Assessment of senescence on oral mucosal model treated with bisphosphonate / Nur Bashira Shaharuddin
Osteonecrosis of the jaw (ONJ) has been associated with bisphosphonate (BP) treatment of Paget’s disease of bone, bone metastases, as well as postmenopausal and steroid-induced osteoporosis. The inhibition of bone resorption has been effectively employed in bone-disease treatment, but bisphosphon...
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Format: | Thesis |
Published: |
2017
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Online Access: | http://studentsrepo.um.edu.my/10431/4/bashira.pdf http://studentsrepo.um.edu.my/10431/ |
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Summary: | Osteonecrosis of the jaw (ONJ) has been associated with bisphosphonate (BP)
treatment of Paget’s disease of bone, bone metastases, as well as postmenopausal and
steroid-induced osteoporosis. The inhibition of bone resorption has been effectively
employed in bone-disease treatment, but bisphosphonate-specific toxicity on oral mucosa
causes impaired soft tissue healing followed by the onset of inflammation. The modern
generation of BPs that contain a nitrogen group (N-BPs) have been intravenously
administered to improve the management and prevention of complications associated
with bone cancer metastasis, but they are potent and accumulate in the bone. This study
presents results of the construction of a three-dimensional model comprised of an airliquid interface co-culture of normal immortalized oral keratinocytes (OKF 6/TERT 2)
and normal human oral fibroblasts (NHOF). Co-culture of OKF 6/TERT 2 and NHOF in
a tissue construct resulted in stratified epithelium and expression of differentiationrelated protein such that the construct mimicked the histological appearance of normal
oral mucosa. The goal of the project is to investigate the senescence effect of a commonly
prescribed N-BP, zoledronic acid (ZOL), on the tissue model’s histoarchitecture and
inflammatory cytokine release. When each of the OKF 6/TERT 2 and NHOF monolayer
cultures were exposed to zoledronic acid at increasing dosage, viability was reduced
proportionally as measured by the MTT assay with NHOF more resistant to zoledronic
acid. When exposed to ZOL at 12 µM, OKF 6/TERT 2, not NHOF underwent senescence
based on a significant increase in expression of the ß-galactosidase enzyme. Our mucosal
model further demonstrated that ZOL induced senescence and potentially impaired reepithelialization of oral mucosa through overactivation of the senescence-associated
inflammatory response that leads to SASP (senescence associated secretory phenotype).
Analysis of histology further showed degradation of the basement membrane
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accompanied by keratinocyte invasion towards the lamina propria and a significant
release of senescence-associated inflammatory cytokines (MMP-3 and IL-8) upon
treatment with zoledronic acid. This study therefore suggests that zoledronic acid may
impair mucosal re-epithelialization by overactivation of the inflammation response due
to senescence. |
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