Considerable progress has been made, despite many challenges, in the development of a stem cell microscope capable of imaging stem cells and their progeny noninvasively inside a living animal. From what we have learned from our first prototype device, we have planned significant improvements for the 2nd year of this grant. We have also developed and demonstrated a prototype device that can simultaneously acquire SPECT and MRI images of a mouse. Together with the microscope, these devices will provide tri-resolution visualization of stem cells and their tissue environment.
In parallel, we have developed and demonstrated successfully a technique to label stem cells and their progeny for observation by the microscope and SPECT. Mouse mesenchymal stem cells (MSCs) are infected by a lentivirus carrying the human sodium iodide symporter (hNIS) gene. These engineered MSCs and their progeny then overexpress hNIS which is normally found only on cell membranes in the thyroid, salivary glands, and the stomach. At any time after the MSCs are introduced into a mouse – even days or months later – they can be labeled with a radioactive tracer and imaged to track their position. An intravenous injection of Technetium-99m-sodium pertechnetate, for example, will result in the hNIS expressing cells taking up significant tracer. The stem cell microscope or small animal microSPECT scanner can then image the stem cells and their progeny.
In year 2 of this grant we will refine the imaging hardware, reconstruction software, and mouse model of Achille’s tendon injury and stem cell therapy. In year 3 we will put the imaging devices and animals together to test the ability to track stem cells and monitor their tissue environment.