CD34-positive cells exhibit increased potency and safety for therapeutic neovascularization after myocardial infarction compared with total mononuclear cells

Role of Exosomes in Cardiovascular Disease: A Key Regulator of Intercellular Communication in Cardiomyocytes

In the cardiovascular system, different types of cardiovascular cells can secrete specific exosomes and participate in the maintenance of cardiovascular function and the occurrence and development of diseases. Exosomes carry biologically active substances such as proteins and nucleic acids from cells of origin and can be used as biomarkers for disease diagnosis and prognosis assessment. In addition, exosome-mediated intercellular communication plays a key role in the occurrence and development of cardiovascular diseases and has become a potential therapeutic target. This article emphasizes the importance of understanding the mechanism of exosomes in cardiovascular diseases and systematically details the current understanding of exosomes as regulators of intercellular communication in cardiomyocytes, providing a basis for future research and therapeutic intervention.

Phase I Study of Intravitreal Injection of Autologous CD34+ Stem Cells from Bone Marrow in Eyes with Vision Loss from Retinitis Pigmentosa

Purpose

To evaluate the feasibility and safety of intravitreal injection of autologous CD34+ stem cells from bone marrow (BMSCs) in eyes with vision loss from retinitis pigmentosa (RP).

Design

Phase I prospective, open-label, single-center study.

Participants

Seven eyes (7 patients) with RP with best-corrected visual acuity (BCVA) of 20/60 to 20/400 or visual field constriction to within 10°.

Methods

A comprehensive examination with ETDRS BCVA, macular OCT, perimetry, and fluorescein angiography was performed at baseline, 1 to 3 months, and 6 months after study treatment. Bone marrow aspiration, isolation of CD34+ BMSCs under good manufacturing practice conditions, and intravitreal cell injection were performed on the same day. The CD34+ cells were isolated from bone marrow using a Ficoll gradient and the Miltenyi CliniMACS system. Isolated CD34+ cells were released for clinical use if viability, sterility, and purity met the release criteria accepted by the United States Food and Drug Administration for this clinical study.

Main Outcome Measures

Number of CD34+ cells isolated for injection and adverse events associated with study treatment during follow-up. Secondary outcome measures are changes in BCVA and perimetry.

Results

All isolated CD34+ cells passed the release criteria. A mean of 3.26 ± 0.66 million viable CD34+ cells (range 1.6 to 7.05 million) were injected intravitreally per eye. No adverse event was noted during the study follow-up except for 1 participant who was noted with transient cells in the anterior chamber with mild elevation in intraocular pressure at 18 hours after study injection which normalized by 24 hours. Best-corrected visual acuity remained within 2 lines of baseline or improved in all participants at 6 months follow-up. Perimetry was stable or improved in all eyes during study follow-up except 1 eye with transient improvement at 1 month and worsening of both eyes at 6 months.

Conclusions

Intravitreal injection of autologous CD34+ BMSCs is feasible and appears to be well tolerated in eyes with vision loss from RP. A larger randomized prospective study would be needed to evaluate further the safety and potential efficacy of this cell therapy for vision loss associated with RP.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Purified CD34+ Cells Transplantation in Patients with Angiitis-Induced Chronic Limb-Threatening Ischemia: A Single-Center Retrospective Study over a 10-Year Period

BACKGROUND

Angiitis-induced chronic limb-threatening ischemia (AICLTI) is defined as chronic limb-threatening ischemia caused by thromboangiitis obliterans or other arteritis-related autoimmunological diseases. In the current study, we aimed to report the 10-year outcomes of AICLTI patients who underwent purified cluster of differentiation 34 positive (CD34+) cells (PCCs) transplantation.

METHODS

AICLTI patients who underwent PCCs transplantation at our center from May 2009 to September 2011 were retrospectively enrolled. The main outcome was major amputation-free survival (MAFS); other outcomes included Rutherford classification, intolerable pain-free walking time, Wong-Baker Faces Pain Rating Scale, recurrence, new lesions, quality of life and patients' posttransplantation work conditions.

RESULTS

Twenty-four patients were enrolled with a mean age of 41.5 ± 7.8 years. Three underwent major amputation during the follow-up, and the 10-year MAFS was 87.5%. Eight were observed to have recurrence, and 2 had new lesions; the 10-year recurrence-free rate was 66.1%. All patients were unable to work at admission, 17 (70.8%) patients were reemployed after transplantation.

CONCLUSIONS

The current study further demonstrated satisfactory long-term efficacy of PCCs transplantation, with a 10-year MAFS of 87.5%. However, the 10-year recurrence-free rate of 66.1% suggested that strict and regular long-term follow-up is necessary.

Evaluation of the lower extremity blood supply in no-option critical limb ischemia patients with stem cell transplantation by time maximum intensity projection CT perfusion: A single-centre prospective study

OBJECTIVES

Cell therapy has had satisfactory safety and efficacy outcomes for no-option critical limb ischaemia (NO-CLI) patients. In the current study, we aimed to compare the image quality of ischaemic lower limb blood vessels shown on volumetric CT-based time maximum intensity projection CT perfusion (t-MIP CTP) versus single-phase CTA (sCTA). We also tried to quantify the blood flow of the ischaemic lower extremity based on the t-MIP technique, not only to precisely show the dynamic change in blood flow from before to after cell therapy but also to detect any relationship between this change and patient prognosis.

METHODS

A total of 31 patients with thromboangiitis obliterans (TAO)-induced NO-CLI who had been referred from the department of vascular surgery to undergo autologous stem cell transplantation into a single limb from January 2020 to March 2021 were prospectively enrolled in this study. Preoperative sCTA or t-MIP CTP and postoperative 1-month t-MIP CTP were performed in all patients. Clinical outcomes, including the 1-month ankle-brachial index (ABI) and 3-month CLI status, were also analysed. Image quality, including objective scores (attenuation, signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]), subjective scores and collateral scores, was compared between preoperative sCTA and t-MIP CTP. Vascular volume was calculated as the total volume (mL) of lower limb arteries within the scanning range. All images and calculations were performed by 2 separate radiologists. Receiver operating characteristic curves were drawn to reveal the sensitivity and specificity of vascular volume and ABI in predicting prognosis.

