title: Cryopreserved aortic homografts contain viable smooth muscle cells capable of expressing transplantation antigens.
abstract: Frozen aortic tissue is increasingly used as homografts in reconstructive cardiovascular surgical procedures. The viability of cells within these cryopreserved tissues, their identity, and their potential immunogenicity have been the subject of controversy. We cultured cells from cryopreserved human aortic homografts that reacted with a monoclonal antibody that recognizes muscle actin isoforms, identifying them as smooth muscle cells. Under basal conditions, these smooth muscle cells contained messenger ribonucleic acid for class I human leukocyte antigens detected by northern blotting and expressed class I human leukocyte antigen on their surfaces as measured by enzyme-linked immunoassay and immunohistochemistry. Unstimulated smooth muscle cells contained no class II human leukocyte antigen messenger ribonucleic acid as determined by northern blotting and displayed almost no class II surface antigen as determined by enzyme-linked immunoassay. Interferon gamma (1000 U/ml, 72 hours), a product of activated T lymphocytes, not only increased the expression of class I human leukocyte antigens by smooth muscle cells, but induced class II human leukocyte antigen messenger ribonucleic acid and elevated surface expression from 22 +/- 7 to 819 +/- 35 enzyme-linked immunoassay units (n = 4). Immunohistochemistry revealed few class II-positive smooth muscle cells under basal culture conditions, but all cells showed high levels of DR antigen after exposure to interferon gamma for 3 days. Similar results were obtained in two independent isolates. We conclude that cryopreserved aortic homografts can contain viable smooth muscle cells capable of expressing major histocompatibility antigens that might render them immunogenic and susceptible to rejection by the recipient's immune system.
authors.affiliation: U.S. Department of Agriculture, Tufts University, Boston, Mass.
authors.forename: R N
authors.initials: RN
authors.lastname: Salomon
authors.forename: G B
authors.initials: GB
authors.lastname: Friedman
authors.forename: A D
authors.initials: AD
authors.lastname: Callow
authors.forename: D D
authors.initials: DD
authors.lastname: Payne
authors.forename: P
authors.initials: P
authors.lastname: Libby
mesh_terms: D001011:Aorta / Q000166:cytology* / Q000276:immunology* / Q000637:transplantation; D002470:Cell Survival; D002478:Cells, Cultured; D015925:Cryopreservation; D015870:Gene Expression; D006680:HLA Antigens / Q000032:analysis* / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008285:Major Histocompatibility Complex / Q000235:genetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000276:immunology*; D014184:Transplantation, Homologous
chemical_list: D006680:HLA Antigens