Presence of lymphatics in a rat tendon lesion model

Abstract

Tendons lack sufficient blood supply and represent a bradytroph tissue with prolonged healing time under pathological conditions. While the role of lymphatics in wound/defect healing in tissues with regular blood supply is well investigated, its involvement in tendon defects is not clear. We here try to identify the role of the lymphatic system in a tendon lesion model with morphological methods. A rat Achilles tendon lesion model (n = 5) was created via surgical intervention. Two weeks after surgery, animals were killed and lesioned site removed and prepared for polarization microscopy (picrosirius red) and immunohistochemistry using the lymphatic markers PROX1, VEGFR3, CCL21, LYVE-1, PDPN, and the vascular marker CD31. Additionally, DAPI was applied. Untreated tendons served as controls, confocal laser-scanning microscopy was used for documentation. At the lesion site, polarization microscopy revealed a structural reintegration while immunohistochemistry detected band-like profiles immunoreactive for PDPN, VEGFR3, CCL21, LYVE1, and CD31, surrounding DAPI-positive nuclei. PROX1-positive nuclei were detected within the lesion forming lines and opposed to each other. These PROX1-positive nuclei were surrounded by LYVE-1- or VEGFR3-positive surfaces. Few CD31-positive profiles contained PROX1-positive nuclei, while the majority of CD31-positive profiles lacked PROX1-positive nuclei. VEGFR3-, PDPN-, and LYVE-1-positive profiles were numerous within the lesion site, but absent in control tissue. Within 2 weeks, a structural rearrangement takes place in this lesion model, with dense lymphatic supply. The role of lymphatics in tendon wound healing is unclear, and proposed model represents a good possibility to study healing dynamics and lymphangiogenesis in a tissue almost completely lacking lymphatics in physiological conditions.

Topography of Lymphatic Markers in Human Iris and Ciliary Body

“…In this sense, it has to be mentioned that CD31 is not exclusively expressed in vascular endothelium, but also in lymphatic endothelium, 23,52-55 but because the here observed iris vessels were lacking PROX1þ nuclei, these were therefore considered vascular capillaries. Additionally, in none of our samples investigated, a typical arrangement of endothelial nuclei resulting in a pearl string-like pattern of PROX1-positivity 55 was obvious. While VEGFR3-imunoreactivity was observed in CD68þ macrophages 51 it is most likely that VEGFR3 þ/ PROX1À/CCL21À cells in the iris and also the VEGFR3-positive cells of similar size and shape in the ciliary body represent macrophages.…”

High-Salt Diet Causes Osmotic Gradients and Hyperosmolality in Skin Without Affecting Interstitial Fluid and Lymph

“…These observations agree well with previous x-ray dispersive studies, where a gradient was demonstrated from epidermis to subcutis in human 29 and in guinea by guest on May 12, 2018 http://hyper.ahajournals.org/ Downloaded from pig skin. 30 In line with these observations, by application of 7T 23 Na + magnetic resonance imaging, it was shown that there was a substantial accumulation of Na + in or directly under epidermis. 31 Interestingly, this Na + accumulation was not associated with a significant volume increase in the same area as would have been expected if the Na + exerted at least some of its crystalloid osmotic effect.…”

“…Because the other major component of the tail, tendon, does not contain lymphatics, 23 the harvested tail lymph will be representative for skin. Moreover, tail skin accumulated salt to a similar extent as back skin and should therefore be representative for skin in general.…”

A high-glucose diet affects Achilles tendon healing in rats

“…4 . For descriptive histology 7 µm thick cryosections were stained either using Hematoxylin & Eosin stain (data not shown), Masson-Goldner’s trichrome stain or Herovici’s polychrome stain according to the manufacturer’s guidelines (see SI methods for further details).…”