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. 2024 Jul 26;7(8):2350–2357. doi: 10.1021/acsptsci.4c00175

MicroPET Imaging of Riboflavin Transporter 3 Expression in Myocardial Infarction/Reperfusion Rat Models with Radiofluorinated Riboflavin

Jindian Li †,‡, Xingfang Hong §, Yingxi Chen ‡, Bin Yin ⊥, Hongzhang Yang ‡, Changrong Shi ‡, Xinying Zeng ‡, Deliang Zhang #,*, Zhide Guo ‡,*, Xianzhong Zhang ∥,*
PMCID: PMC11320726  PMID: 39144563

Abstract

graphic file with name pt4c00175_0006.jpg

Riboflavin transporter 3 (RFVT3) represents a potential cardioprotective biotarget in energetic metabolism reprogramming after myocardial infarction/reperfusion (MI/R). This study investigated the feasibility of noninvasive real-time quantification of RFVT3 expression after MI/R with an radiolabeled probe 18F-RFTA in a preclinical rat model of MI/R. The tracer 18F-RFTA was radio-synthesized manually and characterized on the subjects of radiolabeling yield, radiochemical purity, and stability in vivo. MI/R and sham-operated rat models were confirmed by cardiac magnetic resonance imaging (cMRI) and single-photon-emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with technetium-99m sestamibi (99mTc-MIBI). Positron emission tomography (PET) imaging of MI/R and sham-operated rat models were conducted with 18F-RFTA. Ex vivo autoradiography and RFVT3 immunohistochemical (IHC) staining were conducted to verify the RFVT3 expression in infarcted and normal myocardium. 18F-RFTA injection was prepared with high radiochemical purity (>95%) and kept stable in vitro and in vivo. 18F-RFTA PET revealed significant uptake in the infarcted myocardium at 8 h after reperfusion, as confirmed by lower 99mTc-MIBI perfusion and decreased intensity of cMRI. Conversely, there were only the tiniest uptakes in the normal myocardium and blocked infarcted myocardium, which was further corroborated by ex vivo autoradiography. The RFVT3 expression was further confirmed by IHC staining in the infarcted and normal myocardium. We first demonstrate the feasibility of imaging RFVT3 in infarcted myocardium. 18F-RFTA is an encouraging PET probe for imaging cardioprotective biotarget RFVT3 in mitochondrial energetic metabolism reprogramming after myocardial infarction. Noninvasive imaging of cardioprotective biotarget RFVT3 has potential value in the diagnosis and therapy of patients with MI.

Keywords: myocardial infarction, PET imaging, riboflavin transporter 3, radiopharmaceuticals, radiofluorinated riboflavin

Myocardial infarction (MI) is a major cause of death and disability worldwide.1 Despite advances in antithrombotic and antiplatelet therapies, there remains much progress to be made in molecular precise-targeted diagnosis and therapy based on diverse biological processes to promote heart regeneration and repair of postmyocardial infarction.2 Cardiometabolic biomarkers are very important for the remission of MI via behavioral and/or pharmacological intervention. New cardiometabolic biomarkers may also determine patients who will benefit from the specific interventions.3 Molecular imaging offers a new way to identify novel biomarkers of risk and/or cardioprotection, which may contribute to predicting clinical benefit (or harm) and facilitate the discovery of new drugs.

Molecular imaging, especially nuclear medicine imaging, can determine how specific proteins or pathways function in myocardial infarction biology, thereby contributing to the early diagnosis and effective treatment of patients with MI.4 Integrin αvβ3 antagonist 18F-galacto-RGD can evaluate the integrin expression for the monitoring of angiogenesis after myocardial infarction.5 CXCR4-targeted 68Ga-pentixafor can reflect the time window of CXCR4 expression of inflammatory cells in the infarct region.6 In addition, representative myocardial perfusion imaging (MPI) agents 18F-FP1OP and phosphonium salt 18F-FMBTP reveal good images and correlation to blood flow but cannot give the biological information on repair, protection, and regeneration postmyocardial infarction.7,8 Thus, more biomarkers reflecting myocardial protection and repair and matching specialized tracers are required to improve individualized therapy.

