeoxyuridine (BrdU, 50 mg/kg), once a day, and each subgroup received continuous injection for 1, 7, 14 times for cell proliferation labeling. The rats in the EA group were treated with EA at "Jiaji" (EX-B 2) points 3-4 mm next the spinous process of the upper and lower segments of the injured spinal cord (T9, T11) with a frequency of 2 Hz/100 Hz and intensity of 1-2 mA. The muscle twitch at the treatment site was taken as the degree. The treatment was given 20 min each time, once a day. In the medication group, monosialogangliosides (GM1) was injected intraperitoneally (10 mg/kg), once a day. The subgroups of EA group and medication group were treated for 1, 7, 14 times. The score of Basso Beattie Bresnahan (BBB) was used to evaluate the motor function of hind limbs. The co-expression of BrdU/NG2 positive cells was detected by immunofluorescence, and the expression of Olig2 and Sox10 was detected by Western blot. RESULTS: Compared with the sham operation group, the BBB score was decreased 1 day, 7 days and 14 days after operation in the model group (P<0.05), the expression of Olig2 and Sox10 was increased (P<0.05), and the co-expression of BrdU/NG2 positive cells was increased 7 days and 14 days after operation (P<0.05). Seven days and 14 days after operation, the BBB score in the EA group and medication group was higher than that in the model group (P<0.05), and the co-expression of BrdU/NG2 in the medication group was higher than that in the model group (P<0.05). Fourteen days after operation, the co-expression of BrdU/NG2 in the EA group was higher than that in the model group (P<0.05); 1 day, 7 days and 14 days after operation, the expression of Olig2 and Sox10 in the EA group and medication group was higher than that in the model group (P<0.05). Compared with the medication group, the co-expression of BrdU/NG2 positive cells in the EA group 14 days after operation was decreased (P<0.05); 1 day, 7 days and 14 days after operation, the expression of Olig2 and Sox10 in the EA group was decreased (P<0.05). CONCLUSION: EA at "Jiaji" (EX-B 2) points could promote the expression of Olig2 and Sox10 after spinal cord injury, which has similar effects with GM1. It could promote the proliferation and differentiation of oligodendrocyte precursor cells into oligodendrocytes, so as to promote the recovery of motor function of rats.

Covalent immobilization of recombinant Citrobacter koseri transaminase onto epoxy resins for consecutive asymmetric synthesis of L-phosphinothricin.

Transaminase responsible for alienating prochiral ketone compound is applicable to asymmetric synthesis of herbicide L-phosphinothricin (L-PPT). In this work, the covalent immobilization of recombinant transaminase from Citrobacter koseri (CkTA) was investigated on different epoxy resins. Using optimum ES-105 support, a higher immobilized activity was obtained via optimizing immobilization process in terms of enzyme loading, coupling time and initial PLP concentration. Crucially, due to blocking unreacted epoxy groups on support surface with amino acids, the reaction temperature of blocked immobilized biocatalyst was enhanced from 37 to 57 °C. Its thermostability at 57 °C was also found to be superior to that of free CkTA. The Km value was shifted from 36.75 mM of free CkTA to 39.87 mM of blocked immobilized biocatalyst, demonstrating that the affinity of enzyme to the substrate has not been apparently altered. Accordingly, the biocatalyst performed the consecutive synthesis of L-PPT for 11 cycles (yields>91%) with retaining more than 91.13% of the initial activity. The seemingly the highest reusability demonstrates this biocatalyst has prospective for reducing the costs of consecutive synthesis of L-PPT with high conversion.

Responses of plant productivity and soil nutrient concentrations to different alpine grassland degradation levels.

