From the “Strahlenstich” method to laser microdissection
As early as 1912, the so-called “Strahlenstich” method was used to focus light for micromanipulation in biology and medicine, marking the beginning of experiments that eventually led to laser microdissection (Tschachotin, 1912).
However, it was 1962 before Bessis and Bereiter-Hahn et al. irradiated samples with ruby lasers (Bessis) and UV laser beams (Bereiter-Hahn) to cut tissue. By then it was already possible to use a laser beam as a microsurgical tool for dissecting cells without the generated arc of light causing major damage to the surrounding tissue (Bessis, 1962, Bereiter-Hahn, 1962).
Isenberg et. al. also applied this technology for their experiments: in connection with a Leitz Orthoplan microscope of the Wild-Leitz company (now Leica Microsystems), a high-energy nitrogen laser, a precursor of today’s UV laser, was used to separate actin and myosin fibrils from the surrounding cytoplasm (Isenberg et.al., 1976).
In 1987, Pataki et.al. also published the first results of their research on laser microdissection. Here, manual preparation of tissue for biochemical experiments was replaced by the combination of a microscope with a laser unit. This unit consisted of a pulsed N2 laser and a continuous-wave HeNe laser. The N2 laser generated the necessary laser power, the HeNe laser was used to mark the target and adjust the optics in the red spectral range. Here too, laser energy was harnessed as a tool for the analysis of extremely small tissue samples (Pataki et.al., 1978).
Compared with the previous manual preparation, the cutting of tissue with a laser beam was a tremendous improvement in terms of reproducibility, higher precision and time saving.
At the time, however, scientists had problems with the enzyme inactivity induced by changes at the cut edges. Also, it was only possible to conduct optical analysis; the PCR (polymerase chain reaction) technique was still unknown. So although it already existed in the configuration with the Leitz Orthoplan described above, the technique was not commercially viable. Being far ahead of its time, it fell into oblivion.
Further development of laser technique leads to breakthrough
In the mid nineties, the technological progress that had been made in the meantime enabled Michael R. Emmert-Buck and his team at the National Institutes of Health and the National Cancer Institute (Bethesda, Maryland, USA) to develop another laser microdissection technique. Combining a carbon dioxide laser for polymerization with a transparent thermoplastic membrane (ethylene vinyl acetate polymer), this technique involves the application of the transparent thermoplastic membrane to the surface of a tissue section (full contact with the sample) that can be mounted on a conventional glass slide. When the polymer is irradiated with the laser, it heats up and liquefies, expanding into cavities of the tissue section and fusing with it, thus transferring selected cells/cell aggregates to the membrane. These can then be removed from the specimen slide (Emmert-Buck et.al., 1996).
The system was immediately adopted for further development and marketing by Arcturus with the aim of isolation and molecular analysis of morphologically and phenotypically different cell types. Gradually, further systems appeared on the market, such as the Palm Microbeam System and the LMD system by Leica Microsystems.
Laser microdissection established in a wide variety of applications
Of the laser microdissection systems on the market today, Leica Microsystems uses an upright microscope that is also eminently suitable for work with cell cultures. Leica Microsystems is also the only optics company to have developed a proprietary laser module and laser microdissection principle. The distinctive feature of Leica LMD systems is the combination of the patented laser control and the contact- and contamination-free collection of dissectate material using the force of gravity. Such a combination also offers fascinatingly rapid collection of pure starting material from complex heterogeneous tissue. Leica Microsystems has been in the market since its launch of the Leica AS LMD in the year 2000; meanwhile the company has issued new generations of laser microdissection systems in the form of the Leica LMD6500 and the Leica LMD7000.
Laser microdissection systems offer a wide application spectrum for molecular biology, in particular nucleic acid research, neurosciences, developmental biology, cell culture, cancer research, immunology, forensics, proteomics, plant and climate research.
Bessis M, Gires F, Mayer G and Nomarski G: C. R. Acad. Sci. 255: 1010 (1962).
Pataki et.al.: The laser microbeam as a tool for tissue sampling in biochemistry, Laser und Elektro-Optik, at-Verlag (1978).
Tschachotin S: Biol. Zentralbl. 32: 623 (1912).