RESULTS

Both sCTA and t-MIP CTP images exhibited good quality for diagnosis. t-MIP CTP images showed significantly higher attenuation, SNR and CNR in all arterial segments (popliteal artery, anterior tibial artery, posterior tibial artery and peroneal artery). In subjective and collateral score evaluations, t-MIP CTP images were also significantly better than sCTA images (both p < .05). At 1 month after transplantation, both vascular volume and ABI showed significant improvement (both p < .01). At 3 months after transplantation, 38.71% of patients (12/31) achieved CLI relief (Rutherford class < 4). Through the receiver operating characteristic (ROC) curve, the 1-month vascular volume increase ratio showed better ability to predict the 3-month prognosis (radiologist 1: AUC, 0.757; sensitivity, 0.750; specificity, 0.840; radiologist 2: AUC, 0.803; sensitivity, 0.500; specificity, 1.000) than the 1-month ABI increase ratio (AUC, 0.607; sensitivity, 0.230; specificity, 0.820) or 1-month ABI (AUC, 0.410; sensitivity, 0.080; specificity, 0.580).

CONCLUSION

t-MIP CTP showed significantly higher-quality images of ischaemic limb vascularity than sCTA. t-MIP CTP can reveal the anatomical information of collaterals more accurately, which is of great importance for NO-CLI patients undergoing cell transplantation. The 1-month vascular volume increase ratio can predict the 3-month prognosis more precisely on this basis.

Circulating Progenitor Cells and Coronary Collaterals in Chronic Total Occlusion

BACKGROUND

The role of circulating progenitor cells (CPC) in collateral formation that occurs in the presence of chronic total occlusions (CTO) of a coronary artery is not well established. In stable patients with a CTO, we investigated whether CPC levels are associated with (a) collateral development and (b) ischemic burden, as measured by circulating high sensitivity troponin-I (hsTn-I) levels.

METHODS

CPCs were enumerated by flow cytometry as CD45med+ blood mononuclear cells expressing CD34 and both CD34 and CD133 epitopes. The association between CPC counts and both Rentrop collateral grade (0, 1, 2, or 3) and hsTn-I levels were evaluated using multivariate regression analysis, after adjusting for demographic and clinical characteristics.

RESULTS

In 89 patients (age 65.5, 72% male, 27% Black), a higher CPC count was positively associated with a higher Rentrop collateral grade; [CD34+ adjusted odds ratio (OR) 1.49 95% confidence interval (CI) (0.95, 2.34) P = 0.082] and [CD34+/CD133+ OR 1.57 95% CI (1.05, 2.36) P = 0.028]. Every doubling of CPC counts was also associated with lower hsTn-I levels [CD34+ β -0.35 95% CI (-0.49, -0.15) P = 0.002] and [CD34+/CD133+ β -0.27 95% CI (-0.43, -0.08) P = 0.009] after adjustment.

CONCLUSION

Individuals with higher CPC counts have greater collateral development and lower ischemic burden in the presence of a CTO.

Endothelial progenitor cell-derived extracellular vesicles: the world of potential prospects for the treatment of cardiovascular diseases

Cardiovascular diseases (CVDs) have emerged as a predominant threat to human health, surpassing the incidence and mortality rates of neoplastic diseases. Extracellular vesicles (EVs) serve as vital mediators in intercellular communication and material exchange. Endothelial progenitor cells (EPCs), recognized as precursors of vascular endothelial cells (ECs), have garnered considerable attention in recent years due to the potential therapeutic value of their derived extracellular vesicles (EPC-EVs) in the context of CVDs. This comprehensive review systematically explores the origins, characteristics, and functions of EPCs, alongside the classification, properties, biogenesis, and extraction techniques of EVs, with particular emphasis on their protective roles in CVDs. Additionally, we delve into the essential bioactive components of EPC-EVs, including microRNAs, long non-coding RNAs, and proteins, analyzing their beneficial effects in promoting angiogenesis, anti-inflammatory and anti-oxidant activities, anti-fibrosis, anti-apoptosis, and myocardial regeneration. Furthermore, this review comprehensively investigates the therapeutic potential of EPC-EVs across various CVDs, encompassing acute myocardial infarction, myocardial ischemia-reperfusion injury, atherosclerosis, non-ischemic cardiomyopathies, and diabetic cardiovascular disease. Lastly, we summarize the potential challenges associated with the clinical application of EPC-EVs and outline future directions, aiming to offer a valuable resource for both theoretical insights and practical applications of EPC-EVs in managing CVDs.

A review of therapeutic approaches for post-infarction left ventricular remodeling

Left ventricular remodeling is an adaptive process initially developed in response to acute myocardial infarction (AMI), but it ends up with negative adverse outcomes such as infarcted wall thinning, ventricular dilation, and cardiac dysfunction. A prolonged excessive inflammatory reaction to cardiomyocytes death and necrosis plays the crucial role in the pathophysiological mechanisms. The pharmacological treatment includes nitroglycerine, β-blockers, ACEi/ARBs, SGLT2i, mineralocorticoid receptor antagonists, and some miscellaneous aspects. Stem cells therapy, CD34+ cells transplantation and gene therapy constitute the promissing therapeutic approaches for post AMI cardiac remodeling, thereby enhancing angiogenesis, cardiomyocytes differenciation and left ventricular function on top of inhibiting apoptosis, inflammation, and collagen deposition. All these lead to reduce infarct size, scar formation and myocardial fibrosis.

Acute psychological stress-induced progenitor cell mobilization and cardiovascular events

OBJECTIVE

Certain brain activation responses to psychological stress are associated with worse outcomes in CVD patients. We hypothesized that elevated acute psychological stress, manifesting as greater activity within neural centers for emotional regulation, mobilizes CPC from the bone marrow to the peripheral blood and predicts future cardiovascular events.

METHODS

In 427 patients with stable CAD undergoing a laboratory-based mental stress (MS) test, CPCs were enumerated using flow cytometry as CD34-expressing mononuclear cells (CD34+) before and 45 min after stress. Changes in brain regional blood flow with MS were measured using high resolution-positron emission tomography (HR-PET). Association between the change in CPC with MS and the risk of cardiovascular death or myocardial infarction (MI) during a 5-year follow-up period was analyzed.

RESULTS

MS increased CPC counts by a mean of 150 [630] cells/mL (15%), P < 0.001. Greater limbic lobe activity, indicative of activation of emotion-regulating centers, was associated with greater CPC mobilization (P < 0.005). Using Fine and Gray models after adjustment for demographioc, clinical risk factors and medications use, greater CPC mobilization was associated with a higher adjusted risk of adverse events; a rise of 1000 cells/mL was associated with a 50% higher risk of cardiovascular death/MI [hazards ratio, 1.5, 95% confidence interval, 1.1-2.2).

CONCLUSION

Greater limbic lobe activity, brain areas involved in emotional regulation, is associated with MS-induced CPC mobilization. This mobilization isindependently associated with cardiovascular events. These findings provide novel insights into mechanisms through which psychological stressors modulate cardiovascular risk.

