Aaron Orozco

Flow cytometric analysis of circulating microparticles in plasma

Microparticles, which include exosomes, micro‐vesicles, apoptotic bodies and apoptotic microparticles, are small (0.05 ‐ 3 μm in diameter), membranous vesicles that can contain DNA, RNA, miRNA, intracellular proteins and express extracellular surface markers from the parental cells. They can be secreted from intracellular multivesicular bodies or released from the surface of blebbing membranes. Circulating microparticles are abundant in the plasma of normal individuals and can be derived from circulating blood cells such as platelets, red blood cells and leukocytes as well as from tissue sources, such as endothelial and placental tissues. Elevated levels of microparticles are associated with various diseases such as thrombosis (platelet microparticles), congestive heart failure (endothelial microparticles), breast cancer patients (leukocyte microparticles) and women with preeclampsia (syncytiotrophoblast microparticles). Although microparticles can be detected by microscopy, enzyme‐linked immunoassays and functional assays, flow cytometry is the preferred method because of the ability to quantitate (fluorescent bead‐ or flow rate‐based method) and because of polychromatic capabilities. However, standardization of pre‐analytical and analytical modus operandi for isolating, enumerating and fluorescent labeling of microparticles remains a challenge. The primary focus of this article is to review the preliminary steps required to optimally study circulating in vivo microparticles which include: 1) centrifugation speed used, 2) quantitation of microparticles before antibody labeling, 3) levels of fluorescence intensity of antibody‐labeled microparticles, 4) polychromatic flow cytometric analysis of microparticle sub‐populations and 5) use of polyclonal antibodies designed for Western blotting for flow cytometry. These studies determine a roadmap to develop microparticles as biomarkers for a variety of conditions.

Placental Release of Distinct DNA-associated Micro-particles into Maternal Circulation: Reflective of Gestation Time and Preeclampsia

BACKGROUND The aim of this study was to determine whether DNA-associated micro-particles (MPs) in maternal plasma express fetal-derived human leukocyte antigen-G (HLA-G) or placental alkaline phosphatase (PLAP) and whether the levels differ between women with normotensive pregnancies and preeclampsia. METHODS DNA-associated MPs expressing HLA-G or PLAP were examined in the plasma of normal pregnant women and preeclamptic patients using flow cytometric analysis. RESULTS DNA-associated HLA-G(+) MPs were significantly increased in maternal plasma compared to plasma from non-pregnant controls (p<0.005), with highest levels found in the first and second trimesters. DNA-associated PLAP(+) MPs were also increased in maternal plasma compared to plasma from non-pregnant controls (p<0.006), with highest levels in the second and third trimesters. Term preeclamptic women had higher levels of DNA-associated MPs than control pregnant women. HLA-G(+) MPs from the plasma of preeclamptic women had more DNA per MP than HLA-G(+) MPs from the plasma of normal pregnant women (p<0.03). CONCLUSIONS HLA-G(+) and PLAP(+) MPs increase in maternal circulation at different times during gestation. DNA amounts per HLA-G(+) MP increase in preeclamptic women which might indicate dysfunctional extravillous cytotrophoblasts.

Membrane protected apoptotic trophoblast microparticles contain nucleic acids: Relevance to preeclampsia

Microparticles (MPs) that circulate in blood may be a source of DNA for molecular analyses, including prenatal genetic diagnoses. Because MPs are heterogeneous in nature, however, further characterization is important before use in clinical settings. One key question is whether DNA is either bound to aggregates of blood proteins and lipid micelles or intrinsically associated with MPs from dying cells. To test the latter hypothesis, we asked whether MPs derived in vitro from dying cells were similar to those in maternal plasma. JEG-3 cells model extravillous trophoblasts, which predominate during the first trimester of pregnancy when prenatal diagnosis is most relevant. MPs were derived from apoptosis and increased over 48 hours. Compared with necrotic MPs, DNA in apoptotic MPs was more fragmented and resistant to plasma DNases. Membrane-specific dyes indicated that apoptotic MPs had more membranous material, which protects nucleic acids, including RNA. Flow cytometry showed that MPs derived from dying cells displayed light scatter and DNA staining similar to MPs found in maternal plasma. Quantification of maternal MPs using characteristics defined by MPs generated in vitro revealed a significant increase of DNA(+) MPs in the plasma of women with preeclampsia compared with plasma from women with normal pregnancies. Apoptotic MPs are therefore a likely source of stable DNA that could be enriched for both early genetic diagnosis and monitoring of pathological pregnancies.

