Sex-dependent lifespan extension of ApcMin/+ FAP mice by chronic mTOR inhibition

Background: ApcMin/+ mice model familial adenomatous polyposis (FAP), a disease that causes numerous colon polyps leading to colorectal cancer. We previously showed that chronic treatment of ApcMin/+ females with the anti-aging drug, rapamycin, restored a normal lifespan through reduced polyposis and anemia prevention. Lifespan extension by chronic rapamycin in wildtype UM-HET3 mice is sex-dependent with females gaining the most benefit. Whether ApcMin/+ mice have a similar sex-dependent response to chronic mTOR inhibition is not known. Methods: To address this knowledge gap and gain deeper insight into how chronic mTOR inhibition prevents intestinal polyposis, we compared male and female ApcMin/+ mice responses to chronic treatment with a rapamycin-containing diet. Animals were fed a diet containing either 42 ppm microencapsulate rapamycin or empty capsules, one group was used to determine lifespan and a second group with similar treatment was harvested at 16 weeks of age for cross-sectional studies. Results: We found that the survival of males is greater than females in this setting (P < 0.0197). To explore the potential basis for this difference we analyzed factors affected by chronic rapamycin. Immunoblot assays showed that males and females exhibited approximately the same level of mTORC1 inhibition using phosphorylation of ribosomal protein S6 (rpS6) as an indirect measure. Immunohistochemistry assays of rpS6 phosphorylation showed that rapamycin reduction of mTORC1 activity was on the same level, with the most prominent difference being in intestinal crypt Paneth cells in both sexes. Chronic rapamycin also reduced crypt depths in both male and female ApcMin/+ mice (P < 0.0001), consistent with reduced crypt epithelial cell proliferation. Finally, chronic rapamycin prevented anemia equally in males and females. Conclusions: In males and females, these findings link rapamycin-mediated intestinal polyposis prevention with mTORC1 inhibition in Paneth cells and concomitant reduced epithelial cell proliferation. Keywords: Rapamycin, small intestine, polyposis, mTORC1, Paneth cells, crypt stem cells

The Surgical Management of Gardner Syndrome Manifestation in the Maxillofacial Region: A Case Report

Apstrakt Gardner syndrome is a rare autosomal-dominant genetic disorder, considered a variant of familial adenomatous polyposis. It is characterized by intestinal polyposis and various bone and soft-tissue tumors, including osteomas, epidermal and dermal cysts, lipomas and fibromas. Intestinal polyps have high potential to become malignant, and the screening of intestinal lesions is mandatory. Maxillofacial manifestations, such as jaw osteomas, odontomas, dental abnormalities and soft tissue tumors frequently precede the intestinal manifestations. Thus, maxillofacial surgeons and dental practitioners may have important role in early detection of Gardner syndrome. In this case report we present a 22 year old male patient who was reffered to maxillofacial surgeon due to osteoma of the mandible. After obtaining clinical and radiological examinations, as well as data from family history, Gardner syndrome was suspected, which was later confirmed after gastroenterological examination.

Abstract 53: Ablation of Thrombin Signaling in Platelets but Not in Endothelial Cells Impairs Hemostasis in a Mouse Model of Spontaneous Gastrointestinal Bleeding

Human PAR1 is expressed in endothelial cells as well as in platelets where it facilitates the response to thrombin and platelet activation. Vorapaxar, a PAR1 antagonist, prevents myocardial infarction and stroke in patients with prior MI or peripheral arterial disease at a cost of increased bleeding risk. Par1 is also highly expressed in endothelial cells in mice, and Par1-deficiency is associated with bleeding in the mouse embryo at midgestation. Additionally, known actions of endothelial PAR1 activation suggest pro-hemostatic functions. This raises the question of whether inhibition of PAR1 function in endothelial cells (in addition to PAR1 inhibition in platelets) contributes to the bleeding risk associated with Vorapaxar treatment. Our previous work demonstrated that Par1 deficiency results in loss of thrombin signaling in mouse endothelial cells but not mouse platelets, while Par4 deficiency ablated thrombin-induced platelet activation in mice. Thus, mice allow us to separate loss of thrombin signaling in platelets from loss of thrombin signaling in endothelial cells. Accordingly, we used Apc min/+ mice, which develop intestinal polyposis and spontaneous GI bleeding, as a model to determine whether loss of thrombin signaling in platelets (Par4 KO) or endothelial and other cells (Par1 KO) exacerbates spontaneous bleeding. Hematocrit and other hematologic parameters were measured biweekly from 7 weeks through 15 weeks of age. Hematocrits in mice wild-type for Apc were stable over this period (41.48 ± 0.48 at 7 weeks; 40.48 ± 0.37 at 15 weeks, n=15). Hematocrits in Apc min/+ mice fell approximately linearly from 37.06 ± 0.82 at 7 weeks to 14.39 ± 1.12 at 15 weeks (n=15). Hematocrits in Par1-deficient Apc min/+ mice were indistinguishable from those in Apc min/+ without Par deficiency (14.39 ± 1.12 vs 14.47 ± 1.66 at 15 weeks; n=6-15). By contrast, Par4-deficient Apc min/+ mice were already severely anemic at 7 weeks compared to Apc min/+ mice (19 ± 2.0 vs 39 ± 3.6; p<0.01, n=4). Par-dependent differences in polyp count and size were not detected. Taken together, our results suggest that loss of thrombin signaling in platelets promotes spontaneous GI bleeding in the Apc min model while loss of thrombin signaling in endothelial cells is without effect in this system.