Wednesday, April 21, 2010

ATPase versus Immunohistochemistry for fiber typing in muscle biopsies: which is better?

When I receive a complex muscle biopsy case, I send my specimens to the excellent muscle specialists at the University of Iowa Department of Pathology. I recently got a consultation report back from Dr. Leslie Bruch (pictured) at that institution. In her report, she noted that immunoperoxidase staining for slow and fast myosin heavy chains were performed to assess fiber type distribution. For that purpose, I use ATPase at pH 9.4 and 4.6. I asked Dr. Bruch whether there were any advantages to the immunohistochemistry approach versus ATPase. Here's her response: "The reasons we changed to immunohistochemistry for fiber typing here was that it is more consistently reliable than our ATPase stains, as well as less expensive in terms of tech time and reagents, etc. One limitation is that you cannot subtype the type II fibers as you can with using ATPase at 3 different pHs. We have been happy with it since the change."

If anyone has any further thoughts on the relative advantages of the two methodologies, please comment.


Agent 86 said...

Blue collar NP Alert!

1. Fiber typing is (way) overrated in muscle dx.
2. Myosin IHC can be done by machine & doesn't require ability to use a pH meter.

I do IHC for Slow Myosin HC only.

For the WC NPs, embryonic & perinatal myosins are very good at highlighting regenerating fibers.

Recommended reading:
Vihola A..Udd B. Differences in aberrant expression and splicing of sarcomeric proteins in the myotonic dystrophies DM1 and DM2. Acta Neuropathol. 2010 Apr;119(4):465-79.


Brian E. Moore, MD said...

You could make a reasonable argument that NADH alone would suffice for simple fiber typing, don't you think?

Agent 86 said...

Basically, I agree, especially in light of my comment #1. There is a small literature on this from back in the day..the hardcore fiber typers have also made "reasonable arguments" for why NADH for fiber typing is not completely reliable. I'd been using cytochrome oxidase as a fiber typing surrogate, since I don't do NADH-TR routinely. SDH and/or phosphorylase work, too. The latter can also serve as a (blue-collar) QC assay, as phosphorylase activity is lost more quickly than the other stains that we usually perform.

All of these, as you know, require frozen tissue (as well as decent freezing technique...don't even get me started...).