In vivo perfusion of human skin substitutes with microvessels formed by adult circulating endothelial progenitor cells.

Background: At present, tissue-engineered human skin substitutes (HSSs) mainly function as temporary bioactive dressings due to inadequate perfusion. Failure to form functional vascular networks within the initial posttransplantation period compromises cell survival of the graft and its long-term viability in the wound bed.

Objectives: Our goal was to demonstrate that adult circulating endothelial progenitor cells (EPCs) seeded onto HSS can form functional microvessels capable of graft neovascularization and perfusion.

Vascularization and engraftment of a human skin substitute using circulating progenitor cell-derived endothelial cells.

We seeded tissue engineered human skin substitutes with endothelial cells (EC) differentiated in vitro from progenitors from umbilical cord blood (CB-EC) or adult peripheral blood (AB-EC), comparing the results to previous work using cultured human umbilical vein EC (HUVEC) with or without Bcl-2 transduction. Vascularized skin substitutes were prepared by seeding Bcl-2-transduced or nontransduced HUVEC, CB-EC, or AB-EC on the deep surface of decellularized human dermis following keratinocyte coverage of the epidermal surface. These skin substitutes were transplanted onto C.

Malignant transformation of human cells by constitutive expression of platelet-derived growth factor-BB.

Platelet-derived growth factors (PDGFs) comprise a family of growth factors strongly implicated in human oncogenesis. A number of human tumors overexpress PDGF family members or have translocations activating PDGF receptors. Whereas the epidemiologic evidence implicating PDGF in human tumors is strong, malignant transformation of human cells by overexpression of PDGF has not been demonstrated.

Induction, differentiation, and remodeling of blood vessels after transplantation of Bcl-2-transduced endothelial cells.

Implants of collagen-fibronectin gels containing Bcl-2-transduced human umbilical vein endothelial cells (Bcl-2-HUVECs) induce the formation of human endothelial cell (EC)/murine vascular smooth muscle cell (VSMC) chimeric vessels in immunodeficient mice. Microfil casting of the vasculature 60 d after implantation reveals highly branched microvascular networks within the implants that connect with and induce remodeling of conduit vessels arising from the abdominal wall circulation. Approximately 85% of vessels within the implants are lined by Bcl-2-positive human ECs expressing VEGFR1, VEGFR2, and Tie-2, but not integrin alpha(v)beta(3).

Bcl-2 transduction protects human endothelial cell synthetic microvessel grafts from allogeneic T cells in vivo.

T cell interactions with vascular endothelial cells (EC) are of central importance for immune surveillance of microbes and for pathological processes such as atherosclerosis, allograft rejection, and vasculitis. Animal (especially rodent) models incompletely predict human immune responses, in particular with regard to the immunological functions of EC, and in vitro models may not accurately reflect in vivo findings. In this study, we describe the development of an immunodeficient SCID/bg murine model combining a transplanted human synthetic microvascular bed with adoptive transfer of human T lymphocytes allogeneic to the cells of the graft that more fully recapitulates T cell responses in natural tissues.

Endothelial cells present antigens in vivo.

Background: Immune recognition of vascular endothelial cells (EC) has been implicated in allograft rejection, protection against pathogens, and lymphocyte recruitment. However, EC pervade nearly all tissues and predominate in none, complicating any direct test of immune recognition. Here, we examined antigen presentation by EC in vivo by testing immune responses against E.

Calciphylaxis associated with acute, reversible renal failure in the setting of alcoholic cirrhosis.

We describe a case of calciphylaxis in a 47-year-old man with alcohol-induced end-stage liver disease and acute renal failure secondary to hepatorenal syndrome. Possible contributing factors included transiently impaired renal function, protein C and S deficiencies, elevated calcium-phosphate product, hyperphosphatemia, low serum albumin, repeated albumin infusions, and elevated alkaline phosphatase level.

Tissue engineering: creation of long-lasting blood vessels.

The construction of stable blood vessels is a fundamental challenge for tissue engineering in regenerative medicine. Although certain genes can be introduced into vascular cells to enhance their survival and proliferation, these manipulations may be oncogenic. We show here that a network of long-lasting blood vessels can be formed in mice by co-implantation of vascular endothelial cells and mesenchymal precursor cells, by-passing the need for risky genetic manipulations.

IL-11 protects human microvascular endothelium from alloinjury in vivo by induction of survivin expression.

IL-11 can reduce tissue injury in animal models of inflammation but the mechanism(s) is unknown. When C.B-17 SCID/beige mice bearing human skin grafts are injected i.

Interferon-gamma plays a nonredundant role in mediating T cell-dependent outward vascular remodeling of allogeneic human coronary arteries.

Vascular remodeling (change in vessel diameter) rather than intimal hyperplasia is the most important predictor of luminal loss in immune-mediated arterial injury, yet little is known about its mechanisms. Here, we show that outward vascular remodeling and intimal thickening, two manifestations of arteriosclerosis with opposing effects on luminal size, result from immune effector mechanisms that are T-cell dependent and interferon (IFN)-gamma mediated. In our in vivo model of human coronary artery injury by allogeneic peripheral blood mononuclear cells, both processes occur concurrently and are characterized by T-cell infiltrates with a predominantly IFN-gamma-producing cytokine profile.

Engraftment of a vascularized human skin equivalent.

Clinical performance of currently available human skin equivalents is limited by failure to develop perfusion. To address this problem we have developed a method of endothelial cell transplantation that promotes vascularization of human skin equivalents in vivo. Enhancement of vascularization by Bcl-2 overexpression was demonstrated by seeding human acellular dermis grafts with human umbilical vein endothelial cells (HUVEC) transduced with the survival gene Bcl-2 or an EGFP control transgene, and subcutaneous implantation in immunodeficient mice (n=18).

Immunopathology of human T cell responses to skin, artery and endothelial cell grafts in the human peripheral blood lymphocyte/severe combined immunodeficient mouse.

Blood vessels and their endothelial lining are major stimulators and targets of the rejection response. The immunological properties of human endothelial cells differ significantly from those of other species and new models are needed for proper study of human vessels in the transplant setting. We have employed the human peripheral blood lymphocyte/severe combined immunodeficiency (huPBL/SCID) mouse for this purpose.

Transimmunization and the evolution of extracorporeal photochemotherapy.

We are now aware that extracorporeal photopheresis (ECP) - in which a patient's leukocytes are isolated, passed through an ultrathin clear plastic plate, and exposed to 8-methoxypsoralen (8-MOP) and ultraviolet A light prior to reinfusion - is a simple and efficient dendritic cell (DC) therapy and the first FDA approved selective immunotherapy for cancer. DCs, as the most effective antigen presenting cells (APCs), are central to many ongoing efforts to stimulate immune responses to cancer cells. Moreover, ECP has not only demonstrated efficacy in the treatment of a T cell malignancy--namely cutaneous T-cell lymphoma (CTCL)--but also in treatment of oligoclonal T-cell-mediated diseases such as graft-versus-host-disease (GVHD) and organ transplant rejection.