Markus Thomas Berninger MD, Abstract Co-Author: Nothing to Disclose

Pouyan Mohajerani, Abstract Co-Author: Nothing to Disclose

Bernhard Haller, Abstract Co-Author: Nothing to Disclose

Vasilis Ntziachristos PhD, Abstract Co-Author: Stockholder, iThera Medical GmbH

Reinhard Meier MD, PhD, Abstract Co-Author: Nothing to Disclose

Tobias D. Henning MD, Presenter: Nothing to Disclose

FMT-XCT is a 3D imaging technique that combines the high sensitivity of fluorescence molecular tomography (FMT) with the high resolution of X-ray CT. The purpose of this study was to establish an intermediate sized animal model in a rabbit for FMT-XCT stem cell tracking in the scenario of osteochondral defect repair.

Mesenchymal stem cells (MSC) were isolated from the bone marrow of New Zealand White rabbits. Then, cells were labeled with the near infrared lipophilic carbocyanine dye DiR (1.25 - 20 μg). Induction of apoptosis and toxicity were assessed by Caspase-3/-7-, Trypan Blue- and XTT-testing. Chondrogenic potential was assessed in pellet cultures (n=3) by measurement of glycosaminoglycans. Labeled cells and unlabeled controls (n=3) underwent FMT–XCT imaging before and after chondrogenic differentiation. Then, osteochondral defects (3.8 x 3.5 mm) were created surgically in the femoral condyle of rabbit knees (n=6) and 200.000 unlabeled and labeled MSC were implanted in a fibrin clot and imaged at FMT-XCT. Statistics were performed using a t-test.

Labeling of MSC with DiR resulted in a strong, significant and dose-dependent fluorescence signal at all concentrations on FMT images (p0.05). Thus, a labeling concentration of 5 µg DiR was chosen for animal studies. FMT-XCT of labeled MSC after implantation in osteochondral defects showed a strong and significant signal on FMT (p<0.05) made possible by using anatomical priors afforded by the high resolution of CT and contrast in bone regions.

MSC could be labeled with DiR without toxic side effects or impairment of chondrogenesis. Labeled cells showed a significant fluorescence signal in vitro and were well depicted by FMT-XCT after implantation in osteochondral defects in a rabbit animal model of cartilage repair.

The use of FMT-XCT in an intermediate sized animal model offers high sensitivity and 3D-image detail. Clinical translation of FMT-XCT could be valid in human follow-up studies in tissue engineering.

Berninger, M, Mohajerani, P, Haller, B, Ntziachristos, V, Meier, R, Henning, T, Fluorescence Molecular Tomography of DiR-labeled Mesenchymal Stem Cells Implants in Osteochondral Defects of Rabbit Knees.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045580.html