Cell Therapy in the Treatment of Coronary Heart Disease

Heart failure is a leading cause of death in patients who have suffered a myocardial infarction. Despite the timely use of modern reperfusion therapies such as thrombolysis, surgical revascularization and balloon angioplasty, they are sometimes unable to prevent the development of significant areas of myocardial damage and subsequent heart failure. Research efforts have focused on developing strategies to improve the functional status of myocardial injury areas. Consequently, the restoration of cardiac function using cell therapy is an exciting prospect. This review describes the characteristics of various cell types relevant to cellular cardiomyoplasty and presents findings from experimental and clinical studies investigating cell therapy for coronary heart disease. Cell delivery methods, optimal dosage and potential treatment mechanisms are discussed.

Human Umbilical Mesenchymal Stem Cells-Derived Microvesicles Attenuate Formation of Hypertrophic Scar through Multiple Mechanisms

Mesenchymal stem cells and the derived extracellular microvesicles are potential promising therapy for many disease conditions, including wound healing. Since current therapeutic approaches do not satisfactorily attenuate or ameliorate formation of hypertrophic scars, it is necessary to develop novel drugs to achieve better outcomes. In this study, we investigated the effects and the underlying mechanisms of human umbilical mesenchymal stem cells (HUMSCs)-derived microvesicles (HUMSCs-MVs) on hypertrophic scar formation using a rabbit ear model and a human foreskin fibroblasts (HFF) culture model. The results showed that HUMSCs-MVs reduced formation of hypertrophic scar tissues in the rabbit model based on appearance observation, and hematoxylin and eosin (H&E), Masson, and immunohistochemical stainings. HUMSCs-MVs inhibited invasion of HFF cells and decreased the levels of the α-SMA, N-WASP, and cortacin proteins. HUMSCs-MVs also inhibited cell proliferation of HFF cells. The MMP-1, MMP-3, and TIMP-3 mRNA levels were significantly increased, and the TIMP-4 mRNA level and the NF-kB p65/β-catenin protein levels were significantly decreased in HFF cells after HUMSCs-MVs treatment. The p-SMAD2/3 levels and the ratios of p-SMAD2/3/SMAD2/3 were significantly decreased in both the wound healing tissues and HFF cells after HUMSCs-MVs treatment. CD34 levels were significantly decreased in both wound healing scar tissues and HFF cells after HUMSCs-MVs treatment. The VEGF-A level was also significantly decreased in HFF cells after HUMSCs-MVs treatment. The magnitudes of changes in these markers by HUMSCs-MVs were mostly higher than those by dexamethasone. These results suggested that HUMSCs-MVs attenuated formation of hypertrophic scar during wound healing through inhibiting proliferation and invasion of fibrotic cells, inflammation and oxidative stress, Smad2/3 activation, and angiogenesis. HUMSCs-MVs is a potential promising drug to attenuate formation of hypertrophic scar during wound healing.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications—Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications-Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Human-umbilical cord matrix mesenchymal cells improved left ventricular contractility independently of infarct size in swine myocardial infarction with reperfusion

Background

Human umbilical cord matrix-mesenchymal stromal cells (hUCM-MSC) have demonstrated beneficial effects in experimental acute myocardial infarction (AMI). Reperfusion injury hampers myocardial recovery in a clinical setting and its management is an unmet need. We investigated the efficacy of intracoronary (IC) delivery of xenogeneic hUCM-MSC as reperfusion-adjuvant therapy in a translational model of AMI in swine.

Methods

In a placebo-controlled trial, pot-belied pigs were randomly assigned to a sham-control group (vehicle-injection; n = 8), AMI + vehicle (n = 12) or AMI + IC-injection (n = 11) of 5 × 10⁵ hUCM-MSC/Kg, within 30 min of reperfusion. AMI was created percutaneously by balloon occlusion of the mid-LAD. Left-ventricular function was blindly evaluated at 8-weeks by invasive pressure-volume loop analysis (primary endpoint). Mechanistic readouts included histology, strength-length relationship in skinned cardiomyocytes and gene expression analysis by RNA-sequencing.

Results

As compared to vehicle, hUCM-MSC enhanced systolic function as shown by higher ejection fraction (65 ± 6% vs. 43 ± 4%; p = 0.0048), cardiac index (4.1 ± 0.4 vs. 3.1 ± 0.2 L/min/m²; p = 0.0378), preload recruitable stroke work (75 ± 13 vs. 36 ± 4 mmHg; p = 0.0256) and end-systolic elastance (2.8 ± 0.7 vs. 2.1 ± 0.4 mmHg*m²/ml; p = 0.0663). Infarct size was non-significantly lower in cell-treated animals (13.7 ± 2.2% vs. 15.9 ± 2.7%; Δ = -2.2%; p = 0.23), as was interstitial fibrosis and cardiomyocyte hypertrophy in the remote myocardium. Sarcomere active tension improved, and genes related to extracellular matrix remodelling (including MMP9, TIMP1 and PAI1), collagen fibril organization and glycosaminoglycan biosynthesis were downregulated in animals treated with hUCM-MSC.

Conclusion

Intracoronary transfer of xenogeneic hUCM-MSC shortly after reperfusion improved left-ventricular systolic function, which could not be explained by the observed extent of infarct size reduction alone. Combined contributions of favourable modification of myocardial interstitial fibrosis, matrix remodelling and enhanced cardiomyocyte contractility in the remote myocardium may provide mechanistic insight for the biological effect.

Deciphering the Cardiovascular Potential of Human CD34+ Stem Cells

Ex vivo monitored human CD34⁺ stem cells (SCs) injected into myocardium scar tissue have shown real benefits for the recovery of patients with myocardial infarctions. They have been used previously in clinical trials with hopeful results and are expected to be promising for cardiac regenerative medicine following severe acute myocardial infarctions. However, some debates on their potential efficacy in cardiac regenerative therapies remain to be clarified. To elucidate the levels of CD34⁺ SC implication and contribution in cardiac regeneration, better identification of the main regulators, pathways, and genes involved in their potential cardiovascular differentiation and paracrine secretion needs to be determined. We first developed a protocol thought to commit human CD34⁺ SCs purified from cord blood toward an early cardiovascular lineage. Then, by using a microarray-based approach, we followed their gene expression during differentiation. We compared the transcriptome of undifferentiated CD34⁺ cells to those induced at two stages of differentiation (i.e., day three and day fourteen), with human cardiomyocyte progenitor cells (CMPCs), as well as cardiomyocytes as controls. Interestingly, in the treated cells, we observed an increase in the expressions of the main regulators usually present in cardiovascular cells. We identified cell surface markers of the cardiac mesoderm, such as kinase insert domain receptor (KDR) and the cardiogenic surface receptor Frizzled 4 (FZD4), induced in the differentiated cells in comparison to undifferentiated CD34⁺ cells. The Wnt and TGF-β pathways appeared to be involved in this activation. This study underlined the real capacity of effectively stimulated CD34⁺ SCs to express cardiac markers and, once induced, allowed the identification of markers that are known to be involved in vascular and early cardiogenesis, demonstrating their potential priming towards cardiovascular cells. These findings could complement their paracrine positive effects known in cell therapy for heart disease and may help improve the efficacy and safety of using ex vivo expanded CD34⁺ SCs.

