Once considered a limitation, small cell samples have now led to new technology advances that are providing researchers with faster and more accurate molecular information. These advances include separation methods to obtain pure cell populations, novel gene expression techniques, and accurate quantitation of material during probe development.
Using these technologies together, researchers are now able to obtain important information even from a single cell. Overall, this is reducing costs, improving data quality, and making R&D labs more quantitative.
Microgenomics is the new catch phrase for the precise molecular analysis of very small populations of cells that have been excised, or microdissected from biopsies.
Realizing that there was no technology to allow such analysis of solid tumor biopsies, Thomas M. Baer, Ph.D., founder and chairman of Arcturus Biosciences (www. arctur.com), developed the first Laser Capture Microdissection (LCM) platform with several colleagues at the National Institutes of Health (NIH).
LCM uses a nondamaging infrared laser to adhere specific cells to a thermoplastic film. This ensures integrity of biological molecules like RNA, DNA, and proteins, which are extracted from the targeted cells.
The PixCell IIe is a manually controlled system mounted on an inverted microscope platform, and is geared toward labs with low- to medium-throughput needs. It microdissects single cells efficiently and uses a direct point-and-shoot process.
AutoPix automatically microdissects cells from up to three slides per session and can pool microdissected cells from several samples, isolate up to eight unique cell types in one session, and capture rare cells dispersed across several slides, according to the company. It can dissect from frozen, formalin-fixed paraffin-embedded tissue, or cytology smears, and can identify and capture fluorescently labeled cells automatically.
Veritas Microdissection, the company's latest platform, is a high throughput, fully automated system that performs both laser capture and laser cutting microdissection using two lasers. Using the IR laser and UV laser technologies, coupled with image-recognition software, Veritas Microdissection can harvest single cells and large cell populations quickly.
"Our customers wanted something useful for proteomics applications. When you're dealing with mass spectrometry or Western blot, you need to microdissect tens of thousands of cells," explains Dr. Baer.
Veritas Microdissection is routinely employed in the preclinical research phase of the drug dicovery and development process. It goes hand-in-hand with routine preclinical testing of lead compounds for efficacy, toxicity, and adverse effects.
Scientists can perform a risk assessment of dosage, for example, in a mouse or rat targeted with a lead compound, by looking at the histopathology of a variety of tissues affected by this compound.
Single stained tissue sections from various organs help identify changes in individual cell types that have known drug effects, rather than "grinding up" whole tissues. Ultimately, this process facilitates biomarker identification and confirmtion, helping to narrow the search for which genes are changed or affected and which biomarkers may be tested in the clinic.
Studies have reportedly shown that LCM increases the sensitivity of point mutation analysis of specific genes and identifies differentially expressed genes not visible when standard whole tissue is used. LCM can also enhance the user's ability to locate up- and down-regulated proteins in studies using 2-D gel electrophoresis, mass spectroscopy, and SELDI.
In addition, it has proven useful in providing rapid cell-based analysis of disease progression, which may ultimately lead to personalized medicine and diagnostics.