Reflecting the human lip in vitro: Cleft lip skin and mucosa keratinocytes keep their identities.

OBJECTIVES: Cell models have shown great promise as tools for research, potentially providing intriguing alternatives to animal models. However, the original tissue characteristics must be maintained in culture, a fact that is often assumed, but seldom assessed. We aimed to follow the retention of the original tissue identities of cleft lip-derived skin and mucosa keratinocytes in vitro. METHODS: Cleft lip-derived keratinocytes were isolated from discarded tissue along the cleft margins during cheiloplasty. Cell identities were assessed by immunohistochemistry and quantitative real-time PCR for tissue-specific markers and compared with native lip tissue. Moreover, keratinocytes were regularly analyzed for the retention of the original tissue characteristics by the aforementioned methods as well as by differentiation assays. RESULTS: The various anatomical zones of the human lip could be distinguished using a panel of differentiation and functional-based markers. Using these markers, retention of the original tissue identities could be followed and confirmed in the corresponding primary keratinocytes in culture. CONCLUSIONS: Our findings promote patient-derived cells retaining their original identities as astonishing and clinically relevant in vitro tools. Such cells allow a better molecular understanding of various lip-associated pathologies as well as their modeling in vitro, including but not restricted to orofacial clefts.

In Vitro Effects of Arginine-Containing Toothpastes on Cariogenic Biofilms.

PURPOSE: The effects of arginine as a toothpaste additive were assessed on oral streptococci with and without a known arginine deiminase system (ADS) and cariogenic biofilms. MATERIALS AND METHODS: Suspensions of Streptococcus mutans, S. sobrinus and the ADS-positive (ADS+) S. sanguinis and S. gordonii were cultured with or without 1.5% L-arginine for 24 h. Thereafter, biofilms consisting of the four species were formed on polystyrene surfaces with or without 1.5% L-arginine for up to 10 d. Finally, biofilms that formed on enamel surfaces were exposed to a daily mechanical cleaning with an arginine and sodium monofluorophosphate (SMF+Arg)-containing toothpaste, a sodium monofluorophosphate fluoride (SMF)-containing toothpaste or a negative control for up to 10 weeks. At different incubation times, the pH in the culture media, the citrulline production and the percent of ADS+ bacteria within the biofilms were determined. Microsurface hardness loss was quantified in the experiments using enamel specimens. RESULTS: In the presence of 1.5% arginine, S. sanguinis and S. gordonii showed a high level of production of citrulline after 6 h of incubation, together with an increase in the pH when compared to S. mutans and S. sobrinus. With arginine supplementation, the percentage of ADS+ species was higher at 1, 2 and 4 days and citrulline production was higher at all days of biofilm formation on polystyrene surfaces. After 4 and 10 weeks of treating biofilms on enamel surfaces, the SMF+Arg group had a higher proportion of ADS+ strains than the SMF group; at 4 weeks, the pH was higher in the SMF+Arg group. Loss of enamel hardness was the lowest in the SMF+Arg group and was significantly less in the SMF+Arg group than in the control group after 2, 4 and 10 weeks of treatment. CONCLUSION: Toothbrushing using an arginine-containing toothpaste may protect against dental caries.