Expression of transglutaminase 2 does not differentiate focal myositis from generalized inflammatory myopathies.
OBJECTIVE
Idiopathic inflammatory myopathies (IIM), including dermatomyositis (DM), polymyositis (PM), sporadic inclusion-body myositis (s-IBM) and focal myositis (FM) are a heterogeneous group of autoimmune disorders of skeletal muscle. An increased transglutaminase 2 (TG2) expression has been found in DM, PM and s-IBM. The aim of our study was to investigate TG2 expression in FM in comparison with other IIM.


METHODS
We re-examined tissue material we have gathered in the course of our previous studies on IIM, investigating muscle expression of TG2 in patients with FM in comparison with DM, PM and s-IBM using immunocytochemistry and real-time RT-PCR.


RESULTS
Immunocytochemistry revealed an increased TG2 signal in endomysial vessels, in atrophic and degenerating/regenerating muscle fibres in PM, DM, s-IBM and FM; in s-IBM, some vacuoles were immunostained too. Real-time RT-PCR study confirmed a significantly increased expression of TG2 in all IIM muscles examined.


CONCLUSIONS
Our study demonstrates the presence of TG2 in FM muscles. The study suggests that TG2 expression does not represent a distinctive marker to differentiate FM from generalized IIM. TG2 over-expression in inflamed skeletal muscle does not seem have a pathogenetic role in such a disease, but it could represent a way to contain the inflammatory process.
Macaione
V
V
Department of Biochemical, Physiological and Nutritional Sciences, University of Messina, Messina, Italy. vmacaione@unime.it
Aguennouz
M
M
Mazzeo
A
A
De Pasquale
M G
MG
Russo
M
M
Toscano
A
A
De Luca
G
G
Di Giorgio
R M
RM
Vita
G
G
Rodolico
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D019204:GTP-Binding Proteins / Q000096:biosynthesis*; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000201:enzymology*; D009220:Myositis / Q000175:diagnosis*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D011503:Transglutaminases / Q000096:biosynthesis*
D012333:RNA, Messenger; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins