Reijo Takalo

Cell Surface Structures Influence Lung Clearance Rate of Systemically Infused Mesenchymal Stromal Cells

The promising clinical effects of mesenchymal stromal/stem cells (MSCs) rely especially on paracrine and nonimmunogenic mechanisms. Delivery routes are essential for the efficacy of cell therapy and systemic delivery by infusion is the obvious goal for many forms of MSC therapy. Lung adhesion of MSCs might, however, be a major obstacle yet to overcome. Current knowledge does not allow us to make sound conclusions whether MSC lung entrapment is harmful or beneficial, and thus we wanted to explore MSC lung adhesion in greater detail. We found a striking difference in the lung clearance rate of systemically infused MSCs derived from two different clinical sources, namely bone marrow (BM‐MSCs) and umbilical cord blood (UCB‐MSCs). The BM‐MSCs and UCB‐MSCs used in this study differed in cell size, but our results also indicated other mechanisms behind the lung adherence. A detailed analysis of the cell surface profiles revealed differences in the expression of relevant adhesion molecules. The UCB‐MSCs had higher expression levels of α4 integrin (CD49d, VLA‐4), α6 integrin (CD49f, VLA‐6), and the hepatocyte growth factor receptor (c‐Met) and a higher general fucosylation level. Strikingly, the level of CD49d and CD49f expression could be functionally linked with the lung clearance rate. Additionally, we saw a possible link between MSC lung adherence and higher fibronectin expression and we show that the expression of fibronectin increases with MSC culture confluence. Future studies should aim at developing methods of transiently modifying the cell surface structures in order to improve the delivery of therapeutic cells. STEM CELLS2013;31:317–326

Tutorial on Univariate Autoregressive Spectral Analysis

In the present paper, the theoretical basis of autoregressive (AR) modelling in spectral analysis is explained in simple terms. Spectral analysis gives information about the frequency content and sources of variation in a time series. The AR method is an alternative to discrete Fourier transform, and the method of choice for high-resolution spectral estimation of a short time series. In biomedical engineering, AR modelling is used especially in the spectral analysis of heart rate variability and electroencephalogram tracings. In AR modelling, each value of a time series is regressed on its past values. The number of past values used is called the model order. An AR model or process may be used in either process synthesis or process analysis, each of which can be regarded as a filter. The AR analysis filter divides the time series into two additive components, the predictable time series and the prediction error sequence. When the prediction error sequence has been separated from the modelled time series, the AR model can be inverted, and the prediction error sequence can be regarded as an input and the measured time series as an output to the AR synthesis filter. When a time series passes through a filter, its amplitudes of frequencies are rescaled. The properties of the AR synthesis filter are used to determine the amplitude and frequency of the different components of a time series. Heart rate variability data are here used to illustrate the method of AR spectral analysis. Some basic definitions of discrete-time signals, necessary for understanding of the content of the paper, are also presented.

Acute homing of bone marrow-derived mononuclear cells in intramyocardial vs. intracoronary transplantation

Objectives. Cell homing optimisation after transplantation is critical in myocardial infarction (MI) cell therapy. Design. Eight pigs were randomized to receiving autologous purified 111indium-labeled bone marrow mononuclear cells (BMMCs) (108 cells/2 ml) by intramyocardial (IM) (n=4) or by intracoronary (IC) (n=4) transplantation after 90 minutes occlusion of the CX-coronary artery. Dual isotope SPECT imaging was performed 2 and 24 hours postoperatively. Two animals were additionally analyzed on the sixth postoperative day. Tissue samples from the major organs were analyzed. Results. In SPECT imaging revealed that BMMCs administered using IM injection remained in the injured area. In contrast, minor proportion of IC transplanted cells remained in the myocardium, as most of the cells showed homing in the lungs. Analysis of the biopsies showed a seven-fold greater number of cells in the myocardium for the IM method and a 10-fold greater number of cells in the lungs in the IC group (p < 0.001). Conclusions. In producing persistently high cell homing at the infarction site, the IM transplantation is superior to the IC transplantation. However, the IC administration might be more specific in targeting injured capillaries and epithelial cells within the infarcted myocardium.

