Browsing by Author "McIntyre, Patrick W."

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    Effects of Radiopaque Double Antibiotic Pastes on the Proliferation, Alkaline Phosphatase Activity and Mineral Deposition of Dental Pulp Stem Cells
    (Elsevier, 2020-09) Wu, Jennifer L.; McIntyre, Patrick W.; Hong, Jung Min; Yassen, Ghaeth H.; Bruzzaniti, Angela; Biomedical Sciences and Comprehensive Care, School of Dentistry
    Objective The aim of this study was to investigate the effects of two radiopaque agents, barium sulfate (BaSO4) or zirconium oxide (ZrO2) in double antibiotic paste (DAP), on the proliferation and mineral deposition of human dental pulp stem cells (DPSC). Materials and methods Radiopaque antimicrobial medicaments composed of methylcellulose (MC) thickening polymer with BaSO4 or ZrO2 and either 1 or 5 mg/mL DAP (equal portions of metronidazole and ciprofloxacin) were used to investigate DPSC proliferation after 3 days, and alkaline phosphatase (ALP) activity and mineral deposition after 7 and 14 days. Radiopaque agents without DAP and Ca(OH)2 were used as controls. Results MC-BaSO4 DAP and MC-ZrO2 DAP at 1 or 5 mg/mL had no adverse effect on DPSC proliferation, compared to the media and MC controls. MC-ZrO2 (DAP-free) greatly increased ALP activity after 7 days. DPSC mineral deposition was modestly reduced at 7 days by MC-BaSO4 DAP and MC-ZrO2 DAP, but not by DAP-free radiopaque agents, and was most reduced by 5 mg/mL DAP in the 14-day cultures. Conclusions MC-BaSO4 or MC-ZrO2 medicaments containing up to 5 mg/mL of DAP supported the proliferation and early osteogenic differentiation of DPSC. Low DAP concentrations and short culture times led to more favorable effects on ALP activity and mineral deposition by DPSC. The findings suggest that radiopaque agents added for the purpose of detecting whether medicaments occupy the full extent of the root canal may have clinical applications. Radiopaque antibiotic medicaments containing low DAP concentrations may be an alternative to Ca(OH)2 for regenerative endodontic procedures.
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    Pyk2 deficiency potentiates osteoblast differentiation and mineralizing activity in response to estrogen or raloxifene
    (Elsevier, 2018-10-15) Posritong, Sumana; Hong, Jung Min; Eleniste, Pierre P.; McIntyre, Patrick W.; Wu, Jennifer L.; Himes, Evan R.; Patel, Vruti; Kacena, Melissa A.; Bruzzaniti, Angela; Biomedical Sciences and Comprehensive Care, School of Dentistry
    Bone remodeling is controlled by the actions of bone-degrading osteoclasts and bone-forming osteoblasts (OBs). Aging and loss of estrogen after menopause affects bone mass and quality. Estrogen therapy, including selective estrogen receptor modulators (SERMs), can prevent bone loss and increase bone mineral density in post-menopausal women. Although investigations of the effects of estrogen on osteoclast activity are well advanced, the mechanism of action of estrogen on OBs is still unclear. The proline-rich tyrosine kinase 2 (Pyk2) is important for bone formation and female mice lacking Pyk2 (Pyk2-KO) exhibit elevated bone mass, increased bone formation rate and reduced osteoclast activity. Therefore, in the current study, we examined the role of estrogen signaling on the mechanism of action of Pyk2 in OBs. As expected, Pyk2-KO OBs showed significantly higher proliferation, matrix formation, and mineralization than WT OBs. In addition we found that Pyk2-KO OBs cultured in the presence of either 17β-estradiol (E2) or raloxifene, a SERM used for the treatment of post-menopausal osteoporosis, showed a further robust increase in alkaline phosphatase (ALP) activity and mineralization. We examined the possible mechanism of action and found that Pyk2 deletion promotes the proteasome-mediated degradation of estrogen receptor α (ERα), but not estrogen receptor β (ERβ). As a consequence, E2 signaling via ERβ was enhanced in Pyk2-KO OBs. In addition, we found that Pyk2 deletion and E2 stimulation had an additive effect on ERK phosphorylation, which is known to stimulate cell differentiation and survival. Our findings suggest that in the absence of Pyk2, estrogen exerts an osteogenic effect on OBs through altered ERα and ERβ signaling. Thus, targeting Pyk2, in combination with estrogen or raloxifene, may be a novel strategy for the prevention and/or treatment of bone loss diseases.