The effects of estrogen and hormone replacement therapy on platelet activity: a review.

Many studies have shown that an increase in cardiovascular disease in women is related to hormonal changes occurring particularly after menopause with increasing age. While the results of large clinical trials reporting no benefit of hormone replacement therapy (HRT) in cardiovascular disease have been known for some time, there is an increasing body of knowledge regarding the various mechanisms by which estrogen modulates platelet function that could in part explain the higher cardiovascular risk occurring in postmenopausal women and potential benefits of HRT on cardiovascular health. Our review summarizes our current knowledge regarding the effect of endogenous and exogenous estrogen on platelet activity, which can help researchers design future studies. We collected information from 21 peer-reviewed articles published from 1993 to 2021. Studies have indicated that postmenopausal women have higher platelet activity than premenopausal women, which can increase the risk of thrombo-embolic events and cardiovascular disease. Although some studies have reported pro-thrombotic effects of estrogen replacement therapy such as increased platelet activation and adhesion, other studies demonstrated decreased platelet aggregation by inhibiting GP IIb/IIIa receptor expression. This is mediated by estrogen receptors on the platelet membrane in a non-genomic manner and suggests an opportunity for the usage of estrogen replacement therapy with subtle changes in the formulation and route, particularly if started early after menopause. The effect of estrogen on platelet activity is promising as an important factor in reducing the risk of cardiovascular events, warranting further investigation.

Sutures Possess Strong Regenerative Capacity for Calvarial Bone Injury.

Repair of calvarial bony defects remains challenging for craniofacial surgeons. Injury experiments on animal calvarial bones are widely used to study healing mechanisms and test tissue engineering approaches. Previously, we identified Gli1+ cells within the calvarial sutures as stem cells supporting calvarial bone turnover and injury repair. In this study, we tested the regenerative capacity of the suture region compared with other areas of calvarial bone. Injuries were made to mouse sagittal sutures or other areas of the calvarial bone at varying distances from the suture. Samples were collected at different time points after injury for evaluation. MicroCT and histological analyses were conducted. EdU incorporation analysis was performed to assay cell proliferation. Gli1-CreERT2;Tdtomatoflox mice were used to trace the fate of Gli1+ stem cells after injury. Calvarial sutures possess much stronger regeneration capability than the nonsuture bony areas of the calvaria. The healing rate of the calvarial bone is inversely proportional to the distance between the suture and injury site: injuries closer to the suture heal faster. After complete removal of the sagittal suture, regeneration and restoration of normal organization occur within 6 weeks. Gli1+ cells within the suture mesenchyme are the cellular source for injury repair and bone regeneration. These results demonstrate that calvarial bone healing is not an evenly distributed event on the calvarial surface. Sutures contain stem cells and are the origin of calvarial bone tissue regeneration. Therefore, current practice in calvarial surgery needs to be reevaluated and modified. These findings also necessitate the design of new approaches for repairing calvarial bony defects.

Disruption of the ERK/MAPK pathway in neural crest cells as a potential cause of Pierre Robin sequence.

Disrupted ERK1/2 signaling is associated with several developmental syndromes in humans. To understand the function of ERK2 (MAPK1) in the postmigratory neural crest populating the craniofacial region, we studied two mouse models: Wnt1-Cre;Erk2(fl/fl) and Osr2-Cre;Erk2(fl/fl). Wnt1-Cre;Erk2(fl/fl) mice exhibited cleft palate, malformed tongue, micrognathia and mandibular asymmetry. Cleft palate in these mice was associated with delay/failure of palatal shelf elevation caused by tongue malposition and micrognathia. Osr2-Cre;Erk2(fl/fl) mice, in which the Erk2 deletion is restricted to the palatal mesenchyme, did not display cleft palate, suggesting that palatal clefting in Wnt1-Cre;Erk2(fl/fl) mice is a secondary defect. Tongues in Wnt1-Cre;Erk2(fl/fl) mice exhibited microglossia, malposition, disruption of the muscle patterning and compromised tendon development. The tongue phenotype was extensively rescued after culture in isolation, indicating that it might also be a secondary defect. The primary malformations in Wnt1-Cre;Erk2(fl/fl) mice, namely micrognathia and mandibular asymmetry, are linked to an early osteogenic differentiation defect. Collectively, our study demonstrates that mutation of Erk2 in neural crest derivatives phenocopies the human Pierre Robin sequence and highlights the interconnection of palate, tongue and mandible development. Because the ERK pathway serves as a crucial point of convergence for multiple signaling pathways, our study will facilitate a better understanding of the molecular regulatory mechanisms of craniofacial development.

