Trochanter migrans: late complications due to displacement of the lesser trochanter in trochanteric fractures.

Complications associated with secondary displacement and migration of the lesser trochanter fragment in trochanteric fractures are rare. The complaints expressed by the patient may be misunderstood and attributed to implant-associated or patient-specific problems likely to occur after surgery. This series illustrates potentially dangerous late complications caused by secondary migration of the lesser trochanter. It may help focus the surgeon's attention on possible functional impairment and severe late complications caused by displacement of the lesser trochanter in trochanteric fractures that require prompt intervention.

Longitudinal imaging of T cell-based immunotherapy with multi-spectral, multi-scale optoacoustic tomography.

Most imaging studies of immunotherapy have focused on tracking labeled T cell biodistribution in vivo for understanding trafficking and homing parameters and predicting therapeutic efficacy by the presence of transferred T cells at or in the tumour mass. Conversely, we investigate here a novel concept for longitudinally elucidating anatomical and pathophysiological changes of solid tumours after adoptive T cell transfer in a preclinical set up, using previously unexplored in-tandem macroscopic and mesoscopic optoacoustic (photoacoustic) imaging. We show non-invasive in vivo observations of vessel collapse during tumour rejection across entire tumours and observe for the first time longitudinal tumour rejection in a label-free manner based on optical absorption changes in the tumour mass due to cellular decline. We complement these observations with high resolution episcopic fluorescence imaging of T cell biodistribution using optimized T cell labeling based on two near-infrared dyes targeting the cell membrane and the cytoplasm. We discuss how optoacoustic macroscopy and mesoscopy offer unique contrast and immunotherapy insights, allowing label-free and longitudinal observations of tumour therapy. The results demonstrate optoacoustic imaging as an invaluable tool in understanding and optimizing T cell therapy.

Diagnostic value of MRI-based 3D texture analysis for tissue characterisation and discrimination of low-grade chondrosarcoma from enchondroma: a pilot study.

OBJECTIVES: To explore the diagnostic value of MRI-based 3D texture analysis to identify texture features that can be used for discrimination of low-grade chondrosarcoma from enchondroma. METHODS: Eleven patients with low-grade chondrosarcoma and 11 patients with enchondroma were retrospectively evaluated. Texture analysis was performed using mint Lesion: Kurtosis, entropy, skewness, mean of positive pixels (MPP) and uniformity of positive pixel distribution (UPP) were obtained in four MRI sequences and correlated with histopathology. The Mann-Whitney U-test and receiver operating characteristic (ROC) analysis were performed to identify most discriminative texture features. Sensitivity, specificity, accuracy and optimal cut-off values were calculated. RESULTS: Significant differences were found in four of 20 texture parameters with regard to the different MRI sequences (p<0.01). The area under the ROC curve values to discriminate chondrosarcoma from enchondroma were 0.876 and 0.826 for kurtosis and skewness in contrast-enhanced T1 (ceT1w), respectively; in non-contrast T1, values were 0.851 and 0.822 for entropy and UPP, respectively. The highest discriminatory power had kurtosis in ceT1w with a cut-off ≥3.15 to identify low-grade chondrosarcoma (82 % sensitivity, 91 % specificity, accuracy 86 %). CONCLUSION: MRI-based 3D texture analysis might be able to discriminate low-grade chondrosarcoma from enchondroma by a variety of texture parameters. KEY POINTS: • MRI texture analysis may assist in differentiating low-grade chondrosarcoma from enchondroma. • Kurtosis in the contrast-enhanced T1w has the highest power of discrimination. • Tools provide insight into tumour characterisation as a non-invasive imaging biomarker.

[Chances and Risks of Telemedicine in Orthopaedics and Trauma Surgery]. / Chancen und Risiken der Telemedizin in der Orthopädie und Unfallchirurgie.

