In vivo bioluminescence imaging of hyperglycemia exacerbating stem cells on choroidal neovascularization in mice

AIM： To investigate the influence of hyperglycemia on the severity of choroidal neovascularization（CNV）,especially the involvement of bone marrow-derived cells（BMCs） and underlying mechanisms.·METHODS： BMCs from firefly luciferase（Fluc）/green fluorescent protein（GFP） double transgenic mice were transplanted into C57BL/6J wide-type mice. The recipient mice were injected intraperitoneally with streptozotocin（STZ） daily for 5 consecutive days to induce diabetes mellitus（DM）, followed by CNV laser photocoagulation.The BMCs recruitment in CNV exposed to hyperglycemia was firstly examined in Fluc/GFP chimeric mice by in vivo optical bioluminescence imaging（BLI） and in vitro Fluc assays. The CNV severity was evaluated by H＆E staining and choroidal flatmount. The expression of vascular endothelial growth factor（VEGF） and stromal cell derived factor-1（SDF-1） was detected by Western blot.·RESULTS： BLI showed that the BMCs exerted dynamic effects in CNV model in Fluc/GFP chimeric mice exposed to hyperglycemia. The signal intensity of transplanted Fluc＋GFP＋BMCs in the DM chimeric mice was significantly higher than that in the control chimeric mice with CNV induction at days 5, 7, 14 and 21（121861.67 ±9948.81 vs 144998.33 ±13787.13 photons/second/cm2/sr for control and DM mice, P5d〈0.05; 178791.67±30350.8 vs240166.67 ±22605.3, P7d〈0.05; 124176.67 ±16253.52 vs196376.67 ±18556.79, P14d〈0.05; 97951.60 ±10343.09 vs119510.00 ±14383.76, P21d〈0.05）, which was consistent with in vitro Fluc assay at day 7 [relative light units of Fluc（RLU1）], 215.00±52.05 vs 707.33±88.65, P 〈0.05; RLU1/relative light units of renilla luciferase（RLU2）, 0.90 ±0.17 vs 1.83 ±0.17, P 〈0.05]. The CNVs in the DM mice were wider than those in the control group at days 5, 7, 14 and21（147.83±17.36 vs 220.33±20.17 μm, P5d〈0.05; 212.17 ±24.63 vs 326.83 ±19.49, P7d〈0.05; 163.17 ±18.24 vs265.17 ±20.55, P14d〈0.05; 132.00 ±10.88 vs 205.33 ±12.98,P21d〈0.05）. The average area of CNV in the DM group was larger at 7d（20688.67±3644.96 vs 32218.00±4132.69 μm2,P 〈0.05）. The expression of VEGF and SDF-1 was enhanced in the DM mice.·CONCLUSION： Hyperglycemia promots the vasculo-genesis of CNV, especially the contribution of BMCs,which might be triggered by VEGF and SDF-1 production.

Quantitative Evaluation of Bioluminescence Imaging Based on Radiative Transfer Equation

Bioluminescence imaging is a kind of emerging detection technology at cellular,molecular and genetic level.The most popular bioluminescence imaging model is diffusion approximation(DA).However,because of the ill-posedness of the DA-based inverse problem and the instability of reconstruction algorithms,the location accuracy of the reconstructed sources is low.Radiative transfer equation(RTE),which considers the direction of the photon migration and the effect of absorption and scattering in tissues,can accurately express the transmission of bioluminescent photons through the tissues.In this paper,we studied the bioluminescence imaging based on the RTE.2D simulations were performed,and quantitative evaluation was given by the absolute source position error,the relative source area error and the minimum bounding box.The results of the experiment showed that the imaging quality based on RTE was better than that one based on DA.

