28. Phenotyping circulating endothelial cells as a marker for transplant kidney damage

H. Tejeda Mora, W. Verschoor, R.C. Minnee, K. Boer, D.A. Hesselink, M.W.F. van den Hoogen, L.J.W. van der Laan, C.C. Baan, M. Hoogduijn

Thursday 5 march 2020

0:00 - 0:00h at Toon Hermans Foyer

Parallel session: Postersessie 6 – Basale abstracts

Background: The diagnosis of transplant rejection is mostly based on late and insensitive markers that do not reliably discriminate from other causes of kidney transplant injury. Early, specific and minimally-invasive biomarkers may improve rejection diagnosis. Endothelial cell (EC) layer damage is one of the reasons for functional deterioration or rejecting kidney transplants. Bioassays quantifying circulating EC numbers and its characteristics as a read-out parameter is an attractive method to monitor kidney transplant integrity.

Methods: We examined the association between the count and phenotypic characteristics of circulating EC from peripheral blood or kidney transplant recipients and clinical outcome, including allograft function (eGFR using creatinine). A cohort of 52 kidney recipients transplanted in 2019 was studied. Circulating EC were measured 1 day before transplantation and 3 and 7 days after transplantation. In addition, blood was sampled and analyzed whenever acute rejection was suspected during the first three months after transplantation. Flow cytometry assessed the number of circulating EC by staining for CD31, CD34, CD45, CD105, CD133, and CD146. This panel also included, the kidney injury molecule (KIM-1). Data analysis was performed using a non-linear generalization or principal component analysis (PCA), unsupervised clustering, and t-SNE visualization for unbiased selection of circulating EC.

Results: Paired analysis revealed that the number of circulating EC increased 2.6 [0.5-5] fold at the third day after transplantation, recovering to preoperative levels at day 7 post-transplant. Interestingly, patients who had a biopsy proven acute rejection and recorded a higher amount of circulating EC in comparison to the previous measured time-point, showed a significant (2-fold) increase in the MFI for the damage marker KIM-1 (p < 0.05).

Conclusions: Our results demonstrate a subset of kidney transplant recipients show an increase in circulating EC and KIM-1 expression at the time of rejection. The relevance of these findings will be examined in further studies.