Adult endothelial progenitor cells retain hematopoiesis potential

Induction of tumor inhibitory anti-angiogenic response through immunization with interferon Gamma primed placental endothelial cells: ValloVax™

BACKGROUND

While the concept of angiogenesis blockade as a therapeutic intervention for cancer has been repeatedly demonstrated, the full promise of this approach has yet to be realized. Specifically, drugs such as VEGF-blocking antibodies or kinase inhibitors suffer from the drawbacks of resistance development, as well as off-target toxicities. Previous studies have demonstrated feasibility of specifically inducing immunity towards tumor endothelium without consequences of systemic autoimmunity in both animal models and clinical settings.

METHOD

Placenta-derived endothelial cells were isolated and pretreated with interferon gamma to enhance immunogenicity. Syngeneic mice received subcutaneous administration of B16 melanoma, 4 T1 mammary carcinoma, and Lewis Lung Carcinoma (LLC), followed by administration of control saline, control placental endothelial cells, and interferon gamma primed endothelial cells (ValloVax™). Tumor volume was quantified. An LLC metastasis model was also established and treated under similar conditions. Furthermore, a safety analysis in non-tumor bearing mice bracketing the proposed clinical dose was conducted.

RESULTS

ValloVax™ immunization led to significant reduction of tumor growth and metastasis as compared to administration of non-treated placental endothelial cells. Mitotic inactivation by formalin fixation or irradiation preserved tumor inhibitory activity. Twenty-eight day evaluation of healthy male and female mice immunized with ValloVax™ resulted in no abnormalities or organ toxicities.

CONCLUSION

Given the established rationale behind the potential therapeutic benefit of inhibiting tumor angiogenesis as a treatment for cancer, immunization against a variety of endothelial cell antigens may produce the best clinical response, enhancing efficacy and reducing the likelihood of the development of treatment resistance. These data support the clinical evaluation of irradiated ValloVax™ as an anti-angiogenic cancer vaccine.

Separation of two phenotypically similar cell types via a single common marker in microfluidic channels

To isolate clinically and biologically relevant cell types from a heterogeneous population, fluorescent or magnetic tagging together with knowledge of surface biomarker profiles represents the state of the art. To date, it remains exceedingly difficult to separate phenotypically and physically similar cell types from a mixed population. We report a microfluidic platform engineered to separate two highly similar cell types using a single antibody by taking advantage of subtle variations in surface receptor density and cell size. This platform utilizes antibody-conjugated surfaces in microfluidic channels together with precise modulation of fluid shear stresses to accomplish selective fractionation in a continuous flow process. Antibody conjugation density variation on the adhesive surfaces is achieved by covalently immobilizing an antibody in the presence of poly(ethylene glycol). This platform is used to demonstrate separation of two CD31 positive cell types, human umbilical vein endothelial cells and human micro vascular endothelial cells.

Cord blood endothelial progenitor cells as therapeutic and imaging probes

Numerous studies demonstrated that neovascularization processes associated with severe tissue ischemia commonly found in conditions such as cardiovascular disorders and tumor growth occur via angiogenic and vasculogenic mechanisms. Over the past decade, it has been demonstrated that endothelial progenitor cells (EPCs) play a significant role in neo-angiogenic and neovasculogenic processes. Due to their ability to self-renew, circulate, home to the ischemic sites and differentiate into mature endothelial cells, EPCs derived from various sources hold enormous potential to be used as therapeutic agents in pro- or anti-angiogenic strategies for the treatment of ischemic and tumor conditions, respectively. However, the development of EPC-based therapies requires accompanying, noninvasive imaging protocol for in vivo tracking of transplanted cells. Hence, this review focuses on cord blood-derived EPCs and their role in neovascularization with emphasis on the potential use of EPCs as a therapeutic and imaging probe.

Early alterations of the immune transcriptome in cultured progenitor cells from obese African-American women

Progenitor cells (PCs) are key components of vasculogenic remodeling and hematopoietic development. Decreases in the number and function of angiogenic progenitors have been observed in coronary artery disease, hypertension, and diabetic vasculopathy. Several recent studies have also demonstrated a close relationship between increased visceral fat and cardiovascular disease, implying an association between obesity and vascular dysfunction. However, very little is known about the role of PCs in obesity. We generated whole genome expression profiles of cultured PCs from 18 obese and 6 lean African-American women on Agilent microarrays and analyzed the data through bioinformatic pathway analysis using multiple databases and analytic tools. False-discovery rates (FDR) were calculated to assess statistical significance while controlling for multiple testing. We identified 1,145 upregulated and 2,257 downregulated genes associated with obesity (1.5-fold or greater absolute fold-change). Pathway analysis further identified a statistically significant downregulation of immune-response pathways in the obese subjects, including T-cell receptor signaling, natural killer cell signaling, and chemokine-signaling pathways (FDR <5%). Chemokine gene-expression patterns were consistent with an angiogenic-angiostatic imbalance and a downregulation of CXCR3 receptor-mediated signaling in the PCs from obese subjects. Overall, these findings reveal a novel transcriptional signature in cultured PCs from obese African-American women and further suggest that obesity-associated immune-compromise may originate much earlier in cellular development than currently appreciated. Clinically, this may translate into a lengthier period of immune dysregulation in obese subjects exposing them to greater risks of infection and other morbidities.

Tag-free microfluidic separation of cells against multiple markers

Conventional cell separation against multiple markers generally requires the attachment of antibody tags, typically fluorescent or magnetic, to selected cell types in a heterogeneous suspension. This work describes how such separation can be accomplished in a series of microfluidic systems without the need for such tags. Two capture stages containing antibody-functionalized alginate hydrogels are utilized for the isolation of CD34+ and Flk1+ cells from untreated, whole human blood. The capture-release capability of these degradable coatings is harnessed by a mixing chamber and a simple valving system such that the suspension emerging from the first capture stage is prepared for the second capture stage for further enrichment. With this configuration, we demonstrate the isolation of CD34+/Flk1+ endothelial progenitor cells from blood enabled by the depletion of CD34+/Flk1-hematopoietic stem cells population. This ability to achieve isolation of cells against multiple markers in an untagged separation method is of particular significance in applications involving cell implantation-based therapeutics including tissue engineering and molecular analysis.

Engineered alginate hydrogels for effective microfluidic capture and release of endothelial progenitor cells from whole blood

Microfluidic adhesion-based cell separation systems are of interest in clinical and biological applications where small sample volumes must be processed efficiently and rapidly. While the ability to capture rare cells from complex suspensions such as blood using microfluidic systems has been demonstrated, few methods exist for rapid and nondestructive release of the bound cells. Such detachment is critical for applications in tissue engineering and cell-based therapeutics in contrast with diagnostics wherein immunohistochemical, proteomic, and genomic analyses can be carried out by simply lysing captured cells. This paper demonstrates how the incorporation of four-arm amine-terminated poly(ethylene glycol) (PEG) molecules along with antibodies within alginate hydrogels can enhance the ability of the hydrogels to capture endothelial progenitor cells (EPCs) from whole human blood. The hydrogel coatings are applied conformally onto pillar structures within microfluidic channels and their dissolution with a chelator allows for effective recovery of EPCs following capture.