Faculty Bibliography

Breast cancer often leads to significant alteration of body image and disfigurement of the breast. Reconstruction for breast cancer defects can provide the patient with a restored breast contour. The potential benefit of breast cancer reconstructive surgery is to increase the patient's post-surgical quality of life and alleviate the posttraumatic psychological sequelae of breast cancer surgery. Time of breast cancer diagnosis is an important point of access for patients to receive information on breast reconstruction. Access to this information and plastic surgeons in the early phases of diagnosis is critical to a patient's decision to undergo reconstructive surgery, but is currently underutilized in the United States. Breast cancer reconstruction is a complex process that should be treated in a multidisciplinary fashion. This process must begin with the identification and treatment of psychological issues preceding or accompanying breast cancer diagnosis. These psychological problems should be addressed immediately and can significantly influence a patient's decision toward and level of satisfaction with breast cancer reconstruction. Breast reconstruction continues to be an essential element in helping patients recover from the diagnosis and treatment for breast cancer.

Tissue ischemia promotes vasculogenesis through chemokine-induced recruitment of bone marrow-derived endothelial progenitor cells (EPCs). Diabetes significantly impairs this process. Because hyperglycemia increases reactive oxygen species in a number of cell types, and because many of the defects responsible for impaired vasculogenesis involve HIF1-regulated genes, we hypothesized that HIF1 function is impaired in diabetes because of reactive oxygen species-induced modification of HIF1alpha by the glyoxalase 1 (GLO1) substrate methylglyoxal. Decreasing superoxide in diabetic mice by either transgenic expression of manganese superoxide dismutase or by administration of an superoxide dismutase mimetic corrected post-ischemic defects in neovascularization, oxygen delivery, and chemokine expression, and normalized tissue survival. In hypoxic fibroblasts cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the EPC mobilizing chemokine stromal cell-derived factor-1 (SDF-1) and of vascular epidermal growth factor, which modulates growth and differentiation of recruited EPCs. In hypoxic EPCs cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the SDF-1 receptor CXCR4, and endothelial nitric-oxide synthase, an enzyme essential for EPC mobilization. HIF1alpha modification by methylglyoxal reduced heterodimer formation and HIF1alpha binding to all relevant promoters. These results provide a basis for the rational design of new therapeutics to normalize impaired ischemia-induced vasculogenesis in patients with diabetes

BACKGROUND: Advanced age is known to impair neovascularization. Because endothelial progenitor cells (EPCs) participate in this process, we examined the effects of aging on EPC recruitment and vascular incorporation. METHODS AND RESULTS: Murine neovascularization was examined by use of an ischemic flap model, which demonstrated aged mice (19 to 24 months) had decreased EPC mobilization (percent mobilized 1.4+/-0.2% versus 0.4+/-0.1%, P<0.005) that resulted in impaired gross tissue survival compared with young mice (2 to 6 months). This decrease correlated with diminished tissue perfusion (P<0.005) and decreased CD31+ vascular density (P<0.005). Gender-mismatched bone marrow transplantation demonstrated significantly fewer chimeric vessels in aged mice (P<0.05), which confirmed a deficit in bone marrow-mediated vasculogenesis. Age had no effect on total EPC number in mice or humans. Reciprocal bone marrow transplantations confirmed that impaired neovascularization resulted from defects in the response of aged tissue to hypoxia and not from intrinsic defects in EPC function. We demonstrate that aging decreased hypoxia-inducible factor 1alpha stabilization in ischemic tissues because of increased prolyl hydroxylase-mediated hydroxylation (P<0.05) and proteasomal degradation. This resulted in a diminished hypoxia response, including decreased stromal cell-derived factor 1 (P<0.005) and vascular endothelial growth factor (P<0.0004). This effect can be reversed with the iron chelator deferoxamine, which results in hypoxia-inducible factor 1alpha stabilization and increased tissue survival. CONCLUSIONS: Aging impairs EPC trafficking to sites of ischemia through a failure of aged tissues to normally activate the hypoxia-inducible factor 1alpha-mediated hypoxia response

