Near-infrared Fluorescence Imaging Technique Research Articles

Preliminary exploration of hepatic parenchymal near-infrared fluorescence imaging technique via retrograde biliary approach: a feasibility study (with video)

This paper explores the feasibility and principle of hepatic parenteral fluorescence imaging technology after retrograde injection of indocyanine green (ICG) through endoscopic nasobiliary drainage (ENBD). The data were collected from 53 patients with cholecystolithiasis and choledocholithiasis, from October 2022 to March 2023, diagnosed by fluorescence imaging technique retrograde biliary approach (FIT-RB). We divided the patients into two groups according to the features of liver parenchyma, the poor group (n = 34, including scattered or no imaging) and the good group (n = 19, regular uniform imaging). We compared and analyzed the perioperative results of the two groups and explored the influencing factors of the success of FIT-RB and the ICG concentration suitable for this imaging technique. The good imaging rate of the 53 enrolled cases was 35.8%. The bilirubin level before ENBD and laparoscopic cholecystectomy in the poor group was significantly higher than that in the good group (P < 0.001). The proportion of higher ICG concentrations (0.5 mg/mL) was significantly higher in the good group (P = 0.028). Our results demonstrated that the success rate of good imaging was 4.53 times higher than that of low-dose ICG (0.125 or 0.25 mg/L) cases at 0.5 mg/ml of ICG. The level of total bilirubin and direct bilirubin were negatively correlated with the imaging effect, and total bilirubin and direct bilirubin levels were important predictors of the efficacy of FIT-RB. FIT-RB is safe and feasible in patients with low site bilirubin levels. An ICG concentration of 0.5 mg/ml may be ideal for implementing this technique.

Evaluation of testicular blood flow during testicular torsion surgery in children using the indocyanine green-guided near-infrared fluorescence imaging technique.

This study investigates the feasibility of the indocyanine green-guided near-infrared fluorescence (ICG-NIRF) imaging technique in evaluating testicular blood flow during testicular torsion (TT) surgery in pediatric cases. We retrospectively analyzed the eight pediatric patients with TT who underwent surgery in our hospital between February and July 2023. The intraoperative two-step method of ICG-NIRF imaging and testicular incision was used to evaluate the testicular blood flow, followed by a selection of different surgical methods. The removed testes were pathologically examined after surgery, and all patients were followed up 1 month after surgery to evaluate testicular blood flow using gray-scale ultrasound and color Doppler flow imaging (CDFI). Eight pediatric TT patients aged 1-16 years, with a median age of 11.5 years, were enrolled. Time from the onset ranged from 4 to 72 h (mean 26.13 ± 25.09 h). A total of eight testes were twisted, including four on the left side and four on the right side. The twisting direction of the testes was clockwise in four cases and counterclockwise in four cases. The rotation of torsion was 180°-1,080° (mean 472.5° ± 396°). There was no statistically significant difference in the imaging time between the four patients with testicular blood vessel imaging on both the torsional and normal sides (P > 0.05). The postoperative recovery was uneventful, with no complications during the follow-up period of 1 month. The postoperative histopathological results of three patients who underwent orchiectomy showed extensive hemorrhage, degeneration, and necrosis of the testicular tissue. Among the five patients who underwent orchiopexy, a gray-scale ultrasound and CDFI examinations showed uniform internal echo of the testes and normal blood flow signals in four patients. One patient with no testicular blood vessel imaging on the torsional side showed uneven internal echo of the testis and no blood flow signals. ICG-NIRF imaging is a feasible method to evaluate testicular blood flow during TT surgery. Testicular blood vessel imaging within 5 minutes after ICG injection might be the basis for testicular retention during TT surgery.

Sentinel Node Biopsy for Endometrial Cancer by Retroperitoneal Transvaginal Natural Orifice Transluminal Endoscopic Surgery: A Preliminary Study.

