Angiogenesis PET Tracer Uptake (⁶⁸Ga-NODAGA-E[(cRGDyK)]₂) in Induced Myocardial Infarction and Stromal Cell Treatment in Minipigs

Angiogenesis is considered integral to the reparative process after ischemic injury. The αvβ3 integrin is a critical modulator of angiogenesis and highly expressed in activated endothelial cells. 68Ga-NODAGA-E[(cRGDyK)]2 (RGD) is a positron-emission-tomography (PET) ligand targeted towards αvβ3 integrin. The aim was to present data for the uptake of RGD and correlate it with histology and to further illustrate the differences in angiogenesis due to porcine adipose-derived mesenchymal stromal cell (pASC) or saline treatment in minipigs after induction of myocardial infarction (MI). Three minipigs were treated with direct intra-myocardial injection of pASCs and two minipigs with saline. MI was confirmed by 82Rubidium (82Rb) dipyridamole stress PET. Mean Standardized Uptake Values (SUVmean) of RGD were higher in the infarct compared to non-infarct area one week and one month after MI in both pASC-treated (SUVmean: 1.23 vs. 0.88 and 1.02 vs. 0.86, p < 0.05 for both) and non-pASC-treated minipigs (SUVmean: 1.44 vs. 1.07 and 1.26 vs. 1.04, p < 0.05 for both). However, there was no difference in RGD uptake, ejection fractions, coronary flow reserves or capillary density in histology between the two groups. In summary, indications of angiogenesis were present in the infarcted myocardium. However, no differences between pASC-treated and non-pASC-treated minipigs could be demonstrated

Use of Cis-[18F]Fluoro-Proline for Assessment of Exercise-Related Collagen Synthesis in Musculoskeletal Connective Tissue

Protein turnover in collagen rich tissue is influenced by exercise, but can only with difficulty be studied in vivo due to use of invasive procedure. The present study was done to investigate the possibility of applying the PET-tracer, cis-[18F]fluoro-proline (cis-Fpro), for non-invasive assessment of collagen synthesis in rat musculoskeletal tissues at rest and following short-term (3 days) treadmill running. Musculoskeletal collagen synthesis was studied in rats at rest and 24 h post-exercise. At each session, rats were PET scanned at two time points following injection of cis-FPro: (60 and 240 min p.i). SUV were calculated for Achilles tendon, calf muscle and tibial bone. The PET-derived results were compared to mRNA expression of collagen type I and III. Tibial bone had the highest SUV that increased significantly (p<0.001) from the early (60 min) to the late (240 min) PET scan, while SUV in tendon and muscle decreased (p<0.001). Exercise had no influence on SUV, which was contradicted by an increased gene expression of collagen type I and III in muscle and tendon. The clearly, visible uptake of cis-Fpro in the collagen-rich musculoskeletal tissues is promising for multi-tissue studies in vivo. The tissue-specific differences with the highest basal uptake in bone are in accordance with earlier studies relying on tissue incorporation of isotopic-labelled proline. A possible explanation of the failure to demonstrate enhanced collagen synthesis following exercise, despite augmented collagen type I and III transcription, is that SUV calculations are not sensitive enough to detect minor changes in collagen synthesis. Further studies including kinetic compartment modeling must be performed to establish whether cis-Fpro can be used for non-invasive in-vivo assessment of exercise-induced changes in musculoskeletal collagen synthesis

First-in-Human Study of [68Ga]Ga-NODAGA-E[c(RGDyK)]2 PET for Integrin &alpha;v&beta;3 Imaging in Patients with Breast Cancer and Neuroendocrine Neoplasms: Safety, Dosimetry and Tumor Imaging Ability

Arginine-Glycine-Aspartate (RGD)-recognizing cell surface integrins are involved in tumor growth, invasiveness/metastases, and angiogenesis, and are therefore an attractive treatment target in cancers. The subtype integrin &alpha;v&beta;3 is upregulated on endothelial cells during angiogenesis and on tumor cells. In vivo assessment of integrin &alpha;v&beta;3 is possible with positron emission tomography (PET). Preclinical data on radiochemical properties, tumor uptake and radiation exposure identified [68Ga]Ga-NODAGA-E[c(RGDyK)]2 as a promising candidate for clinical translation. In this first-in-human phase I study, we evaluate [68Ga]Ga-NODAGA-E[c(RGDyK)]2 PET in patients with neuroendocrine neoplasms (NEN) and breast cancer (BC). The aim was to investigate safety, biodistribution and dosimetry as well as tracer uptake in tumor lesions. A total of 10 patients (5 breast cancer, 5 neuroendocrine neoplasm) received a single intravenous dose of approximately 200 MBq [68Ga]Ga-NODAGA-E[c(RGDyK)]2. Biodistribution profile and dosimetry were assessed by whole-body PET/CT performed at 10 min, 1 h and 2 h after injection. Safety assessment with vital parameters, electrocardiograms and blood tests were performed before and after injection. In vivo stability of [68Ga]Ga-NODAGA-E[c(RGDyK)]2 was determined by analysis of blood and urine. PET images were analyzed for tracer uptake in tumors and background organs. No adverse events or pharmacologic effects were observed in the 10 patients. [68Ga]Ga-NODAGA-E[c(RGDyK)]2 exhibited good in vivo stability and fast clearance, primarily by renal excretion. The effective dose was 0.022 mSv/MBq, equaling a radiation exposure of 4.4 mSv at an injected activity of 200 MBq. The tracer demonstrated stable tumor retention and good image contrast. In conclusion, this first-in-human phase I trial demonstrated safe use of [68Ga]Ga-NODAGA-E[c(RGDyK)]2 for integrin &alpha;v&beta;3 imaging in cancer patients, low radiation exposure and favorable uptake in tumors. Further studies are warranted to establish whether [68Ga]Ga-NODAGA-E[c(RGDyK)]2 may become a tool for early identification of patients eligible for treatments targeting integrin &alpha;v&beta;3 and for risk stratification of patients

