We read
with interest the paper published by Boschi, et. al.[1]
in which immunohistochemistry was performed on orbital tissues from
patients with thyroid associated ophthalmopathy (TAO) and compared to
non...
We read
with interest the paper published by Boschi, et. al.[1]
in which immunohistochemistry was performed on orbital tissues from
patients with thyroid associated ophthalmopathy (TAO) and compared to
non-diseased orbital tissue.
Our
laboratory recently reported positive TSH receptor staining within
normal human muscle fibres, using one of the same antibodies (3G4) as
Boschi et. al., (supplied by Costagliola) and a commercial antibody
(3B12) [2].
Our
findings differ from Boschi et. al.’s as no staining of the
muscle fibres was visible in their experience.
Assessing
the techniques used gave some possibilities as to why our findings
differ. Our paraffin-embedded tissues were subjected to a proteolytic
antigen retrieval step, as commonly used in avidin-biotin
staining.[3]
The reason for this is that formalin used in fixation is notorious
for altering protein immunoreactivity, and hence masking protein
expression.[4][5]
Moreover,
the amplification immunohistochemistry kit used in our experiments is
possibly more sensitive than conventional immunohistochemistry used
in the experiments of Boschi, et. al.[6]
We do not
dispute the finding that TSHR expression is elevated in orbital
connective tissue of diseased patients. Combined with our findings,
Boschi et. al.’s paper also suggests that expression of TSH-R
on normal muscle fibres is lower than in the connective tissue of
diseased patients. Boschi et. al. has successfully produced more
evidence that connective tissues in the orbit are active in TAO
affected patients, however the potential role of the extraocular
muscle in the pathogenesis of TAO should also be considered.
Yours
sincerely,
Steven J.
Kloprogge and Albert G. Frauman
References
1
Boschi A, Daumerie C, Spiritus M, et al. Quantification of cells
expressing the thyrotropin receptor in extraocular muscles in
thyroid associated orbitopathy. Br J Ophthalmol 2005;89(6):724-9.
2
Kloprogge SJ, Busuttil BE, Frauman AG. TSH receptor protein is
selectively expressed in normal human extraocular muscle. Muscle
Nerve. 2005;32(1):95-8.
3
Thompson LD, Miettinen M, Wenig BM. Sinonasal-type
hemangiopericytoma: a clinicopathologic and immunophenotypic
analysis of 104 cases showing perivascular myoid differentiation. Am
J Surg Pathol. 2003;27(6):737-49.
4
Fox CH, Johnson FB, Whiting J, et. al. Formaldehyde fixation. J
Histochem Cytochem 1985;33(8):845-53.
5
Puchtler H, Meloan SN. On the chemistry of formaldehyde fixation and
its effects on immunohistochemical reactions. Histochemistry
1985;82(3):201-4.
6Erber
WN, Willis JI, Hoffman GJ. An enhanced immunocytochemical method for
staining bone marrow trephine sections. J Clin Pathol.
1997;50(5):389-93.