The riboflavin transporter 3 (RFVT3) protein encoded by SLC52A3 was unknown until 2009,9 which is significantly overexpressed under pathological status, especially in angio-cardiopathies,10 cancers,11,12 and nervous system diseases.13 Riboflavin (RF, Figure 1a) is a key ingredient of cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) for the production of adenosine triphosphate such as the oxidative phosphorylation and tricarboxylic acid cycle.14 Moreover, these flavoenzymes not only reduce the production of proinflammatory mediators and oxygen radicals against reperfusion oxidative injury in myocardial infarction and cardiac allotransplantation15,16 but also accelerate protein folding and DNA repair.17,18 Recently, the role of RFVT3 in cardiovascular disease has been focused on. RF metabolism demonstrated significant increases during the cardiac regeneration period from 1-day-old and 7-day-old newborn mice as well as FMN and FAD.19 Moreover, the administration of RF and multivitamins in patients with cardiovascular disease can reduce the rate of pooled arteriosclerotic cardiovascular disease outcomes in a phase II/III clinical trial (NCT00064753). Therefore, RFVT3 is a potential and valuable new target or cardiometabolic predictor for the diagnosis and therapy of cardiovascular diseases, especially myocardial infarction. Nuclear medicine imaging of RFVT3 may have potential value in the diagnosis and treatment guidance of patients with MI. In our previous study, we first proposed RFVT3 as a novel biotarget for nuclear medicine imaging to evaluate the reprogramming of mitochondrial energetic metabolism, and a series of probes such as 131I-RFLA and 18F-RFTA were developed and used for the early diagnosis of stroke and tumors.20−22

Figure 1.

Figure 1

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Radiosynthesis and characteristics. (a) Flowchart of 18F-RFTA radiosynthesis. (b) Radio-HPLC profile of 18F-RFTA after the purification. (c–e) Stability of 18F-RFTA in saline (2 h), blood (1 h p.i.), and urine (2 h p.i.) as determined by radio-HPLC. (f) Major pharmacokinetic parameters and time–activity curve (TAC) of 18F-RFTA in the blood of healthy rats. t1/2z: elimination half-life; AUC(0–t) and AUC(0–∞): area under the curve; Cmax: peak concentration; CLz: clearance. The values are expressed as mean ± SD (n = 3).

We attempt to further assess the imaging feasibility of energetic metabolism reprogramming after MI/R occurs. We designed and synthesized a highly specific probe, 18F-RFTA (Figure 1a), which has recently been reported for PET imaging of RFVT3 in glioma by our research group.21 The main studies include the radiosynthesis of 18F-RFTA, analysis of physicochemical properties such as radiochemical purity and stability, PET imaging in myocardial infarction rat models, autoradiography, and IHC staining of RFVT3.

Results

Radiosynthesis

In this study, a manual radiolabeling procedure of 18F-RFTA was developed using a one-pot two-step strategy to shorten the synthesis time and obtain higher radiochemical yield (Figure 1a). Compared with the two steps and twice high-performance liquid chromatography (HPLC) purity procedures reported previously,21 this only once HPLC purity procedure for the radiosynthesis of 18F-RFTA had a shorter synthesis time and higher labeling yield. The radiosynthesis time was about 90 min (vs 120 min), and the decay-corrected radiochemical yield was 30.07 ± 3.64% (n = 3) (vs 20.1 ± 2.0%, n = 3). The radiochemical purity of the final product 18F-RFTA is greater than 98% by quantitative analysis of the HPLC chromatogram (Figure 1b). The risk of radiation exposure is increased in the exploratory process of manual labeling, which provides critical data for fully automated synthesis of 18F-RFTA with a one-pot two-step strategy in the future. The molar activity of 18F-RFTA was about 11.6 GBq/μmol.