Bone Marrow Characteristics Associated With Changes in Infarct Size After STEMI A Biorepository Evaluation From the CCTRN TIME Trial

Rationale: Despite significant interest in bone marrow mononuclear cell (BMC) therapy for ischemic heart disease, current techniques have resulted in only modest benefits. However, selected patients have shown improvements after autologous BMC therapy, but the contributing factors are unclear. Objective: The purpose of this study was to identify BMC characteristics associated with a reduction in infarct size after ST-segment-elevation–myocardial infarction. Methods and Results: This prospective study comprised patients consecutively enrolled in the CCTRN TIME (Cardiovascular Cell Therapy Research Network Timing in Myocardial Infarction Evaluation) trial who agreed to have their BMCs stored and analyzed at the CCTRN Biorepository. Change in infarct size between baseline (3 days after percutaneous coronary intervention) and 6-month follow-up was measured by cardiac MRI. Infarct-size measurements and BMC phenotype and function data were obtained for 101 patients (mean age, 56.5 years; mean screening ejection fraction, 37%; mean baseline cardiac MRI ejection fraction, 45%). At 6 months, 75 patients (74.3%) showed a reduction in infarct size (mean change, −21.0±17.6%). Multiple regression analysis indicated that infarct size reduction was greater in patients who had a larger percentage of CD31+ BMCs ( P =0.046) and in those with faster BMC growth rates in colony-forming unit Hill and endothelial-colony forming cell functional assays ( P =0.033 and P =0.032, respectively). Conclusions: This study identified BMC characteristics associated with a better clinical outcome in patients with segment-elevation–myocardial infarction and highlighted the importance of endothelial precursor activity in regenerating infarcted myocardium. Furthermore, it suggests that for these patients with segment-elevation–myocardial infarction, myocardial repair was more dependent on baseline BMC characteristics than on whether the patient underwent intracoronary BMC transplantation. Clinical Trial Registration Information: URL: . Unique identifier: [NCT00684021][1]. # Novelty and Significance {#article-title-44} [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00684021&atom=%2Fcircresaha%2F116%2F1%2F99.atomRationale: Despite significant interest in bone marrow mononuclear cell (BMC) therapy for ischemic heart disease, current techniques have resulted in only modest benefits. However, selected patients have shown improvements after autologous BMC therapy, but the contributing factors are unclear. Objective: The purpose of this study was to identify BMC characteristics associated with a reduction in infarct size after ST-segment-elevation–myocardial infarction. Methods and Results: This prospective study comprised patients consecutively enrolled in the CCTRN TIME (Cardiovascular Cell Therapy Research Network Timing in Myocardial Infarction Evaluation) trial who agreed to have their BMCs stored and analyzed at the CCTRN Biorepository. Change in infarct size between baseline (3 days after percutaneous coronary intervention) and 6-month follow-up was measured by cardiac MRI. Infarct-size measurements and BMC phenotype and function data were obtained for 101 patients (mean age, 56.5 years; mean screening ejection fraction, 37%; mean baseline cardiac MRI ejection fraction, 45%). At 6 months, 75 patients (74.3%) showed a reduction in infarct size (mean change, −21.0±17.6%). Multiple regression analysis indicated that infarct size reduction was greater in patients who had a larger percentage of CD31+ BMCs (P=0.046) and in those with faster BMC growth rates in colony-forming unit Hill and endothelial-colony forming cell functional assays (P=0.033 and P=0.032, respectively). Conclusions: This study identified BMC characteristics associated with a better clinical outcome in patients with segment-elevation–myocardial infarction and highlighted the importance of endothelial precursor activity in regenerating infarcted myocardium. Furthermore, it suggests that for these patients with segment-elevation–myocardial infarction, myocardial repair was more dependent on baseline BMC characteristics than on whether the patient underwent intracoronary BMC transplantation. Clinical Trial Registration Information: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00684021.