Although grassland degradation simultaneously affects plant productivity and soil nutrient concentrations, the relationship between plant productivity and soil nutrient concentrations during the process of grassland degradation is not yet well documented. A 4-year survey in the Qinghai-Tibetan Plateau was conducted to simultaneously investigate the relationships between plant productivity and soil nutrient concentrations in an alpine grassland at an overall degradation level and individual degradation levels. Our results showed that the total plant, sedge, and forb biomasses decreased, whereas the grass and legume biomasses first increased and then decreased as the level of alpine grassland degradation increased. Soil organic carbon (C), total nitrogen (N), total phosphorus (P), available N, and available P concentrations also decreased with the increase in degradation level. Our results also showed that plant productivity was positively correlated with soil nutrient concentrations (soil organic C, total T, total P, available N, available P) at an overall degradation level, whereas plant productivity was positively correlated with only the soil organic C concentration at each degradation level. Our findings suggested that the alpine grassland degradation conditions had different effects on the plant productivity of four functional groups (sedges, grasses, legumes, forbs) and affected the relationship between plant productivity and soil nutrient concentrations.

Asymmetric synthesis of l-phosphinothricin using thermostable alpha-transaminase mined from Citrobacter koseri.

α-Transaminase (α-TA) responsible for catalyzing the reversible transfer of amino groups between amine donors and amine acceptors, is applicable to enzymatic route for asymmetric synthesis of herbicide l-phosphinothricin (l-PPT). In the search for α-TAs with better catalysis performance, three α-TAs were discovered by genome mining approach using a known sequence encoding Escherichia coli tyrosine TA (TyrB) as probe. Through detailed comparison of their expression amount, activities and characteristics, Citrobacter koseri TA (CkTA) exhibited better activity and thermostability, which retain 65.9% of initial activity after incubation at 57 °C for 4 h. The Km and kcat/Km values of CkTA were 36.75 mM and 34.29 mM-1 min-1, respectively. In addition, recombinant CkTA cells were immobilized onto Celite 545 using tris(hydroxymethyl)phosphine as crosslinker. During five repetitive asymmetric synthesis of l-PPT from 20 g/L prostereogenic ketone using l-Glu as amine donor, all the yields of l-PPT reached up to 91.2% (＞99% ee). These characteristics made CkTA a valuable addition to the currently scarce α-TA library for stereospecific synthesis of l-PPT.

The association between clinical prognostic factors and epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) efficacy in advanced non-small-cell lung cancer patients: a retrospective assessment of 94 cases with EGFR mutations.

OBJECTIVE: This study aimed to examine the association of clinical prognostic factors with epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) efficacy in advanced non-small-cell lung cancer (NSCLC) patients. METHODS: The demographic and clinical characteristics of 94 patients with stage IV NSCLC were retrospectively reviewed, and the association between clinical factors and EGFR-TKIs efficacy was evaluated. RESULTS: Of the 94 stage IV NSCLC patients enrolled in this study, a 74.5% objective response rate (ORR) and 97.9% disease control rate (DCR) were observed for EGFR-TKIs treatment, and a higher ORR was seen in patients with 0 and 1 ECOG scores than those with 2 or greater scores (P = 0.049). The subjects had a median PFS of 11 months and a median OS of 31 months after EGFR-TKIs treatment. ECOG score and timing of targeted therapy were factors affecting PFS, and ECOG score, smoking status and brain metastasis were factors affecting OS. In addition, ECOG score was an independent prognostic factor for PFS in stage IV NSCLC patients, and the patients with EGFR 19del mutation had a longer PFS than those with exon 21 L855R mutation (P = 0.003), while ECOG score and brain metastasis were independent prognostic factors for OS. CONCLUSIONS: The results of this study demonstrate that EGFR-TKI therapy results in survival benefits for EGFR-mutant advanced NSCLC patients, regardless of gender, smoking history, pathologic type, type of EGFR mutations, brain metastasis and timing of targeted therapy. ECOG score is an independent prognostic factor for PFS, and ECOG score and brain metastasis are independent prognostic factors for OS in advanced NSCLC patients.

miR-150 Suppresses the Proliferation and Tumorigenicity of Leukemia Stem Cells by Targeting the Nanog Signaling Pathway.

