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Alligators hold secret to tooth renewal

For the first time, a global team of researchers has uncovered unique cellular and molecular mechanisms behind tooth renewal in American alligators. The finding may help scientists learn how to stimulate tooth regeneration in people.

The new research was led by the Keck School of Medicine of USC.

“Humans naturally only have two sets of teeth—baby teeth and adult teeth,” said USC pathology Professor Cheng-Ming Chuong, M.D., Ph.D., who led the team.
“Ultimately, we want to identify stem cells that can be used as a resource to stimulate tooth renewal in adult humans who have lost teeth. But, to do that, we must first understand how they renew in other animals and why they stop in people,” Chuong noted.

Whereas most vertebrates can replace teeth throughout their lives, human teeth are naturally replaced only once, despite the lingering presence of a band of epithelial tissue called the dental lamina, which is crucial to tooth development.

 Because alligators have well-organized teeth with similar form and structure as mammalian teeth and are capable of lifelong tooth renewal, the authors reasoned that they might serve as models for mammalian tooth replacement.

“Alligator teeth are implanted in sockets of the dental bone, like human teeth. They have 80 teeth, each of which can be replaced up to 50 times over their lifetime, making them the ideal model for comparison to human teeth,” said Ping Wu, Ph.D., assistant professor of pathology at the Keck School of Medicine and first author of the study.

USC researchers identified three developmental phases for each alligator tooth unit, comprising a functional tooth (f), replacement tooth (r) and dental lamina.

2-osteoporosis drug combo increases bone density

Researchers have claimed that a combination of two FDA-approved osteoporosis drugs having different mechanisms of action increases bone density better than treatment with either drug alone.

The Massachusetts General Hospital (MGH) investigators found that a treatment that combined denosumab (Prolia) and teriparatide (Forteo) was superior to single-agent treatment in a 12-month trial in women with postmenopausal osteoporosis. For the study, the researchers enrolled 100 postmenopausal women found to be at high fracture risk, based on their bone density and other risk factors, and randomly divided them into three groups.

Over the 12-month study period, one group received a subcutaneous 60 mg dose of denosumab every six months, another group self-administered daily 20-microgram injections of teriparatide, and the third group received both drugs at the same dosage schedules.

Bone density and blood tests were taken at the outset of the study and after 3, 6 and 12 months, and the final analysis included 94 participants who completed at least one follow-up visit.

Slim women likelier to develop endometriosis

Women with a lean body shape have a greater risk of developing endometriosis than women who are morbidly obese, a new study has revealed.

The study found that the risk of endometriosis was 39 percent lower in morbidly obese women – those with a body mass index (BMI) greater than 40 kg/m2 – compared with women with a current BMI in the low normal range (18.5-22.4 kg/m2).

When the researchers looked back at the women's BMIs when they were 18, they found that women who were morbidly obese at that point in their lives had a 41 percent lower risk of developing endometriosis than women with low normal BMI.

The association was strongest in the group of women who were infertile – those who had been trying to become pregnant for more than a year: there was a significantly lower rate of endometriosis (62 percent) among the currently morbidly obese compared with those with a low normal BMI, while it was 77 percent lower among women who were morbidly obese at age 18 compared with those with a low normal BMI at 18.

The authors of the study stress that although their findings establish firm evidence of a link between endometriosis and BMI, it does not show that low BMI causes endometriosis.

"It is important to note that despite the strength of the evidence underlying the association between body weight and endometriosis, inferences regarding causation or the pathophysiologic process underlying these relations cannot be made," they said.

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