Hypoxia-induced membrane-bound apoptotic DNA particles: potential mechanism of fetal DNA in maternal plasma.

Abstract:  Fetal DNA is found in the plasma of pregnant women that appears to be stable for PCR amplification. Although the underlying mechanism giving rise to this DNA in plasma remains unclear, the source of these fragments may be from apoptotic bodies (Apo‐Bodies) created from dying cells. Trophoblast apoptosis is essential for normal placental development, given the enormous amount of proliferation, differentiation, and migration during pregnancy. Through flow cytometric analysis coupled with real‐time PCR, our lab has shown that aggregates of acridine orange (AO)‐stained material (apoptotic particles) are resistant to DNase treatment, disrupted by sodium dodecyl sulfate (SDS), and contain fetal DNA. Because the placenta continuously remodels in an hypoxic environment, our hypothesis is that fetal DNA in maternal plasma comes from hypoxia‐induced dying trophoblasts and that this DNA circulates predominately in the form of Apo‐Bodies. We have developed a model culture system for analysis of Apo‐Bodies derived from JEG‐3 cells, an extravillous trophoblastic cell line, undergoing various methods of cell death: hypoxia‐induced, etoposide‐induced, and heat stress (necrosis like)–induced cell death. Under conditions of similar propidium iodide (PI) uptake, suggesting comparable levels of death, both hypoxia‐ and etoposide‐induced Apo‐Bodies increase in concentration over time, whereas heat‐induced levels of particles remain fairly constant, indicating that production of DNA‐associated Apo‐Bodies is a continuous process. Hypoxia, which is likely to be responsible for trophoblast cell death in vivo, produced membrane‐bound Apo‐Bodies containing DNA. Our results are consistent with the characteristics of membrane‐bound particles containing fetal DNA found in maternal plasma.

Identification of bone marrow cell subpopulations associated with improved functional outcomes in patients with chronic left ventricular dysfunction: An embedded cohort evaluation of the FOCUS-CCTRN trial

In the current study, we sought to identify bone marrow-derived mononuclear cell (BM-MNC) subpopulations associated with a combined improvement in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and maximal oxygen consumption (VO2 max) in patients with chronic ischemic cardiomyopathy 6 months after receiving transendocardial injections of autologous BM-MNCs or placebo. For this prospectively planned analysis, we conducted an embedded cohort study comprising 78 patients from the FOCUS-Cardiovascular Cell Therapy Research Network (CCTRN) trial. Baseline BM-MNC immunophenotypes and progenitor cell activity were determined by flow cytometry and colony-forming assays, respectively. Previously stable patients who demonstrated improvement in LVEF, LVESV, and VO2 max during the 6-month course of the FOCUS-CCTRN study (group 1, n = 17) were compared to those who showed no change or worsened in one to three of these endpoints (group 2, n = 61) and to a subset of patients from group 2 who declined in all three functional endpoints (group 2A, n = 11). Group 1 had higher frequencies of B-cell and CXCR4+ BM-MNC subpopulations at study baseline than group 2 or 2A. Furthermore, patients in group 1 had fewer endothelial colony-forming cells and monocytes/macrophages in their bone marrow than those in group 2A. To our knowledge, this is the first study to show that in patients with ischemic cardiomyopathy, certain bone marrow-derived cell subsets are associated with improvement in LVEF, LVESV, and VO2 max at 6 months. These results suggest that the presence of both progenitor and immune cell populations in the bone marrow may influence the natural history of chronic ischemic cardiomyopathy—even in stable patients. Thus, it may be important to consider the bone marrow composition and associated regenerative capacity of patients when assigning them to treatment groups and evaluating the results of cell therapy trials.

