To determine whether the sequestration of inflammatory cells plays a role in the antiinflammatory effects of amniotic membrane transplantation to the ocular surface.
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- × 3-cm segments, rinsed in phosphate buffered saline, and stored in dimethyl sulfoxide solutions at −80°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.
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 β1 and β2 integrins.
Amniotic membrane attracts and traps inflammatory cells infiltrating the ocular surface, which may explain some of the antiinflammatory properties of the fetal tissue.