Cell-kinetic evidence for increased recruitment of cycling epidermal cells in psoriasis: the ratio of histone and Ki-67 antigen expression is constant.
BACKGROUND
One of the hallmarks of the psoriatic plaque is increased epidermal proliferation. Whether this is the result of an increased recruitment of cycling epidermal cells or a decrease in cell cycle time has been a matter of debate for years.


OBJECTIVE
Calculating cell-kinetic information from the number of S phase cells in psoriasis by in situ hybridisation using a histone probe and the number of cycling epidermal cells by immunohistochemistry using the MIB-1 antibody.


METHODS
Immunohistochemistry and non-isotopic in situ hybridisation were performed on serial sections of 33 untreated psoriatic samples and 14 tacalcitol-treated samples.


RESULTS
The labelling index (number of cells in S phase/number cycling cells per millimetre length of section) in psoriatic untreated as well as in treated plaques is 16%. The amount of S phase cells in our experiment is equal compared with the number of cells in S phase as determined by BrdU incorporation.


CONCLUSIONS
Using this direct approach to study cell-kinetic behaviour of psoriatic skin, we reconfirm that the psoriatic abnormality is due to a defect in the G(0)-G(1) recruitment mechanism (by increased recruitment of G(0) cells), a decrease in apoptosis or an increase in the number of cell divisions in the transit-amplifying compartment, rather than a reduction in the cell cycle time.
Castelijns
F A
FA
Department of Dermatology, University Hospital Nijmegen, The Netherlands. f.castelijns@derma.azn.nl
Gerritsen
M J
MJ
van Erp
P E
PE
van de Kerkhof
P C
PC
D002453:Cell Cycle; D000078404:Epidermal Cells; D004817:Epidermis / Q000737:chemistry; D015870:Gene Expression; D006657:Histones / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D019394:Ki-67 Antigen / Q000096:biosynthesis; D007700:Kinetics; D011565:Psoriasis / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016196:S Phase; D012867:Skin / Q000737:chemistry / Q000378:metabolism / Q000473:pathology
D006657:Histones; D019394:Ki-67 Antigen; D012333:RNA, Messenger