Stem cell proliferation under low intensity laser irradiation: A preliminary study

Background and Objectives: Phototherapy with low intensity laser irradiation has shown to be effective in promoting the proliferation of different cells. The aim of this in vitro study was to evaluate the potential effect of laser phototherapy (660 nm) on human dental pulp stem cell (hDPSC) proliferation. Study Design/Materials and Methods: The hDPSC cell strain was used. Cells cultured under nutritional deficit (10% FBS) were either irradiated or not (control) using two different power settings (20 mW/6 seconds to 40 mW/3 seconds), with an InGaAIP diode laser. The cell growth was indirectly assessed by measuring the cell mitochondrial activity through the MTT reduction-based cytotoxicity assay. Results: The group irradiated with the 20 mW setting presented significantly higher MTT activity at 72 hours than the other two groups (negative control-10% FBSand lased 40 mW with 3 seconds exposure time). After 24 hours of the first irradiation, cultures grown under nutritional deficit (10% FBS) and irradiated presented significantly higher viable cells than the non-irradiated cultures grown under the same nutritional conditions. Conclusions: Under the conditions of this study it was possible to conclude that the cell strain hDPSC responds positively to laser phototherapy by improving the cell growth when cultured under nutritional deficit conditions. Thus, the association of laser phototherapy and hDPSC cells could be of importance for future tissue engineering and regenerative medicine. Moreover, it opens the possibility of using laser phototherapy for improving the cell growth of other types of stem cells.

Tooth Tissue Engineering: Optimal Dental Stem Cell Harvest Based on Tooth Development

Our long-term objective is to devise reliable methods to generate biological replacement teeth exhibiting the physical properties and functions of naturally formed human teeth. Previously, we demonstrated the successful use of tissue engineering approaches to generate small, bioengineered tooth crowns from harvested pig and rat postnatal dental stem cells (DSCs). To facilitate characterizations of human DSCs, we have developed a novel radiographic staging system to accurately correlate human third molar tooth developmental stage with anticipated harvested DSC yield. Our results demonstrated that DSC yields were higher in less developed teeth (Stages 1 and 2), and lower in more developed teeth (Stages 3, 4, and 5). The greatest cell yields and colony-forming units (CFUs) capability was obtained from Stages 1 and 2 tooth dental pulp. We conclude that radiographic developmental staging can be used to accurately assess the utility of harvested human teeth for future dental tissue engineering applications.

Being breastfed in infancy and breast cancer incidence in adult life: Results from the two Nurses' Health studies

Events during perinatal and early life may influence the incidence of breast cancer in adult life, and some case-control studies suggest that having been breastfed may reduce breast cancer risk. The authors studied this association among premenopausal and postmenopausal women by using data from the two Nurses' Health Studies, the Nurses' Health Study (using data from 1992 to 1996) and the Nurses' Health Study II (using data from 1991 to 1997). A history of being breastfed was self-reported by the study participants. During a total of 695,655 person-years, 1,073 cases of invasive breast cancer were diagnosed. The authors did not observe any important overall association between having been breastfed and the development of breast cancer later in life among premenopausal women (covariate-adjusted relative risk = 0.97, 95% confidence interval (CI): 0.78, 1.20) or postmenopausal women (covariate-adjusted relative risk = 1.12, 95% CI: 0.92, 1.37). No significant trend was observed with increasing duration of breastfeeding. The authors also used data on breastfeeding retrospectively collected from 2,103 mothers of participants of the two Nurses' Health Studies. With the mothers' reports, the covariate-adjusted odds ratio of breast cancer was 1.11 (95% CI: 0.88, 1.39) for women who were breastfed compared with those who were not. Data from these two large cohorts do not support the hypothesis that being breastfed confers protection against subsequent breast cancer.

Postmenopausal Hormone Use, Screening, and Breast Cancer: Characterization and Control of a Bias

Previous investigators have suggested that screening-related biases may explain associations between postmenopausal hormone use and breast cancer. To investigate these biases, we studied postmenopausal women in the Nurses' Health Study from 1988 to 1994. Hormone use is associated with increased subsequent screening. Among women not screened in the previous 2 years, the probability difference, comparing current hormone users with others, for having mammography in the following 2 years is 19.5%; among women previously screened, the difference is 4.9%. These differences persist after control for other factors. If the increase in screening is causal, screening by mammogram could be intermediate in the causal pathway to breast cancer diagnosis. To deal with this problem, we restrict attention to a subset of the cohort in which the effect of postmenopausal hormone use on screening is small (women previously screened). In this subset, the rate ratio comparing breast cancer rates among current postmenopausal hormone users with others is 1.28. In a sensitivity analysis, the bias could not by itself plausibly account for the associations in our data. Our data provide evidence of an association between postmenopausal hormone use and breast cancer that is not solely the product of a detection bias.

Long-term outcomes of genetic counseling in women at increased risk of developing hereditary breast cancer Information,

This multicenter study evaluated the impact of genetic counseling in 218 women at risk of developing hereditary breast cancer. Women were assessed prior to counseling and 12-month post-counseling using self-administered, mailed questionnaires. Compared to baseline, breast cancer genetics knowledge was increased significantly at follow-up. and greater increases in knowledge were associated with educational level. Breast cancer anxiety decreased significantly from baseline to follow-up, and these decreases were associated with improvements in perceived risk. A significant decrease in clinical breast examination was observed at the 12-month follow-up. Findings suggest that women with a family history of breast cancer benefit from attending familial cancer clinics as it leads to increases in breast cancer genetics knowledge and decreases in breast cancer anxiety. The lowered rates of clinical breast examination indicate that the content of genetic counseling may need to be reviewed to ensure that women receive and take away the right message. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Proteomics of breast cancer for marker discovery and signal pathway profiling

Breast cancer is the most common form of cancer among women and the identification of markers to discriminate tumorigenic from normal cells, as well as the different stages of this pathology, is of critical importance. Two-dimensional electrophoresis has been used before for studying breast cancer, but the progressive completion of human genomic sequencing and the introduction of mass spectrometry, combined with advanced bioinformatics for protein identification, have considerably increased the possibilities for characterizing new markers and therapeutic targets. Breast cancer proteomics has already identified markers of potential clinical interest (such as the molecular chaperone 14-3-3 sigma) and technological innovations such as large scale and high throughput analysis are now driving the field. Methods in functional proteomics have also been developed to study the intracellular signaling pathways that underlie the development of breast cancer. As illustrated with fibroblast growth factor-2, a mitogen and motogen factor for breast cancer cells, proteomics is a powerful approach to identify signaling proteins and to decipher the complex signaling circuitry involved in tumor growth. Together with genomics, proteomics is well on the way to molecularly characterizing the different types of breast tumor, and thus defining new therapeutic targets for future treatment.