BMP-SHH signaling network controls epithelial stem cell fate via regulation of its niche in the developing tooth.

During embryogenesis, ectodermal stem cells adopt different fates and form diverse ectodermal organs, such as teeth, hair follicles, mammary glands, and salivary glands. Interestingly, these ectodermal organs differ in their tissue homeostasis, which leads to differential abilities for continuous growth postnatally. Mouse molars lose the ability to grow continuously, whereas incisors retain this ability. In this study, we found that a BMP-Smad4-SHH-Gli1 signaling network may provide a niche supporting transient Sox2+ dental epithelial stem cells in mouse molars. This mechanism also plays a role in continuously growing mouse incisors. The differential fate of epithelial stem cells in mouse molars and incisors is controlled by this BMP/SHH signaling network, which partially accounts for the different postnatal growth potential of molars and incisors. Collectively, our study highlights the importance of crosstalk between two signaling pathways, BMP and SHH, in regulating the fate of epithelial stem cells during organogenesis.

Integration of comprehensive 3D microCT and signaling analysis reveals differential regulatory mechanisms of craniofacial bone development.

Growth factor signaling regulates tissue-tissue interactions to control organogenesis and tissue homeostasis. Specifically, transforming growth factor beta (TGFß) signaling plays a crucial role in the development of cranial neural crest (CNC) cell-derived bone, and loss of Tgfbr2 in CNC cells results in craniofacial skeletal malformations. Our recent studies indicate that non-canonical TGFß signaling is activated whereas canonical TGFß signaling is compromised in the absence of Tgfbr2 (in Tgfbr2(fl/fl);Wnt1-Cre mice). A haploinsufficiency of Tgfbr1 (aka Alk5) (Tgfbr2(fl/fl);Wnt1-Cre;Alk5(fl/+)) largely rescues craniofacial deformities in Tgfbr2 mutant mice by reducing ectopic non-canonical TGFß signaling. However, the relative involvement of canonical and non-canonical TGFß signaling in regulating specific craniofacial bone formation remains unclear. We compared the size and volume of CNC-derived craniofacial bones (frontal bone, premaxilla, maxilla, palatine bone, and mandible) from E18.5 control, Tgfbr2(fl/fl);Wnt1-Cre, and Tgfbr2(fl/fl);Wnt1-Cre;Alk5(fl/+)mice. By analyzing three dimensional (3D) micro-computed tomography (microCT) images, we found that different craniofacial bones were restored to different degrees in Tgfbr2(fl/fl);Wnt1-Cre;Alk5(fl/+) mice. Our study provides comprehensive information on anatomical landmarks and the size and volume of each craniofacial bone, as well as insights into the extent that canonical and non-canonical TGFß signaling cascades contribute to the formation of each CNC-derived bone. Our data will serve as an important resource for developmental biologists who are interested in craniofacial morphogenesis.

A novel design of combining the angiotensin converting enzyme (ACE) inhibitor captopril with the angiotensin receptor blocker (ARB) losartan using homo coupling via PEG diacid linker.

Cardiovascular disease is the leading cause of death in American adults. Furthermore, the incidence of congestive heart failure is on the rise as a major cause of hospitalization and mortality in this population. Angiotensin Converting Enzyme (ACE) inhibitors prevent the production of angiotensin II, which has been shown to reduce mortality in patients with congestive heart failure. Angiotensin II receptor blockers (ARB) were developed as a direct inhibitor of angiotensin II. ARBs have been shown to be effective in the treatment of patients with systolic heart failure but do not cause chronic coughing which is a common side effect of ACE inhibitors. In theory, a compound that has the combined effect of an ACE inhibitor and an ARB should be more effective in treating heart failure patients than either agents alone. Therefore, the purpose of this manuscript is to design and discuss the benefits of a new molecule, which combines captopril, an ACE inhibitor, with losartan, an ARB. In this experiment Captopril and Losartan were modified and synthesized separately and combined by homo or mono coupling. This was achieved by taking advantage of PEG (Polyethylene glycol) as a linker. It is expected that this molecule will have the combined modes of action of both ACEs and ARBs. Benefits from combination therapy include; increased efficacy, reduced adverse effects, convenience, compliance, and prolonged duration. Consequently, this combined molecule is expected to block the production of angiotensin II more efficiently and effectively. Although captopril and losartan work in the same system by blocking the effect of angiotensin II they have different action sites and mechanisms some patents are also discussed. Losartan blocks the AT1 receptor which is expressed on the cell surface, while captopril inhibits ACE, preventing production of angiotensin II, which is present in both the plasma and on the cell surface, especially on endothelial and smooth muscle cells.