Multiplexed bioluminescence imaging of cancer cell response to hypoxia and inflammation in the caudal-artery injection model of bone metastasis during zoledronic acid treatment

Aim:Therapeutic agents suppressing bone remodeling have been clinically approved to delay metastatic progression and skeletal-related events in patients with bone metastasis.However,therapeutic agents including zoledronic acid(ZA)are insufficient to regress established bone metastasis.Therefore,new treatment strategies are desired,and unraveling the status of cancer cells during bone metastatic progression will help develop therapeutic strategies.Methods:We developed a unique multiplexed reporter system for bioluminescent imaging(MRS-BLI)using three luciferase reporter genes.This system allows for the noninvasive and quantitative monitoring of tumor growth and activities of nuclear factor-kappa B(NF-κB)and hypoxia-inducible factor(HIF),which are the key transcriptional factors in response to inflammation and hypoxia,respectively.PC-3/MRS-BLI,a human prostate cancer cell line that stably retains the MRS-BLI reporter genes,was applied to the caudal-artery injection model of bone metastasis to observe the status of cancer cells during bone metastasis development and ZA treatment(<1 month).Results:MRS-BLI reveals key events during the bone metastasis development:NF-κB and HIF are activated in cancer cells after migration to the bone marrow and are transiently reduced,followed by rapid activation before proliferation begins.ZA treatment suppresses the growth of metastasized cancer cells by suppressing NF-κB and HIF activities that may be indirectly induced by osteoclast activation.Conclusion:By visualizing the NF-κB and HIF activities of PC-3/MRS-BLI in bone,MRS-BLI has enabled new discoveries regarding the regulation of bone metastases.Further analysis of the progression of bone metastases using MRS-BLI may provide important information for developing new therapeutic strategies.

The 9L^(LUC)/Wistar rat glioma model is not suitable for immunotherapy

The availability of a well-characterized animal brain tumor model will play an important role in identifying treatments for human brain tumors. Wistar rats bearing 9L glioma cells can develop solid, well-circumcised tumors, and may be a useful animal model for the evaluation of various therapeutic approaches for gliosarcomas. In this study, the 9L/Wistar rat glioma model was produced by intracerebral implantation of 9L^LUC glioma cells syngenic to Fischer 344 （F344） rats. Bioluminescence imaging showed that tumors progressively grew from day 7 to day 21 in 9L^LUC/F344 rats, and tumor regression was found in some 9L^LUC/Wistar rats. Hematoxylin-eosin staining verified that intracranial tumors were gliomas. Immunohistochemistry results demonstrated that no CD4- and CD8-positive cells were found in the syngeneic 9L^LUC/F344 model. However, many infiltrating CD4- and CD8-positive cells were observed within the tumors of the 9L^LUC/Wistar model. Our data suggests that compared with 9L/F344 rats, 9L glioma Wistar rats may not be suitable for evaluating brain glioma immunotherapies, even though the model induced an immune response and exhibited tumor regression.

Optimizing a high-sensitivity NanoLuc-based bioluminescence system for in vivo evaluation of antimicrobial treatment

Focal and systemic infections are serious threats to human health.Preclinical models enable the development of new drugs and therapeutic regimens.In vivo,animal bioluminescence(BL)imaging has been used with bacterial reporter strains to evaluate antimicrobial treatment effects.However,high-sensitivity bioluminescent systems are required because of the limited tissue penetration and low brightness of the BL signals of existing approaches.Here,we report that NanoLuc(Nluc)showed better performance than LuxCDABE in bacteria.However,the retention rate of plasmid constructs in bacteria was low.To construct stable Staphylococcus aureus reporter strains,a partner protein enolase(Eno)was identified by screening of S.aureus strain USA300 for fusion expression of Nluc-based luciferases,including Nluc,Teluc,and Antares2.Different substrates,such as hydrofurimazine(HFZ),furimazine(FUR),and diphenylterazine(DTZ),were used to optimize a stable reporter strain/substrate pair for BL imaging.S.aureus USA300/Eno-Antares2/HFZ produced the highest number of photons of orange-red light in vitro and enabled sensitive BL tracking of S.aureus in vivo,with sensitivities of approximately 10 CFU from mouse skin and 750 CFU from mouse kidneys.USA300/Eno-Antares2/HFZ was a powerful combination based on the longitudinal evaluation of the therapeutic efficacy of antibiotics.The optimized S.aureus Eno-Antares2/HFZ pair provides a technological advancement for the in vivo evaluation of antimicrobial treatment.