ObjectiveThe primary objective was to determine the intraoperative and postoperative surgical complications of sentinel lymph node biopsy (SLNB) by retroperitoneal transvaginal natural orifice transluminal endoscopic surgery (vNOTES). The secondary objective was to assess the feasibility of this surgical technique.MethodsThis was a descriptive study realized in a non-university hospital in Switzerland. Seven patients with endometrial cancer or endometrial complex atypical hyperplasia underwent surgical staging with SLNB by retroperitoneal vNOTES using an indocyanine green-based near-infrared fluorescence imaging technique (October 2021–February 2022).ResultsThe median operative time was 113 (81–211) minutes. The median estimated blood loss was 20 (20–400) mL. The overall bilateral detection rate was 100% (7/7). Upon histopathological examination, 5 patients presented an endometrial adenocarcinoma, and we found endometrial complex atypical hyperplasia in 2 cases. We successfully completed all procedures without significant intraoperative complications, but 1 case required conversion to conventional laparoscopy. The median postoperative stay was 2 (2–4) days, and we observed no postoperative complications during this period. We observed 1 case of postoperative deep vein thrombosis and an asymptomatic vaginal vault hematoma in the same patient.ConclusionsOur preliminary study suggests that retroperitoneal vNOTES could be a feasible, safe, and valuable approach to perform SLNB in endometrial cancer. However, strong evidence of its feasibility, the effective benefits, and the long-term oncological outcomes is needed before expanding the use of vNOTES in endometrial cancer outside study settings.

A narrative review of indocyanine green near-infrared fluorescence imaging technique: a new application in thoracic surgery

: In clinical work of thoracic surgery, accurate anatomic location of pulmonary nodules, precise demarcation of segmental and sub-segmental plane, tracing of sentinel lymph nodes (SLNs), protection of thoracic nerve, averting of anastomotic fistula etc. always puzzling the surgeons. Indocyanine green (ICG) is a near-infrared fluorescence (NIRF) contrast agent that is the only reagent approved by the Food and Drug Administration (FDA) for use in human subjects due to its low toxicity and high absorbance in the near-infrared spectrum. The application of ICG NIRF imaging technology in surgery is safe and feasible, it can offer real-time fluorescing information and help surgeons make important decisions during surgery. Many studies demonstrated that ICG NIRF can be used to determine tissue perfusion, lymphatic reflux and other fields. In recent years, it has been reported in the field of thoracic surgery and got success. It can provide more information compared to conventional video-assisted thoracoscopic surgery (VATS). In this review, the research results of this technique in animal models and clinical trials in recent years are reviewed the application of ICG NIRF technique in accurate positioning of pulmonary nodules, precise demarcation of segmental and sub-segmental plane, SLNs tracing, thoracic nerve protection, anastomotic leakage and chylothorax prevention.

Technological evolution of laparoscopic gastrointestinal surgery in China

After 30 years of development in China, laparoscopic gastrointestinal surgery has been widely accepted and popularized. In recent years, the application of a series of novel technologies, such as 3D laparoscopic system, 4k high-definition laparoscopy, near-infrared fluorescence imaging technique and telesurgery with 5G wireless system has injected new vitality to the laparoscopic gastrointestinal surgery in new era. It also well contributes to the further promotion and standardization of minimally invasive gastrointestinal surgery. This article reviews the application and development of novel techniques in minimally invasive gastrointestinal surgery. It is concluded that great progress has been made in clinical application of minimally invasive gastrointestinal surgery in China. In terms of surgical technology and equipment development, the period of mechanical imitation has passed and a new era focusing on innovation and originality is coming in China. The authors believe that Chinese laparoscopic gastrointestinal surgeons should remember their original intention, insist on the patient-centered concept in diagnosis and treatment, maintain innovative thinking and attitude and thus, push the development of minimally invasive gastrointestinal surgery to a new height in China.

Dynamic evaluation of the protective effect of Dendrobium officinale polysaccharide on acute alcoholic liver injury mice in vitro and in vivo by NIR fluorescence imaging.

