title: Study of telomerase reverse transcriptase (hTERT) expression in normal, aged, and photo-aged skin.
abstract: BACKGROUND
  Telomerase is a ribonucleoprotein enzyme capable of extending chromosome ends with telomeric DNA sequences. It protects the germline and stem cells from senescence by preventing telomere attrition. Cutaneous aging includes intrinsic aging, and photo-aging. Telomere-associated cellular senescence contributes to certain age-related cutaneous disorders, including increased cancer incidence. Premature skin aging in xeroderma pigmentosa (XP) is expected to show increased telomere attrition. We aimed to study human telomerase reverse transcriptase (hTERT) expression in normal, aged and photo-aged skin and to investigate its possible role in the pathogenesis of aging and photo-aging.
  
  
  METHODS
  hTERT expression using immunohistochemistry was studied in 75 subjects comprising four groups: group I, 10 subjects with aged skin; group II, 20 subjects with photo-aging; group III, Five patients with XP; and group IV, 40 subjects comprising the control groups.
  
  
  RESULTS
  We found positive hTERT in normal skin and in the basal and sometimes in supra-basal layers. We reported positive hTERT expression in dermal fibroblasts, histiocytes, and skin appendages (other than hair follicles) in some cases from all the studied groups. Photo-aged and prematurely photo-aged skin showed greater hTERT expression than young and aged skin.
  
  
  CONCLUSIONS
  Telomeres rather than telomerase are involved in cellular senescence. Yet, telomerase is intimately related to photo-aging in which lifetime cumulative sun exposure is an important factor. However, genetic damage in XP is the decisive factor and not merely ultraviolet exposure.
authors.affiliation: Department of Dermatology and Venereology, Faculty of Medicine, Ain Shams University, Cairo, Egypt. annosah74@hotmail.com
authors.forename: Enas A S
authors.initials: EA
authors.lastname: Attia
authors.forename: Laila S
authors.initials: LS
authors.lastname: Seada
authors.forename: Mahira H
authors.initials: MH
authors.lastname: El-Sayed
authors.forename: Saleh M
authors.initials: SM
authors.lastname: El-Shiemy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism* / Q000473:pathology; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D004817:Epidermis / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D015595:Skin Aging / Q000473:pathology / Q000502:physiology*; D019098:Telomerase / Q000378:metabolism*; D055815:Young Adult
chemical_list: C509186:TERT protein, human; D019098:Telomerase