Proliferation, a key feature of cancer cells, accounts for the majority of cancer-related diseases resulting in mortality. MicroRNAs (miRNAs) plays important post-transcriptional modulation roles by acting on multiple signaling pathways, but the underlying mechanism in proliferation and tumorigenicity is unclear. Here, we identified the role of miR-150 in proliferation and tumorigenicity in leukemia stem cells (LSCs; CD34+CD38- cells). miR-150 expression was significantly down-regulated in LSCs from leukemia cell lines and clinical samples. Functional assays demonstrated that increased miR-150 expression inhibited proliferation and clonal and clonogenic growth, enhanced chemosensitivity, and attenuated tumorigenic activity of LSCs in vitro. Transplantation animal studies revealed that miR-150 overexpression progressively abrogates tumor growth. Immunohistochemistry assays demonstrated that miR-150 overexpression enhanced caspase-3 level and reduced Ki-67 level. Moreover, luciferase reporter assays indicated Nanog is a direct and functional target of miR-150. Nanog silencing using small interfering RNA recapitulated anti-proliferation and tumorigenicity inhibition effects. Furthermore, miR-150 directly down-regulated the expression of other cancer stem cell factors including Notch2 and CTNNB1. These results provide insights into the specific biological behavior of miR-150 in regulating LSC proliferation and tumorigenicity. Targeting this miR-150/Nanog axis would be a helpful therapeutic strategy to treat acute myeloid leukemia.

Reciprocal activation between STAT3 and miR-181b regulates the proliferation of esophageal cancer stem-like cells via the CYLD pathway.

BACKGROUND: Recent studies have suggested that cancer cells contain subpopulations that can initiate tumor growth, self-renew, and maintain tumor cell growth. However, for esophageal cancer cells, the relationship between STAT3, microRNAs and cancer stem cells remains unclear. METHODS: Serum-free culture was used to enrich esophageal cancer stem-like cells (ECSLC). Flow cytometry determined the proportion of ECSLC. qPCR were performed to examine expression level of stemness factors, mesenchymal markers, ATP-binding cassette (ABC) transporters, STAT3, miR-181b, CYLD. Western blot were performed to analyze the expression of STAT3, p-STAT3 and CYLD (cylindromatosis). BALB/c mice xenograft studies were conducted to evaluate the tumorigenicity of enriched ECSLC. Sphere formation assay and colony formation assays were employed to analyze the relationship between STAT3 and miR-181b. Luciferase assays were used to evaluate activity which CYLD is a target of miR-181b. RESULTS: Sphere formation cells (SFCs) with properties of ECSLC were enriched. Enriched SFCs in serum-free suspension culture exhibited cancer stem-like cell properties and increased single-positive CD44 + CD24-, stemness factor, mesenchymal marker expression ABC transporters and tumorigenicity in vivo compared with the parental cells. Additionally, we found that reciprocal activation between STAT3 and miR-181b regulated SFCs proliferation. Moreover, STAT3 directly activated miR-181b transcription in SFCs and miR-181b then potentiated p-STAT3 activity. Luciferase assays indicated that CYLD was a direct and functional target of miR-181b. CONCLUSION: The mutual regulation between STAT3 and miR-181b in SFCs was required for proliferation and apoptosis resistance. STAT3 and miR-181b control each other's expression in a positive feedback loop that regulates SFCs via CYLD pathway. These findings maybe is helpful for targeting ECSLC and providing approach for esophageal cancer treatments.

Molecular cloning, sequence characteristics, and tissue expression analysis of ECE1 gene in Tibetan pig.

Low air pressure and low oxygen partial pressure at high altitude seriously affect the survival and development of human beings and animals. ECE1 is a recently discovered gene that is involved in anti-hypoxia, but the full-length cDNA sequence has not been obtained. For a better understanding of the structure and function of the ECE1 gene and to study its effect in Tibetan pig, the cDNA of the ECE1 gene from the muscle of Tibetan pig was cloned, sequenced and characterized. The ECE1 full-length cDNA sequence consists of 2262 bp coding sequence (CDS) that encodes 753 amino acids with a molecular mass of 85,449 kD, 2 bp 5'UTR and 1507 bp 3'UTR. In addition, the phylogenetic tree analysis revealed that the Tibetan pig ECE1 has a closer genetic relationship and evolution distance with the land mammals ECE1. Furthermore, analysis by qPCR showed that the ECE1 transcript is constitutively expressed in the 10 tissues tested: the liver, subcutaneous fat, kidney, muscle, stomach, heart, brain, spleen, pancreas, and lung. These results serve as a foundation for further insight into the Tibetan pig ECE1 gene.