CD34+ cell-derived fibroblast-macrophage cross-talk drives limb ischemia recovery through the OSM-ANGPTL signaling axis

CD34⁺ cells improve the perfusion and function of ischemic limbs in humans and mice. However, there is no direct evidence of the differentiation potential and functional role of these cells in the ischemic muscle microenvironment. Here, we combined the single-cell RNA sequencing and genetic lineage tracing technology, then provided exact single-cell atlases of normal and ischemic limb tissues in human and mouse, and consequently found that bone marrow (BM)-derived macrophages with antigen-presenting function migrated to the ischemic site, while resident macrophages underwent apoptosis. The macrophage oncostatin M (OSM) regulatory pathway was specifically turned on by ischemia. Simultaneously, BM CD34⁺-derived proregenerative fibroblasts were recruited to the ischemia niche, where they received macrophage-released OSM and promoted angiopoietin-like protein-associated angiogenesis. These findings provided mechanisms on the cellular events and cell-cell communications during tissue ischemia and regeneration and provided evidence that CD34⁺ cells serve as fibroblast progenitors promoting tissue regeneration.

Human Hematopoietic Stem/Progenitor Cells in Type One Diabetes Mellitus Treatment: Is There an Ideal Candidate?

Type 1 diabetes mellitus (T1DM) is a highly prevalent autoimmune disease causing the destruction of pancreatic islet β-cells. The resulting insulin production deficiency leads to a lifelong need for insulin re-placement therapy, systemic complications, and reduced life quality and expectancy. Cell therapy has been extensively attempted to restore insulin independence (IID), and autologous nonmyeloablative hematopoietic stem cell transplantation (AHST) has appeared to give the most promising results, but with a highly variable quote of patients achieving IID across the studies. We performed a comprehensive review of the trials involving stem cells, and in particular AHST, for the treatment of T1DM. We then pooled the patients enrolled in the different trials and looked for the patient characteristics that could be associated with the achievement of IID. We found a significantly higher probability of achieving IID in older patients (OR 1.17, 95%CI 1.06–1.33, p = 0.002) and a significantly lower probability in patients with a history of ketoacidosis (OR 0.23, 95%CI 0.06–0.78, p = 0.023). This suggests that there could be a population of patients more likely to benefit from AHST, but further data would be required to depict the profile of the ideal candidate.

The Role of miRNA in the Regulation of Angiogenesis in Ischemic Heart Disease

Despite continued improvements in primary prevention and treatment, ischemic heart disease (IHD) is the most common cause of mortality in both developing and developed countries. Promoting angiogenesis and reconstructing vascular network in ischemic myocardium are critical process of postischemic tissue repair. Effective strategies to promote survival and avoid apoptosis of endothelial cells in the ischemic myocardium can help to achieve long-term cardiac angiogenesis. Therefore, it is of great importance to investigate the molecular pathophysiology of angiogenesis in-depth and to find the key targets that promote angiogenesis. Recently years, many studies have found that microRNAs play important regulatory roles in almost all process of angiogenesis, including vascular sprouting, proliferation, survival and migration of vascular endothelial cells, recruitment of vascular progenitor cells, and control of angiopoietin expression. This review presents detailed information about the regulatory role of miRNAs in the angiogenesis of IHD in recent years, and provides new therapeutic ideas for the treatment of IHD.

Novel Concepts in the Management of Angina in Coronary Artery Disease

Coronary artery disease remains a condition with high prevalence and detrimental effects on the quality of life of affected individuals. Its most frequent manifestation, stable angina pectoris, may be challenging to manage despite the available antianginal pharmacotherapy and adequate risk factor control, especially in subjects not amenable to revascularization. In the direction of refractory angina pectoris, several approaches have been developed over the years with varying degrees of success. Among the most recognized techniques in managing angina is enhanced external counterpulsation, which utilizes mechanical compression of the lower extremities to increase blood flow to the heart. Moving to coronary sinus reduction, it leads to an increase in coronary sinus backward pressure, ultimately augmenting myocardial blood flow redistribution to ischemic regions and ameliorating chronic angina. Clinical trial results of the above-mentioned techniques have been encouraging but are based on small sample sizes to justify their widespread application. Other interventional approaches, such as transmyocardial laser revascularization, extracorporeal shockwave myocardial revascularization, and spinal cord stimulation, have been met with either controversial or negative results, and their use is not recommended. Lastly, angiogenic therapy with targeted intramyocardial vascular endothelial growth factor injection or CD34+ cell therapy may be beneficial and warrants further investigation. In this review, we summarize the current knowledge in the field of angina management, highlighting the potential and the gaps in the existing evidence that ought to be addressed in future larger-scale, randomized studies before these techniques can be safely adapted in the clinical practice of patients with refractory angina pectoris.

CLINICAL, INSTRUMENTAL AND BIOCHEMICAL ASSOCIATIONS OF THE DEGREE OF PHYSICAL RECOVERY IN PATIENTS SUFFERED FROM ACUTE CORONARY SYNDROME AT THE COMPLETION OF IN-HOSPITAL REHABILITATION PERIOD

OBJECTIVE

The aim: To determine the clinical, instrumental and biochemical factors associated with the degree of physical recovery in patients suffered from acute coronary syndrome (ACS) at the completion of in-hospital rehabilitation period.

PATIENTS AND METHODS

Materials and methods: We enrolled 88 patients (all were males); 77 patients had ACS/STEMI and 11 with ACS/unstable angina. The mean age was (median, interquartile range) was 58 (49-64) years. We analyzed clinical, laboratory (including the circulating proprotein convertase subtilisin/kexin type 9 (PSK9) level in blood serum), transthoracic echocardiography and (urgent or delayed) coronary angiography data. Symptom-limited exercise tolerance (ET) test was performed predominantly at the second week of in-hospital stay. According to ET-test results, patients were subdivided into the groups with low (G1; 43 [48,9 %]) and high ET (G2; n=45 [51,1 %]).

