Mesenchymal Stem Cells Can Affect Solid Organ Allograft Survival
ABSTRACT It has recently been recognized that mesenchymal stem cells (MSCs) isolated from adult bone marrow are able to modify the alloimmune response in vitro and in vivo. MSCs can be expanded into large quantities in culture, thereby facilitating potential future applications in solid organ transplantation. To develop novel MSC-based antirejection treatments, the mechanism behind the immunomodulatory ability of MSCs has to be elucidated further. At present, a variety of possible in vitro effects of MSCs on immune system effector cells have been reported, but little is known about their in vivo properties. Here, we discuss recent findings regarding the influence of MSCs on different effector cell populations in vitro and summarize the available data describing their in vivo properties.
- SourceAvailable from: Dietrich Polenz
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- "Our data in a renal transplant model are in contrast to the clear beneficial effects of the day-4 MSC application in a rat model of heterotopic heart transplantation with the same MMF immunosuppressive regimen (Popp et al., 2009). We neither see a prolonged graft survival, nor the development of partial tolerance. "
ABSTRACT: Mesenchymal stromal cells (MSC) have shown immunomodulatory and tissue repair potential including partial tolerance induction by pre-treatment of donor-specific cells in a rat heart transplantation model. Very recently, we could show that autologous MSC attenuated ischemia reperfusion injury in a highly mismatched donor-recipient rat kidney transplant model. Therefore, we investigated donor-specific MSC pre-treatment in this rat kidney transplantation model to study whether graft function could be improved, or if tolerance could be induced. Donor- and recipient-type MSC or PBS as a control were injected i.v. four days before kidney transplantation. Mycophenolate mofetil (MMF) immunosuppression (20 mg/kg body weight) was applied for 7 days. Kidney grafts and spleens were harvested between days 8-10 and analyzed by quantitative RT-PCR and immunohistology. In addition, creatinine levels in the blood were measured and serum was screened for the presence of donor-specific antibodies. Surprisingly, application of both donor- and recipient-specific MSC resulted in enhanced humoral immune responses verified by intragraft B cell infiltration and complement factor C4d deposits. Moreover, signs of inflammation and rejection were generally enhanced in both MSC-treated groups relative to PBS control group. Additionally, pre-treatment with donor-specific MSC significantly enhanced the level of donor-specific antibody formation when compared with PBS- or recipient-MSC-treated groups. Pre-treatment with both MSC types resulted in a higher degree of kidney cortex tissue damage and elevated creatinine levels at the time point of rejection. Thus, MSC pre-sensitization in this model impairs the allograft outcome. Our data from this pre-clinical kidney transplantation model indicate that pre-operative MSC administration may not be optimal in kidney transplantation and caution must be exerted before moving forward with clinical studies in order to avoid adverse effects.Frontiers in Immunology 07/2012; 3:202. DOI:10.3389/fimmu.2012.00202
Conference Paper: High-speed systolic implementation of fast QR adaptive filters[Show abstract] [Hide abstract]
ABSTRACT: A rectangular systolic array of processing units is presented for implementation of the QR adaptive filter. This array requires approximately 8 N processing units to exactly solve the least-squares adaptive filtering problem using QR factorization. If a processing unit takes 50 ns to perform a task, the array can be implemented at an adaptive-filter input sampling rate of 20 MHz, with no loss in characteristic high performance (of least squares), numerical stability, or accuracy. This improves on widely used gradient methods for adaptive filtering, which must insert increasing amounts of performance-degrading delay into the adaptive updating when either the speed of implementation or number of taps increase. A discussion of the structure and interconnection of the processing units is included, as well as computer simulations that verify the stability and performance of the adaptive processing arrayAcoustics, Speech, and Signal Processing, 1988. ICASSP-88., 1988 International Conference on; 05/1988
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ABSTRACT: An adaptive space-time processing system for dynamic spatial channels in a CDMA mobile communications network is presented. The proposed system consists of an adaptive sensor array that estimates the desired directions and waveforms, followed by adaptive linear equalizers that refine the waveform estimates by compensating for the mobile radio uplink channel. Capacity gains are achieved through code reuse, which is made possible by performing the spatial processing after the codes have been decorrelated with one another. Simulation results for a two sensor array in a variety of interference scenarios are presented in the form of bit error rate curves.Proceedings - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing 01/1995; 3:1749-1752. DOI:10.1109/ICASSP.1995.480036