[The clinical study of femtosecond lenticule extraction for myopia].

OBJECTIVE: To evaluate the clinical efficacy, safety and predictability of femtosecond lenticule extraction (FLEx) for myopia. METHODS: This is a prospective Clinical trial involved 10 cases (10 eyes). The patients aged from 18 years old to 53 years old, an average of (34 ± 11) years old. Femtosecond lenticule extraction (FLEx) was used to treat myopia from -4.88 DS to -9.25 DS, an average of (-6.94 ± 1.50) DS with cylinder from 0.50 DC to 3.0 µm DC an average of (1.28 ± 0.73)DC. Their corneal thickness were (527.10 ± 29.05) µm in an average. The patients were followed up for 6 to 10 months with visual acuity, manifest refraction, intraocular pressure, wavefront aberration, corneal topography and optical coherence tomography (OCT). SPSS software was used to analysis. RESULTS: FLEx procedure was done well in every patients without any scanning problem. No infection happened to in the trial. The patients' UCVA improved to 0.6 - 1.2 while BCVA improved 0.7 - 1.2 postoperatively. BCVA improved more than 2 lines in 2 eyes whereas 1 line in 2 eyes. No eye lost BCVA. The difference between pre-and postoperative refraction was within ± 0.75 DS, an average of SE (-0.25 ± 0.33) DS. No epicenter showed in topography. Spherical aberration increased slightly in 8 eyes but decreased in 2 eyes. OCT showed that stroma bed fit to each other very well. CONCLUSION: Femtosecond lenticule extraction appears to be efficiency, safety and predictable for myopia. Femtosecond lenticule extraction could have a good stroma fit. Its wavefront aberration changes need to further investigation.

Processable hybrids of ferrocene-containing poly(phenylacetylene)s and carbon nanotubes: fabrication and properties.

A group of ferrocene-containing poly(phenylacetylene)s (PPAs) with different alkyl spacers were synthesized by using organorhodium complexes [Rh(diene)Cl](2) and Rh (+)(nbd)[C(6)H(5)B (-)(C(6)H(5))(3)] as catalysts. With the aid of pi-pi interactions between the walls of carbon nanotubes (CNTs) and the PPA skeleton together with the ferrocene pendants, the polymer (P 1, P2(5) and P2(10)) chains effectively wrapped round the shells of both single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). The "additive effect" of the PPA skeleton and the ferrocene pendants in dispersing the SWNTs and MWNTs resulted in the generation of highly soluble hybrids. The solubilities of P 1-functionalized SWNTs and MWNTs in tetrahydrofuran (THF) are up to 633 mg/L and 967 mg/L, respectively. They are much higher than the solubilities of M 1-modified SWNTs and MWNTs, which are only 167 mg/L and 133 mg/L in THF. The results indicate the existence of a powerful polymer effect on dispersing CNTs. The high solubilities of the hybrids in organic solvents allowed us to fabricate high-quality and large-area films. Meanwhile, the desirable loading of ferrocene-containing PPAs onto the CNTs offered polymer/CNTs hybrids with multiple redox centers and ferrocene-featured electrochemical properties. The P 1/MWNT hybrid exhibits evident optical-limiting properties. At high incident laser fluence, the optical-limiting power of P 1/MWNT is higher than that of C(60), a well-known optical limiter. Thermal analyses indicate that the decomposition temperatures ( T(d), the temperature at which a sample loses its 5% weight) for P1 and P1/MWNT are 342 and 346 degrees C, respectively, much higher than that for PPA (225 degrees C). Thus the attachment of a ferrocene pendant to a PPA backbone, followed by hybridization with CNTs, improved the thermal stability. Upon pyrolysis, both the polymer and the polymer/CNTs hybrid gave rise to superparamagnetic ceramics; the saturation magnetizations ( M(s)) of the ceramics derived from P1 and P1/MWNT are 29.9 and 26.9 emu/g, respectively. The latter datum is in the list of the best results reported for the magnetic nanocomposites obtained by the attachment of magnetic nanoparticles onto CNTs.

