Morphological features of the porcine lacrimal gland and its compatibility for human lacrimal gland xenografting

In this study, we present first data concerning the anatomical structure, blood supply and location of the lacrimal gland of the pig. Our data indicate that the porcine lacrimal gland may serve as a potential xenograft candidate in humans or as an animal model for engineering of a bioartificial lacrimal gland tissue construct for clinical application. For this purpose, we used different macroscopic preparation techniques and digital reconstruction of the histological gland morphology to gain new insights and important information concerning the feasibility of a lacrimal gland transplantation from pig to humans in general. Our results show that the lacrimal gland of the pig reveals a lot of morphological similarities to the analogous human lacrimal gland and thus might be regarded as a xenograft in the future. This is true for a similar anatomical location within the orbit as well as for the feeding artery supply to the organ. Functional differences concerning the composition of the tear fluid, due to a different secretory unit distribution within the gland tissue will, however, be a challenge in future investigations.

Transplantation of newborn lacrimal gland cells in a rat model of reduced tear secretion

BACKGROUND

Decreased lacrimal gland output may cause dry eye syndrome. Using a rat model, we examined the feasibility of transplanting lacrimal gland cells from newborns.

OBJECTIVES

To restore lacrimal gland function in eyes with compromised tear production.

METHODS

A model of dry eye in adult rats was developed by unilateral surgical removal of the main lacrimal gland. Tear secretion in both eyes was then assessed by masked Schirmer's test. Lacrimal gland tissue from newborn rats was transplanted into the fibrous connective tissue in which the lacrimal gland had been embedded. Masked Schirmer's test was repeated 4, 8 and 12 weeks after transplantation.

RESULTS

Schirmer's test performed in 13 rats 10 days after unilateral lacrimal gland excision revealed significantly less wetting on the side with excised gland compared with the normal side (P < 0.003). The lack of secreting cells on the operated side was verified histologically. The reduction in tear secretion on the operated side remained significant for 8 weeks on average. In the six rats with transplanted lacrimal gland tissue however, there were no differences in tear reduction between the two eyes at 4, 8 or 12 weeks after the operation (P = 0.81, 0.56 and 0.8, respectively).

CONCLUSIONS

Transplantation of lacrimal gland tissue from newborn rats effectively restored eye wetting in this new model. Further research is needed to evaluate this new approach for treating lacrimal gland dysfunction. Using this model might also facilitate evaluation of potential clinical treatments for dry eyes.

Sjögren syndrome

Sjögren syndrome is a chronic systemic disease characterized by polyglandular tissue destruction leading to keratoconjunctivitis sicca (KCS) and xerostomia. Patients with primary Sjögren syndrome show evidence of KCS and xerostomia, whereas patients with secondary Sjögren syndrome suffer from KCS, xerostomia, and an autoimmune disease, most commonly rheumatoid arthritis. Certain factors cause autoimmune dysregulation leading to destruction of the acinar cells and ductal epithelia with subsequent dry eyes and dry mouth. Activated lymphocytes in patients with autoimmune diseases appear to have selective homing into the lacrimal and salivary glands leading to tissue damage. Understanding the factors involved in the immune dysregulation may improve our diagnostic and therapeutic approaches in Sjögren syndrome. Current therapeutic measures include means to increase secretion, relieve symptoms, and repair damage of the ocular surface.

[Partial canaliculus transplantation--further results]

Partial canaliculus transplantation is a suitable method of substituting the canaliculus when the nasal lower lid region has been damaged by tumor. Two cases are described, illustrating that the area of indication may be extended to substitution surgery of parts of the canaliculus next to the lacrimal sac and that, analogously to complete lid transplantation, the method can be combined with sliding plasty. During the observation period, which lasted for 17 to 20 months, the partial canaliculus transplantations followed up proved to be patent.

[Partial canaliculus transplantation (author's transl)]

In some cases of palpebral tumors, causing epiphora by canalicular obstruction, surgical reconstruction of the lacrimal system is necessary . The defect of the nasal part of the lower lid is closed by transplantation of the nasal part of the upper lid of the other eye, including a part of the canaliculus. Three patients suffering from basaliomas in the region of the lower canaliculus were treated by this method. Good cosmetic and functional results were achieved.