Metabolic Stability and Pharmacokinetics in Rat

To determine the stability of 18F-RFTA in saline (in vitro) and in the blood of rats (in vivo), the samples were collected and analyzed using radio-HPLC. 18F-RFTA remained stable in vitro and in vivo (Figure 1c,d). Meanwhile, 18F-RFTA had better stability in the urine of rats (Figure 1e) than mice.21 Based on the result of stability in vivo, the pharmacokinetic property of 18F-RFTA in rats was evaluated, the time–activity curve (TAC) of blood is depicted, and the pharmacokinetics data are listed in Figure 1f. The elimination half-life (t1/2z) of 18F-RFTA in blood was calculated as 2.85 ± 1.45 h, and then the effective half-life was derived as about 1.11 h, which was propitious to the microPET-CT imaging with high infarcted myocardium–muscle and infarcted myocardium–blood ratios.

MI/R Model Determination

Echocardiography was employed to assess the cardiac function. The transthoracic M-mode echocardiography images of the sham-operated control and MI/R rats are shown in Figure 2a–c. ST segment elevations in MI/R rats confirmed the success of the animal model. Midventricle level (M-mode) ultrasound showed that left ventricular fractional shortening (FS) and ejection fraction (EF) decreased from 43.57 ± 6.03 to 24.27 ± 2.32% (P < 0.01) and 68.13 ± 5.44 to 45.88 ± 3.78% (P < 0.05) in rats after reperfusion, respectively. Furthermore, to evaluate the anatomical alteration of infarcted myocardium, the sham-operated control and MI/R rats were detected by noncontrast T2W-CMR (Figure 2d,e). cMRI showed that the signal intensity tended to decrease in the infarcted myocardium, in contrast to the sham-operated myocardium. In addition, technetium-99m sestamibi (99mTc-MIBI) SPECT can provide an anatomic reference to the site of infarction and reflect the blood perfusion of the infarcted area. An attenuated 99mTc-MIBI uptake in the infarcted myocardium is due to the lower perfusion rate compared with that in the normal myocardium (Figure 2f,g). In general, the rat model was verified by echocardiography, cMRI, and 99mTc-MIBI SPECT imaging.

Figure 2.

Figure 2

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Cardiac functional assessment using high-resolution ultrasound, cMRI, and 99mTc-MIBI MPI. ECG change (a1, a2), M-mode ultrasound at midventricle level (b1, b2), the contraction of the left ventricular wall (c1, c2), the significantly weakened signal of axial positions T2W and T2W pseudocolor MR image (d1, d2, e1, e2), and 99mTc-MIBI MPI (f1, f2, g1, g2) at sham-operated rats and MI/R model rats. The yellow arrow indicates the infarct zone.

MicroPET-CT Imaging and Quantitative Analysis

Representative myocardial coronal and transverse images, the quantitative analysis of main organs’ biodistribution, and target-to-nontarget ratios are shown in Figure 3. The infarcted myocardium area was clearly visible with good contrast to the normal myocardium (0.37 ± 0.10 vs 0.13 ± 0.01%ID/g, P < 0.05) after the administration of 18F-RFTA. High ratios of infarcted myocardium-to-normal myocardium (IM/Nor myocardium = 2.86 ± 1.00), infarcted myocardium-to-muscle (IM/Muscle = 4.15 ± 1.97), and infarcted myocardium-to-lung (IM/Lung = 2.58 ± 0.84) were observed. However, the infarcted myocardium-to-liver ratio was relatively low (IM/Liver = 0.28 ± 0.10). RFVT3 binding specificity of 18F-RFTA was confirmed by blocking assay. The 18F-RFTA uptake in the impaired myocardium was remarkably blocked by superfluous riboflavin, which was obviously lower than that of the unblocked group (0.16 ± 0.03 vs 0.37 ± 0.10%ID/g, P < 0.05). Therefore, the results verified the RFVT3 specificity of 18F-RFTA.