Long-term in vivo chimeric cells tracking in non-human primate

Non-human primates(NHPs)are increasingly used in preclinical trials to test the safety and efficacy of biotech-nology therapies.Nonetheless,given the ethical issues and costs associated with this model,it would be highly advantageous to use NHP cellular models in clinical studies.However,developing and maintaining the naive state of primate pluripotent stem cells(PSCs)remains difficult as does in vivo detection of PSCs,thus limiting biotech-nology application in the cynomolgus monkey.Here,we report a chemically defined,xeno-free culture system for culturing and deriving monkey PSCs in vitro.The cells display global gene expression and genome-wide hypometh-ylation patterns distinct from monkey-primed cells.We also found expression of signaling pathways components that may increase the potential for chimera formation.Crucially for biomedical applications,we were also able to integrate bioluminescent reporter genes into monkey PsCs and track them in chimeric embryos in vivo and in vitro.The engineered cells retained embryonic and extra-embryonic developmental potential.Meanwhile,we generated a chimeric monkey carrying bioluminescent cells,which were able to track chimeric cells for more than 2 years in living animals.Our study could have broad utility in primate stem cell engineering and in utilizing chimeric monkey models forclinical studies.

A versatile Tn7 transposon-based bioluminescence tagging tool for quantitative and spatial detection of bacteria in plants

Investigation of plant-bacteria interactions requires quantification of in planta bacterial titers by means of cumbersome and time-consuming colony-counting assays.Here,we devised a broadly applicable tool for bioluminescence-based quantitative and spatial detection of bacteria in plants.We developed vectors that enable Tn7 transposon-mediated integration of the luxCDABEluciferase operon into a specific genomic location found ubiquitously across bacterial phyla.These vectors allowed for the generation of bioluminescent transformants of various plant pathogenic bacteria from the genera Pseudomonas,Rhizobium(Agrobacterium),and Ralstonia.Direct luminescence measurements of plant tissues inoculated with bioluminescent Pseudomonas syringae pv.tomato DC3000(Pto-lux)reported bacterial titers as accurately as conventional colony-counting assays in Arabidopsis thaliana,Solanum lycopersicum,Nicotiana benthamiana,and Marchantia polymorpha.We further showed the usefulness of our vectors in converting previously generated Pto derivatives to isogenic bioluminescent strains.Importantly,quantitative bioluminescence assays using these Pto-lux strains accurately reported the effects of plant immunity and bacterial effectors on bacterial growth,with a dynamic range of four orders of magnitude.Moreover,macroscopic bioluminescence imaging illuminated the spatial patterns of Pto-lux growth in/on inoculated plant tissues.In conclusion,our vectors offer untapped opportunities to develop bioluminescence-based assays for a variety of plant-bacteria interactions.

Multimodality imaging assessments of response to metformin therapy for breast cancer in nude mice

