Ki-67 and cytokeratin 16 expression in several lesion types of hidradenitis suppurativa compared to keratosis pilaris and psoriasis inversa. A pilot investigation

This study protocol concerns a follow-up investigation of the recently
completed study *Expression of cytokeratins and notch in the healthy
folliculopilosebaceous unit*. Currently, results about the cytokeratin
expression (CKs) have been analyzed. In short, the aim of that study was to
investigate the expression of various CKs in the epidermis and intact
folliculopilosebaceous units (FPSU) in perilesional and lesional HS skin and to
compare this to the FPSUs of healthy controls. The main finding was that CK16
expression was significantly increased in lesional HS skin compared to healthy
controls at the interfollicular epidermis (IFE) and infundibulum (IFN) of the
FPSU. This upregulation appears to be secondary to activation of the IFE and
IFN reflected by interfollicular and infundibular hyperkeratosis in lesional
skin, but not in perilesional skin. CK 1, 2e, 10, 14, 15, 17 and 25 did not
show an altered expression profile. Moreover, CK expression in HFs below the
IFN of HS skin was normal. In this follow-up study we further want to
investigate the role of CK16 in the pathogenesis of HS.

To investigate whether the upregulation of CK16 and Ki-67 (a marker for cell
proliferation) in the FPSU is specific for HS, measured in inflammatory nodules
and pseudo-comedones, in comparison to other dermatologic conditions that have
comparable (histo)pathological features such as follicular hyperkeratinisation
and inflammation: keratosis pilaris and psoriasis inversa.

design:
observational study

study:
four months

Setting:
Department of Dermatology of the University Medical Center Groningen

Procedure:
Skin samples (four millimeter (mm) punch biopsies are taken, under a local
anesthetic The biopsy will be taken in the direction of the hair in order to
optimize the chances of obtaining the full PFSU in the biopsy:
1. Healthy volunteers:
the skin biopsy samples from 5 healthy volunteers will be analyzed. Locations:
armpits and groin
2. Patients with keratosis pilaris:
the skin biopsies from 5 patients will be analyzed. Locations: upper arms,
thighs, buttocks.
3. Patients with psoriasis inversa:
the skin biopsies from 5 patients will be analyzed. Locations: armpits and groin
4. Patients with pseudo-comedones lesions in hidradenitis suppurativa:
the skin biopsies from 5 patients will be analyzed. Locations: armpits and groin
5. Patients with inflammatory nodules in hidradenitis suppurativa:
the skin biopsies from 5 patients will be analyzed. Locations: armpits and groin

Stainings:
A hematoxylin and eosin (HE) staining is performed to evaluate the presence of
the various segments of the FPSU. Only if at least the infundibulum and the
interfollicular epidermis are present, the expression of the proteins
cytokeratin 16 and Ki-67 can be explored.

Important note: From earlier studies we learned that the chance of obtaining
these sections of the FPSU in a biopsy is about 50%. Unfortunately, there is no
technique available that increases the chance of obtaining of a complete FPSU.
Because we aim at examining 5 biopsies per skin condition mentioned above, we
ask for permission of taking a maximum of 10 biopsies per skin condition. In
other words, a maximum of 50 biopsies will be taken from 50 individuals, of
which is expected that 25 will be suitable for further analysis.

Immunohistochemistry for Ki-67 is performed on the coupes which comply with the
above. Thereafter, the coupes willen be stained by immunofluorescence technique
for cytokeratin 16.

Scoring:
The intensity of the staining are scored by 2 independent investigators.

The burden and risks associated with participation in the control group is
negligible. Punch biopsies are part of everyday practice at the Dermatology
department and seldom lead to complications like wound infection. The procedure
will take approximately 5 to 10 minutes and no further visits are required
except for removal of the stitch (takes approximately 2 minutes).