Tissue Microdissection for Molecular Analysis of Disease States and Normal Development – Target Activated Microdissection (TAM)

Project Collaborators (sorted by Institute): 
Laboratory of Pathology, Experimental Pathology Laboratory, NCI
Biomedical Engineering & Physical Science Shared Resource Program, NIBIB
Section on Medical Biophysics, Program in Physical Biology, NICHD
Molecular Mechanisms of Cellular Stress and Inflammation, Integrative Neuroscience Research Branch, NIDA
Project Brief: 

Laser Capture Microdissection (LCM) is a well-established technology used to isolate cells of interest from surrounding tissue cells on a microscope slide. As early co-inventors of LCM in the mid-90s, SPIS staff have continued to develop innovative tissue microdissection technologies, working with partners in NCI, NICHD, NIBIB, NIMH, NIDA, and industry.  Although LCM is already commercially successful, the method requires a skilled operator to select the cells for capture, which leads to operator variability and limits overall throughput. In more recent years, SPIS and collaborators have developed Target Activated Microdissection (TAM) to address these limitations associated with some applications. TAM uses targeted molecular probes and light-absorbing tissue stains that generate localized heat under suitable illumination, bonding the desired cells to a thin thermoplastic placed in contact with the tissue. The initial TAM prototype used a scanned laser to illuminate the entire tissue section, in which the following performance enhancements were achieved:

  • Increased dissection rate by orders of magnitude
  • Increased dissection precision to the subcellular level
  • Removed requirement for operator target selection, permitting process standardization
  • Eliminated targeting difficulties due to poor image quality of histology sections
  • Maintained spatial relationship of tissue morphology, allowing better image documentation

 

To further improve TAM performance, SPIS designed and produced a custom light source that delivers a brief, high-power, burst of light over the entire surface area of the tissue, reducing the time required to dissect tissue from a whole slide with subcellular precision to under a minute. During validation studies, SPIS introduced a variety of TAM instrumentation features, such as the ability to use multiple pulses in quick succession, the ability to alter the spectrum of light with filters, and the ability to save and reload settings for repeatable experiments. TAM developments have resulted in patents, licensing, and MTAs.

Overview of TAM Process

As an evolution of Laser Capture Microdissection, the Target Activated Microdissection (TAM) process facilitates microdissection use in clinical genomics, epigenomics, gene expression diagnostics, proteomics, and functional biomarker applications. The TAM process (I) begins with an immunolabeled or stained tissue section. A thin thermoplastic film is placed in direct contact with the tissue with the aid of a vacuum, and light is applied over the entire tissue section (II). The labeled tissue targets absorb the light and increase in temperature, causing adhesion to the film, which is then removed along with the labeled tissue targets (III).

fTAM instrumentation 3D model and prototype

Development of flashlamp Target Activated Microdissection (fTAM). The earliest prototypes of TAM technology leveraged existing Laser Capture Microdissection (LCM) instrumentation based on laser systems. While effective, these LCM systems did not fully realize the benefits of TAM due to their limited light spectrum (single wavelength lasers) and limited speeds (small diameter laser beams were raster scanned over the entire tissue sample). SPIS engineers designed and built a novel TAM light source based on a high-power flashlamp.  This development utilized a wide range of SPIS capabilities including analog circuit design (for bulb charging, bulb flashing, and safety locks), microcontroller programming (for user interface, logging, and configuration), optics design (for filters, bulb placement, reflectors), 3D modeling (I and II), and a variety of fabrication techniques, including in-house printed circuit boards, laser cutting, 3D printed parts, and mechanical assembly (III and IV).

Tech Transfer: