A Look at the Bone Marrow Predicts the Global Outcome

The Long Telling Story of "Endothelial Progenitor Cells": Where Are We at Now?

Endothelial progenitor cells (EPCs): The name embodies years of research and clinical expectations, but where are we now? Do these cells really represent the El Dorado of regenerative medicine? Here, past and recent literature about this eclectic, still unknown and therefore fascinating cell population will be discussed. This review will take the reader through a temporal journey that, from the first discovery, will pass through years of research devoted to attempts at their definition and understanding their biology in health and disease, ending with the most recent evidence about their pathobiological role in cardiovascular disease and their recent applications in regenerative medicine.

Impaired haematopoietic stem / progenitor cell traffic and multi-organ damage in diabetes

During antenatal development, hematopoietic stem/progenitor cells (HSPCs) arise from a specialized endothelium and migrate from the extraembryonic mesoderm to the fetal liver before establishing hematopoiesis in the bone marrow (BM). It is still debated whether, in adulthood, HSPCs display such ontologic overlap with vascular cells and capacity for endothelial differentiation. Yet, adult HSPCs retain a prominent migratory activity and traffic in the bloodstream to secondary lymphoid organs and all peripheral tissues, before eventually returning to the BM. While patrolling parenchymatous organs, HSPCs locate close to the vasculature, where they establish local hematopoietic islands and contribute to tissue homeostasis by paracrine signals. Solid evidence shows that diabetes mellitus jeopardizes the traffic of HSPCs from BM to the circulation and peripheral tissues, a condition called “mobilopathy.” A reduction in the levels of circulating HSPCs is the most immediate and apparent consequence, which has been consistently observed in human diabetes, and is strongly associated with future risk for multi-organ damage, including micro- and macro-angiopathy. But the shortage of HSPCs in the blood is only the visible tip of the iceberg. Abnormal HSPC traffic results from a complex interplay among metabolism, innate immunity, and hematopoiesis. Notably, mobilopathy is mechanistically connected with diabetes-induced myelopoiesis. Impaired traffic of HSPCs and enhanced generation of pro-inflammatory cells synergize for tissue damage and impair the resolution of inflammation. We herein summarize the current evidence that diabetes affects HSPC traffic, which are the causes and consequences of such alteration, and how it contributes to the overall disease burden.

Cell therapy for the treatment of heart disease: Renovation work on the broken heart is still in progress

Cardiovascular disease (CVD) continues to be the number one killer in the aging population. Heart failure (HF) is also an important cause of morbidity and mortality in patients with congenital heart disease (CHD). Novel therapeutic approaches that could restore stable heart function are much needed in both paediatric and adult patients. Regenerative medicine holds promises to provide definitive solutions for correction of congenital and acquired cardiac defects. In this review article, we recap some important aspects of cardiovascular cell therapy. First, we report quantifiable data regarding the scientific advancements in the field and how this has been translated into tangible outcomes according clinical studies and related meta-analyses. We then comment on emerging trends and technologies, such as the use of second-generation cell products, including pericyte-like vascular progenitors, and reprogramming of cells by different approaches including modulation of oxidative stress. The more affordable and feasible strategy of repurposing clinically available drugs to awaken the intrinsic healing potential of the heart will be discussed in the light of current social, financial, and ethical context. Cell therapy remains a work in progress field. Uncertainty in the ability of the experts and policy makers to solve urgent medical problems is growing in a world that is significantly influenced by them. This is particularly true in the field of regenerative medicine, due to great public expectations, polarization of leadership and funding, and insufficient translational vision. Cardiovascular regenerative medicine should be contextualized in a holistic program with defined priorities to allow a complete realization. Reshaping the notion of medical expertise is fundamental to fill the current gap in translation.

Concise Review: Perspectives and Clinical Implications of Bone Marrow and Circulating Stem Cell Defects in Diabetes

Diabetes mellitus is a complex systemic disease characterized by severe morbidity and excess mortality. The burden of its multiorgan complications relies on an imbalance between hyperglycemic cell damage and defective endogenous reparative mechanisms. Inflammation and abnormalities in several hematopoietic components are typically found in diabetes. The discovery that diabetes reduces circulating stem/progenitor cells and impairs their function has opened an entire new field of study where diabetology comes into contact with hematology and regenerative medicine. It is being progressively recognized that such rare circulating cell populations mirror finely regulated processes involved in hematopoiesis, immunosurveillance, and peripheral tissue homeostasis. From a clinical perspective, pauperization of circulating stem cells predicts adverse outcomes and death. Furthermore, studies in murine models and humans have identified the bone marrow (BM) as a previously neglected site of diabetic end-organ damage, characterized by microangiopathy, neuropathy, fat deposition, and inflammation. As a result, diabetes impairs the mobilization of BM stem/progenitor cells, a defect known as mobilopathy or myelokathexis, with negative consequences for physiologic hematopoiesis, immune regulation, and tissue regeneration. A better understanding of the molecular and cellular processes that govern the BM stem cell niche, cell mobilization, and kinetics in peripheral tissues may uncover new therapeutic strategies for patients with diabetes. This concise review summarizes the current knowledge on the interplay between the BM, circulating stem cells, and diabetes, and sets the stages for future developments in the field. Stem Cells 2017;35:106-116.