BACKGROUND: The use of information technology (IT) in health care has continuously increased. This includes software solutions for digitalisation, data storage and innovative approaches in diagnostics. The facilitation of the access to specific information, even by the patient, has changed daily clinical work. Patients inform themselves about symptoms, diagnostic methods and treatment options. This urge for information and the wish for the best treatment is summarised in the expression "patient empowerment". In some countries, the gap between do-it-yourself diagnosis and telemedicine via the telephone has already been closed. A sophisticated telemedical hotline may help to improve consultation and treatment of patients living in remote regions or rural communities. Traumatology telemedicine may also be used in trauma environments, such as disasters or mass casualties. Therefore, the purpose of this study was to assess the demand for e-health solutions among patients seeking the help of the emergency department in a trauma hospital. METHODS: A total of 255 patients (age range 18 - 75 years) were included in the study and were surveyed with the use of a questionnaire. As regards personal data, the questionnaire asked the patient about their Internet habits and about interesting topics they had researched in the world wide web. However, the questionnaire was specifically designed to ask for potential benefits and the patient's expectations for e-health solutions. Expected weaknesses and procedures for telemedical services were also included in a subsection. RESULTS: 43.5% of the patient cohort were woman and 56.5% men. The average distance to the hospital was 39.86 km. 223 patients were insured by the governmental health service providers and 32 had private insurance coverage. Aside from online shopping and online banking, the search for health topics was most frequent. The greatest fear was the lack of personal contact to the doctor (71.2%). Patients were also concerned about the safety of individual health data in privately run databanks (54.3%). On the other hand, patients were neutral towards the web-based scheduling of medical appointments. Automatic reminders for such appointments were desired via e-mail (68.8%) or SMS (66.5%). CONCLUSION: Patients are demanding mobile solutions for scheduling medical appointments, including reminders of these. Patients are keen to be involved in the communications and would like to receive overall information about their health status. Online chats or video calls with physicians are not their first choice but might be a possibility until personal presentation.

Characterization of Cardiac Dynamics in an Acute Myocardial Infarction Model by Four-Dimensional Optoacoustic and Magnetic Resonance Imaging.

Extraction of murine cardiac functional parameters on a beat-by-beat basis is limited with the existing imaging modalities due to insufficient three-dimensional temporal resolution. Faster volumetric imaging methods enabling in vivo characterization of functional parameters are poised to advance cardiovascular research and provide a better understanding of the mechanisms underlying cardiac diseases. We present a new approach based on analyzing contrast-enhanced optoacoustic (OA) images acquired at high volumetric frame rate without using cardiac gating or other approaches for motion correction. We apply an acute murine myocardial infarction model optimized for acquisition of artifact-free optoacoustic imaging data to study cardiovascular hemodynamics. Infarcted hearts (n = 21) could be clearly differentiated from healthy controls (n = 9) based on a significantly higher pulmonary transit time (PTT) (2.25 [2.00-2.41] s versus 1.34 [1.25-1.67] s, p = 0.0235), while no statistically significant difference was observed in the heart rate (318 [252-361] bpm versus 264 [252-320] bpm, p = 0.3129). Nevertheless, nonlinear heartbeat dynamics was stronger in the healthy hearts, as evidenced by the third harmonic component in the heartbeat spectra. MRI data acquired from the same mice further revealed that the PTT increases with the size of infarction and similarly increases with reduced ejection fraction. Moreover, an inverse relationship between infarct PTT and time post-surgery was found, which suggests the occurrence of cardiac healing. In combination with the proven ability of optoacoustics to track targeted probes within the injured myocardium, our method can depict cardiac anatomy, function, and molecular signatures, with both high spatial and temporal resolution. Volumetric four-dimensional optoacoustic characterization of cardiac dynamics with supreme temporal resolution can capture cardiovascular dynamics on a beat-by-beat basis in mouse models of myocardial ischemia.

Multispectral Optoacoustic Tomography (MSOT) of Human Breast Cancer.