Acute alcoholic liver injury (AALI) is a threat to human health. Dendrobium officinale polysaccharide (DOP) has the potential to protect the liver by enhancing the anti-oxidative system to maintain the relative balance of ROS (active oxygen species) and antioxidants in AALI mice. However, the dynamic improvement effect of DOP on AALI is still not clear and accurate medication guidance is not available, which limits the clinical application of DOP. Because of the advantages of high sensitivity, noninvasiveness, and visualization, near-infrared (NIR) fluorescence imaging has been widely studied in biochemistry and biomedicine. As the glutathione (GSH) level in the liver is closely related to the progression of AALI, herein, an NIR fluorescent probe for GSH, HCG was used to dynamically evaluate the effect of DOP on AALI mice. In this study, DOP was proven to maintain the relative balance of GSH content in the liver to protect it from damage. To the best of our knowledge, it is the first time to assess the effect of DOP on AALI mice through a NIR fluorescence imaging technique. This study may also provide a potential NIR imaging agent for the clinical research to improve the management of liver injury-related diseases.

3D Printing and NIR Fluorescence Imaging Techniques for the Fabrication of Implants.

Three-dimensional (3D) printing technology holds great potential to fabricate complex constructs in the field of regenerative medicine. Researchers in the surgical fields have used 3D printing techniques and their associated biomaterials for education, training, consultation, organ transplantation, plastic surgery, surgical planning, dentures, and more. In addition, the universal utilization of 3D printing techniques enables researchers to exploit different types of hardware and software in, for example, the surgical fields. To realize the 3D-printed structures to implant them in the body and tissue regeneration, it is important to understand 3D printing technology and its enabling technologies. This paper concisely reviews 3D printing techniques in terms of hardware, software, and materials with a focus on surgery. In addition, it reviews bioprinting technology and a non-invasive monitoring method using near-infrared (NIR) fluorescence, with special attention to the 3D-bioprinted tissue constructs. NIR fluorescence imaging applied to 3D printing technology can play a significant role in monitoring the therapeutic efficacy of 3D structures for clinical implants. Consequently, these techniques can provide individually customized products and improve the treatment outcome of surgeries.

Methods of Granulocyte Isolation from Human Blood and Labeling with Multimodal Superparamagnetic Iron Oxide Nanoparticles.

This in vitro study aimed to find the best method of granulocyte isolation for subsequent labeling with multimodal nanoparticles (magnetic and fluorescent properties) to enable detection by optical and magnetic resonance imaging (MRI) techniques. The granulocytes were obtained from venous blood samples from 12 healthy volunteers. To achieve high purity and yield, four different methods of granulocyte isolation were evaluated. The isolated granulocytes were labeled with multimodal superparamagnetic iron oxide nanoparticles (M-SPIONs) coated with dextran, and the iron load was evaluated qualitatively and quantitatively by MRI, near-infrared fluorescence (NIRF) and inductively coupled plasma mass spectrometry (ICP-MS). The best method of granulocyte isolation was Percoll with Ficoll, which showed 95.92% purity and 94% viability. After labeling with M-SPIONs, the granulocytes showed 98.0% purity with a yield of 3.5 × 106 cells/mL and more than 98.6% viability. The iron-loading value in the labeled granulocytes, as obtained by MRI, was 6.40 ± 0.18 pg/cell. Similar values were found with the ICP-MS and NIRF imaging techniques. Therefore, our study shows that it is possible to isolate granulocytes with high purity and yield and labeling with M-SPIONs provides a high internalized iron load and low toxicity to cells. Therefore, these M-SPION-labeled granulocytes could be a promising candidate for future use in inflammation/infection detection by optical and MRI techniques.

Preparation, Characterization, and Pharmacokinetic Study of a Novel Long-Acting Targeted Paclitaxel Liposome with Antitumor Activity.