Levels of Circulating Progenitor Cells, Cardiovascular Outcomes and Death

Rationale:

Circulating progenitor cells (CPCs), including endothelial progenitor cells (EPCs) are biologically related to many aspects of cardiovascular disease, as they promote angiogenesis and vascular repair.

Objective:

We herein aimed to meta-analyze studies reporting the prognostic role of the CPC/EPC measure on cardiovascular outcomes and death.

Methods and Results:

We screened the English-language literature for longitudinal studies reporting the association between baseline CPC/EPC levels, future cardiovascular events, and death. We retrieved 28 studies, 21 of which contained poolable data and entered the meta-analysis, for a total of 4155 patients, mostly with a high baseline cardiovascular risk. Sixty percent of the studies met at least 11 of 16 items of quality assessment. Overall, reduced CPC/EPC levels were associated with a ≈2-fold increased risk of future cardiovascular events and cardiovascular death. The most predictive phenotype was CD34 + CD133 + : low versus high levels predicted cardiovascular events, restenosis after endovascular intervention, cardiovascular death, and all-cause mortality. Heterogeneity among studies and according to the CPC/EPC phenotype was generally high. Excluding studies for which the risk estimate had to be extrapolated or limiting the analyses to higher quality studies still indicated a significant risk for future cardiovascular events and death in patients with low versus high progenitor cell counts.

Conclusions:

This meta-analysis shows that a reduction in the levels of circulating cells putatively provided with vasculoregenerative properties represents a risk factor for adverse cardiovascular outcomes and death.

Circulating Stem Cells Associate With Adiposity and Future Metabolic Deterioration in Healthy Subjects

CONTEXT

Obesity and metabolic syndrome are associated with mild leukocytosis, but whether hematopoietic stem/progenitor cells (HSPCs) play a role in metabolic deterioration is unknown.

OBJECTIVE

Our objective was to analyze the cross-sectional and longitudinal associations between CD34(+) HSPCs, adiposity, and metabolic syndrome features.

DESIGN

This is a cross-sectional study on 242 participants, 155 of whom were followed and included in a longitudinal assessment.

SETTING

This study took place in a tertiary referral center for metabolic diseases.

PARTICIPANTS

Healthy working individuals attending a cardiovascular screening program (total n = 3158) and having a baseline measure of circulating CD34(+) cells participated.

MAIN OUTCOME MEASURES

We collected demographic and anthropometric data, cardiovascular risk factors, and metabolic syndrome parameters.

RESULTS

Participants (34.7% males, mean age 45.9 ± 0.5 years) were free from diabetes and cardiovascular disease. Cross-sectionally, absolute CD34(+) cell counts were directly correlated with body mass index and waist circumference, inversely correlated with high-density lipoprotein cholesterol and the quantitative insulin sensitivity check index, and were higher in individuals with the metabolic syndrome. The hematopoietic component contributed most to the association of CD34(+) cells with adiposity. During a 6.3-year follow-up, high absolute levels of CD34(+) cells were associated with increasing waist circumference, declining quantitative insulin sensitivity check index and high-density lipoprotein cholesterol, and with incidence of metabolic syndrome. Relative CD34(+) cell counts showed weaker associations with metabolic parameters than absolute levels, but were longitudinally associated with increasing waist circumference and metabolic syndrome development.

CONCLUSIONS

A mild elevation of circulating CD34(+) progenitor cells, reflecting expansion of HSPCs, is associated with adiposity and future metabolic deterioration in healthy individuals.

Circulating Progenitor Cell Count Predicts Microvascular Outcomes in Type 2 Diabetic Patients

CONTEXT

Diabetes reduces the levels of circulating progenitor cells (CPCs) and endothelial progenitor cells (EPCs), which promote vascular repair and are inversely correlated with cardiovascular risk.

OBJECTIVE

The objective of the study was to test whether CPC/EPC levels predict onset/progression of microangiopathy in a cohort of type 2 diabetic (T2D) patients.

DESIGN

This was a pseudoprospective study with a 3.9-year follow-up.

SETTING

The study was conducted at a tertial referral diabetes outpatient clinic.

PATIENTS

A total of 187 T2D patients having a baseline determination of CPCs/EPCs participated in the study.

INTERVENTION

Baseline data on demographics, anthropometrics, concomitant risk factors, diabetic complications, and medications were collected.

MAIN OUTCOME MEASURE

Onset or progression of microangiopathy was assessed at follow-up compared with baseline.

RESULTS

New onset or progression of microalbuminuria, chronic kidney disease, retinopathy, and neuropathy occurred in 70 patients (9.5%/y). After controlling the false discovery rate, baseline CD34(+) CPCs and EPCs were significantly lower in patients with onset/progression of microalbuminuria and any microangiopathy. Patients with baseline CD34(+) CPC or CD133(+)/kinase insert domain-containing receptor(+)/EPC levels below the median were more likely to experience worsening microangiopathy than those with high cell levels. Independently from confounders, including age, sex, glycated hemoglobin, and diabetes duration, CD34(+) cells predicted onset/progression of microalbuminuria, retinopathy, and any microangiopathy in false discovery rate-adjusted analyses. A low CD34(+) cell count limited the beneficial effects of renin-angiotensin system blockers on microalbuminuria progression.

CONCLUSIONS

Levels of circulating (endothelial) progenitor cells predict microvascular outcomes in T2D. Together with previous studies showing an association with cardiovascular events, these data indicate that CPCs/EPCs represent biomarkers of the global complication burden in diabetes.