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

Abstract

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.

Figure 1. Sagittal dissected pig head fixed in formaldehyde solution.

The artery blood supply of the lacrimal gland is shown as the lateral view on the right side of the head. ECA: external carotid artery; MA: maxillary artery; LPM: lateral pterygoid muscle; EOA: external ophthalmic artery; EB: eyeball; LRM: lateral rectus muscle; LA: lacrimal artery; LG: lacrimal gland.

Figure 2. Sagittal dissected pig head fixed in formaldehyde solution.

The artery blood supply of the lacrimal gland in the dorsal view on the right side of the head. MA: maxillary artery; EOA: external ophthalmic artery; EB: eyeball; LA: lacrimal artery; LG: lacrimal gland; MLB: medial lacrimal branch; LLB: lateral lacrimal branch; BEM: branch for extraocular muscles; BPA: branch for palpebral area; FS: frontal sinus; ZA: zygomatic arch.

Figure 3. Vascular corrosion cast of the lacrimal artery with intraglandular artery divisions.

The lacrimal gland was added as a graphic illustration to get a steric impression of the blood supply. Frontal view on the left lacrimal artery. LA: lacrimal artery; MLB: medial lacrimal branch; LLB: lateral lacrimal branch; LG: lacrimal gland.

Figure 4. Excretory ducts of the left lacrimal system in pig.

Conjunctival view at the level of the eye angle, left scale bar: 2 mm. EB: eyeball; LEA: left eye angle; 1–6: excretory ducts. Right bottom square: higher magnification of an excretory duct, scale bar: 200 µm.

Figure 5. 3D reconstruction by digitized and computer based processed histological sections of the pig lacrimal gland.

A) Visualization of seven excretory lacrimal ducts (different colors) within the paraffin embedded lacrimal gland (grey). B) Separate exposure of each lacrimal duct in different colors with surrounding gland tissue reconstruction. Only the yellow-marked duct system is displayed alone, without gland tissue reconstruction.