Muscle Phenotyping Stains
Many different staining techniques are used in the analysis of muscle tissue. The preferred method for a project depends on the type of data that must be collected.
Hematoxylin and Eosin for Morphology
Routine H&E staining, while fast and inexpensive, lacks the specificity needed for automated myofiber detection. Manual editing of the boundaries between fibers is needed.
Immunofluorescence for Morphology
In this image, red indicates laminin, green indicates dystrophin, blue indicates the dna in nuclei.
Ideally, identification of the borders of individual myocytes can be accomplished by immunostaining of dystrophin or laminin. This can be combined with nuclear staining. Since myofibers frequently appear bundled together, having a specific label to indicate the boundary of each greatly increases the automation analysis.
ATPase Staining for Fibertyping
ATPase staining performed on serial tissue sections can be used to identify fiber types. Alkaline (pH 10.8) medium stains type II fibers darkly. Acid (pH 4.5) medium stains type I fibers darkly and IIa lightest. Acid (pH4.3) medium stains type I fibers darkly and type IIa and IIb lightest.
ATPase staining can be used with automated myofiber detection because of the strong contrast between stained and unstained myofibers. Some editing will still be required to separate adjacent stained fibers. Unstained fibers will not be analyzed unless they are manually drawn.
Immunohistochemical Staining for Fibertyping
The upper row shows mAb A4951 antibody staining for type I fibers. The bottom row shows mAb N2.261 antibody staining for type IIa fibers.
NADH-TR Staining for Fibertyping
The purple coloring is concentrated in the mitochondria. Type I fibers stain more darkly than type II. The uneven color of the stain across the myofiber makes NADH staining problematic for automated myofiber detection.
Multi-channel Fluorescent Staining for Fibertyping
Multi-channel fluorescent staining. Red: type IIB. Blue: type I. Green: type IIA. Purple: IIX / IIAX.
While more expensive and technically complex to perform, multi-channel immunofluorescence requires only a single section physical section and significantly simplifies imaging and automated fiber typing.