Dopa reaction of fetal melanocytes before and after skin transplantation on to nude mice

Coenzyme Q(10) enhances dermal elastin expression, inhibits IL-1α production and melanin synthesis in vitro

Coenzyme Q(10) (CoQ(10) ) is a well-known antioxidant and has been used in many skincare products for anti-ageing purpose. However, the molecular mechanisms of CoQ(10) function in skin cells are not fully understood. In this paper, we compared the effects of CoQ(10) on primary human dermal fibroblasts from three individuals, including adult. We demonstrated that CoQ(10) treatment promoted proliferation of fibroblasts, increased type IV collagen expression and reduced UVR-induced matrix metalloproteinases-1 (MMP-1) level in embryonic and adult cells. In addition, CoQ(10) treatment increased elastin gene expression in cultured fibroblasts and significantly decreased UVR-induced IL-1α production in HaCat cells. Taken together, CoQ(10) presented anti-ageing benefits against intrinsic ageing as well as photo damage. Interestingly, CoQ(10) was able to inhibit tyrosinase activity, resulting in reduced melanin content in B16 cells. Thus, CoQ(10) may have potential depigmentation effects for skincare.

5,7-dimethoxyflavone induces melanogenesis in B16F10 melanoma cells through cAMP-dependent signalling

Melanin protects the skin against ultraviolet radiation (UVR) and diverse free radicals. Agents that increase melanin synthesis in melanocytes may reduce UVR-induced skin damage and skin cancer. In the present study, we evaluated the effects of 5,7-dimethoxyflavone (5,7-DMF) on melanogenic protein expression and signalling pathways. We found that 5,7-DMF significantly increased melanin content by upregulating microphthalmia-associated transcription factor and related melanogenic proteins. Additionally, 5,7-DMF increased cAMP levels, which activates a cascade of reactions, such as cAMP responsive element-binding protein and Akt/glycogen synthase kinase-3β (GSK-3β) signalling. Thus, 5,7-DMF may be an effective pigmentation stimulator for photoprotection and hypopigmentation disorders.

Sphingolipid-mediated restoration of Mitf expression and repigmentation in vivo in a mouse model of hair graying

Recent advances in the identification and characterisation of stem cell populations has led to substantial interest in understanding the precise triggers that would operate to induce activation of quiescent stem cells. Melanocyte stem cells (MSCs) reside in the bulge region of the hair follicles and are characterised by reduced expression of the microphthalmia-associated transcription factor (Mitf) and its target genes implicated in differentiation. Vitiligo is characterised by progressive destruction of differentiated melanocytes. However, therapies using UV irradiation therapy can induce a degree of repigmentation, suggesting that MSCs may be activated. As Mitf is implicated in control of proliferation, we have explored the possibility that inducing Mitf expression via lipid-mediated activation of the p38 stress-signalling pathway may represent a re-pigmentation strategy. Here we have isolated from placental extract a C18:0 sphingolipid able to induce Mitf and tyrosinase expression via activation of the p38 stress-signalling pathway. Strikingly, in age-onset gray-haired C57BL/6J mice that exhibit decaying Mitf expression, topical application of placental sphingolipid leads to increased Mitf in follicular melanocytes and fresh dense black hair growth. The results raise the possibility that lipid-mediated activation of the p38 pathway may represent a novel approach to an effective vitiligo therapy.