Background Metformin is the most widely used anti-diabetic drug in the world.An increasing body of evidence shows metformin also blocks cell cycle progression and selectively induces apoptosis via caspase activation in some breast tumor cells.Diffusion-weighted imaging （DWl） and bioluminescence imaging （BLI） have great potential in the evaluation of the early response to cancer therapies.We used DWl and BLI in evaluating the response of breast cancer to metformin.Methods The luciferase-engineered human breast cancer cell line MDA-MB-231 was inoculated into the mammary fat pad of nude mice.Twelve female nude mice bearing tumors were divided into two groups.The mice in the treatment group received metformin （2 mg/ml in drinking water daily） after tumor inoculation,and the mice in the control group were offered drinking water without any drug added.We performed 7T magnetic resonance imaging and optical imaging every week.Imaging included T1-and T2-weighted imaging,DWl,and BLI.After imaging.The tumors were collected and subjected to histological analysis.Results The mean photons/second of tumors in the treatment group was （3.00±0.43）×106 at day one,（1.01±0.14）×107 at 2 weeks,（5.79±1.42）×107 at 4 weeks,and （2.33±0.70）×107 at 8 weeks.The mean photons/second of tumors in the control group was （3.29±0.59）×106 at day one,（3.59±0.63）×107 at 2 weeks,（3.87±0.56）×108 at 4 weeks,and （4.12±1.72）x108 at 8 weeks.Compared to the control group,the treatment group showed an obvious decrease in the mean bioluminescence （photons/s） of the tumors and fewer metastases.Histological examination confirmed the presence of fewer metastases.DWI showed the apparent diffusion coefficient （ADC） value of the tumors; the mean ADC value was （0.9287±0.04346）x10-3 mm2/s in the treated tumors and （0.7553±0.01804）x103 mm2/s in the untreated tumors.The ADC value of tumors in the treatment group was significantly higher than the control tumors （P=0.0013）.Conclusions The growth and metastasis of MDA-MB-231 breast cancer may be inhibited by metformin.DWI and BLI have great potentials in the evaluation of the early response to metformin treatment.BLI has a high degree of sensitivity and is able to detect micrometastasis,thus can be used for identifying tumor metastasis in vivo.

Luminescence of coelenterazine derivatives with C-8 extended electronic conjugation

Replacement of the methylene group at the C-8 position with an extended electronic conjugation is a new promising method to develop red-shifted coelenterazine derivatives. In this paper, we have described an oxygen-containing coelenterazine derivative with a significant red-shifted（63 nm）bioluminescence signal maximum relative to coelenterazine 400a（Deep Blue C^（TM）, 1）. In cell imaging, the sulfur-containing coelenterazine derivative displayed a significantly（1.77 ± 0.09;P≤0.01） higher luminescence signal compared to coelenterazine 400 a and the oxygen-containing coelenterazine derivative exhibited a slightly（0.74 ± 0.08; P≤0.05） lower luminescence signal. It is beneficial to understand further the underlying mechanisms of bioluminescence.

AAV6 as an effective gene delivery vector for prolonged transgene expression in intervertebral disc cells in vivo

Intervertebral disc degeneration is the main contributor to low back pain,now the leading cause of disability worldwide.Gene transfer,either in a therapeutic attempt or in basic research to understand the mechanisms of disc degeneration,is a fascinating and promising tool to manipulate the complex physiology of the disc.Viral vectors based on the adeno-associated virus(AAV)have emerged as powerful transgene delivery vehicles yet a systematic investigation into their respective tropism,transduction efficiency,and relative toxicity have not yet been performed in the disc in vivo.Herein,we used in vivo bioluminescence imaging to systematically compare multiple AAV serotypes,injection volumes,titers,promoters,and luciferase reporters to determine which result in high transduction efficiency of murine nucleus pulposus(NP)cells in vivo.We find that AAV6 using a CAG promoter to drive transgene expression,delivered into the NP of murine caudal discs at a titer of 1011 GC/mL,provides excellent transduction efficiency/kinetics and low toxicity in vivo.We also show,for the first time,that the transduction of NP cells can be significantly boosted in vivo by the use of small cell permeabilization peptides.Finally,to our knowledge,we are the first to demonstrate the use of optical tissue clearing and three-dimensional lightsheet microscopy in the disc,which was used to visualize fine details of tissue and cell architecture in whole intact discs following AAV6 delivery.Taken together,these data will contribute to the success of using AAV-mediated gene delivery for basic and translational studies of the IVD.