Stem Cell Based Tissue Engineering and Regenerative Medicine: A Review Focusing on Adult Stem Cells

Tissue engineering has emerged as a field that attempts to harness the bodies\u27 own developmental and repair features to treat diseases and illnesses. Many of these illnesses are caused by necrosis or loss of functionality of complete organs or specific cell types. Early discoveries in embryonic stem cells fueled a wave of research that led to claims about possibly regenerating nonfunctioning organs. Although we are still far away from being able to grow functional organs in a Petri dish, the field continues to progress forward, and new clinical trials have been approved for using both embryonic and adult stem cell based solutions for regenerative medicine and tissue engineering. Current trends have moved towards adult stem cells for cell based therapies as they offer an autologous source and are less tumorigenic than their embryonic and induced-pluripotent stem cell counter parts. This review will begin with an outline of stem cell classes and then focus on current therapies in myocardial tissue repair, neural tissue repair, diabetes, as well as osteogenic and chondrogenic differentiation are also reviewed

NEXT Propellant Management System Integration With Multiple Ion Thrusters

As a critical part of the NEXT test validation process, a multiple-string integration test was performed on the NEXT propellant management system and ion thrusters. The objectives of this test were to verify that the PMS is capable of providing stable flow control to multiple thrusters operating over the NEXT system throttling range and to demonstrate to potential users that the NEXT PMS is ready for transition to flight. A test plan was developed for the sub-system integration test for verification of PMS and thruster system performance and functionality requirements. Propellant management system calibrations were checked during the single and multi-thruster testing. The low pressure assembly total flow rates to the thruster(s) were within 1.4 percent of the calibrated support equipment flow rates. The inlet pressures to the main, cathode, and neutralizer ports of Thruster PM1R were measured as the PMS operated in 1-thruster, 2-thruster, and 3-thruster configurations. It was found that the inlet pressures to Thruster PM1R for 2-thruster and 3-thruster operation as well as single thruster operation with the PMS compare very favorably indicating that flow rates to Thruster PM1R were similar in all cases. Characterizations of discharge losses, accelerator grid current, and neutralizer performance were performed as more operating thrusters were added to the PMS. There were no variations in these parameters as thrusters were throttled and single and multiple thruster operations were conducted. The propellant management system power consumption was at a fixed voltage to the DCIU and a fixed thermal throttle temperature of 75 C. The total power consumed by the PMS was 10.0, 17.9, and 25.2 W, respectively, for single, 2-thruster, and 3-thruster operation with the PMS. These sub-system integration tests of the PMS, the DCIU Simulator, and multiple thrusters addressed, in part, the NEXT PMS and propulsion system performance and functionality requirements

NASA's Evolutionary Xenon Thruster (NEXT) Component Verification Testing

Component testing is a critical facet of the comprehensive thruster life validation strategy devised by the NASA s Evolutionary Xenon Thruster (NEXT) program. Component testing to-date has consisted of long-duration high voltage propellant isolator and high-cycle heater life validation testing. The high voltage propellant isolator, a heritage design, will be operated under different environmental condition in the NEXT ion thruster requiring verification testing. The life test of two NEXT isolators was initiated with comparable voltage and pressure conditions with a higher temperature than measured for the NEXT prototype-model thruster. To date the NEXT isolators have accumulated 18,300 h of operation. Measurements indicate a negligible increase in leakage current over the testing duration to date. NEXT 1/2 in. heaters, whose manufacturing and control processes have heritage, were selected for verification testing based upon the change in physical dimensions resulting in a higher operating voltage as well as potential differences in thermal environment. The heater fabrication processes, developed for the International Space Station (ISS) plasma contactor hollow cathode assembly, were utilized with modification of heater dimensions to accommodate a larger cathode. Cyclic testing of five 1/22 in. diameter heaters was initiated to validate these modified fabrication processes while retaining high reliability heaters. To date two of the heaters have been cycled to 10,000 cycles and suspended to preserve hardware. Three of the heaters have been cycled to failure giving a B10 life of 12,615 cycles, approximately 6,000 more cycles than the established qualification B10 life of the ISS plasma contactor heaters

Progress of Mesenchymal Stem Cell Therapy for Neural and Retinal Diseases

Complex circuitry and limited regenerative power make central nervous system (CNS) disorders the most challenging and difficult for functional repair. With elusive disease mechanisms, traditional surgical and medical interventions merely slow down the progression of the neurodegenerative diseases. However, the number of neurons still diminishes in many patients. Recently, stem cell therapy has been proposed as a viable option. Mesenchymal stem cells (MSCs), a widely-studied human adult stem cell population, have been discovered for more than 20 years. MSCs have been found all over the body and can be conveniently obtained from different accessible tissues: bone marrow, blood, and adipose and dental tissue. MSCs have high proliferative and differentiation abilities, providing an inexhaustible source of neurons and glia for cell replacement therapy. Moreover, MSCs also show neuroprotective effects without any genetic modification or reprogramming. In addition, the extraordinary immunomodulatory properties of MSCs enable autologous and heterologous transplantation. These qualities heighten the clinical applicability of MSCs when dealing with the pathologies of CNS disorders. Here, we summarize the latest progress of MSC experimental research as well as human clinical trials for neural and retinal diseases. This review article will focus on multiple sclerosis, spinal cord injury, autism, glaucoma, retinitis pigmentosa and age-related macular degeneration

Pluripotent Adult Stem Cells: A Potential Revolution in Regenerative Medicine and Tissue Engineering

Stem cells have generated a lot of excitement among the researchers, clinicians and the public alike. Various types of stem cells are being evaluated for their regenerative potential. Marginal benefit resulting by transplanting autologus stem cells (deemed to be absolutely safe) in various clinical conditions has been proposed to be a growth factor effect rather than true regeneration. In contrast, various pre-clinical studies have been undertaken, using differentiated cells from embryonic stem cells or induced pluripotent stem cells have shown promise, functional improvement and no signs of teratoma formation. The scientists are not in a rush to reach the clinic but a handful of clinical studies have shown promise. This book is a collection of studies/reviews, beginning with an introduction to the pluripotent stem cells and covering various aspects like derivation, differentiation, ethics, etc., and hence would provide insight into the recent standing on the pluripotent stem cells biology. The chapters have been categorized into three sections, covering subjects ranging from the generation of pluripotent stem cells and various means of their derivation from embryonic as well as adult tissues, the mechanistic understanding of pluripotency and narrating the potential therapeutic implications of these in vitro generated cells in various diseases, in addition to the associated pros and cons in the same.https://nsuworks.nova.edu/cnso_bio_facbooks/1014/thumbnail.jp

Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

We present initial results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra's superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the `ionization cone' in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the spatially resolved spectra as a function of distance from the nucleus.Comment: 5 pages, 2 figures, 1 video. To appear in refereed Proceedings of "X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September 7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin