Evaluation of cell death and proliferation in psoriatic epidermis.
BACKGROUND
Previous studies of psoriatic epidermis using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) method, a type of apoptotic detection method, showed that TUNEL-positive keratinocytes were abundantly distributed in all layers of the psoriatic epidermis, although psoriasis is a hyperproliferative disorder.


OBJECTIVE
We sought to clarify the nature of cell kinetics in a psoriatic epidermis on the basis of differences in the reactivities in TUNEL and formamide-induced DNA denaturation assay combined with the detection of denatured DNA with a monoclonal antibody (MAb) against single-stranded DNA (formamide-MAb assay) between the normal and psoriatic epidermides.


METHODS
The kinetics of keratinocytes was evaluated by the immunohistochemistry of Ki-67 for proliferation activity and by TUNEL, TUNEL combined with transmission electron microscopy (TUNEL/TEM), and formamide-MAb assay for apoptosis.


RESULTS
The number of Ki-67-positive cells in the psoriatic epidermis was significantly higher than that in the normal epidermis. In the normal epidermis, both TUNEL and formamide-MAb assay showed a similar distribution pattern, that is, both TUNEL and formamide-MAb assay-positive keratinocytes were present only in the upper granular layer. In the psoriatic epidermis, most keratinocytes were negative for the formamide-MAb assay, while TUNEL-positive cells were abundantly distributed in all layers of the psoriatic epidermis. TUNEL/TEM method clearly demonstrated that many immunogold particles that stain the sites of 3'-OH DNA ends were evenly distributed on the euchromatin in psoriatic keratinocyte nuclei, in contrast to their presence on the peripheral condensed chromatin in normal keratinocyte nuclei.


CONCLUSIONS
The increased TUNEL reactivity in psoriatic lesions is due to the increase in the number of DNA nicks resulting from active DNA replication but not due to DNA double-strand breaks produced during the apoptotic process, and the formamide-MAb assay is a reliable method for the detection of apoptosis, particularly in the epidermis.
Kawashima
Keisei
K
Department of Anatomy and Biology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
Doi
Hisao
H
Ito
Yuko
Y
Shibata
Masa-Aki
MA
Yoshinaka
Ryoji
R
Otsuki
Yoshinori
Y
D000911:Antibodies, Monoclonal; D017209:Apoptosis; D002455:Cell Division; D004277:DNA, Single-Stranded / Q000276:immunology; D004817:Epidermis / Q000473:pathology*; D005559:Formamides; D006801:Humans; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D019394:Ki-67 Antigen / Q000378:metabolism; D008854:Microscopy, Electron; D011565:Psoriasis / Q000473:pathology*
D000911:Antibodies, Monoclonal; D004277:DNA, Single-Stranded; D005559:Formamides; D019394:Ki-67 Antigen; C031066:formamide