[Correlation of hepatitis B virus infection to non-Hodgkin's lymphoma].

BACKGROUND & OBJECTIVE: Previous studies showed that the infection rate of hepatitis B virus (HBV) is higher in non-Hodgkin's lymphoma (NHL) patients than in non-primary liver cancer solid tumor patients and general population in the same region, but the correlation of HBV infection to NHL is inconclusive. This study was to compare HBV infection rate of NHL patients with that of non-primary liver cancer solid tumor patients, and explore the correlation of HBV infection to NHL. METHODS: The infection of hepatitis B virus surface antigen (HBsAg) in 109 NHL patients and 128 colorectal carcinoma patients was detected. The positive rates of HBsAg in the patients and general population were compared by Chi-square test. RESULTS: The positive rate of HBsAg was significantly higher in NHL patients than in colorectal carcinoma patients and general population (40.4% vs. 14.1% and 17.3%, P<0.01). Regarding colorectal carcinoma patients as a reference group, odds ratio (OR) of NHL in HbsAg-positive population was 2.87, and the 95% confidence interval (95% CI) was 1.830-4.502. CONCLUSION: The positive rate of HBsAg is higher in NHL patients than in colorectal carcinoma patients and general population.

Hybridization of thiol-functionalized poly(phenylacetylene) with cadmium sulfide nanorods: improved miscibility and enhanced photoconductivity.

Molecules of a thiol-functionalized phenylacetylene derivative were assembled on the CdS nanorod surface and copolymerized with phenylacetylene, affording an inorganic semiconductor-conjugated polymer hybrid with excellent solubility and high photoconductivity.

[Regulatory expression of human interferon-gamma gene in murine bone marrow stromal cells by Tet-off system].

BACKGROUND & OBJECTIVE: The Tet-off system is a gene expression regulating system, which has high efficiency, low toxicity and strict turning-off function. This study was to investigate the regulatory expression of human interferon-gamma (IFNgamma) gene in murine bone marrow stromal cells (BMSCs) by Tet-off system. METHODS: Plasmid pTre and human IFNgamma gene were digested using Sac II and Xba I, purified, and ligated by T4 ligase. The recombinant pTre-IFNgamma was identified by restriction analysis and sequencing. pTet-off and pTre-IFNgamma were co-transfected into murine BMSCs. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect IFNgamma mRNA 48 h after transfection. ELISA was used to detect IFNgamma protein in the cell culture medium everyday to analyze the secretary mode of IFNgamma. Then, Tetracycline was added to the culture medium immediately after co-transfection in gradient concentration and 48 h after co-transfection to observe its effect on IFNgamma secretion. RESULTS: Restriction analysis and sequencing confirmed the orientation and sequence of the recombinant plasmid pTre-IFNgamma were correct. RT-PCR detected IFNgamma mRNA in BMSCs 48 h after co-transfection. ELISA showed the secretion of IFNgamma lasted 6 days and a peak appeared in the third 24 h, which was (720.09+/-241.51) pg per 1 x10(6) cells. Increasing tetracycline decreased the secretion of IFNgamma in the first 48 h: 10-100 ng/ml tetracycline decreased the secretion to nearly 0. When tetracycline was added 48 h after co-transfection, the secretion was obviously suppressed 8 h later, and the suppression was strengthened as time went by. CONCLUSION: The Tet-off system can efficiently and rapidly down-regulate the expression of human IFNgamma gene in murine BMSCs.