RESULTS

Results: G1 (vs. G2) was characterized by older age, lower estimated glomerular filtration rate (eGFR) and higher left atrial (LA) dimension. The cases of any left anterior descending artery (LAD) lesion were more frequent in G1 (25 % vs. 2 % in G2, respectively; p=0,004). We revealed a decrease in PSK9 level after ET-test (pre-ET vs. post-ET: 824,0 (371,0-1073,0) vs. 676,0 (441,9-995,9) ng/ml, respectively; p=0,004 [N=35]).

CONCLUSION

Conclusions: At the completion of in-hospital rehabilitation period, the insufficient physical recovery in patients suffered from ACS associated with older age, lower eGFR, higher LA dimension, and more frequent any LDA lesion cases. Physical exercises favored the decrease in PCSK9 levels in blood serum.

CD34 positive cells as endothelial progenitor cells in biology and medicine

CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34⁺ cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34⁺ cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34⁺ cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34⁺ cell therapy in various diseases. However, the clinical application of CD34⁺ cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34⁺ cells as well as the preclinical/clinical details of CD34⁺ cell therapy for regenerative medicine.

Stem Cell-based Therapies in Cardiovascular Diseases: From Pathophysiology to Clinical Outcomes

Over 20 years of intensified research in the field of stem cells brought about unprecedented possibilities in treating heart diseases. The investigators were initially fascinated by the idea of regenerating the lost myocardium and replacing it with new functional cardiomyocytes, but this was extremely challenging. However, the multifactorial effects of stem cell-based therapies beyond mere cardiomyocyte generation, caused by paracrine signaling, would open up new possibilities in treating cardiovascular diseases. To date, there is a strong body of evidence that the anti-inflammatory, anti-apoptotic, and immunomodulatory effects of stem cell therapy may alleviate atherosclerosis progression. In the present review, our objective is to provide a brief overview of the stem cell-based therapeutic options. We aim to delineate the pathophysiological mechanisms of their beneficial effects in cardiovascular diseases especially in coronary artery disease and to highlight some conclusions from important clinical studies in the field of regenerative medicine in cardiovascular diseases and how we could further move onwards.

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.

Therapeutic Angiogenesis Using Autologous CD34-Positive Cells for Vascular Diseases

CD34 is a cell surface marker, which is expressed in various somatic stem/progenitor cells such as bone marrow (BM)-derived hematopoietic stem cells and endothelial progenitor cells (EPCs), skeletal muscle satellite cells, epithelial hair follicle stem cells, and adipose tissue mesenchymal stem cells. CD34+ cells in BM and peripheral blood are known as a rich source of EPCs. Thus, vascular regeneration therapy using granulocyte colony stimulating factor (G-CSF) mobilized- or BM CD34+ cells has been carried out in patients with various vascular diseases such as chronic severe lower limb ischemia, acute myocardial infarction, refractory angina, ischemic cardiomyopathy, and dilated cardiomyopathy as well as ischemic stroke. Pilot and randomized clinical trials demonstrated the safety, feasibility, and effectiveness of the CD34+ cell therapy in peripheral arterial, cardiovascular, and cerebrovascular diseases. This review provides an overview of the preclinical and clinical reports of CD34+ cell therapy for vascular regeneration.

The association between baseline circulating progenitor cells and vascular function: The role of aging and risk factors

BACKGROUND

To investigate the cross-sectional and longitudinal relationships between vascular function and circulating progenitor cell (CPC) counts with respect to aging and exposure to risk factors.

METHODS

In 797 adult participants, CPCs were enumerated by flow cytometry as CD45med mononuclear cells expressing CD34 epitope and its subsets co-expressing CD133, and chemokine C-X-C motif receptor 4 (CXCR4+). Arterial stiffness was evaluated by tonometry-derived pulse wave velocity (PWV) and microvascular function was assessed as digital reactive hyperemia index (RHI).

RESULTS

In cross-sectional analyses, for every doubling in CD34+ cell counts, PWV was 15% higher and RHI was 9% lower, after adjusting for baseline characteristics and risk factors (p for all < 0.01). There were significant CPC-by-age-by-risk factor interactions (p <0.05) for both vascular measures. Among younger subjects (< 48 years), CPC counts were higher in those with risk factors and vascular function was better in those with higher compared to those with lower CPC counts (p for all < 0.0l). In contrast, in older participants, CPCs were not higher in those with risk factors, and vascular function was worse compared to the younger age group. A lower CPC count at baseline was an independent predictor of worsening vascular function during 2-year follow-up.

CONCLUSION

A higher CPC count in the presence of risk factors is associated with better vascular function among younger individuals. There is no increase in CPC count with risk factors in older individuals who have worse vascular function. Moreover, a higher CPC count is associated with less vascular dysfunction with aging.

Extracellular Vesicles in Cardiovascular Diseases: Diagnosis and Therapy

Cardiovascular diseases (CVDs) are the leading cause of global mortality. Therapy of CVDs is still a great challenge since many advanced therapies have been developed. Multiple cell types produce nano-sized extracellular vesicles (EVs), including cardiovascular system-related cells and stem cells. Compelling evidence reveals that EVs are associated with the pathophysiological processes of CVDs. Recently researches focus on the clinical transformation in EVs-based diagnosis, prognosis, therapies, and drug delivery systems. In this review, we firstly discuss the current knowledge about the biophysical properties and biological components of EVs. Secondly, we will focus on the functions of EVs on CVDs, and outline the latest advances of EVs as prognostic and diagnostic biomarkers, and therapeutic agents. Finally, we will introduce the specific application of EVs as a novel drug delivery system and its application in CVDs therapy. Specific attention will be paid to summarize the perspectives, challenges, and applications on EVs’ clinical and industrial transformation.

Industrialized GMP Production of CD34+ Cells (ProtheraCytes®) at Clinical Scale for Treatment of Ischemic Cardiac Diseases Is Feasible and Safe

Regenerative medicine now needs to pass a crucial turning point, from academic research to the market. Several sources/types of cells have been experimented with, more or less successfully. CD34⁺ cells have demonstrated multipotent or even pluripotent capacities, making them good candidates for regenerative medicine, particularly for treating heart diseases. Strongly encouraged by the results we achieved in a pilot study using CD34⁺ stem cells in patients with poor-prognosis acute myocardial infarcts (AMIs), we soon began the development of an industrialized platform making use of a closed automated device (StemXpand^®) and a disposable kit (StemPack^®) for the large-scale expansion of CD34⁺ cells with reproducible good manufacturing practice (GMP). This scalable platform can produce expanded CD34⁺ cells (ProtheraCytes^®) of sufficient quality that, interestingly, express early markers of the cardiac and endothelial pathways and early cardiac-mesoderm markers. They also contain CD34⁺ pluripotent cells characterized as very small embryonic-like stem cells (VSELs), capable of differentiating under appropriate stimuli into different tissue lineages, including endothelial and cardiomyocytic ones.

