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Title: Salisphere development for salivary gland regeneration
Author: Saleem, Rimah Abdullah A.
ISNI:       0000 0004 7427 9323
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2018
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Salivary gland stem/progenitor cells are considered a promising solution for ameliorating salivary gland damage. mTOR signalling is known to play a role during salivary gland atrophy as ligation of the salivary main excretory duct results in the activation of mammalian target of rapamycin (mTOR). Cultured mouse and human salivary gland stem/progenitor cells in vitro are able to form spherical non-adherent clusters named salispheres. As mTOR plays a role during glandular atrophy, salispheres were cultured from un-operated, ligated and de-ligated glands. This project aimed to understand several factors on the culture of salispheres. Indeed, mTOR is inactivated in healthy glands but activated during atrophy. Measuring changes in mTOR activity in growing salispheres highlighted the importance of this network for salisphere survival, and a potential correlation between glandular atrophy and salisphere culture. Rapamycin treatment illustrated the necessity of mTOR for growing salispheres, whereas LiCl treatment suggested that GSK-3 inhibition stimulated the expansion of salispheres. Interestingly, injury appeared to alter the growth behaviour of salispheres compared to controls. Mainly, salispheres adhere to a surface of the plastic dish and acquire fibroblastic-like structures suggesting that signalling alterations might be responsible for these changes. The detection of 4e-bp1 and S6 rp expression in salispheres suggested that mTOR was responsible for salisphere growth because it is involved in protein translation, but it was not responsible for the morphological modification post-injury. Changes in the ability of salispheres to adhere to a surface raised two questions. First, were morphological alterations mediated by the cytoskeletal rearrangement? For this reason, RhoA/ROCK and mTORC2 were investigated, as they are both involved in the cytoskeletal organisation. The use of a ROCK inhibitor and torin1 to inhibit ROCK signalling and mTORC2 respectively, suggested that ROCK might played a role during atrophy as increased expression of p-FAK and CK5 expression in cultured salispheres from ligated glands and treated salispheres with ROCK inhibitor. Second, was the neural input affected by injury and involved in the adherence of salispheres? In vivo and in vitro experiments of BoNT/A and neuropeptides were included to investigate if these treatments led to similar effects on salispheres as injury. However, only in vivo experiments of BoNT/A showed minor similarities, implying an unknown complex mechanism is responsible for these changes. To translate the effect of the in vitro treatments on salivary glands, in vivo experiments were included. Injections of treated salispheres with several inhibitors were initially applied to normal salivary glands to determine their physiological response. Among the different inhibitors, LiCl not only showed significant effects on salispheres culture such as preventing salispheres from branching in collagen/matrigel culture and supporting their survival, but also showed an effect on glandular recovery during de-ligation. This suggested that LiCl might played a role in glandular recovery through salispheres. However, in vivo transplantation of ROCKi treated salispheres, which mimicked salispheres from ligated glands, had little or no effects on normal salivary glands. However, the activation of mTOR post ROCKi injection implies that ROCK signalling might be involved in the atrophic process. In conclusion, my results show that mTOR an essential factor for salisphere growth and survival, and LiCl might be a promising tool for enhancing the recovery of glands post-injury. Finally, the inhibition of RhoA/ROCK could be a factor associated with salivary gland atrophy, through ROCK associations with mTOR.
Supervisor: Carpenter, Guy Howard ; Proctor, Gordon Burgess Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available