The influence of cervical and thoracic lymphadenectomy on corneal allograft rejection in inbred rats.

AIM: To investigate the site of alloantigen presentation in the rat following orthotopic corneal transplantation. METHODS: Adult inbred Fischer 344 rats received penetrating corneal allografts from inbred Wistar Furth donors (n=17), without lymphadenectomy. A second group (n=8) underwent bilateral removal of superficial cervical and facial lymph nodes 7 days before transplantation. A third group (n=9) underwent bilateral removal of superficial cervical, facial, internal jugular and posterior cervical nodes. Graft survival was assessed by corneal clarity and rejection was confirmed histologically. RESULTS: All allografts underwent rejection. The median time to rejection for unmodified allografts was day 15, compared with day 14.5 for minimally lymphadenectomised recipients and day 18 for more extensively lymphadenectomised recipients (p>0.05, all comparisons). The median day to rejection for the combined group of lymphadenectomised rats was day 17 (p>0.05 compared with unmodified grafts). The rejection process was similar in all recipients. CONCLUSIONS: Removal of multiple lymph nodes in the neck and thorax did not significantly influence the incidence, tempo or nature of the corneal allograft response. Sensitisation and clonal expansion of corneal alloantigen-reactive cells cannot occur only in superficial cervical, facial, internal jugular and posterior cervical lymph nodes in the rat.

Over-expression of sphingosine kinase-1 enhances a progenitor phenotype in human endothelial cells.

OBJECTIVES: The use of endothelial progenitor cells in vascular therapies has been limited due to their low numbers present in the bone marrow and peripheral blood. The aim of this study was to investigate the effect of sphingosine kinase on the de-differentiation of mature human endothelial cells toward a progenitor phenotype. METHODS: The lipid enzyme sphingosine kinase-1 was lentivirally over-expressed in human umbilical vein endothelial cells and cells were analyzed for progenitor phenotype and function. RESULTS: Sphingosine kinase-1 mRNA expression was induced approximately 150-fold with a resultant 20-fold increase in sphingosine kinase-1 enzymatic activity. The mRNA expression of the progenitor cell markers CD34, CD133, and CD117 and transcription factor NANOG increased, while the endothelial cell markers analyzed were largely unchanged. The protein level of mature endothelial cell surface markers CD31, CD144, and von Willebrand factor significantly decreased compared to controls. In addition, functional assays provided further evidence for a de-differentiated phenotype with increased viability, reduced uptake of acetylated low-density lipoprotein and decreased tube formation in Matrigel in the cells over-expressing sphingosine kinase-1. CONCLUSIONS: These findings suggest that over-expression of sphingosine kinase-1 in human endothelial cells promotes, in part, their de-differentiation to a progenitor cell phenotype, and is thus a potential tool for the generation of a large population of vascular progenitor cells for therapeutic use.