Expression of cytokeratins and notch in the healthy folliculopilosebaceous unit

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease that mainly
occurs on the apocrine gland bearing skin. The pathogenesis of HS is largely
unknown but
several studies have shown that the initiating event takes place at the hair
follicle. Histological studies showed hyperkeratosis of the infundibulum and
epidermal psoriatiform hyperplasia. Recently, the European S1 guideline for the
treatment of HS was published. In this guideline it is stated that cytokeratin
17 has been shown to be absent from infundibular-like keratinized epithelium,
suggesting fragility of the draining sinus epithelium, which may be responsible
for rupture. Another recent study showed loss of function mutations in genes
encoding components the transmembrane protease gamma-secretase (GS) in HS
patients. GS cleaves the intracellular domain of Notch which leads to
intracellular Notch signaling. The activation of Notch signaling results in the
promotion of growth arrest and onset of differentiation. In mice, it was shown
that deficient notch signaling results in occlusion of hair follicles,
formation of epidermal cysts and insufficient feedback suppression of innate
immunity. In psoriasis, it was hypothesized that decrements in Notch molecules
might cause aberrant expression of cytokeratin 10 and cytokeratin 14 leading
tot anomalous differentiation of the epidermis. We hypothesize that both
cytokeratins and Notch are involved in the pathogenesis of HS. Notch might be
responsible for disturbed expression of cytokeratins in the FPSU of HS. The
exact expression of Notch and cytokeratins in healthy FPSUs is unknown. In
future projects we would like to examine the expression of cytokeratins and
Notch in FPSUs of HS patients. To be able to do this, it is first necessary to
investigate these proteins in healthy human FPSUs.

1) to examine the expression of cytokeratins and Notch in healthy human FPSUs
at different segments.
2) to describe the association between expression of the cytokeratins and Notch
1 in the FPSUs of healthy volunteers.

Design: observational study
Study duration: four months
Setting: department of Dermatology at the University Medical Center Groningen
Procedure:
Healthy volunteers: skin samples of healthy volunteers will be analyzed. A
total of 20 subjects will be included; 10 for skin samples of the axilla region
and 10 for skin samples from the groin.
Collecting skin samples: four milimetre (mm) punch biopsies will be taken
either from the axilla or the groin under local anesthesia. The biopsy will be
taken in the direction of the hair in order to optimize the chance of obtaining
the whole PFSU in the biopsy.
Stainings: A hematoxylin and eosin (HE) staining will be performed to evaluate
the presence of the different segments of the FPSU. Only if all segments are
present, the expression of the different proteins can be examined. From earlier
studies we learned that the chance of obtaining a complete 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 10
biopsies, we ask for permission of taking 20 biopsies. DIF will be performed on
the biopsies that include all segments of the FPSU for cytokeratin 1,5, 10,14,
15, 16, 17 and 19 and Notch 1.
Scoring: Image J will be used to analyze the intensity of the IF staining of
the different segments.
Evaluation of endpoints:
Primary endpoints: the intensity of the stainings of the different proteins at
the different segments of the FPSU
Secondary endpoints: the association between the intensity of the different
cytokeratins and Notch 1 in the FPSUs

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).