Purpose: In a pilot study, we introduce fast handheld multispectral optoacoustic tomography (MSOT) of the breast at 28 wavelengths, aiming to identify high-resolution optoacoustic (photoacoustic) patterns of breast cancer and noncancerous breast tissue.Experimental Design: We imaged 10 female patients ages 48-81 years with malignant nonspecific breast cancer or invasive lobular carcinoma. Three healthy volunteers ages 31-36 years were also imaged. Fast-MSOT was based on unique single-frame-per-pulse (SFPP) image acquisition employed to improve the accuracy of spectral differentiation over using a small number of wavelengths. Breast tissue was illuminated at the 700-970 nm spectral range over 0.56 seconds total scan time. MSOT data were guided by ultrasonography and X-ray mammography or MRI.Results: The extended spectral range allowed the computation of oxygenated hemoglobin (HBO2), deoxygenated hemoglobin (HB), total blood volume (TBV), lipid, and water contributions, allowing first insights into in vivo high-resolution breast tissue MSOT cancer patterns. TBV and Hb/HBO2 images resolved marked differences between cancer and control tissue, manifested as a vessel-rich tumor periphery with highly heterogeneous spatial appearance compared with healthy tissue. We observe significant TBV variations between different tumors and between tumors over healthy tissues. Water and fat lipid layers appear disrupted in cancer versus healthy tissue; however, offer weaker contrast compared with TBV images.Conclusions: In contrast to optical methods, MSOT resolves physiologic cancer features with high resolution and revealed patterns not offered by other radiologic modalities. The new features relate to personalized and precision medicine potential. Clin Cancer Res; 23(22); 6912-22. ©2017 AACR.

[First results with a resorbable MgYREZr compression screw in unstable scaphoid fractures show extensive bone cysts]. / Erste Ergebnisse mit einer resorbierbaren MgYREZr-Kompressionsschraube bei der instabilen Kahnbeinfraktur zeigen eine massive Zystenbildung.

Osteosynthesis with headless compression screws is an established treatment option for unstable scaphoid fractures. Common implants are made of titanium alloy or steel and usually remain in place. Due to implant density and ferromagnetic properties, artefacts are common in postoperative imaging procedures, e.g. MRI. Now resorbable implants made of magnesium alloy (MgYREZr) have become available. They have biomechanical properties equivalent to human bone and may be used as an alternative to the nonresorbable screw systems.5 patients with acute scaphoid fractures were treated with a double-threaded screw made of MgYREZr. The fractures included three type A2 fractures, one type B2 fracture, and one type B3 fracture. All patients underwent clinical and radiological follow-up postoperatively, 6 weeks, 3 and 6 months and 1 year after surgery. ROM, gross grip strength and pain (VAS) were documented. The Modified Mayo Wrist Score was used. Standard X-rays of the wrist were taken preoperatively and at all follow-up visits. A CT scan was performed at least before and three months after surgery. In all X-rays malunion, resorption of the implant, implant loosening, cysts and bone healing (bridging trabecular structures) were described.All patients had a very good wrist score (95-100 points) after one year. There were no clinical complications. However, the X-rays revealed extensive resorption cysts in 3 out of the 5 patients. It was only after 6 months that the fractures were consolidated enough to allow physical work. Due to this considerable osteolysis, we did not include any further patients. Due to the observed extensive bone cysts and the long time period for bone healing, MgYREZr compression screws are currently not recommended for clinical use in scaphoid fractures. Further fundamental research is necessary.

Fluorescence molecular tomography of DiR-labeled mesenchymal stem cell implants for osteochondral defect repair in rabbit knees.

