Antiinflammatory effects of amniotic membrane transplantation in ocular surface disorders

Abstract

Purpose: To determine whether the sequestration of inflammatory cells plays a role in the antiinflammatory effects of amniotic membrane transplantation to the ocular surface.

Methods: Amniotic membrane grafts were prepared from placental tissue procured from mothers undergoing planned Cesarean sections. A detailed explanation was given to all donors, and a written consent was obtained before processing. Amniotic membrane tissue was dissected into 3- x 3-cm segments, rinsed in phosphate buffered saline, and stored in dimethyl sulfoxide solutions at -80 degrees C until use. In a clinical series, amniotic membrane patches of the ocular surface were performed in 20 eyes of 20 patients with persistent corneal epithelial defects, or as a prophylactic measure after corneal limbal transplantation. Amniotic membrane patches were harvested after a 1-week observation period and were subjected to histopathologic examinations by hematoxylin and eosin staining. Inflammatory cells trapped within the amniotic membrane were labeled by immunocytochemistry using anti-CD14, CD4, CD8, and CD20 antibodies. TUNEL (TdT-mediated dUTP nick end labeling) staining was done to observe cells undergoing apoptosis. The T cell line Molt 4 was co-cultured with amniotic membrane in vitro to observe adhesion of T cells to amniotic membrane.

Results: Various degrees of inflammatory cell infiltration were observed in all clinical samples of amniotic membrane patches. Most of the inflammatory cells stained positively with anti-CD14 antibodies, indicating that these cells were of monocyte/macrophage lineage. Subsets of T cells included both CD4(+) and CD8(+) cells, whereas CD20(+) cells were sparse. TUNEL assays revealed that trapped inflammatory cells exhibited characteristics of cells undergoing apoptosis. Molt 4 invaded within amniotic membrane in an in vitro assay, which was not inhibited by blocking antibodies to beta1 and beta2 integrins.

Conclusion: Amniotic membrane attracts and traps inflammatory cells infiltrating the ocular surface, which may explain some of the antiinflammatory properties of the fetal tissue.