Granzyme B‐ and Fas ligand‐mediated cytotoxic function induced by mitogenic CD28 stimulation of human memory CD4+ T cells

Some human memory CD4+ T cells have cytotoxic functions best understood in the context of viral infections; however, their possible role in pathologic processes is understudied. The novel discovery that mitogenic CD28 antibodies induced proliferation and expansion of Tregs offered therapeutic promise for autoimmune disorders. However, the failed TGN1412 trial forced reassessment of this concept. As memory CD4+ T cells are known to produce toxic molecules, including granzyme B (GrzB) and FasL, we wondered whether mitogenic CD28 was able to induce these cytotoxic molecules. A commercially available mitogenic human CD28 mAb (clone ANC28.1) was used to determine whether mitogenic CD28 induces cytotoxic function from human memory CD4+ T cells. We found that stimulation of memory CD4+ T cells by ANC28.1, as well as by conventional costimulation (CD3/CD28 mAb), robustly induced enzymatically active GrzB, along with increased surface expression of FasL. These functional phenotypes were induced in association with increased expression of T cell activation markers CD69 and CD25, and elimination of target cells by ANC28.1‐activated memory CD4+ T cells involved both GrzB and FasL. Additionally, ANC28.1‐activated memory CD4+ T cells caused disruption of epithelial cell monolayer integrity, which was partially mediated by GrzB. These findings reveal functions of memory CD4+ T cells previously unknown to be induced by mitogenic CD28, and suggest that these pathogenic mechanisms may have been responsible for some of the widespread tissue destruction that occurred in the TGN1412 trial recipients.

Bone marrow cell characteristics associated with patient profile and cardiac performance outcomes in the LateTIME-Cardiovascular Cell Therapy Research Network (CCTRN) trial.

BACKGROUND Although several preclinical studies have shown that bone marrow cell (BMC) transplantation promotes cardiac recovery after myocardial infarction, clinical trials with unfractionated bone marrow have shown variable improvements in cardiac function. METHODS To determine whether in a population of post-myocardial infarction patients, functional recovery after BM transplant is associated with specific BMC subpopulation, we examined the association between BMCs with left ventricular (LV) function in the LateTIME-CCTRN trial. RESULTS In this population, we found that older individuals had higher numbers of BM CD133(+) and CD3(+) cells. Bone marrow from individuals with high body mass index had lower CD45(dim)/CD11b(dim) levels, whereas those with hypertension and higher C-reactive protein levels had higher numbers of CD133(+) cells. Smoking was associated with higher levels of CD133(+)/CD34(+)/VEGFR2(+) cells and lower levels of CD3(+) cells. Adjusted multivariate analysis indicated that CD11b(dim) cells were negatively associated with changes in LV ejection fraction and wall motion in both the infarct and border zones. Change in LV ejection fraction was positively associated with CD133(+), CD34(+), and CD45(+)/CXCR4(dim) cells as well as faster BMC growth rates in endothelial colony forming assays. CONCLUSIONS In the LateTIME population, BM composition varied with patient characteristics and treatment. Irrespective of cell therapy, recovery of LV function was greater in patients with greater BM abundance of CD133(+) and CD34(+) cells and worse in those with higher levels of CD11b(dim) cells. Bone marrow phenotype might predict clinical response before BMC therapy and administration of selected BM constituents could potentially improve outcomes of other future clinical trials.

Signature of Responders—Lessons from Clinical Samples

Stem cell therapy has emerged as a promising approach for myocardial repair. Characterization of cellular phenotype and function of different stem cell populations have been used and provided a better understanding of cellular regenerative properties that could advance cardiovascular cell therapy outcomes. In this chapter, we will discuss the unique characteristics of adult stem/progenitor cell populations and the mechanisms underlying cell-based cardiac repair.