Comparison of two new angiogenesis PET tracers 68Ga-NODAGA-E[c(RGDyK)]2 and 64Cu-NODAGA-E[c(RGDyK)]2; in vivo imaging studies in human xenograft tumors

AbstractIntroductionThe aim of this study was to synthesize and perform a side-by-side comparison of two new tumor-angiogenesis PET tracers 68Ga-NODAGA-E[c(RGDyK)]2 and 64Cu-NODAGA-E[c(RGDyK)]2 in vivo using human xenograft tumors in mice. Human radiation burden was estimated to evaluate potential for future use as clinical PET tracers for imaging of neo-angiogenesis.MethodsA 68Ge/68Ga generator was used for the synthesis of 68Ga-NODAGA-E[c(RGDyK)]2. 68Ga and 64Cu labeled NODAGA-E[c(RGDyK)]2 tracers were administrated in nude mice bearing either human glioblastoma (U87MG) or human neuroendocrine (H727) xenograft tumors. PET/CT scans at 3 time points were used for calculating the tracer uptake in tumors (%ID/g), integrin αVβ3 target specificity was shown by blocking with cold NODAGA-E[c(RGDyK)]2, and biodistribution in normal organs were also examined. From biodistribution data in mice human radiation-absorbed doses were estimated using OLINDA/EXM software.Results68Ga-NODAGA-E[c(RGDyK)]2 was synthesized with a radiochemical purity of 89%–99% and a specific activity (SA) of 16–153MBq/nmol. 64Cu-NODAGA-E[c(RGDyK)]2 had a purity of 92%–99% and an SA of 64–78MBq/nmol.Both tracers showed similar uptake in xenograft tumors 1h after injection (U87MG: 2.23 vs. 2.31%ID/g; H727: 1.53 vs. 1.48%ID/g). Both RGD dimers showed similar tracer uptake in non-tumoral tissues and a human radiation burden of less than 10mSv with an administered dose of 200MBq was estimated.Conclusion68Ga-NODAGA-E[c(RGDyK)]2 and 64Cu-NODAGA-E[c(RGDyK)]2 can be easily synthesized and are both promising candidates for PET imaging of integrin αVβ3 positive tumor cells. 68Ga-NODAGA-E[c(RGDyK)]2 showed slightly more stable tumor retention. With the advantage of in-house commercially 68Ge/68Ga generators, 68Ga-NODAGA-E[c(RGDyK)]2 may be the best choice for future clinical PET imaging in humans

Angiogenesis PET Tracer Uptake (68Ga-NODAGA-E[(cRGDyK)]2) in Induced Myocardial Infarction in Minipigs

Angiogenesis is part of the healing process following an ischemic injury and is vital for the post-ischemic repair of the myocardium. Therefore, it is of particular interest to be able to noninvasively monitor angiogenesis. This might, not only permit risk stratification of patients following myocardial infarction, but could also facilitate development and improvement of new therapies directed towards stimulation of the angiogenic response. During angiogenesis endothelial cells must adhere to one another to form new microvessels. αvβ3 integrin has been found to be highly expressed in activated endothelial cells and has been identified as a critical modulator of angiogenesis. 68Ga-NODAGA-E[c(RGDyK)]2 (RGD) has recently been developed by us as an angiogenesis positron-emission-tomography (PET) ligand targeted towards αvβ3 integrin. In the present study, we induced myocardial infarction in Göttingen minipigs. Successful infarction was documented by 82Rubidium-dipyridamole stress PET and computed tomography. RGD uptake was demonstrated in the infarcted myocardium one week and one month after induction of infarction by RGD-PET. In conclusion, we demonstrated angiogenesis by noninvasive imaging using RGD-PET in minipigs hearts, which resemble human hearts. The perspectives are very intriguing and might permit the evaluation of new treatment strategies targeted towards increasing the angiogenetic response, e.g., stem-cell treatment

Gene expression of COL1A1 and COL3A1.

<p>COL1A1 and CoL3A1 mRNA normalized to tissue weight, presented as fold changes in the exercise group (filled bars) relative to the mean of the control group (open bars) in Achilles tendon and soleus muscle. In tendon COL3A1 mRNA was significantly increased (p<0.05) in the Exercise group and COL1A1 mRNA showed a strong tendency to an increase (p = 0.09). In exercised soleus muscle both COL1A1 (p<0.01) and COL3A1 (p<0.001) were significantly increased. Values are geometric means ± SEM.</p

PCR Primers.

<p>PCR Primers.</p