BackgroundBreast cancer is the leading cause of cancer death in women. Chemotherapy to inhibit the proliferation of cancer cells is considered to be the most important therapeutic strategy. The development of long-circulating PEG and targeting liposomes is a major advance in drug delivery. However, the techniques used in liposome preparation mainly involve conventional liposomes, which have a short half-life, high concentrations in the liver and spleen reticuloendothelial system, and no active targeting.MethodsFour kinds of paclitaxel liposomes were prepared and characterized by various analytical techniques. The long-term targeting effect of liposomes was verified by fluorescence detection methods in vivo and in vitro. Pharmacokinetic and acute toxicity tests were conducted in ICR mice to evaluate the safety of different paclitaxel preparations. The antitumor activity of ES-SSL-PTX was investigated in detail using in vitro and in vivo human breast cancer MCF-7 cell models.ResultsER-targeting liposomes had a particle size of 137.93±1.22 nm and an acceptable encapsulation efficiency of 88.07±1.25%. The liposome preparation is best stored at 4°C, and is stable for up to 48 hrs. Cytotoxicity test on MCF-7 cells demonstrated the stronger cytotoxic activity of liposomes in comparison to free paclitaxel. We used the near-infrared fluorescence imaging technique to confirm that ES-SSL-PTX was effectively targeted and could quickly and specifically identify the tumor site. Pharmacokinetics and acute toxicity in vivo experiments were carried out. The results showed that ES-SSL-PTX could significantly prolong the half-life of the drug, increase its circulation time in vivo, improve its bioavailability and reduce its toxicity and side effects. ES-SSL-PTX can significantly improve the pharmacokinetic properties of paclitaxel, avoid allergic reaction of the original solvent, increase antitumor efficacy and reduce drug toxicity and side effects.ConclusionES-SSL-PTX has great potential for improving the treatment of breast cancer, thereby improving patient prognosis and quality of life.

Targeted Near-Infrared Fluorescence Imaging for Regenerative Medicine

Advances in tissue engineering and regenerative medicine over the last three decades have made great progress in the development of diagnostic and therapeutic methodologies for damaged tissues. However, regenerative medicine is still not the first line of treatment for patients due to limited understanding of the tissue regeneration process. Therefore, it is prerequisite to develop molecular imaging strategies combined with appropriate contrast agents to validate the therapeutic progress of damaged tissues. The goal of this review is to discuss the progress in the development of near-infrared (NIR) contrast agents and their biomedical applications for labeling cells and scaffolds, as well as monitoring the treatment progress of native tissue in living organisms. We also discuss the design consideration of NIR contrast agents for tissue engineering and regenerative medicine in terms of their physicochemical and optical properties. The use of NIR imaging system and targeted contrast agents can provide high-resolution and high sensitivity imaging to track/monitor the in vivo fate of administered cells, the degradation rate of implanted scaffolds, and the tissue growth and integration of surrounding cells during the therapeutic period. NIR fluorescence imaging techniques combined with targeted contrast agents can play a significant role in regenerative medicine by monitoring the therapeutic efficacy of implanted cells and scaffolds which would enhance the development of cell therapies and promote their successful clinical translations.

Methylene Blue-Based Near-Infrared Fluorescence Imaging for Breast Cancer Visualization in Resected Human Tissues.

Breast-conserving surgery is facing the challenge of objective tumor margin identification intraoperatively. Near-infrared fluorescence imaging would be an ideal approach to visualize tumor margins during surgeries. In this preliminary study, the feasibility of methylene blue–based near-infrared fluorescence imaging technique for breast cancer detection was assessed in resected human breast specimens after breast cancer surgeries. Thirty patients with breast cancer scheduled for surgical treatment were enrolled, including 10 patients with preoperative chemotherapy and 20 patients without. Each of them received an injection of 1 mg/kg methylene blue intravenously 3 hours before the surgery. Then, a home-developed methylene blue–specific near-infrared fluorescence imaging system was employed to image the resected breast tissues and identify the tumor by the fluorescence contrast. Specimens were taken for pathological examinations as the reference. There were no severe adverse events attributable to methylene blue. Of 20 patients, who did not receive preoperative chemotherapy, 16 exhibited fluorescent contrast on their resected tissues (signal-to-background ratio: 1.94 ± 0.71). In contrast, tumors were identified in 3 of 10 specimens from patients who underwent preoperative chemotherapy (signal-to-background ratio: 1.63 ± 0.38). A total of 35 tissues were sampled from 30 specimens. Besides 30 tumor samples, 5 more suspicious samples with fluorescence signal were confirmed to be benign hemorrhagic tissues. Therefore, a sensitivity of 0.63 and a positive predictive value of 0.79 were achieved by the methylene blue fluorescence imaging strategy. Here, we demonstrate the feasibility of using methylene blue fluorescence imaging to identify breast cancer. Preoperative chemotherapy had an impact on imaging effect, which may reduce the detection rate. After all, methylene blue fluorescence imaging has great potential to be used into breast-conserving surgery for tumor-positive margins detection, but further clinical trial study is needed (http://www.chictr.org.cn/ Clinical Trial Registry ID: ChiCTR1800015400, Near-infrared fluorescence imaging applied in breast cancer identification with methylene blue).