OBJECTIVE: The mechanism of neovascularization during the proliferative phase of infantile hemangioma is poorly understood. It is known that circulating bone marrow-derived endothelial progenitor cells (EPCs) form new blood vessels in ischemic tissues using mediators regulated by the transcription factor, HIF-1alpha. Mobilization of EPCs is enhanced by VEGF-A, matrix metalloproteinase (MMP)-9, and estrogen, whereas homing is secondary to localized expression of stromal cell-derived factor-1alpha (SDF-1alpha). We examined whether these mediators of EPC trafficking are upregulated during the proliferation of infantile hemangioma. METHODS AND RESULTS: Surgical specimens and blood samples were obtained from children with proliferating hemangioma and age-matched controls (n=10, each group). VEGF-A and MMP-9 levels were measured in blood, and tissue sections were analyzed for SDF-1alpha, MMP-9, VEGF-A, and HIF-1alpha. The role of estrogen as a modulator of hemangioma endothelial cell growth was also investigated. We found that all these mediators of EPC trafficking are elevated in blood and specimens from children with proliferating infantile hemangioma. In vitro, the combination of hypoxia and estrogen demonstrated a synergistic effect on hemangioma endothelial cell proliferation. CONCLUSIONS: These findings demonstrate that proliferating hemangiomas express known mediators of vasculogenesis and suggest that this process may play a role in the initiation or progression of this disease

BACKGROUND: Diabetics suffer from vascular dysfunction with increased risks of coronary artery disease and peripheral vascular disease secondary to an impaired ability to respond to tissue ischemia. Because endothelial progenitor cells are known to home to sites of ischemia and participate in new blood vessel growth, the authors examined the effects of diabetes on human endothelial progenitor cell function and peripheral tissue signaling in hypoxia, and determined whether these cells might be a useful cell-based therapy for diabetic vascular complications. METHODS: Circulating human endothelial progenitor cells from type 2 diabetic patients and controls were isolated and subjected to in vitro adhesion, migration, and proliferation assays (n = 5). Cell mobilization and recruitment were studied in vivo in diabetic and nondiabetic environments (n = 6). Exogenous human diabetic and normal cells were analyzed for therapeutic efficacy in a murine ischemia model (n = 6). RESULTS: Adhesion, migration, and proliferation of human diabetic endothelial progenitor cells in response to hypoxia was significantly reduced compared with controls. In diabetic mice, cell mobilization from the bone marrow and recruitment into ischemic tissue was significantly reduced compared with controls. Normal cells injected systemically as replacement therapy in a diabetic mouse increased but did not normalize ischemic tissue survival. CONCLUSIONS: These findings suggest that diabetes causes defects in both the endothelial progenitor cell and peripheral tissue responses to hypoxia. These changes in endothelial progenitor cell function and signaling offer a novel explanation for the poor clinical outcome of type 2 diabetics following ischemic events. Based on these findings, it is unlikely that endothelial progenitor cell-based cellular therapies will be able to prevent diabetic complications

BACKGROUND: Gene therapy for cancer holds enormous therapeutic promise, but its clinical application has been limited by the inability to achieve targeted, high-level transgene expression with limited systemic toxicity. The authors have developed a novel method for delivering genes to microvascular free flaps (commonly used during reconstructive surgery) to avoid these problems. METHODS: During the finite period in which a free flap is separated from the host (ex vivo), it can be perfused with extremely high titers of genetic material through the afferent artery, resulting in efficient transduction of the tissue. Before reanastomosis, unincorporated genetic material is flushed from the flap, minimizing systemic toxicity. RESULTS: In a rodent model using an adenoviral vector containing the lacZ reporter gene, high regional expression of beta-galactosidase was achieved in all the different cells in a microvascular free flap. Moreover, no beta-galactosidase staining was observed outside of the transduced flap, and viral sequence was undetectable by polymerase chain reaction analysis in other tissues. Further analysis confirmed that high-level transgene expression was precisely localized to the explanted tissue, with no collateral transduction. CONCLUSIONS: Targeting gene delivery with minimal systemic toxicity is essential for successful gene therapy. This form of 'biological brachytherapy' provides a new opportunity to deliver targeted therapeutic transgenes to patients undergoing reconstructive surgery and allows microvascular free flaps to perform therapeutic and reconstructive functions