Tutorial on Multivariate Autoregressive Modelling

In the present paper, the theoretical background of multivariate autoregressive modelling (MAR) is explained. The motivation for MAR modelling is the need to study the linear relationships between signals. In biomedical engineering, MAR modelling is used especially in the analysis of cardiovascular dynamics and electroencephalographic signals, because it allows determination of physiologically relevant connections between the measured signals. In a MAR model, the value of each variable at each time instance is predicted from the values of the same series and those of all other time series. The number of past values used is called the model order. Because of the inter-signal connections, a MAR model can describe causality, delays, closed-loop effects and simultaneous phenomena. To provide a better insight into the subject matter, MAR modelling is here illustrated with a model between systolic blood pressure, RR interval and instantaneous lung volume.

Transient Proteolytic Modification of Mesenchymal Stromal Cells Increases Lung Clearance Rate and Targeting to Injured Tissue

Systemic infusion of therapeutic cells would be the most practical and least invasive method of administration in many cellular therapies. One of the main obstacles especially in intravenous delivery of cells is a massive cell retention in the lungs, which impairs homing to the target tissue and may decrease the therapeutic outcome. In this study we showed that an alternative cell detachment of mesenchymal stromal/stem cells (MSCs) with pronase instead of trypsin significantly accelerated the lung clearance of the cells and, importantly, increased their targeting to an area of injury. Cell detachment with pronase transiently altered the MSC surface protein profile without compromising cell viability, multipotent cell characteristics, or immunomodulative and angiogenic potential. The transient modification of the cell surface protein profile was sufficient to produce effective changes in cell rolling behavior in vitro and, importantly, in the in vivo biodistribution of the cells in mouse, rat, and porcine models. In conclusion, pronase detachment could be used as a method to improve the MSC lung clearance and targeting in vivo. This may have a major impact on the bioavailability of MSCs in future therapeutic regimes.

Safety and biodistribution study of bone marrow–derived mesenchymal stromal cells and mononuclear cells and the impact of the administration route in an intact porcine model

BACKGROUND AIMS Bone marrow mononuclear cells (BM-MNCs) and bone marrow-derived mesenchymal stem stromal cells (BM-MSCs) could have therapeutic potential for numerous conditions, including ischemia-related injury. Cells transplanted intravascularly may become entrapped in the lungs, which potentially decreases their therapeutic effect and increases the risk for embolism. METHODS Twelve pigs were divided into groups of 3 and received (99m)Tc- hydroxymethyl-propylene-amine-oxime-labeled autologous BM-MNCs or allogeneic BM-MSCs by either intravenous (IV) or intra-arterial (IA) transplantation. A whole body scan and single photon emission computed tomography/computed tomography (SPECT/CT) were performed 8 h later, and tissue biopsies were collected for gamma counting. A helical CT scan was also performed on 4 pigs to detect possible pulmonary embolism, 2 after IV BM-MSC injection and 2 after saline injection. RESULTS The transplantation route had a greater impact on the biodistribution of the BM-MSCs than the BM-MNCs. The BM-MNCs accumulated in the spleen and bones, irrespective of the administration route. The BM-MSCs had relatively higher uptake in the kidneys. The IA transplantation decreased the deposition of BM-MSCs in the lungs and increased uptake in other organs, especially in the liver. Lung atelectases were frequent due to mechanical ventilation and attracted transplanted cells. CT did not reveal any pulmonary embolism. CONCLUSIONS Both administration routes were found to be safe, but iatrogenic atelectasis might be an issue when cells accumulate in the lungs. The IA administration is effective in avoiding pulmonary entrapment of BM-MSCs. The cell type and administration method both have a major impact on the acute homing.

Late‐presenting vascular graft infection caused by Aspergillus in an immunocompetent patient

Marko Rahkonen, Timo Hautala, Erkki Syväniemi, Reijo Takalo and Heikki Kauma Department of Internal Medicine, Oulu University Hospital, Oulu, Finland, Department of Pathology, Oulu University Hospital, Oulu, Finland, Department of Radiology, Oulu University Hospital, Oulu, Finland, Institute of Diagnostics, Department of Medical Microbiology, University of Oulu, Oulu, Finland and Institute of Diagnostics, Department of Pathology, University of Oulu, Oulu, Finland

Adaptive autoregressive model for reduction of poisson noise in scintigraphic images.