Cryopreservation of fetal skin is improved by extracellular trehalose

In this study, we tested a non-permeating cryoprotectant, trehalose, in combination with dimethyl sulfoxide (Me(2)SO) in the cryopreservation of human fetal skin and compared it to Me(2)SO and glycerol, protocols that are routinely used by skin banks. The viability of fetal skin from four groups (fresh, and cryopreserved with glycerol, Me(2)SO, or trehalose/Me(2)SO) were evaluated using an in vitro membrane integrity assay and by transplantation to immunodeficient mice. The membrane integrity assay showed a 90% integrity in fresh, unfrozen fetal skin. The number of intact cells dropped to 23 and 44% in fetal skin cryopreserved with glycerol and Me(2)SO, respectively. When trehalose was added to the cryopreservation medium containing Me(2)SO, the membrane integrity rose to 65%. When transplanted to immunodeficient mice, fetal skin cryopreserved with trehalose/Me(2)SO showed a graft performance indistinguishable from fresh unfrozen fetal skin and strikingly better graft take than that of fetal skin cryopreserved with Me(2)SO or glycerol only. These results suggest that cryopreservation protocols routinely used the skin banks can be improved by combining sugars such as trehalose with a permeating cryoprotectant.

Survival of fetal skin grafts is prolonged on the human peripheral blood lymphocyte reconstituted-severe combined immunodeficient mouse/skin allograft model

BACKGROUND

Fetal tissue is considered to be immune privileged and is under extensive investigation as a source of tissue for transplantation. In this paper, we analyzed the immune properties of human fetal and neonatal skin before and after transplantation to severe combined immunodeficient (SCID) mice. Using a human peripheral blood mononuclear cell reconstituted SCID (huPBMC-SCID) mouse model of allograft rejection, we compared the immune response to transplanted fetal and neonatal skin.

METHODS

We analyzed human fetal (55-122 days of gestation) and neonatal skin samples by routine histology and immunohistochemistry for the expression of (MHC class I and II antigens before and after transplantation to SCID mice. After transplantation, we injected the mice with huPBMCs and analyzed the survival of neonatal and fetal skin grafts both visually and microscopically.

RESULTS

We detected no class II expression in fetal skin of all gestational ages and only weak class I expression after 89 days compared with abundant class I and II expression in neonatal skin before transplantation. When transplanted to SCID mice, fetal skin grafts differentiated and expressed class I and II, but the levels were lower than neonatal grafts. In mice injected with huPBMCs, rejection of neonatal grafts started on day 5, and by day 9 all grafts were rejected. In contrast, rejection of fetal skin grafts was significantly delayed. Rejection started on day 13 and was complete by day 23 (P<0.00005). Histology sections from the rejected grafts showed marked CD3+ T cell infiltration in the human skin with a sharp demarcation between the human and mouse skin, with no T-cell infiltration in the mouse skin. CD4+ and CD8+ T cells were present in the rejected sites in similar densities.

CONCLUSIONS

Our results show that fetal skin differentiates and expresses increased amounts of MHC class I and class II antigens when transplanted to SCID mice. However, these levels are much lower than the levels found in neonatal skin. We demonstrate that the survival of human fetal skin allografts is markedly prolonged compared with that of neonatal skin grafts in the huPBMC-SCID mouse model. Our results support the hypothesis that low levels of MHC antigen expression lead to a delay in the rejection of fetal skin and further demonstrate the utility of the huPBMC-SCID mouse model to investigate the molecular and cellular mechanisms of the immune response to human fetal tissues.

Alternative splicing of the tyrosinase gene transcript in normal human melanocytes and lymphocytes

We have identified and isolated ectopically expressed tyrosinase transcripts in normal human melanocytes and lymphocytes and in a human melanoma (MNT-1) cell line to establish a baseline for the expression pattern of this gene in normal tissue. Tyrosinase mRNA from human lymphoblastoid cell lines was reverse transcribed and amplified using specific "nested" primers. This amplification yielded eight identifiable transcripts; five that resulted from alternative splicing patterns arising from the utilization of normal and alternative splice sequences. Identical splicing patterns were found in transcripts from human primary melanocytes in culture and a melanoma cell line, indicating that lymphoblastoid cell lines provide an accurate reflection of transcript processing in melanocytes. Similar splicing patterns have also been found with murine melanocyte tyrosinase transcripts. Our results demonstrate that alternative splicing of human tyrosinase gene transcript produces a number of predictable and identifiable transcripts, and that human lymphoblastoid cell lines provide a source of ectopically expressed transcripts that can be used to study the biology of tyrosinase gene expression in humans.