OBJECTIVES: To assess labelling efficiency of rabbit mesenchymal stem cells (MSCs) using the near-infrared dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) and detection of labelled MSCs for osteochondral defect repair in a rabbit model using fluorescence molecular tomography-X-ray computed tomography (FMT-XCT). METHODS: MSCs were isolated from New Zealand White rabbits and labelled with DiR (1.25-20 µg/mL). Viability and induction of apoptosis were assessed by XTT- and Caspase-3/-7-testing. Chondrogenic potential was evaluated by measurement of glycosaminoglycans. Labelled cells and unlabeled controls (n = 3) underwent FMT-XCT imaging before and after chondrogenic differentiation. Osteochondral defects were created surgically in rabbit knees (n = 6). Unlabeled and labelled MSCs were implanted in fibrin-clots and imaged by FMT-XCT. Statistical analyses were performed using multiple regression models. RESULTS: DiR-labelling of MSCs resulted in a dose-dependent fluorescence signal on planar images in trans-illumination mode. No significant reduction in viability or induction of apoptosis was detected at concentrations below 10 µg DiR/mL (p > .05); the chondrogenic potential of MSCs was not affected (p > .05). FMT-XCT of labelled MSCs in osteochondral defects showed a significant signal of the transplant (p < .05) with additional high-resolution anatomical information about its osteochondral integration. CONCLUSIONS: FMT-XCT allows for detection of stem cell implantation within osteochondral regeneration processes. KEY POINTS: • DiR-labelling of MSCs shows no toxic side effects or impairment of chondrogenesis. • Fluorescence molecular tomography allows for detection of MSCs for osteochondral defect repair. • FMT-XCT helps to improve evaluation of cell implantation and osteochondral regeneration processes.

Quantification of inflammatory activity in patients with Crohn's disease using diffusion weighted imaging (DWI) in MR enteroclysis and MR enterography.

Background Individual studies have demonstrated the potential of diffusion-weighted magnetic resonance imaging (DWI-MRI) for identifying inflamed bowel segments. However, these studies were conducted with rather small patient cohorts and in most cases by means of MR enterography only. Purpose To demonstrate the feasibility of detecting inflamed bowel segments in a large collective of patients with Crohn's disease using DWI in MR enteroclysis and MR enterography and to compare the results of both techniques, also considering clinical parameters by means of the Harvey-Bradshaw Index (HBI). Material and Methods Ninety-six patients underwent MRI enteroclysis and 35 patients MR enterography, both with additional DWI. The HBI as well as apparent diffusion coefficients (ADC) in areas of inflamed and normal bowel wall were determined. Thus resulting in 208 bowel segments that were visualized and subsequently statistically analyzed. Results There were no significant differences in ADC values in MR enteroclysis and MR enterography ( P = 0.383 in inflammation, P = 0.223 in normal wall). Areas of inflammation showed statistically highly significant lower ADC values than areas of normal bowel wall ( P < 0.001). An ADC threshold of 1.56 × 10-3 mm2/s can distinguish between normal and inflamed bowel segments with a sensitivity of 97.4% and a specificity of 99.2%. A highly significant correlation could be shown between ADC and HBI values ( P = 0.001). Conclusion DWI-MRI facilitates recognition of inflamed bowel segments in patients with Crohn's disease and the ADC values show an excellent correlation to the HBI. There were no significant differences in ADC values in MR enteroclysis and MR enterography. An ADC threshold of 1.56 × 10-3 mm2/s differentiates between normal and inflamed bowel wall.

Polyurethane versus silicone catheters for central venous port devices implanted at the forearm.