Application of Sentinel Lymph Node Technique to Transvaginal Natural Orifices Transluminal Endoscopic Surgery in Endometrial Cancer

Study ObjectiveThis report outlines our first experience of sentinel lymph node (SLN) mapping in the natural orifices transluminal endoscopic surgery (NOTES) technique, which is the combination of the least invasive surgical approach and the least invasive way of assessing lymph node status. DesignDescriptive study (Canadian Task Force classification III). SettingTertiary referral and educational center. PatientsFour patients with endometrial cancer clinical stage 1. InterventionsNOTES with SLN mapping using an indocyanine green–based near-infrared fluorescence imaging technique. Measurements and Main ResultsThe average operative time was 182.75 minutes (standard deviation, 34.5). Mean estimated blood loss was 67.5 mL (standard deviation, 39.4). All patients had surgical staging of International Federation of Gynecology and Obstetrics stage IA (pT1aN0). The overall detection rate and bilateral detection rate were 100% (4/4). All procedures were successfully completed without complication or conversion to conventional laparoscopy. ConclusionIn our preliminary experience, SLN mapping in NOTES surgery appears to be feasible and safe. It can be considered as an alternative method to reduce morbidity from radical lymphadenectomy and provide the benefits from the NOTES technique. However, studies in a larger population are necessary.

Real-time in vivo imaging of metastatic bone tumors with a targeted near-infrared fluorophore.

Tumors of the prostate or breast are particularly likely to metastasize to the bone, and early diagnosis of metastatic bone tumors is important for designing an effective treatment strategy. Imaging modalities for the detection of bone metastasis are limited, and radiation-based techniques are commonly used. Here, we investigated the efficacy of selective near-infrared (NIR) fluorescence detection of metastatic bone tumors and its role in the detection of bone metastasis in prostate and breast cancer cell lines and in a xenograft mouse model. A targeted NIR fluorophore was used to monitor metastatic bone tumors using a NIR fluorescence imaging system in real time, enabling the diagnosis of bone metastasis in vivo by providing the location of the metastatic bone tumor. The NIR fluorescence imaging technique using targeted NIR contrast agents is a potential tool for the early diagnosis of bone tumors.

In vivo near-infrared fluorescence imaging of Leishmania amazonensis expressing infrared fluorescence protein (iRFP) for real-time monitoring of cutaneous leishmaniasis in mice

The use of Leishmania amazonensis-infected BALB/c mice is an important model for the study of experimental cutaneous leishmaniasis. Here we report the development of a non-invasive method to directly evaluate and measure parasite burden during the course of the infection, based on the near-infrared fluorescence detection of a recombinant L. amazonensis strain. So, we generated a L. amazonensis strain that stably expresses the near-infrared protein (iRFP) gene and compared the maintenance of its vitro and in vivo characteristics, such as fitness, pathogenicity and fluorescence emission. After that, we followed the disease development, as well as the parasite burden in BALB/c mice footpads infected with L. amazonensis-iRFP, by using an in vivo near-infrared fluorescence scanner. In vitro results showed a linear correlation between the fluorescence emission and the number of parasites. The in vivo study showed that the use of iRFP-transfected L. amazonensis enables the monitoring of parasite burden by measuring fluorescence signals. Therefore, this technique can be confidently used to directly monitor parasitic load and infection overtime and could be an excellent tool for in vitro and in vivo screening of anti-leishmanial drugs and vaccine efficiency. This is the first report of the use of the near-infrared fluorescence imaging technique for monitoring in vivo cutaneous leishmaniasis.