Figure 3.

Figure 3

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MicroPET-CT imaging of rat models with 18F-RFTA. (a–f) Representative PET-CT imaging in sham (a, d), MI (b, e), and MI-blocking (c, f) rat models. Quantitative analysis of mean percent injected dose per gram (%ID/g) (g) and infarcted myocardium-to-liver (IM/liver) ratio, infarcted myocardium-to-lung (IM/lung), infarcted myocardium-to-muscle (IM/muscle), and infarcted myocardium-to-normal myocardium (IM/nor myocardium) (h).

Autoradiography and TTC Staining

The autoradiography further validated the quantitative PET results. Typical images and radioactivity ratios are listed in Figure 4. Increased intensity was demonstrated in the ischemic areas (Figure 4a–c), evidenced by TTC stains (Figure 4d–f). No significant 18F-RFTA uptakes were observed in the normal myocardium or the infarcted myocardium blocked by excess nonlabeled riboflavin. The quantitative results revealed that the infarct/noninfarct signal intensity ratios in the assay, sham-operated, and blocking group were 3.05 ± 0.28, 1.30 ± 0.11, and 1.49 ± 0.09, respectively (Figure 4g,h). Therefore, the ex vivo results double-validated the substantiated specificity of RFVT3-targeting imaging of myocardial infarction.

Figure 4.

Figure 4

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Representative TTC staining photographs and autoradiographs of 18F-RFTA radioactivity and quantitative analysis in the myocardium. Autoradiographs (a-c) and TTC staining photographs (d-f) from the sham-operated (a, d), infarcted (b, e), and nonlabeled riboflavin-blocked (c, f) myocardial slices demonstrate increased 18F-RFTA uptake in the infarcted area, whereas the uptake is negligible for the normal myocardium or infarcted myocardium with blocking quantitative uptakes. Furthermore, autoradiography image-derived quantitation (g) of normal myocardium (Nor Myo) and infarcted myocardium (Inf Myo) and their uptake ratios (h) were derived from the autoradiography images.

Hematoxylin–Eosin (H&E) and IHC Stainings

To further investigate the mechanism of 18F-RFTA high uptake in the infarcted myocardium, we performed H&E and RFVT3 IHC stainings to investigate RFVT3 expression. As shown in Figure 5, the histological micrographs for the H&E staining indicated that normal myocardium showed a compact structure with complete nuclei, no signs of fibrosis, and coagulative necrosis. However, the damaged myocardium revealed a looseness of structure and nucleus enrichment or lysis (Figure 5a–c). Meanwhile, few RFVT3-positive signals were presented in normal myocardium from the sham-operated group. As we expected, in cardiac sections adjacent to the site of the infarcted myocardium, enhanced and predominant sarcolemma staining of RFVT3 was observed on the infarcted myocardium (Figure 5d–f). The RFVT3 IHC signal corresponded to the radioactivity distribution of 18F-RFTA in the infarcted and normal regions, which further demonstrated the RFVT3 specificity of 18F-RFTA.

Figure 5.

Figure 5

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H&E and IHC stainings. (a–c) H&E staining of normal myocardium and MI/R myocardium. (d–f) IHC staining of normal myocardium, MI/R myocardium, and their boundary.

Discussion

RFVT3 is a new target for the reprogramming of mitochondrial energy metabolism, which is a key protein in the cardioprotective signal transduction pathways. Our present study first revealed the feasibility of PET imaging overexpressed RFVT3 in the MI/R model with 18F-RFTA. The specificity of the PET signal was further verified by blocking assay and IHC staining. The signal from 18F-RFTA can provide the dynamic expression spectrogram of cardioprotective predictor RFVT3, and therefore, it is fundamentally different from contrast enhancement on MRI and SPECT MPI with 99mTc-MIBI. Thus, RFVT3-targeted PET imaging using 18F-RFTA in the infarcted myocardium will be beneficial for the early diagnosis and cardioprotective therapy of MI.

