Human keratinocytes derived from the bulge region of hair follicles are refractory to differentiation.
Human keratinocyte strains derived from the bulge region of plucked human follicles were successfully established from all 43 donors (age 24-76) regardless of the age and gender. The total cell number, number of population doublings and population doubling time were similar among the strains. These bulge-derived keratinocytes, BDKs, expressed keratin family genes specific to basal cell layers of the epidermis. They also expressed CD34, one of the bulge stem cell marker genes. The growth behavior and positivity of CD34 indicate that BDKs contain stem cells. BDKs were cultured until confluency or treated with CaCl2 to induce differentiation. Morphology and expression of keratin family genes in BDKs before and after differentiation induction with CaCl2 were similar to those of epidermal keratinocytes obtained from skin biopsies (NHEKs). However, expression levels of keratin-10, a prickle cell layer marker, in CaCl2-treated BDKs were lower than those in CaCl2-treated NHEKs. Higher expression of integrin-alpha6, a basal cell layer marker, was also noted in BDKs than in NHEKs after differentiation induction. Expression of stem cell marker genes other than CD34, including CD200, Sox2 and NANOG, was about the same at confluency in both cells, but significantly higher in BDKs than NHEKs after differentiation. These results indicate that BDKs were more refractory to differentiation than NHEKs. We then examined Wnt signaling inhibitor genes, DKK-3 and WIF-1 that function as tumor suppressors. DKK-3 expression decreased in both BDKs and NHEKs after CaCl2-induced differentiation. Expression of WIF-1 decreased 50% in BDKs one day after CaCl2 treatment and remained low, but was induced 1.7 times in NHEKs one day after CaCl2 treatment and further induced thereafter (>2.5 times), suggesting that WIF-1 may be involved in maintaining the differentiation-refractory status of BDKs. Since cancer stem cells in the skin have been reported to be similar to bulge-derived stem cells, our BDK strains may be of use in studying characteristics of cancer stem cells of the epidermis.
Department of Genetics, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan.
Yusuke
Y
Sasahara
Yoshie
Y
Yoshikawa
Tomonori
T
Morinaga
Yoshiro
Y
Nakano
Nozomi
N
Kanazawa
Joji
J
Kotani
Shin
S
Kawamata
Yoshinobu
Y
Murakami
Katsuyuki
K
Takeuchi
Chizuko
C
Inoue
Yukio
Y
Kitano
Tomoko
T
Hashimoto-Tamaoki
D000328:Adult; D053687:Adult Stem Cells / Q000187:drug effects / Q000502:physiology; D000368:Aged; D001706:Biopsy; D002118:Calcium / Q000494:pharmacology; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D005260:Female; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D020869:Gene Expression Profiling; D018859:Hair Follicle / Q000166:cytology*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000473:pathology; D055815:Young Adult
D002118:Calcium