Transitioning From Clinical to Research

Making a smooth transition from Clinical Histology to Research Histology takes time. Longer than you may think. In my experience, it takes roughly 6 months to one year before one really begins to find a comfort zone in our research facility.

Good candidates for research positions are techs who possess a solid, thorough knowledge of histological techniques used in the clinical lab, pay close attention to detail, are interested in continuing education opportunities, and really like facing challenges. While these same traits make for highly confident and competent clinical histology techs, they provide merely a solid starting place for research histology techs. One thing I have heard from many research histology techs (which I agree with) is “you learn something new every day.” Be prepared to feel like you are starting all over. Be prepared to feel like you just don’t know enough. Be prepared to get paid to think.

If you’ve never had to serially section a paraffin block, you’ll now have to learn strategies to keep ribbons from blowing away or falling onto the waterbath. Not every research facility requires this. However, folks using tiny embryonic samples know that they won’t get very many sections from that tissue, especially if they’re looking for one particular structure. So sample positioning and serial sectioning can be absolutely critical for visualizing the area of interest. This can be especially challenging if your sample is less than 1-2 mm even before paraffin processing! We do the paraffin and frozen section embedding using a stereomicroscope—magnifying glasses just don’t have enough magnification!

Common research models include mouse (Mus), rat (Rattus), chick (Gallus), fruitfly (Drosophila), zebrafish (Danio), worm (C. elegans), yeast (Saccharomyces), and frog (Xenopus). Less common are dogs, cats, rabbits, primates, reptiles, and humans. Performing paraffin histology on these animal models usually requires using different paraffin processing schedules than those used in clinical labs. The NSH has an animal tissue processing manual that provides various schedules for a variety of animal and tissue types. It is a very worthwhile purchase and a very useful research histology lab resource. Also, any time you can find a published atlas of the animal model you are using, it is well worth having in the lab as a reference for anatomical structures and morphology.

Samples to be cryosectioned are either frozen fresh, or fixed with formaldehyde (10% NBF or formalin made from Paraformaldehyde powder in Phosphate buffer) and then cryopreserved in graded concentrations of sucrose in PBS. Samples are usually embedded after the sample sinks after immersion in a 30% sucrose/PBS solution. Some have had difficulty sectioning fixed and cryopreserved tissues due to the sticky and gooey nature of the sucrose and its effect in frozen tissue.

Be prepared to use fixatives, stains, antibodies, and techniques you’ve only read about in the textbooks but never tried. Working in a research histology lab means you might learn to do vibrating microtome sectioning in samples embedded in agarose or gelatin. Or you may work in a bone lab and do undecalcified bone methacrylate processing, sectioning, grinding and staining. You may learn to do IHC, ISH, and histochemical staining on whole mount samples rather than slide-mounted samples. Or you might possibly be performing experiments on plastics, matrices, plants, metals, or glass. The possibilities are mind-boggling!

Performing immunohistochemistry on animal tissues is like learning to do immunohistochemistry all over again. Now it matters what species your primary and secondary antibodies are raised in and their relationship to the species of tissue you’re staining. Anti-mouse secondary antibodies can sometimes react with rat tissue unless your antibody has been adsorbed for rat. And using anti-mouse IgG secondary antibodies will recognize native IgG in mouse tissue, so it is sometimes necessary to use kits or other strategies for immunostaining using mouse primary antibodies in mouse tissue samples. It is not good practice to use multi-link (anti-rabbit + anti-mouse) secondary antibodies for your IHC experiments. The anti-mouse component of the secondary antibody may react with mouse or rat tissues when labeling a rabbit antibody. Learn to love fluorescence.

Dakocytomation has an excellent (free) handbook on IHC and ISH techniques, and Richard Dapson, PhD, Ada Feldman, and Dee Wolfe at Anatech published a booklet “Lessons in Immunohistochemistry” that also is a very useful reference.

I cannot stress strongly enough to surround yourself with excellent reference material. Read, read, read, and then when you’re tired of reading, read some more. If your institution supports subscribing to journals, pick several that are useful to you in your work. I have subscriptions to the Journal of Histotechnology, Journal of Histochemistry and Cytochemistry, and Applied Immunohistochemistry and Molecular Morphology. There are many others which might be useful in your line of work. I have purchased most of my reference books from www.amazon.com, but there are certainly other suitable places to purchase them from. One lifeline for me in my transition (and beyond) is the Histonet: http://lists.utsouthwestern.edu/mailman/listinfo/histonet and the Histonet archives: www.histosearch.com/histonet.

Learn to use Pubmed and internet search engines. Email journal article authors your questions on techniques you’re trying that aren’t working, and follow up with a phone call if that isn’t fruitful. Take whatever college classes would be helpful to you if you can, i.e. Biology, Chemistry, Anatomy, Genetics, or have textbooks on hand if you cannot attend classes.

Research histology is an adventure for sure. It’s not for the faint of heart. You will fail! One of the most difficult things the research histology tech will face is dealing with failure. It is important to keep in mind that failure does provide us with significant learning experiences. Be prepared to learn from them.

Submitted by:
Teri Johnson HT(ASCP)QIHC
Managing Director Histology Facility
Stowers Institute for Medical Research
Kansas City, MO