Endothelial Progenitor Cells as Biomarkers of Cardiovascular Pathologies: A Narrative Review

Endothelial progenitor cells (EPC) may influence the integrity and stability of the vascular endothelium. The association of an altered total EPC number and function with cardiovascular diseases (CVD) and risk factors (CVF) was discussed; however, their role and applicability as biomarkers for clinical purposes have not yet been defined. Endothelial dysfunction is one of the key mechanisms in CVD. The assessment of endothelial dysfunction in vivo remains a major challenge, especially for a clinical evaluation of the need for therapeutic interventions or for primary prevention of CVD. One of the main challenges is the heterogeneity of this particular cell population. Endothelial cells (EC) can become senescent, and the majority of circulating endothelial cells (CEC) show evidence of apoptosis or necrosis. There are a few viable CECs that have properties similar to those of an endothelial progenitor cell. To use EPC levels as a biomarker for vascular function and cumulative cardiovascular risk, a correct definition of their phenotype, as well as an update on the clinical application and practicability of current isolation methods, are an urgent priority.

Cell Therapy in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is the most common cause of hospitalisation for heart failure. However, only limited effective treatments are available. Recent evidence suggests that HFpEF may result from a systemic proinflammatory state, microvascular endothelial inflammation and microvascular rarefaction. Formation of new microvasculature in ischaemic tissues is dependent on CD34+ cells, which incorporate into the newly developing vasculature and produce pro-angiogenic cytokines. In HFpEF patients, worsening of diastolic function appears to correlate with decreased numbers of CD34+ cells. Therefore, it is plausible that increasing the myocardial numbers of CD34+ cells could theoretically lead to improved microvascular function and improved diastolic parameters in HFpEF. In accordance with this hypothesis, recent pilot clinical data suggest that CD34+ cell therapy may indeed be associated with improved diastolic function and better functional capacity in HFpEF patients and could thus represent a promising novel therapeutic modality for this patient population.

Autologous CD34+ Stem Cell Therapy Increases Coronary Flow Reserve and Reduces Angina in Patients With Coronary Microvascular Dysfunction

BACKGROUND

Coronary microvascular dysfunction results in angina and adverse outcomes in patients with evidence of ischemia and nonobstructive coronary artery disease; however, no specific therapy exists. CD34+ cell therapy increases microvasculature in preclinical models and improves symptoms, exercise tolerance, and mortality in refractory angina patients with obstructive coronary artery disease. The objective of this research was to evaluate the safety, tolerability, and efficacy of intracoronary CD34+ cell therapy in patients with coronary microvascular dysfunction.

METHODS

We conducted a 2-center, 20-participant trial of autologous CD34+ cell therapy (protocol CLBS16-P01; NCT03508609) in patients with ischemia and nonobstructive coronary artery disease with persistent angina and coronary flow reserve ≤2.5. Efficacy measures included coronary flow reserve, angina frequency, Canadian Cardiovascular Society angina class, Seattle Angina Questionnaire, SF-36, and modified Bruce exercise treadmill test obtained at baseline and 6 months after treatment. Autologous CD34+ cells (CLBS16) were mobilized by administration of granulocyte-colony stimulating factor 5µg/kg/day for 5 days and collected by leukapheresis. Participants received a single intracoronary left anterior descending infusion of isolated CD34+ cells in medium that enhances cell function.

RESULTS

Coronary flow reserve improved from 2.08±0.32 at baseline to 2.68±0.79 at 6 months after treatment (P<0.005). Angina frequency decreased (P<0.004), Canadian Cardiovascular Society class improved (P<0.001), and quality of life improved as assessed by the Seattle Angina Questionnaire (P≤0.03, all scales) and SF-36 (P≤0.04, all scales). There were no cell-related serious adverse events.

CONCLUSIONS

In this pilot clinical trial of microvascular angina, patients with ischemia and nonobstructive coronary artery disease receiving intracoronary infusion of CD34+ cell therapy had higher coronary flow reserve, less severe angina, and better quality of life at 6 months. The current study supports a potential therapeutic role for CD34+ cells in patients with microvascular angina. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03508609.

Transendocardial CD34+ Cell Therapy Improves Local Mechanical Dyssynchrony in Patients With Nonischemic Dilated Cardiomyopathy

We investigated the effects of cell therapy on local mechanical dyssynchrony (LMD) in patients with nonischemic dilated cardiomyopathy (NICM). We analyzed electromechanical data of 30 NICM patients undergoing CD34⁺ cell transplantation. All patients underwent bone marrow stimulation; CD34⁺ cells were collected by apheresis and injected transendocardially. At baseline and at 6 months after therapy, we performed electromechanical mapping and measured unipolar voltage (UV) and LMD at cell injection sites. LMD was defined as a temporal difference between global and segmental peak systolic displacement normalized to the average duration of the RR interval. Favorable clinical response was defined as increase in the left ventricular ejection fraction (LVEF) ≥5% between baseline and 6 months. Using paired electromechanical point-by-point analysis, we were able to identify 233 sites of CD34⁺ cell injections in 30 patients. We found no overall differences in local UV between baseline and 6 months (10.7 ± 4.1 mV vs 10.0 ± 3.6 mV, P = 0.42). In contrast, LMD decreased significantly (17 ± 17% at baseline vs 13 ± 12% at 6 months, P = 0.00007). Favorable clinical response at 6 months was found in 19 (63%) patients (group A), and 11 (37%) patients did not respond to cell therapy (group B). At baseline, the two groups did not differ in age, gender, LVEF, or N terminal-pro brain natriuretic peptide (NT-proBNP) levels. Similarly, we found no differences in baseline UV (9.5 ± 2.9 mV in group A vs 8.6 ± 2.4 mV in group B, P = 0.41) or LMD at cell injection sites (17 ± 19% vs 16 ± 14%, P = 0.64). In contrast, at 6 months, we found higher UV in group A (10.0 ± 3.1 mV vs 7.4 ± 1.9 mV in group B, P = 0.04). Furthermore, when compared with group B, patients in group A displayed a significantly lower LMD (11 ± 12% vs 16 ± 10%, P = 0.002). Thus, it appears that favorable clinical effects of cell therapy in NICM patients may be associated with a decrease of LMD at cell injection sites.

IMPROvE-CED Trial: Intracoronary Autologous CD34+ Cell Therapy for Treatment of Coronary Endothelial Dysfunction in Patients With Angina and Non-Obstructive Coronary Arteries

Background: Coronary endothelial dysfunction (CED) causes angina/ischemia in patients with no-obstructive CAD (NOCAD). Patients with CED have decreased number and function of CD34+ cells involved in normal vascular repair with microcirculatory regenerative potential and paracrine anti-inflammatory effects. We evaluated safety and potential efficacy of intracoronary (IC) autologous CD34+ cell therapy for CED.