Near-infrared fluorescence cholangiography assisted laparoscopic cholecystectomy versus conventional laparoscopic cholecystectomy (FALCON trial): study protocol for a multicentre randomised controlled trial

IntroductionMisidentification of the extrahepatic bile duct anatomy during laparoscopic cholecystectomy (LC) is the main cause of bile duct injury. Easier intraoperative recognition of the biliary anatomy may be accomplished by...

Study on intralymphatic-targeted hyaluronic acid-modified nanoliposome: Influence of formulation factors on the lymphatic targeting

In this study, hyaluronic acid-modified docetaxel-loaded liposomes were prepared to evaluate the lymphatic targeting after subcutaneous administration, and formulation factors affecting the lymphatic targeting were examined, including free hyaluronic acid, molecular weight, hyaluronic acid-density and particle diameter. The high molecular weight hyaluronic acid-modified docetaxel-loaded liposomes (HA-LPs) and low molecular weight hyaluronic acid-modified docetaxel-loaded liposomes (LMWHA-LPs) were prepared via electrostatic attraction. The physicochemical properties and in vitro drug release were evaluated. The lymphatic drainage and the lymph node uptake were investigated by pharmacokinetics and distribution recovery of docetaxel in lymph nodes, injection site and plasma. The lymphatic targeting ability of optimized Cy7-loaded LMWHA-LPs (LMWHA-LPs/Cy7) was evaluated by near-infrared fluorescence imaging technique. The result showed that HA-LPs and LMWHA-LPs with suitable and stable physicochemical properties could be used for in vivo lymphatic targeting studies. Hyaluronic acid-modified liposome significantly increased the docetaxel recovery in lymph nodes, and displayed higher AUC(0-24h) and longer retention time compared to unmodified liposomes in vivo. In contrast, the presence of free hyaluronic acid hindered the lymphatic drainage and increased the plasma-drug concentration. Importantly, LMWHA-modification improved lymphatic drainage and lymph node uptake of liposomes compared with HA-modification. And Lymph node uptake of LMWHA-LPs depended mainly on LMWHA-density instead of particle size. The results of in vivo imaging showed that LMWHA-LPs/Cy7 significantly located in the lymphatic system. And both DTX-loaded and Cy7-loaded LMWHA-LPs had similar and stable lymphatic target level. Our investigation showed that LMWHA-LPs were a highly promising lymphatic targeting carrier for chemotherapy drugs and diagnostic fluorescence agents.

Theranostic nanoparticles based on PEGylated hyaluronic acid for the diagnosis, therapy and monitoring of colon cancer

Colon cancer is the second leading cause of cancer-related death in the United States. The considerable mortality from colon cancer is due to metastasis to other organs, mainly the liver. In the management of colon cancer, early detection and targeted therapy are crucial. In this study, we aimed to establish a versatile theranostic system for early tumor detection and targeted tumor therapy by using poly(ethylene glycol)-conjugated hyaluronic acid nanoparticles (P-HA-NPs) which can selectively accumulate in tumor tissue. For the diagnostic application, a near-infrared fluorescence (NIRF) imaging dye (Cy 5.5) was chemically conjugated onto the HA backbone of P-HA-NPs. After intravenous injection of Cy5.5-P-HA-NPs into the tumor-bearing mice, small-sized colon tumors as well as liver-implanted colon tumors were effectively visualized using the NIRF imaging technique. For targeted therapy, we physically encapsulated the anticancer drug, irinotecan (IRT), into the hydrophobic cores of P-HA-NPs. Owing to their notable tumor targeting capability, IRT-P-HA-NPs exhibited an excellent antitumor activity while showing a reduction in undesirable systemic toxicity. Importantly, we demonstrated the theranostic application using Cy5.5-P-HA-NPs and IRT-P-HA-NPs in orthotopic colon cancer models. Following the systemic administration of Cy5.5-P-HA-NPs, neoplasia was clearly visualized, and the tumor growth was effectively suppressed by intravenous injection of IRT-P-HA-NPs. It should be emphasized that the therapeutic responses could be simultaneously monitored by Cy5.5-P-HA-NPs. Our results suggest that P-HA-NPs can be used as a versatile theranostic system for the early detection, targeted therapy, and therapeutic monitoring of colon cancer.

