Salivary gland and autoimmunity

Occlusional Modifications Reversibly Alter Aquaporin 5 Expression and Localization in Rat Salivary Glands

Background

Aquaporin 5 (AQP5) is a water channel–forming protein that plays a key role in saliva secretion. A decrease in masticatory function associated with the molar extraction adversely affects the submandibular salivary gland (SMG) in rats, inducing hypertrophic changes in the acinar cells and the expression of AQP5 in acinar cells or intercalated duct of the SMG. However, changes in AQP5 expression and localization in the SMG in association with occlusal modification have not been fully characterized.

Methods

We examined the influence of the decline and recovery of masticatory function on expression and localization of AQP5 in the rat SMG by inserting and removing an incisor bite plate (IBP). Thirty 5-week-old male Wistar rats were randomly divided into IBP (n = 12), recovery (REC) (n = 6), and control (CON) (n = 12) groups. Each rat in both the IBP and REC groups was fitted with the IBP on its maxillary incisors. Rats without the IBPs served as controls. All rats were fed powder diet and water ad libitum. Rats in the IBP and CON groups were sacrificed after 14 (n = 6) and 28 (n = 6) days after the IBP attachment. In the REC group, the IBP was detached on the 14th day and sacrificed on 28th day after the IBP attachment. AQP5 mRNA expression was quantified by reverse transcription–polymerase chain reaction. Changes in the localization of AQP5 were tracked by immunohistochemical staining.

Results

Attachment of IBP resulted in a decrease in the expression of AQP5 in the IBP group. Changes in the localization of AQP5 were observed between 14 and 28 days in the IBP group. In contrast, changes in the expression and localization of AQP5 were not observed in the REC group.

Conclusion

Findings suggested that a loss of molar occlusion, due to the IBP attachment, altered AQP5 expression and localization in the rat SMG. However, removal of the bite plate allowed the recovery of both AQP5 expression and its normal localization in the SMGs.

Functional ectodermal organ regeneration as the next generation of organ replacement therapy

In this decade, substantial progress in the fields of developmental biology and stem cell biology has ushered in a new era for three-dimensional organ regenerative therapy. The emergence of novel three-dimensional cell manipulation technologies enables the effective mimicking of embryonic organ germ formation using the fate-determined organ-inductive potential of epithelial and mesenchymal stem cells. This advance shows great potential for the regeneration of functional organs with substitution of complete original function in situ. Organoids generated from multipotent stem cells or tissue stem cells via establishment of an organ-forming field can only partially recover original organ function owing to the size limitation; they are considered ‘mini-organs’. Nevertheless, they hold great promise to realize regenerative medicine. In particular, regeneration of a functional salivary gland and an integumentary organ system by orthotopic and heterotopic implantation of organoids clearly points to the future direction of organ regeneration research. In this review, we describe multiple strategies and recent progress in regenerating functional three-dimensional organs, focusing on ectodermal organs, and discuss their potential and future directions to achieve organ replacement therapy as a next-generation regenerative medicine.

Involvement of the T-box transcription factor Brachyury in early-stage embryonic mouse salivary gland

The mouse submandibular gland (SMG) is important organ for embryonic development, and branching morphogenesis is regulated by many molecules containing transcription factors. Real-time reverse transcriptase polymerase chain reaction revealed that the expression of Brachyury increased in the SMG and peaked between E12.5-E13.5, concomitant with the early stage of branching morphogenesis. The expression of Brachyury in SMG rudiments between E12.5-E13.5 was confirmed by western blotting. In addition, fibronectin and Btbd7 (regulated by fibronectin), which are both essential for cleft formation, were expressed strongly during the same period. The Sox2 and Wnt3a, which regulate cell growth, were also expressed strongly during E12.5-E13.5. On the other hand, cleft formation and branching morphogenesis was suppressed by knockdown of Brachyury gene, suggesting that Brachyury plays a central role in regulating cell growth and cleft formation in early-stage embryonic mouse salivary gland development.

Functional peptide KP24 enhances submandibular gland tissue growth in vitro

Introduction

Salivary gland hypofunction, also known as xerostomia, occurs as a result of radiotherapy for head and neck cancer, autoimmune diseases, or aging. Xerostomia leads to oral health problems and thus affects the quality of life. Biological salivary gland tissue generated in vitro would provide an alternative mode of treatment for this disease.

Methods

To develop a novel method for modulating salivary gland tissue growth in vitro, we prepared a KP24 peptide-immobilized hydrogel sheet, wherein the peptide comprised repeating proline and lysine sequences, and evaluated the effect of this peptide on salivary gland tissue growth.

Results

We found that the KP24 peptide has the potential to enhance glandular tissue growth in vitro. This enhancement is associated with neurite outgrowth and increasing neural innervation.

Conclusion

KP24 peptide modified material would be a promising material for the modulation of salivary gland tissue growth in vitro.

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KP24 immobilized hydrogel enhanced the growth of submandibular gland tissue in vitro.

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KP24 immobilized hydrogel is related to the neuronal innervasion and neurite outgrowth in growing submandibular gland tissue.

Functional salivary gland regeneration by transplantation of a bioengineered organ germ

Salivary gland hypofunction, also known as xerostomia, occurs as a result of radiation therapy for head cancer, Sjögren’s syndrome or aging, and can cause a variety of critical oral health issues, including dental decay, bacterial infection, mastication dysfunction, swallowing dysfunction and reduced quality of life. Here we demonstrate the full functional regeneration of a salivary gland that reproduces the morphogenesis induced by reciprocal epithelial and mesenchymal interactions through the orthotopic transplantation of a bioengineered salivary gland germ as a regenerative organ replacement therapy. The bioengineered germ develops into a mature gland through acinar formations with a myoepithelium and innervation. The bioengineered submandibular gland produces saliva in response to the administration of pilocarpine and gustatory stimulation by citrate, protects against oral bacterial infection and restores normal swallowing in a salivary gland-defective mouse model. This study thus provides a proof-of-concept for bioengineered salivary gland regeneration as a potential treatment of xerostomia.

Salivary gland dysfunction as a result of diseases or ageing reduces the quality of life and causes various oral health problems. Here the authors show that the salivary gland function of mice can be recovered by orthotopic transplantation of a bioengineered salivary gland germ.