BACKGROUND: Long-term survival of a skin graft is dependent on eventual revascularization. The authors' aim in the present study was to determine whether skin graft vascularization occurs by (1) simple reconnection of vessels, (2) ingrowth of recipient vasculature, (3) outgrowth of donor-derived vessels, and/or (4) recruitment of bone marrow-derived endothelial progenitor cells. METHODS: Full-thickness skin grafts (1 x 1 cm) were transferred between wild-type FVB/N mice (n = 20) and transgenic tie2/lacZ mice (n = 20), where lacZ expression is controlled by the endothelial specific tie2 promoter, allowing differentiation of recipient and donor endothelial cells. The contribution of endothelial progenitor cells to skin graft neovascularization was determined using a bone marrow transplant model where tie2/lacZ bone marrow was transplanted into wild-type mice (n = 20). RESULTS: Vascular regression in the graft was observed at the periphery starting on day 3 and moving centrally through day 21, sparing graft vessels in the absolute center of the graft. At the same time, vascular ingrowth occurred from the wound bed to replace the regressing vessels. Furthermore, bone marrow-derived endothelial progenitor cells contributed to these new vessels starting as early as day 7. Surprisingly, the contribution of bone marrow-derived vessels to the overall process was approximately 15 to 20 percent of new endothelial cells. CONCLUSIONS: Replacement of the donor graft vasculature by endothelial and endothelial progenitor cells from the recipient along preexisting channels is the predominant mechanism for skin graft revascularization. This mechanism is likely similar for all nonvascularized free grafts and suggests novel strategies for optimizing the vascularization of tissue constructs engineered in vitro

Vascular complications in diabetes are a significant source of human morbidity and mortality, affecting multiple organ systems and persisting despite tight glucose control. Many of these complications can be linked to impairments in vasculogenesis, the process by which circulating and bone marrow-derived endothelial progenitor cells (EPCs) contribute to new vessel formation. Recent evidence suggests that hyperglycemia alone, through the mitochondrial overproduction of reactive oxygen species (ROS), can induce changes in gene expression and cellular behavior in diabetes. In this review, we examine how hyperglycemia-induced overproduction of ROS could explain EPC impairments observed in diabetes. Experimentally, impairments in EPC function prevent new blood vessel growth and are potentially reversible by manipulations to decrease ROS. Novel strategies aimed at reducing hyperglycemia-induced ROS may be a useful adjuvant to antihyperglycemic therapies in the restoration of vasculogenesis and the prevention of diabetic complications

BACKGROUND: Ischemia is a limiting factor during distraction osteogenesis. The authors sought to determine the extent of ischemia in the distraction zone and whether endothelial progenitor cells home to the distraction zone and participate in local vasculogenesis. METHODS: Laser Doppler imaging was used to assess the extent of blood flow in the distraction zone in gradually distracted, immediately distracted, and osteotomized rat mandibles during activation and consolidation. Animals (n = 50; 25 rats with unilateral gradual distraction and contralateral osteotomy as an internal control, and 25 rats with unilateral immediate distraction) were examined on postoperative days 4, 6, and 8 of activation, and after 1 and 2 weeks of consolidation. Endothelial progenitor cells isolated from human peripheral blood were labeled with fluorescent DiI dye, and 0.5 x 10 cells were injected intra-arterially under direct vision into each carotid artery at the start of activation in nude rats (n = 18) that then underwent the distraction protocol outlined above. RESULTS: Doppler flow analysis demonstrated relative ischemia during the activation period in the distraction osteogenesis group and increased blood flow in the osteotomized control group as compared with flow in a normal hemimandible [normal, 1 (standardized); distraction osteogenesis, 0.58 +/- 0.05; control, 2.58 +/- 0.21; p < 0.05 for both results]. We observed a significantly increased endothelial progenitor cell population at the generate site versus controls at midactivation and at 1 and 2 weeks of consolidation [25 +/- 1.9 versus 1 +/- 0.3 DiI-positive cells per high-power field (p < 0.05), 124 +/- 21 versus 8 +/- 4 DiI-positive cells per high-power field (p < 0.05), and 106 +/- 18 versus 9 +/- 3 DiI-positive cells per high-power field (p < 0.05), respectively]. CONCLUSIONS: These data suggest that the distraction zone becomes relatively ischemic during activation and that endothelial progenitor cells home to the ischemic generate site during the activation phase and remain during the consolidation phase. Selective expansion of these stem cells may be useful in overcoming ischemic limitations of distraction osteogenesis. Moreover, their homing capability may be used to effect site-specific transgene delivery to the generate