PURPOSE: We aimed to analyse short and long-term complications of polyurethane (PU) versus silicone catheters used in totally implantable venous-access ports (TIVAPs) implanted at the forearm. METHODS: Retrospective analysis of 698 consecutively implanted TIVAPs was performed. Primary end-points were defined as rates of major complications associated with either type of central venous port catheter. Technical success rate, device service interval as well as minor complications not requiring port explantation were defined as secondary end-points. RESULTS: A total of 698 port devices were implanted in 681 patients, 396 equipped with a PU catheter, 302 with a silicone catheter. The technical success rate was 99.9% with no major periprocedural complications. During follow-up a total of 211 complications in 146 patients were observed (1.0/1000 catheter days), 183 occurred associated with PU catheters (1.8/100 catheter days), 28 (0.3/1000 catheter days) with silicone catheters (log rank test p < 0.0001). Catheter-related bloodstream infections as well as thrombotic complications occurred significantly more frequently with PU catheters, while silicone catheters exhibited a trend towards a higher rate of mechanical failure such as disconnection or catheter rupture. Major complications requiring explantation of the device occurred more frequently with PU-based catheters (10.6%) compared to silicone catheter carrying ports (4.6%, log rank test p < 0.001). CONCLUSION: PU catheters are more susceptible to catheter-related infections and exhibit a higher thrombogenicity, compared to silicone catheters. Silicone catheters instead exhibit a trend towards decreased mechanical stability.

View-Angle Tilting and Slice-Encoding Metal Artifact Correction for Artifact Reduction in MRI: Experimental Sequence Optimization for Orthopaedic Tumor Endoprostheses and Clinical Application.

BACKGROUND: MRI plays a major role in follow-up of patients with malignant bone tumors. However, after limb salvage surgery, orthopaedic tumor endoprostheses might cause significant metal-induced susceptibility artifacts. PURPOSES: To evaluate the benefit of view-angle tilting (VAT) and slice-encoding metal artifact correction (SEMAC) for MRI of large-sized orthopaedic tumor endoprostheses in an experimental model and to demonstrate clinical benefits for assessment of periprosthetic soft tissue abnormalities. METHODS: In an experimental setting, tumor endoprostheses (n=4) were scanned at 1.5T with three versions of optimized high-bandwidth turbo-spin-echo pulse sequences: (i) standard, (ii) VAT and (iii) combined VAT and SEMAC (VAT&SEMAC). Pulse sequences included coronal short-tau-inversion-recovery (STIR), coronal T1-weighted (w), transverse T1-w and T2-w TSE sequences. For clinical evaluation, VAT&SEMAC was compared to conventional metal artifact-reducing MR sequences (conventional MR) in n=25 patients with metal implants and clinical suspicion of tumor recurrence or infection. Diameters of artifacts were measured quantitatively. Qualitative parameters were assessed on a five-point scale (1=best, 5=worst): "image distortion", "artificial signal changes at the edges" and "diagnostic confidence". Imaging findings were correlated with pathology. T-tests and Wilcoxon-signed rank tests were used for statistical analyses. RESULTS: The true size of the prostheses was overestimated on MRI (P<0.05). A significant reduction of artifacts was achieved by VAT (P<0.001) and VAT&SEMAC (P=0.003) compared to the standard group. Quantitative scores improved in the VAT and VAT&SEMAC group (P<0.05). On clinical MR images, artifact diameters were significantly reduced in the VAT&SEMAC-group as compared with the conventional-group (P<0.001). Distortion and artificial signal changes were reduced and diagnostic confidence improved (P<0.05). In two cases, tumor-recurrence, in ten cases infection and in thirteen cases other pathologies were diagnosed. CONCLUSIONS: Significant reduction of metallic artifacts was achieved by VAT and SEMAC. Clinical results suggest, that these new techniques will be beneficial for detecting periprosthetic pathologies during postoperative follow-up.

Diagnostic utility of Acoustic Radiation Force Impulse (ARFI) imaging in primary Sjoegren`s syndrome.

