PET Assessment of Immune Cell Activity and Therapeutic Monitoring Following Myocardial Infarction

Potential utility of SPECT/CT with 99mTc-Tektrotyd for imaging of post-myocardial infarction inflammation

BACKGROUND

There is a need to develop methods for post-myocardial infarction (MI) inflammation monitoring. Scintigraphy with somatostatin receptor targeted radiotracers has potential in this field. The purpose was to study the association of 99mTc-Tektrotyd uptake intensity in MI area with heart contractility indices over 6-month follow-up.

METHODS

Fourteen patients with acute ST-segment elevation anterior MI (STEMI) were examined with 99mTc-Tektrotyd SPECT/CT, myocardial perfusion scintigraphy (MPS) at rest, cardiac magnetic resonance imaging (cMRI) and transthoracic echocardiography (TTE). Scintigraphic results were compared with 6-month TTE indices.

RESULTS

On the 7th day after a MI onset, cardiac 99mTc-Tektrotyd uptake was found in 7 of 14 patients. Median of 99mTc-Tektrotyd SUVmax was 1.59 (1.38; 2.83), the summed rest score (SRS) was 11 (5; 18), infarct size (by cMRI)-13.15 (3.3; 32.2) %. 99mTc-Tektrotyd SUVmax strongly correlated with 6-month heart contractility indices (r = 0.81, P < 0.05 for the end diastolic volume; r = 0.61 P < 0.05 for Δ end diastolic volume), with SRS (r = 0.85, P < 0.05) and infarct size (by cMRI) (r = 0.79, P < 0.05).

CONCLUSION

The intensity (SUVmax) of 99mTc-Tektrotyd uptake in the area of recent MI directly depends on the size of ischemic myocardial injury and correlates with changes of heart contractility indexes over the 6 month follow-up.

Subacute myocardial infarction detected by technetium-99m-labeled somatostatin analog scintigraphy

Recently, the applicability of somatostatin receptor-targeted (SSTR-t) radiotracers for post-ischemic myocardial inflammation imaging has been shown using PET. Currently, there are no studies which demonstrate ability of SPECT and technetium-99m SSTR-t radiotracers to detect inflammation, which appears in response to acute myocardial infarction (AMI). A case of 51-year-old male with acute anterior myocardial infarction (AMI) with ST elevation has been presented. This patient on 7th day after AMI onset underwent SPECT/CT (by cardiac cadmium-zinc-telluride gamma-camera) with 99mTc-Tectrotide, cardiac MRI with gadolinium and, on 9th day after AMI, myocardial perfusion scintigraphy (MPS) at rest. Clear myocardial uptake of 99mTc-Tectrotide, predominantly in apical and intermediate anterior wall of left ventricle was detected. The uptake matched with areas of hypoperfusion (by SPECT) and myocardial injury (by MRI). This case demonstrated the applicability of technetium-99m-labeled SSTR-t radiotracers for post-infarction inflammation imaging. Currently assumed, that SSTR-t radiotracers reflect an increased number of activated macrophages infiltrating infarcted myocardium, which is not possible using any other imaging technique. Thus, potentially, SSTR scintigraphy may be useful for diagnosis and monitoring of myocardial post-infarction inflammation as well as for anti-inflammatory image-guide therapy assessment.

Inhibition of miR-182-5p attenuates ROS and protects against myocardial ischemia-reperfusion injury by targeting STK17A

Reperfusion therapy for acute myocardial infarction inevitably leads to ischemia-reperfusion (I/R) injury. A number of miRNAs are reported to be involved in I/R injury. This study aims to investigate the role and underlying mechanism of miR-182-5p in I/R injury. An in vivo model of I/R-induced rat myocardial injury and an in vitro model of H/R H9c2 cells were established to investigate the role and mechanism of miR-182-5p in I/R injury. The myocardial infarct size was determined by TTC staining. The serum CK-MB level was determined by ELISA kit. The miR-182-5p inhibitors or mimics were used to down-regulate or up-regulate its expression. The apoptosis and ROS were detected by flow cytometry. The expression of the proteins was detected by western blot. The binding of STK17A and miR-182-5p was validated by dual-luciferase reporter assay. The miR-182-5p was confirmed to be highly expressed in I/R injury rats and H/R H9c2 cells. Inhibition of miR-182-5p significantly reduced the infarct size and decreased the serum CK-MB level of I/R rats, and significantly reduced the ROS level but increased the level of MnSOD and catalase. While, an opposite effect was observed in the miR-182-5p mimics group. Furthermore, our results suggested that miR-182-5p targeted STK17A, and TK17A knockdown significantly increased the apoptotic rate and ROS level. The inhibitory effect of miR-182-5p inhibitors on apoptotic rate, ROS, MnSOD, and catalase levels were abrogated by siSTK17A. These results indicate that miR-182-5p regulates the apoptosis and ROS and protects against myocardial I/R injury by targeting STK17A.

Emerging Preclinical and Clinical Applications of Theranostics for Nononcological Disorders

Studies in nuclear medicine have shed light on molecular imaging and therapeutic approaches for oncological and nononcological conditions. Using the same radiopharmaceuticals for diagnosis and therapeutics of malignancies, the theranostics approach, has improved clinical management of patients. Theranostic approaches for nononcological conditions are recognized as emerging topics of research. This review focuses on preclinical and clinical studies of nononcological disorders that include theranostic strategies. Theranostic approaches are demonstrated as possible in the clinical management of infections and inflammations. There is an emerging need for randomized trials to specify the factors affecting validity and efficacy of theranostic approaches in nononcological diseases.

Molecular Imaging of Inflammation and Fibrosis in Pressure Overload Heart Failure

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