Although 18F-FDG PET is the most sensitive imaging method for detecting myocardium vitality,23 there are some shortcomings in giving information about targets related to myocardial repair. Integrin αvβ3-targeting probe 18F-AlF-NOTA-PRGD224 and CXCR4-targeting probes 68Ga-pentixafor6 and 125I-pentixather25 have been reported for imaging angiogenesis and inflammatory response after myocardial infarction occurred. However, these probes cannot directly reflect the mitochondrial metabolic activity. PET MPI with representative mitochondrial targeted agents 18F-R1004, 18F-FDHR, 18F-FPTP, and 18F-FMBTP demonstrates high uptake in normal myocardium and correlation to blood flow.8,26 However, these negative PET imaging for damaged myocardium cannot give the expression information on biotargets for repair, protection, and regeneration in infarcted myocardium. 18F-RFTA PET is a positive imaging for infarcted myocardium and directly reflects the expression of cardioprotective biotarget RFVT3 in mitochondrial energetic metabolism reprogramming after myocardial infarction, which has the potential to guide relevant therapy. Therefore, the new diagnostic approach targeting RFVT3 would put forward a better understanding of mitochondrial metabolic reprogramming in the infarcted myocardium.

However, this proof-of-concept study inevitably has several limitations. First, the chemical structure of 18F-RFTA needs to be optimized to lower the abdominal uptakes such as in the liver and intestine. Second, no comparison was made with the previously reported RFVT3-targeted SPECT probe 131I-RFLA and other probes targeting myocardial biomarkers. Third, there are no more animal cardiomyopathy models of different species. Finally, more time points after myocardial infarction should be evaluated to investigate the expression pattern of RFVT3.

Summarily, high contrast images of the infarcted myocardium of MI/R rats were obtained using PET imaging with 18F-RFTA, which is an RFVT3-targeted radiotracer with high affinity and specificity, indicating the possibility for noninvasive diagnosis of infarcted myocardium. The PET imaging of RFVT3 expression will provide new insights into mitochondrial metabolic reprogramming after MI and other cardiac pathologic conditions. In the future, it is worth applying various radionuclides such as 99mTc and 68Ga to label riboflavin analogs for pharmacokinetics optimization and further investigate their potentialities for the diagnosis and image-guided therapy of RFVT3-related diseases.

Experimental Section

Radiochemistry

18F-RFTA has been radiolabeled manually based on the procedure reported by our group previously21 with a slight modification of the amounts of reagents for the manual one-pot two-step method. Briefly, after the procedure of [18F]fluoride drying, 1 mg of 2-(2-azidoethoxy)ethyl 4-methylbenzenesulfonate was used for the first step of radiolabeling. Without further HPLC purification, the mixture solution of the first step was applied for the second step radiosynthesis based on a click reaction. The detailed procedures for radiosynthesis, HPLC analysis, purification, and molar activity calculation of 18F-RFTA are presented in the Supporting File.

Stability Studies

For the in vitro stability study, 18F-RFTA (3.7–7.4 MBq) was incubated in saline (500 μL) for 2 h at 37 °C. After the intravenous (i.v.) injection of 18F-RFTA (14.8–18.5 MBq/200 μL) through the healthy Wistar rat (220–280 g, n = 3) tail vein, the samples of blood and urine were collected at 1 and 2 h postinjection (p.i.), respectively, for the in vivo stability study. Before the radio-HPLC analysis, the blood samples (about 200 μL) were precipitated with trifluoroacetic acid (10 μL) and centrifuged for 5 min at 12,000 rpm. The urine samples were analyzed by radio-HPLC after being filtered with 0.22 μm sterile syringe filters to assess the metabolic stability of 18F-RFTA in rats.