OBJECTIVES: The purpose of the study was to assess the diagnostic utility of acoustic radiation force impulse (ARFI) imaging in primary Sjögren's syndrome (pSS). METHODS: One hundred fifty-seven patients with sicca symptoms and/or salivary gland swelling were included. Sicca symptoms, Schirmer test, unstimulated whole saliva (UWS), SS-A/B antibodies, and histology were assessed according to American-European Consensus group (AECG) criteria. All patients underwent high-resolution ultrasound and ARFI imaging of the parotid (PG) and submandibular glands (SMG). RESULTS: Seventy patients were classified as having pSS. The remaining 87 patients suffered from idiopathic sicca (n = 24), rheumatoid arthritis (n = 12), sarcoidosis (n = 9), cutaneous/systemic lupus erythematosus (n = 7), scleroderma (n = 2), dermatomyositis (n = 1), HBV/HCV (n = 2), and panarteritis nodosa (n = 1), and disorders in 29 patients were classified as not otherwise specified. ARFI values of the PG were significantly higher in the pSS versus non-pSS groups (2.86 ± 0.07 m/s vs. 2.15 ± 0.11 m/s, p < 0.0001). ARFI imaging demonstrated diagnostic sensitivity and specificity of 81 % and 67 %, respectively. CONCLUSIONS: In addition to histology, ARFI imaging was the most important diagnostic tool for identifying early pSS. KEY POINTS: • Early stages in Sjögren's syndrome become apparent with major salivary gland enlargements. • Schirmer and unstimulated whole saliva tests demonstrated insufficient sensitivity/specificity for early-stage diagnosis. • Acoustic radiation force impulse imaging is a reliable tool for diagnosing early disease stages.

Bone marrow oedema on MR imaging indicates ARCO stage 3 disease in patients with AVN of the femoral head.

OBJECTIVES: To test the hypothesis that bone marrow oedema (BME) observed on MRI in patients with avascular necrosis (AVN) of the femoral head represents an indicator of subchondral fracture. METHODS: Thirty-seven symptomatic hips of 27 consecutive patients (53% women, mean age 49.2) with AVN of the femoral head and associated BME on magnetic resonance (MR) imaging were included. MR findings were correlated with computed tomography (CT) of the hip and confirmed by histopathological examination of the resected femoral head. Imaging studies were analysed by two radiologists with use of the ARCO classification. RESULTS: On MR imaging a fracture line could be identified in 19/37 (51%) cases, which were classified as ARCO stage 3 (n = 15) and stage 4 (n = 4). The remaining 18/37 (49%) cases were classified as ARCO stage 2. However, in all 37/37 (100%) cases a subchondral fracture was identified on CT, indicating ARCO stage 3/4 disease. The extent of subchondral fractures and the femoral head collapse was graded higher on CT as compared to MRI (P < 0.05). Histopathological analysis confirmed bone necrosis and subchondral fractures. CONCLUSIONS: In patients with AVN, BME of the femoral head represents a secondary sign of subchondral fracture and thus indicates ARCO stage 3 disease. KEY POINTS: BME on MRI in AVN of femoral head indicates a subchondral fracture. BME in AVN of the femoral head represents ARCO stage 3/4 disease. CT identifies subchondral fractures and femoral head collapse better than MR imaging. This knowledge helps to avoid understaging and to trigger adequate treatment.

Multimodality multiparametric imaging of early tumor response to a novel antiangiogenic therapy based on anticalins.

Anticalins are a novel class of targeted protein therapeutics. The PEGylated Anticalin Angiocal (PRS-050-PEG40) is directed against VEGF-A. The purpose of our study was to compare the performance of diffusion weighted imaging (DWI), dynamic contrast enhanced magnetic resonance imaging (DCE)-MRI and positron emission tomography with the tracer [18F]fluorodeoxyglucose (FDG-PET) for monitoring early response to antiangiogenic therapy with PRS-050-PEG40. 31 mice were implanted subcutaneously with A673 rhabdomyosarcoma xenografts and underwent DWI, DCE-MRI and FDG-PET before and 2 days after i.p. injection of PRS-050-PEG40 (n = 13), Avastin (n = 6) or PBS (n = 12). Tumor size was measured manually with a caliper. Imaging results were correlated with histopathology. In the results, the tumor size was not significantly different in the treatment groups when compared to the control group on day 2 after therapy onset (P = 0.09). In contrast the imaging modalities DWI, DCE-MRI and FDG-PET showed significant differences between the therapeutic compared to the control group as early as 2 days after therapy onset (P<0.001). There was a strong correlation of the early changes in DWI, DCE-MRI and FDG-PET at day 2 after therapy onset and the change in tumor size at the end of therapy (r = -0.58, 0.71 and 0.67 respectively). The imaging results were confirmed by histopathology, showing early necrosis and necroptosis in the tumors. Thus multimodality multiparametric imaging was able to predict therapeutic success of PRS-050-PEG40 and Avastin as early as 2 days after onset of therapy and thus promising for monitoring early response of antiangiogenic therapy.

