Automated Methods for the Analysis of Skeletal Muscle Fiber Size and Metabolic Type - International Review of Cell and Molecular Biology - page 271

8. Summary 317

Acknowledgments 318

References 318

Abstract
It is of interest to quantify the size, shape, and metabolic subtype of skeletal muscle
fibers in many areas of biomedical research. To do so, skeletal muscle samples are sec-
tioned transversely to the length of the muscle and labeled for extracellular or mem-
brane proteins to delineate the fiber boundaries and additionally for biomarkers
related to function or metabolism. The samples are digitally photographed and the
fibers “ outlined ” for quantification of fiber cross-sectional area (CSA) using pointing
devices interfaced to a computer, which is tedious, prone to error, and can be nonob-
jective. Here, we review methods for characterizing skeletal muscle fibers and describe
new automated techniques, which rapidly quantify CSA and biomarkers. We discuss the
applications of these methods to the characterization of mitochondrial dysfunctions,
which underlie a variety of human afflictions, and we present a novel approach, utilizing
images from the online Human Protein Atlas to predict relationships between fiber-
specific protein expression, function, and metabolism.

1. INTRODUCTION
Skeletal muscle is one of three major types of muscle tissue in verte-
brates (skeletal, cardiac, and smooth muscle). Both skeletal muscle and car-
diac muscle feature a “striated” appearance resulting from the highly
organized contractile apparatus that dominates the cellular and tissue orga-
nization. The tissue is fascinating as its structure is related to its contractile
function in a visually intuitive manner. Furthermore, the structure and
changes that occur to it in response to developmental, nutritional, life style,
or pathological processes are readily quantified via microscopy-based
methods, an area that is rapidly evolving with the recent advances in digital
cameras, automated microscopes, computers, and image-analysis tech-
niques. In this chapter, we will briefly review skeletal muscle structure
and relevance to biomedicine, provide historical review on the development
of methods for the analysis of skeletal muscle fiber-type, with an emphasis on
the use of automated microscopy and digital analysis, and present likely sce-
narios for future applications of this technology for medical and

research applications.
During early phases of muscle development, skeletal muscle precursor
cells align and fuse into multinucleated cells, termed “muscle fibers,” which