In the present paper, a 2-dimensional adaptive autoregressive filter is proposed for noise reduction in images degraded with Poisson noise. In autoregressive models, each value of an image is regressed on its neighborhood pixel values, called the prediction region. The autoregressive models are linear prediction models that split an image into 2 additive components, a predictable image and a prediction error image. Methods: In this research, unfiltered images were split into smaller blocks, and best combinations of a prediction region and a block size for the image quality of predictable images were sought by using 3 Poisson noise–corrupted images with different image statistics. The images had dimensions of 128 × 128 pixels. Image quality was assessed by means of the mean squared error of the image. The adaptive autoregressive model was fitted into each block separately. Different degrees of overlapping of the image blocks were tested, and for each pixel the mean predictor coefficient of the different models was determined. The prediction error image was calculated for the entire image, and the filtered image was obtained by subtracting the prediction error image from the original image. The effect of the best adaptive autoregressive filter was illustrated using real scintigraphic data. Results: Generally, a prediction region of 4 orthogonal neighbors of the predicted pixel with a block size of 5 × 5 showed the best results. The use of 75% overlapping of the image blocks and 1 iteration of the filtering was found to improve prediction accuracy. The results were further improved when the 2 error term images were summed and subjected to adaptive autoregressive filtering and the resulting predictable image was added to the iteratively filtered image, allowing both noise reduction and edge preservation. Patient data illustrated effective noise reduction. Conclusion: The proposed method provided a convenient way to reduce Poisson noise in scintigraphic images on a pixel-by-pixel basis.

Three-Phase Bone Scintigraphy in Chronic Epicondylitis

OBJECTIVE To assess the utility of 3-phase bone scintigraphy as a complementary diagnostic method in chronic epicondylitis. DESIGN A cross-sectional study. SETTING Hospital outpatient clinic admitting patients with musculoskeletal disorders. PARTICIPANTS Patients (N=59; 68% women) with unilateral chronic epicondylitis. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Three-phase bone scintigraphy was performed after an intravenous injection of 550MBq (99m)technetium-labeled hydroxymethyline diphosphonate ((99m)Tc-HDP) in the patients. Blood flow and blood pool phases were graded visually as normative or abnormal. In the bone metabolic phase, the scintigraphic radiograph images were evaluated using a transmission densitometer. The ratio between maximal bone uptake of (99m)Tc-HDP in each epicondyle and the mean of that in the adjacent humerus was used as a bone uptake measure, which was compared with clinical data (pain questionnaire, pain drawing, cubital pain thresholds, muscle strength) and with work ability and lifestyle factors. RESULTS The bone uptake of (99m)Tc-HDP of the affected epicondyle was 33% and 17% higher in men and women, respectively, compared with the corresponding healthy epicondyle (P<.001 and P=.007). High bone uptake of (99m)Tc-HDP was associated with better work ability, grip strength, and muscle performance in both sexes but was not correlated with the pain measures. Blood flow phases had a positive correlation with the duration of symptoms and a negative correlation with the bone uptake of (99m)Tc-HDP, grip strength, and work ability. CONCLUSIONS High bone uptake of (99m)Tc-HDP among patients with chronic epicondylitis was associated with better muscle strength, work ability, and arm function. In chronic cases, a higher degree of bone uptake of (99m)Tc-HDP may thus indicate a healing response in the bone tissue.

Intra-arterial bone marrow mononuclear cell distribution in experimental global brain ischaemia

Abstract Objectives. Bone marrow mononuclear cells (BM-MNCs) can ameliorate focal ischaemic brain injury. A global ischaemic brain injury, which can occur after cardiac or thoracic surgery, could be an essential target for BM-MNCs. No studies using BM-MNCs for this indication have been conducted. Design. Ten porcine underwent a global normothermic ischaemic insult, followed by an intra-arterial injection of Technetium99m-HMPAO-labelled BM-MNCs after 2, 4, 6, 12 or 24 hours. A whole-body scan and a SPECT/CT were performed 2 hours after the injection. Severity of the injury was assessed with EEG and tissue biopsies were analysed by scintigraphy. Results. The majority of the cells appeared in the lungs and the liver. Only a minimal number of cells were located in the brain. Median distribution of cells between organs in all animals was as follows: lungs 32.7% (30.6–38.2), liver 14.2% (12.0–17.2), spleen 7.3% (3.3–11.3) and kidneys 2.5% (2.0–3.3). The transplanted cells could not be detected within the brain tissue by radionuclide imaging. Conclusions. Intra-arterially transplanted BM-MNCs did not migrate to the damaged brain tissue in significant quantity when transplanted during the first 24 hours after the global ischaemic insult, contrary to results with models of focal brain injury.