Polyglycerolsulfate functionalized gold nanorods as optoacoustic signal nanoamplifiers for in vivo bioimaging of rheumatoid arthritis.

We have synthesized a targeted imaging agent for rheumatoid arthritis based on polysulfated gold nanorods. The CTAB layer on gold nanorods was first replaced with PEG-thiol and then with dendritic polyglycerolsulfate at elevated temperature, which resulted in significantly reduced cytotoxicity compared to polyanionic gold nanorods functionalized by non-covalent approaches. In addition to classical characterization methods, we have established a facile UV-VIS based BaCl2 agglomeration assay to confirm a quantitative removal of unbound ligand. With the help of a competitive surface plasmon resonance-based L-selectin binding assay and a leukocyte adhesion-based flow cell assay, we have demonstrated the high inflammation targeting potential of the synthesized gold nanorods in vitro. In combination with the surface plasmon resonance band of AuNRs at 780 nm, these findings permitted the imaging of inflammation in an in vivo mouse model for rheumatoid arthritis with high contrast using multispectral optoacoustic tomography. The study offers a robust method for otherwise difficult to obtain covalently functionalized polyanionic gold nanorods, which are suitable for biological applications as well as a low-cost, actively targeted, and high contrast imaging agent for the diagnosis of rheumatoid arthritis. This paves the way for further research in other inflammation associated pathologies, in particular, when photothermal therapy can be applied.

MR imaging features of gadofluorine-labeled matrix-associated stem cell implants in cartilage defects.

OBJECTIVES: The purpose of our study was to assess the chondrogenic potential and the MR signal effects of GadofluorineM-Cy labeled matrix associated stem cell implants (MASI) in pig knee specimen. MATERIALS AND METHODS: Human mesenchymal stem cells (hMSCs) were labeled with the micelle-based contrast agent GadofluorineM-Cy. Ferucarbotran-labeled hMSCs, non-labeled hMSCs and scaffold only served as controls. Chondrogenic differentiation was induced and gene expression and histologic evaluation were performed. The proportions of spindle-shaped vs. round cells of chondrogenic pellets were compared between experimental groups using the Fisher's exact test. Labeled and unlabeled hMSCs and chondrocytes in scaffolds were implanted into cartilage defects of porcine femoral condyles and underwent MR imaging with T1- and T2-weighted SE and GE sequences. Contrast-to-noise ratios (CNR) between implants and adjacent cartilage were determined and analyzed for significant differences between different experimental groups using the Kruskal-Wallis test. Significance was assigned for p<0.017, considering a Bonferroni correction for multiple comparisons. RESULTS: Collagen type II gene expression levels were not significantly different between different groups (p>0.017). However, hMSC differentiation into chondrocytes was superior for unlabeled and GadofluorineM-Cy-labeled cells compared with Ferucarbotran-labeled cells, as evidenced by a significantly higher proportion of spindle cells in chondrogenic pellets (p<0.05). GadofluorineM-Cy-labeled hMSCs and chondrocytes showed a positive signal effect on T1-weighted images and a negative signal effect on T2-weighted images while Ferucarbotran-labeled cells provided a negative signal effect on all sequences. CNR data for both GadofluorineM-Cy-labeled and Ferucarbotran-labeled hMSCs were significantly different compared to unlabeled control cells on T1-weighted SE and T2*-weighted MR images (p<0.017). CONCLUSION: hMSCs can be labeled by simple incubation with GadofluorineM-Cy. The labeled cells provide significant MR signal effects and less impaired chondrogenesis compared to Ferucarbotran-labeled hMSCs. Thus, GadoflurineM-Cy might represent an alternative MR cell marker to Ferucarbotran, which is not distributed any more in Europe or North America.