Polysaccharide-based near-infrared fluorescence nanoprobes for cancer diagnosis.

Near-infrared fluorescence (NIRF) imaging is most exciting and rapidly progressing area for sensitive cancer detection at the early stage and management of tumors. Recent advances of nanobiotechnology allow researchers to combine new nanoprobes with NIRF imaging techniques. Among a variety of nanomaterials, polysaccharide-based nanoparticles have been extensively investigated for biomedical applications due to their biocompatibility and biodegradability, cost effectiveness, and the ease of modifications, and so on. The main focus of this article is to describe the targeting approaches (i.e., passive targeting via enhanced permeability and retention effects and microenvironments, and active targeting) of polysaccharide-based NIRF nanoprobes, and review their primary applications for cancer in vivo molecular imaging.

Intracerebral, but not intravenous, transplantation of bone marrow stromal cells enhances functional recovery in rat cerebral infarct: An optical imaging study

Recent studies have indicated that bone marrow stromal cells (BMSC) may improve neurological function when transplanted into an animal model of CNS disorders, including cerebral infarct. However, there are few studies that evaluate the therapeutic benefits of intracerebral and intravenous BMSC transplantation for cerebral infarct. This study was aimed to clarify the favorable route of cell delivery for cerebral infarct in rats. The rats were subjected to permanent middle cerebral artery occlusion. The BMSC were labeled with near infrared (NIR)-emitting quantum dots and were transplanted stereotactically (1 × 10⁶ cells) or intravenously (3 × 10⁶ cells) at 7 days after the insult. Using in vivo NIR fluorescence imaging technique, the behaviors of BMSC were serially visualized during 4 weeks after transplantation. Motor function was also assessed. Immunohistochemistry was performed to evaluate the fate of the engrafted BMSC. Intracerebral, but not intravenous, transplantation of BMSC significantly enhanced functional recovery. In vivo NIR fluorescence imaging could clearly visualize their migration toward the cerebral infarct during 4 weeks after transplantation in the intracerebral group, but not in the intravenous, group. The BMSC were widely distributed in the ischemic brain and some of them expressed neural cell markers in the intracerebral group, but not in the intravenous group. These findings strongly suggest that intravenous administration of BMSC has limited effectiveness at clinically relevant timing and intracerebral administration should be chosen for patients with ischemic stroke, although further studies would be warranted to establish the treatment protocol.

Near-Infrared Fluorescence Labeling Allows Noninvasive Tracking of Bone Marrow Stromal Cells Transplanted Into Rat Infarct Brain

Noninvasive imaging techniques would be needed to validate the therapeutic benefits of cell transplantation therapy for central nervous system disorders. To evaluate whether near-infrared (NIR)-emitting fluorescence tracer, quantum dots, would be useful to noninvasively visualize the bone marrow stromal cells (BMSC) transplanted into the infarct brain in living animals. Rat BMSCs were labeled with QD800. In vitro and in vivo conditions to visualize NIR fluorescence were precisely optimized. The QD800-labeled BMSCs were stereotactically transplanted into the ipsilateral striatum of the rats subjected to permanent middle cerebral artery occlusion 7 days after the insult. Using the NIR fluorescence imaging technique, the behaviors of BMSCs were serially visualized during the 8 weeks after transplantation. NIR fluorescence imaging could noninvasively detect the NIR fluorescence emitted from the transplanted BMSCs engrafted in the peri-infarct neocortex through the scalp up to 8 weeks after transplantation. The intensity gradually increased and reached the peak at 4 weeks. The results were supported by the findings on ex vivo NIR fluorescence imaging and histological analysis. NIR fluorescence imaging is valuable in monitoring the behaviors of donor cells in the rodent brain. The results would allow new opportunities to develop noninvasive NIR fluorescence imaging as a modality to track the BMSCs transplanted into the brain.