The human fetal lung Xenograft: Validation as model of microvascular remodeling in the postglandular lung

Abstract

Background Coordinated remodeling of epithelium and vasculature is essential for normal postglandular lung development. The value of the human-to-rodent lung xenograft as model of fetal microvascular development remains poorly defined. Aim The aim of this study was to determine the fate of the endogenous (human-derived) microvasculature in fetal lung xenografts. Methods Lung tissues were obtained from spontaneous pregnancy losses (14–22 weeks’ gestation) and implanted in the renal subcapsular or dorsal subcutaneous space of SCID-beige mice (T, B and NK-cell-deficient) and/or nude rats (T-cell-deficient). Informed parental consent was obtained. Lung morphogenesis, microvascular angiogenesis and epithelial differentiation were assessed at two and four weeks post-transplantation by light microscopy, immunohistochemical and gene expression studies. Archival age-matched postmortem lungs served as control. Results The vascular morphology, density and proliferation of renal subcapsular grafts in SCID-beige mice were similar to age-matched control lungs, with preservation of the physiologic association between epithelium and vasculature. The microvasculature of subcutaneous grafts in SCID-beige mice was underdeveloped and dysmorphic, associated with significantly lower VEGF, endoglin, and angiopoietin-2 mRNA expression than renal grafts. Grafts at both sites displayed mild airspace dysplasia. Renal subcapsular grafts in nude rats showed frequent infiltration by host lymphocytes and obliterating bronchiolitis-like changes, associated with markedly decreased endogenous angiogenesis. Conclusion This study demonstrates the critical importance of host and site selection to ensure optimal xenograft development. When transplanted to severely immune suppressed, NK-cell-deficient hosts and engrafted in the renal subcapsular site, the human-to-rodent fetal lung xenograft provides a valid model of postglandular microvascular lung remodeling.

Intussusceptive-like angiogenesis in human fetal lung xenografts: Link with bronchopulmonary dysplasia-associated microvascular dysangiogenesis?

“…Samples for transplantation (1–2 mm 3 pieces) were taken from the peripheral parenchyma of the right lung. Transplantation was performed at the Xenotransplant Core Facility at Brown University (Providence, RI), as previously described 20, 21 . Recipients of the renal subcapsular xenografts were 6 to 12-week-old male SCID-beige mice (Fox Chase SCID beige, Charles River, Wilmington, MA).…”

“…The CD31, CAIX and Ki-67 immunohistochemical studies were performed using an avidin-biotin-peroxidase system, as described before 6 . Endothelial cell proliferation was assessed by double immunofluorescence studies combining labeling for Ki-67 and CD31, as described before 6, 20 . Controls for specificity consisted of omission of the primary antibody, which abolished all staining.…”

“…In the course of recent studies that employed a human-to-rodent fetal lung xenograft model 20, 21 , we identified unusual patterns of microvascular growth in a subset of human fetal lung grafts. The microscopic appearance of these aberrant vascular patterns was strongly reminiscent of the microvascular dysmorphism previously described in postmortem studies of premature ventilated infants and infants with BPD 6 .…”

Xenotransplantation of human fetal adipose tissue: a model of in vivo adipose tissue expansion and adipogenesis

“…Details of the fetal examination and other pertinent information gathering have been described by De Paepe et al ( 17 ). Once obtained, tissue was rinsed one time in Hank's balanced salt solution and then transferred to ice-cold Leibovitz's L-15 medium (Invitrogen, Grand Island, NY) supplemented with gentamicin (50 g/ml) and penicillin/streptomycin (50 g/ml) for transport to Brown University's Xenotransplant Core Facility.…”

“…Avidin-biotin immunoperoxidase staining for CD31 (platelet endothelial cell adhesion molecule, PECAM-1) was performed as previously described ( 17 ). The antibody used for these analyses is specifi c for human CD31; it does not react with mouse CD31.…”