Pharmacokinetics in Rat

Three Wistar rats (220–280 g) were intravenously injected with 18F-RFTA (18.5 MBq/200 μL), and the blood samples (10 μL each) were collected at 2, 10, and 30 min, 1, 2, and 4 h p.i. via tail vein, respectively.27 Then the counts (CPM) of the blood samples were measured by an automatic γ-counter with background subtraction and decay correction. The activity (mega becquerel/liter, MBq/L) of the sample was calculated using the following formula

graphic file with name pt4c00175_m001.jpg

The noncompartment model was employed to calculate the pharmacokinetic parameters using Drug and Statistics for Windows 2.0 software (SAS Inc., Cary, NC).

MI/R Model

The animal assays were approved and supervised by Xiamen University’s animal care and use committee. MI/R animal models (Wistar rat, 220–280 g) were prepared following the literature. In brief, the fur of the rat chest was shaved by an electric shaver under narcotism. Then, intubation and artificial ventilation were performed after sterilization. With preparations completed, surgery of an open chest was conducted. The left anterior descending artery was transiently ligated. Coronary reperfusion was conducted after 60 min of left coronary artery occlusion. The detailed procedures of MI/R model preparation are available in the Supporting File.

Echocardiography

To assess cardiac function, echocardiography was carried out on sham-operated and MI/R rats about 1 h after the surgery following the reported procedure.25 The animals were set on the scanning plate under narcotism with isoflurane (2%) and then echocardiograms were acquired with an echocardiography system (the Vevo 2100 system, VisualSonics, Canada). A two-dimensional (2D) M-mode was performed to measure the parameters.

cMRI

Cardiac magnetic resonance imaging (cMRI) was conducted using a 9.4T microMRI (Biospec 94/20USR, Bruker)28,29 after the echocardiography to localize the anatomic region of the 18F-RFTA PET detected signal. For gated cardiac imaging, the rats were secured and placed at the isocenter of the MRI scanner under narcotism with isoflurane (1.5–2%). Short-axis T1 images were acquired using the FLASH sequence with the following parameters: FOV = 5.1 cm × 5.1 cm; matrix: 256 × 192; TR = 16 ms, TE = 1.6 ms; slice thickness = 2 mm.

Myocardial Perfusion SPECT Imaging

To further reflect the blood perfusion of the myocardium, 99mTc-MIBI SPECT was employed to depict the perfusion of the infarcted myocardium due to the high perfusion rate of normal myocardium about 4 h after the surgery.25 MicroSPECT-CT (Mediso, nanoScan) imaging was performed after 1 h i.v. administration of 99mTc-MIBI (111–185 MBq). CT images were acquired with the following parameters: X-ray voltage (50 kVp), energy peak (140 keV) for 99mTc, window width (20%), matrix (256 × 256), and frame (30 s).

MicroPET-CT Imaging

According to previous literature reports,30 multiple inflammatory biomarkers such as CD40 ligand, C-reactive protein (CRP), high-sensitivity CRP (hs-CRP), interleukin-6 (IL-6), and high-sensitivity cardiac troponin T (hs-cTnT) start to rapidly proliferate at 8 h after MI. The overexpression of these inflammatory biomarkers needs mitochondria to provide a lot of energy. Therefore, we hypothesized that RFVT3 expression also increased rapidly at about 8 h postreperfusion. Meanwhile, we choose 30 min postinjection of 18F-RFTA for PET/CT imaging according to the pharmacokinetic parameters. To noninvasively image the expression of RFVT3 in the early injured myocardium in vivo, 10 min static PET images were acquired at 8 h after surgery using 18F-RFTA on a microPET-CT (Inveon, Siemens) and were reconstructed using a two-dimensional ordered subset expectation maximum (2D OSEM) algorithm.24 After 30 min i.v. injection of 18F-RFTA (about 18.5 MBq/200 μL) through the tail vein, a 10 min static scan was conducted. To test the specificity, RF as a blocking agent was intravenously injected (15 mg/kg) 10 min before 18F-RFTA administration. The regions of interest (ROIs) were drawn on decay-corrected whole-body coronal images, and then infarcted myocardium-to-normal myocardium (IM/Nor myocardium), infarcted myocardium-to-lung (IM/Lung), infarcted myocardium-to-muscle (IM/Muscle), and infarcted myocardium-to-liver (IM/Liver) ratios were obtained to characterize the effectiveness of 18F-RFTA PET imaging.