Bone Marrow Characteristics Associated With Changes in Infarct Size After STEMI

Rationale: Despite significant interest in bone marrow mononuclear cell (BMC) therapy for ischemic heart disease, current techniques have resulted in only modest benefits. However, selected patients have shown improvements after autologous BMC therapy, but the contributing factors are unclear. Objective: The purpose of this study was to identify BMC characteristics associated with a reduction in infarct size after ST-segment-elevation–myocardial infarction. Methods and Results: This prospective study comprised patients consecutively enrolled in the CCTRN TIME (Cardiovascular Cell Therapy Research Network Timing in Myocardial Infarction Evaluation) trial who agreed to have their BMCs stored and analyzed at the CCTRN Biorepository. Change in infarct size between baseline (3 days after percutaneous coronary intervention) and 6-month follow-up was measured by cardiac MRI. Infarct-size measurements and BMC phenotype and function data were obtained for 101 patients (mean age, 56.5 years; mean screening ejection fraction, 37%; mean baseline cardiac MRI ejection fraction, 45%). At 6 months, 75 patients (74.3%) showed a reduction in infarct size (mean change, −21.0±17.6%). Multiple regression analysis indicated that infarct size reduction was greater in patients who had a larger percentage of CD31+ BMCs ( P =0.046) and in those with faster BMC growth rates in colony-forming unit Hill and endothelial-colony forming cell functional assays ( P =0.033 and P =0.032, respectively). Conclusions: This study identified BMC characteristics associated with a better clinical outcome in patients with segment-elevation–myocardial infarction and highlighted the importance of endothelial precursor activity in regenerating infarcted myocardium. Furthermore, it suggests that for these patients with segment-elevation–myocardial infarction, myocardial repair was more dependent on baseline BMC characteristics than on whether the patient underwent intracoronary BMC transplantation. Clinical Trial Registration Information: URL: . Unique identifier: [NCT00684021][1]. # Novelty and Significance {#article-title-44} [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00684021&atom=%2Fcircresaha%2F116%2F1%2F99.atomRationale: Despite significant interest in bone marrow mononuclear cell (BMC) therapy for ischemic heart disease, current techniques have resulted in only modest benefits. However, selected patients have shown improvements after autologous BMC therapy, but the contributing factors are unclear. Objective: The purpose of this study was to identify BMC characteristics associated with a reduction in infarct size after ST-segment-elevation–myocardial infarction. Methods and Results: This prospective study comprised patients consecutively enrolled in the CCTRN TIME (Cardiovascular Cell Therapy Research Network Timing in Myocardial Infarction Evaluation) trial who agreed to have their BMCs stored and analyzed at the CCTRN Biorepository. Change in infarct size between baseline (3 days after percutaneous coronary intervention) and 6-month follow-up was measured by cardiac MRI. Infarct-size measurements and BMC phenotype and function data were obtained for 101 patients (mean age, 56.5 years; mean screening ejection fraction, 37%; mean baseline cardiac MRI ejection fraction, 45%). At 6 months, 75 patients (74.3%) showed a reduction in infarct size (mean change, −21.0±17.6%). Multiple regression analysis indicated that infarct size reduction was greater in patients who had a larger percentage of CD31+ BMCs (P=0.046) and in those with faster BMC growth rates in colony-forming unit Hill and endothelial-colony forming cell functional assays (P=0.033 and P=0.032, respectively). Conclusions: This study identified BMC characteristics associated with a better clinical outcome in patients with segment-elevation–myocardial infarction and highlighted the importance of endothelial precursor activity in regenerating infarcted myocardium. Furthermore, it suggests that for these patients with segment-elevation–myocardial infarction, myocardial repair was more dependent on baseline BMC characteristics than on whether the patient underwent intracoronary BMC transplantation. Clinical Trial Registration Information: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00684021.