Glycobiology to the rescue !

Abstract

Epidermal homoeostasis is maintained by a fine balance of keratinocyte proliferation and terminal differentiation. In skin homoeostasis, cells which enter the differentiation programme must be compensated by cell replenishment in the epidermal basal layer. Today, it is admitted that two distinct proliferative cells coexist in the basal layer of epidermis, namely slow-cycling stem cells and committed progenitor 4Of note, the basement membrane and the uppermost dermis are key components of the epidermal stem cells' niche. 5From a histological point of view, skin ageing is mainly characterized by a flattening of the dermal-epidermal junction, an epidermal thinning in some body sites like scalp, a decreased basal cell density, a delamination of the basement membrane and alteration of the superficial dermis. 6 Of note, the most striking alterations reported so far deal with extracellular matrix and more precisely, with decreased expression of glycosaminoglycans and related proteoglycans. In parallel, the ability to in vitro give rise to holoclones progressively decline while the number of paraclones increases. 4 Of note, in human hair follicles, an age-related progressive decline in holoclone production was also observed. 9 Altogether, these results suggest an agerelated progressive loss of human epidermal stem cells' functionality. More generally speaking, glycans which are endowed with a unique and huge molecular diversity, represent the third language of life, besides nucleic acids and proteins, 12 and as such, must be taken into consideration more fully as key actors of skin biology and important factors in investigative dermatology. Considering the molecular

Crocin, a natural molecule with potentially beneficial effects against skin ageing

“…Considering that (i) profound changes in the synthesis and degradation of skin glycosaminoglycans and related proteoglycans occur during ageing , (ii) glycans must be considered as key actors of skin biology and (iii) crocin is a di‐gentiobiosyl derivative of crocetin, the possible role of crocin in skin glycobiology was further investigated.…”

“…Considering that (i) profound changes in the synthesis and degradation of skin glycosaminoglycans and related proteoglycans occur during ageing [3], (ii) glycans must be considered as key actors of skin biology [51][52][53] and (iii) crocin is a di-gentiobiosyl derivative of crocetin, the possible role of crocin in skin glycobiology was further investigated. GLYcoDiag technology allows carbohydrate-conjugated neoglycoprotein interactions with a cell surface to be quantified, in the absence or presence of possibly a competing or inhibiting moleculein the present case crocin, a carotenoid-di-gentiobioside.…”

Tick saliva: paving the way for the stowaway Borrelia

“…Furthermore, TLR2-siRNA experiments also revealed a role of TLR2 in the induction of IL-8 in this scenario, whereas TLR2 was dispensable for the induction of TNF-alpha and hBD-2. Together, this study illustrates that the co-activation of keratinocytes by Borrelia and TLR3 induces a strong induction of inflammatory defense mediators via different pathways (12).…”

“…The most interesting finding of the study of Bernard et al (12) was provided by the observation that the induction of IL-8, TNFalpha and hBD-2 by poly (I:C) alone as well as in the presence of OspC from Borrelia was significantly reduced by the tick saliva. These findings highlight an yet unknown suppressive effect of the tick saliva on the TLR3 pathway in keratinocytes.…”

“…To gain further insight into how the tick saliva interferes with the cutaneous defense system, Bernard et al (12), with Nathalie Boulanger as senior author, now investigated the role of Tolllike receptor 3 (TLR3). Their study is based on the scenario that skin injury can lead to the activation of TLR3 by RNA from damaged cells (13)(14)(15).…”