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lacrimal glands has been established, thanks to the development of tissue engineer-
ing using 3D cell manipulation procedure called an organ germ method (Nakao
et al. 2007 ; Ikeda and Tsuji 2008 ; Oshima et al. 2012 ; Ogawa and Tsuji 2015 ;
Hirayama et al. 2013b). We have investigated a possibility of functional lacrimal
gland organ regeneration by using our organ germ method (Hirayama et al. 2013a).
The bioengineered lacrimal gland germ, which was generated by in vitro cell com-
partmentation of epithelial and mesenchymal cells from the lacrimal gland germ of
ED 16.5 mice, successfully progressed its branching morphogenesis followed by
epithelial elongation and cleft formation in organ culture (Fig. 8.3a). Bioengineered
harderian gland germs were also developed by using the organ germ method.
8.6.1 Transplantation of Bioengineered Lacrimal Gland Germ
with Duct Connection
Duct formation, which connects the lacrimal glands and the ocular surface, also
develops during organogenesis, and its reconstruction is indispensable to secretion
of the tear (Schechter et al. 2010 ). To achieve this, both of the bioengineered lacri-
mal gland germ and the bioengineered harderian gland germ were transplanted to an
extra-orbital lacrimal gland-removed mouse. By using our thread-guided transplan-
tation methods, the duct epithelium of bioengineered glands was connected to the
recipient’s lacrimal excretory duct (Toyoshima et al. 2012 ) (Fig. 8.3b,c). After
engraftment with this method, the bioengineered lacrimal and harderian glands
developed into the appropriate histo-architecture, including acini-expressing aqua-
porin- 5 and myoepithelial cells, duct, and nerve fibers, by reproducing the develop-
mental process in recipient mouse (Fig. 8.3d). The transplantation of bioengineered
organ germ of lacrimal gland and harderian gland could achieve mature secretory
gland structure in vivo.
8.6.2 Tear Secretion Ability of the Bioengineered Lacrimal
Gland
Tear secretion is strictly regulated by neural stimulation to appropriately respond to
the outer environment (Dartt 2004 , 2009 ). Cooling stimulation to the ocular surface
leads to tearing, which is activated through corneal thermoreceptors, a representa-
tive neural pathway for lacrimal gland function (Parra et al. 2010 ; Robbins et al.
2012 ). We proved the bioengineered lacrimal glands could have physiological func-
tion in coordination with the peripheral and central nervous system, because it
secreted tears in response to the cooling stimulation to ocular surface. Acini of the
lacrimal glands or harderian glands secrete not only aqueous tear but also tear com-
ponents including tear proteins such as lactoferrin and lipids (Schechter et al. 2010 ).
M. Hirayama et al.