Autoradiography and TTC Staining

The rats were immediately sacrificed and anatomized after microPET-CT imaging under anesthesia. The normal and infarcted myocardium obtained following the guidance of the microPET-CT images was cut into about 2 mm blocks. The sections were stained in a 2% buffered 2,3,5-triphenyl tetrazolium chloride (TTC) solution for 15 min at 37 °C.25 Subsequently, a high-performance storage phosphor screen (Canberra-Packard, Ontario, Canada) was employed to expose the sections for 30 min. A Phosphor Imager scanner (Cyclone Plus; PerkinElmer) was utilized to read the screen.

H&E and IHC Stainings

The different expressions of RFVT3 in infarcted and normal myocardium were evaluated as reported previously.21 In brief, formalin-fixed, paraffin-embedded, deparaffinated, and antigen-retrieval sections of the myocardium (5 μm) were stained for RFVT3 using an RFVT3 antibody (Abcam, Cambridge) for 1 h. Subsequently, the washed sections were incubated with a secondary antibody for 30 min and then with DAPI for 10 min. H&E staining was performed to counterstain for 10 min. Finally, the images were captured by a Zeiss microscope (Carl Zeiss, Heidelberg, Germany).

Statistical Analysis

The data were expressed as mean ± standard deviation (SD) and analyzed using Microsoft Excel 2010 software with an unpaired Student’s t test for comparisons of two independent values (P < 0.05 indicates statistical significance).

Acknowledgments

This work was supported by the National Natural Science Foundation of China (21976150), the China Postdoctoral Science Foundation (2021M702730), the Shanghai Pujiang Program (22PJ1401700), the National Isotope Engineering Technology Research Center Funding (GJTWSGCZX-202306), the Key Laboratory of Nuclear Physics and Ion-beam Application of Fudan University Funding (JIH5913201/010), and the National High Level Hospital Clinical Research Funding (2022-PUMCH-B-071 and 2023-PUMCH-E-007). The authors thank Dr. Honghui Li for the small animal high-resolution echocardiography study. The authors also acknowledge Lixia Feng for the microPET-CT scanning.

Glossary

Abbreviations

RFVT3

riboflavin transporter 3

RF

riboflavin

MI/R

myocardial infarction/reperfusion

cMRI

cardiac magnetic resonance imaging

SPECT

single-photon-emission computed tomography

PET

positron emission tomography

IHC

immunohistochemical

FMN

flavin mononucleotide

FAD

flavin adenine dinucleotide

TTC

2,3,5-triphenyl tetrazolium chloride

H&E

hematoxylin–eosin

TAC

time–activity curve

FS

fractional shortening

EF

ejection fraction

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsptsci.4c00175.

  • Radiochemistry and HPLC analysis for18F-RFTA, and procedures of MI/R model (PDF)

Author Contributions

∇ J.L., X.H., Y.C., and B.Y. contributed equally to this work. X.Z., J.L., Z.G., and X.H. designed the research; J.L., H.Y., and Y.C. performed organic synthesis; J.L. and Y.C. carried out radiolabeling experiments; J.L., Y.C., and B.Y. conducted MI/R rat model; J.L., C.S., and X.Z. performed in vivo studies; D.Z. and Y.C. carried out ex vivo assays; X.Z., J.L., and X.H. wrote the manuscript.

The authors declare no competing financial interest.

Supplementary Material

pt4c00175_si_001.pdf (107.3KB, pdf)

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