Methods: Twenty NOCAD patients with invasively-diagnosed CED and persistent angina despite maximally-tolerated medical therapy (MTMT) underwent baseline exercise stress test (EST), GCSF-mediated CD34+ cell-mobilization, leukapheresis, and selective 1x105 CD34+ cells/kg infusion into LAD. Invasive CED evaluation and EST were repeated 6-months after cell infusion. Primary endpoints were safety and effect of IC autologous CD34+ cell therapy on CED at 6-months follow-up. Secondary endpoints were change in CCS angina class, as-needed sublingual nitroglycerin use/day, Seattle Angina Questionnaire (SAQ) scores, and exercise time at 6-months. Change in CED was compared to that of 51 historic-control NOCAD patients treated with MTMT alone.

Results: Mean age was 52{plus minus}13 years, 75% women. No death, myocardial infarction, or stroke occurred. IC CD34+ cell infusion improved microvascular CED [% acetylcholine-mediated coronary blood flow increased from 7.2 (-18.0-32.4) to 57.6 (16.3-98.3) %, p=0.014], decreased CCS angina class (3.7{plus minus}0.5 to 1.7{plus minus}0.9, Wilcoxon signed-rank test p=0.00018) and sublingual nitroglycerin use/day [1 (0.4-3.5) to 0 (0-1), Wilcoxon signed-rank test p=0.00047], and improved all SAQ scores with no significant change in exercise time at 6-months follow-up. Historic-control patients had no significant change in CED.

Conclusion: A single IC autologous CD34+ cell infusion was safe and may potentially be an effective disease-modifying therapy for microvascular CED in humans. Clinical Trial Registration: NCT03471611

Associations Between Inflammation, Cardiovascular Regenerative Capacity, and Cardiovascular Events: A Cohort Study

Objective

Circulating progenitor cells possess immune modulatory properties and might mitigate inflammation that is characteristic of patients with coronary artery disease. We hypothesized that patients with fewer circulating progenitor cells (CPCs) will have higher inflammatory markers and worse outcomes.

Approach and Results

Patients with stable coronary artery disease were enrolled in a prospective study enumerating CPCs as CD (cluster of differentiation)-34-expressing mononuclear cells (CD34+) and inflammation as levels of IL (interleukin)-6 and high-sensitivity CRP (C-reactive protein) levels. Patients were followed for 5 years for the end points of death and myocardial infarction with repeat inflammatory biomarkers measured after a median of 2 years. In the entire cohort of 392 patients, IL-6 and high-sensitivity CRP levels remained unchanged (0.3+/-2.4 pg/mL and 0.1+/-1.0 mg/L; P=0.45) after 2 years. CPC counts (log-transformed) were inversely correlated with the change in IL-6 levels (r, -0.17; P<0.001). Using linear regression, IL-6 and high-sensitivity CRP levels declined by -0.59 (95% CI, -0.90 to -0.20) pg/mL and -0.13 (-0.28 to 0.01) mg/L per 1 log higher CPC counts after adjustment for the demographic and clinical variables, as well as medications. Using Cox models adjusted for these risk factors, a rise in 1 pg/mL of IL-6 was associated with a 11% (95% CI, 9-13) greater risk of death/myocardial infarction. We found that the change in IL6 level partly (by 40%) mediated the higher risk of adverse events among those with low CPC counts.

Conclusions

Reduced cardiovascular regenerative capacity is independently associated with progressive inflammation in patients with coronary artery disease that in turn is associated with poor outcomes.

Human umbilical cord tissue-derived mesenchymal stromal cells as adjuvant therapy for myocardial infarction: a review of current evidence focusing on pre-clinical large animal models and early human trials

Although biologically appealing, the concept of tissue regeneration underlying first- and second-generation cell therapies has failed to translate into consistent results in clinical trials. Several types of cells from different origins have been tested in pre-clinical models and in patients with acute myocardial infarction (AMI). Mesenchymal stromal cells (MSCs) have gained attention because of their potential for immune modulation and ability to promote endogenous tissue repair, mainly through their secretome. MSCs can be easily obtained from several human tissues, the umbilical cord being the most abundant source, and further expanded in culture, making them attractive as an allogeneic "of-the-shelf" cell product, suitable for the AMI setting. The available evidence concerning umbilical cord-derived MSCs in AMI is reviewed, focusing on large animal pre-clinical studies and early human trials. Molecular and cellular mechanisms as well as current limitations and possible translational solutions are also discussed.

Isolation Methods for Human CD34 Subsets Using Fluorescent and Magnetic Activated Cell Sorting: an In Vivo Comparative Study

INTRODUCTION

Acute myocardial infarction (AMI) and resulting cardiac damage and heart failure are leading causes of morbidity and mortality worldwide. Multiple studies have examined the utility of CD34⁺ cells for the treatment of acute and ischemic heart disease. However, the optimal strategy to enrich CD34 cells from clinical sources is not known. We examined the efficacy of fluorescence activated cell sorting (FACS) and magnetic beads cell sorting (MACS) methods for CD34 cell isolation from mobilized human mononuclear peripheral blood cells (mhPBMNCs).

METHODS

mhPBCs were processed following acquisition using FACS or MACS according to clinically established protocols. Cell viability, CD34 cell purity and characterization of surface marker expression were assessed using a flow cytometer. For in vivo characterization of cardiac repair, we conducted LAD ligation surgery on 8-10 weeks female NOD/SCID mice followed by intramyocardial transplantation of unselected mhPBMNCs, FACS or MACS enriched CD34⁺ cells.

RESULTS

Both MACS and FACS isolation methods achieved high purity rates, viability, and enrichment of CD34⁺ cells. In vivo studies following myocardial infarction demonstrated retention of CD34⁺ in the peri-infarct region for up to 30 days after transplantation. Retained CD34⁺ cells were associated with enhanced angiogenesis and reduced inflammation compared to unselected mhPBMNCs or PBS treatment arms. Cardiac scar and fibrosis as assessed by immunohistochemistry were reduced in FACS and MACS CD34⁺ treatment groups. Finally, reduced scar and augmented angiogenesis resulted in improved cardiac functional recovery, both on the global and regional function and remodeling assessments by echocardiography.

CONCLUSION

Cell based therapy using enriched CD34⁺ cells sorted by FACS or MACS result in better cardiac recovery after ischemic injury compared to unselected mhPBMNCs. Both enrichment techniques offer excellent recovery and purity and can be equally used for clinical applications.