Somatic differentiation and MR imaging of magnetically labeled human embryonic stem cells.

Magnetic resonance (MR) imaging of superparamagnetic iron oxide (SPIO)-labeled stem cells offers a noninvasive evaluation of stem cell engraftment in host organs. Excessive cellular iron load from SPIO labeling, however, impairs stem cell differentiation. The purpose of this study was to magnetically label human embryonic stem cells (hESCs) via a reduced exposure protocol that maintains a significant MR signal and no significant impairment to cellular pluripotency or differentiation potential. hESCs were labeled by simple incubation with Food and Drug Administration-approved ferumoxides, using concentrations of 50- 200 µg Fe/ml and incubation times of 3-24 h. The most reduced exposure labeling protocol that still provided a significant MR signal comparable to accepted labeling protocols was selected for subsequent studies. Labeled hESCs were compared to unlabeled controls for differences in pluripotency as studied by fluorescence staining for SSEA-1, SSEA-4, TRA-60, and TRA-81 and in differentiation capacity as studied by quantitative real-time PCR for hOCT4, hACTC1, hSOX1, and hAFP after differentiation into embryoid bodies (EBs). Subsequent MR and microscopy imaging were performed to evaluate for cellular iron distribution and long-term persistence of the label. An incubation concentration of 50 µg Fe/ml and incubation time of 3 h demonstrated a significantly reduced exposure protocol that yielded an intracellular iron uptake of 4.50 ± 0.27 pg, an iron content comparable to currently accepted SPIO labeling protocols. Labeled and unlabeled hESCs showed no difference in pluripotency or differentiation capacity. Ferumoxide-labeled hESCs demonstrated persistent MR contrast effects as embryoid bodies for 21 days. Electron microscopy confirmed persistent lysosomal storage of iron oxide particles in EBs up to 9 days, while additional microscopy visualization confirmed the iron distribution within single and multiple EBs. Labeling hESCs with ferumoxides by this tailored protocol reduces exposure of cells to the labeling agent while allowing for long-term visualization with MR imaging and the retention of cellular pluripotency and differentiation potential.

Magnetic resonance imaging of ferumoxide-labeled mesenchymal stem cells in cartilage defects: in vitro and in vivo investigations.

The purpose of this study was to (1) compare three different techniques for ferumoxide labeling of mesenchymal stem cells (MSCs), (2) evaluate if ferumoxide labeling allows in vivo tracking of matrix-associated stem cell implants (MASIs) in an animal model, and (3) compare the magnetic resonance imaging (MRI) characteristics of ferumoxide-labeled viable and apoptotic MSCs. MSCs labeled with ferumoxide by simple incubation, protamine transfection, or Lipofectin transfection were evaluated with MRI and histopathology. Ferumoxide-labeled and unlabeled viable and apoptotic MSCs in osteochondral defects of rat knee joints were evaluated over 12 weeks with MRI. Signal to noise ratios (SNRs) of viable and apoptotic labeled MASIs were tested for significant differences using t-tests. A simple incubation labeling protocol demonstrated the best compromise between significant magnetic resonance signal effects and preserved cell viability and potential for immediate clinical translation. Labeled viable and apoptotic MASIs did not show significant differences in SNR. Labeled viable but not apoptotic MSCs demonstrated an increasing area of T2 signal loss over time, which correlated to stem cell proliferation at the transplantation site. Histopathology confirmed successful engraftment of viable MSCs. The engraftment of iron oxide-labeled MASIs by simple incubation can be monitored over several weeks with MRI. Viable and apoptotic MASIs can be distinguished via imaging signs of cell proliferation at the transplantation site.