Transplantation of CD34+ cells for myocardial ischemia

CD34+ cells are multipotent hematopoietic stem cells also known as endothelial progenitor cells and are useful in regenerative medicine. Naturally, these cells are mobilized from the bone marrow into peripheral circulation in response to ischemic tissue injury. CD34+ cells are known for their high proliferative and differentiation capacities that play a crucial role in the repair process of myocardial damage. They have an important paracrine activity in secreting factors to stimulate vasculogenesis, reduce endothelial cells and cardiomyocytes apoptosis, remodel extracellular matrix and activate additional progenitor cells. Once they migrate to the target site, they enhance angiogenesis, neovascularization and tissue regeneration. Several trials have demonstrated the safety and efficacy of CD34+ cell therapy in different settings, such as peripheral limb ischemia, stroke and cardiovascular disease. Herein, we review the potential utility of CD34+ cell transplantation in acute myocardial infarction, refractory angina and ischemic heart failure.

Application of stem cell-derived exosomes in ischemic diseases: opportunity and limitations

Ischemic diseases characterized by an insufficient blood flow that leads to a decrease in oxygen and nutrient uptake by cells have emerged as an important contributor to both disability and death worldwide. Up-regulation of angiogenesis may be a key factor for the improvement of ischemic diseases. This article searched articles in PubMed with the following keywords: stem cells, exosomes, angiogenesis, ischemic diseases either alone or in grouping form. The most relevant selected items were stem cell-derived exosomes and ischemic diseases. A growing body of evidence indicates that stem cells produce exosomes, which is the novel emerging approach to cell-to-cell communication and offers a new standpoint on known therapeutic strategies of ischemic diseases. Exosomes transport biological molecules such as many types of proteins, RNAs, DNA fragments, signaling molecules, and lipids between cells. Different stem cells release exosomes representing beneficial effects on ischemic diseases as they promote angiogenesis both in vitro and in vivo experiments. Application of exosomes for therapeutic angiogenesis opened new opportunities in the regenerative medicine, however, some limitations regarding exosomes isolation and application remain concerned. In addition, most of the experiments were conducted in preclinical and therefore translation of these results from bench to bed requires more effort in this field. Exosomes from stem cells are a promising tool for the treatment of ischemic diseases. In addition, translation of pre-clinic results into clinic needs further studies in this field.

Three-year outcomes of peripheral blood mononuclear cells vs purified CD34+ cells in the treatment of angiitis-induced no-option critical limb ischemia and a cost-effectiveness assessment: A randomized single-blinded noninferiority trial

For patients with angiitis-induced critical limb ischemia (AICLI), cell transplantation, such as purified CD34+ cells (PCCs) and peripheral blood mononuclear cells (PBMNCs), is gradually being used as a promising treatment. This was the first randomized single-blinded noninferiority trial (number: NCT02089828) specifically designed to evaluate the therapeutic efficacies of the transplantation of PCCs vs those of PBMNCs for the treatment of AICLI. We aimed to compare the mid-term safety and efficacy between the two groups and determine their respective advantages. From April 2014 to September 2019, 50 patients with AICLI were equally allocated to the two groups, except for 1 lost patient, 1 amputee, and 1 patient who died of heart disease. The other 47 patients completed the 36-month follow-up. The endpoints were as follows: major amputation-free survival and total amputation-free survival at 6 months, which were 96.0% and 84.0% in the PBMNCs group and 96.0% and 72.0% in the PCCs group, respectively. These rates remained stable at 12, 24, and 36 months. The PCCs group had a significant higher probability of rest pain relief than the PBMNCs group, whereas earlier significant improvements in the Rutherford classification were observed in the PBMNCs group. Accordingly, PCCs would be preferred for patients with significant pain, whereas PBMNCs may be a good option for patients with two or more critically ischemic limbs. Concerning cost-effectiveness, PCCs are not more cost-effective than PBMNCs. These outcomes require verification from long-term trials involving larger numbers of patients.

The Therapeutic Applications of Exosomes in Different Types of Diseases: A Review

Exosomes are nano-sized vesicles secreted by nearly all cells and have received massive attention recently. In addition to their roles in pathophysiological processes and diagnostic evaluations, recently, several studies have applied exosomes to design novel therapeutic applications. Exosomes can be derived from a variety of cells and tissues and based on the source, they can carry different native contents such as DNAs, non-coding small RNAs, mRNAs, and proteins. They can also be engineered by adding desirable agents including specific biomolecules or drugs. Both forms can be therapeutically used for delivering their cargoes to the target cells and desirably alter their functions. The present study aimed to provide a comprehensive review of the various studies which applied exosomes as a therapeutic tool in the treatment of different types of diseases including cancer, cardiovascular, neurologic, psychiatric, liver, and kidney diseases.

Stem Cells in Cardiovascular Diseases: 30,000-Foot View

Stem cell and regenerative approaches that might rejuvenate the heart have immense intuitive appeal for the public and scientific communities. Hopes were fueled by initial findings from preclinical models that suggested that easily obtained bone marrow cells might have significant reparative capabilities; however, after initial encouraging pre-clinical and early clinical findings, the realities of clinical development have placed a damper on the field. Clinical trials were often designed to detect exceptionally large treatment effects with modest patient numbers with subsequent disappointing results. First generation approaches were likely overly simplistic and relied on a relatively primitive understanding of regenerative mechanisms and capabilities. Nonetheless, the field continues to move forward and novel cell derivatives, platforms, and cell/device combinations, coupled with a better understanding of the mechanisms that lead to regenerative capabilities in more primitive models and modifications in clinical trial design suggest a brighter future.

Ex vivo conditioning of peripheral blood mononuclear cells of diabetic patients promotes vasculogenic wound healing

The quality and quantity of endothelial progenitor cells (EPCs) are impaired in patients with diabetes mellitus patients, leading to reduced tissue repair during autologous EPC therapy. This study aimed to address the limitations of the previously described serum-free Quantity and Quality Control Culture System (QQc) using CD34+ cells by investigating the therapeutic potential of a novel mononuclear cell (MNC)-QQ. MNCs were isolated from 50 mL of peripheral blood of patients with diabetes mellitus and healthy volunteers (n = 13 each) and subjected to QQc for 7 days in serum-free expansion media with VEGF, Flt-3 ligand, TPO, IL-6, and SCF. The vascular regeneration capability of MNC-QQ cells pre- or post-QQc was evaluated with an EPC colony-forming assay, FACS, EPC culture, tube formation assay, and quantitative real time PCR. For in vivo assessment, 1 × 10⁴ pre- and post-MNC-QQc cells from diabetic donors were injected into a murine wound-healing model using Balb/c nude mice. The percentage of wound closure and angio-vasculogenesis was then assessed. This study revealed vasculogenic, anti-inflammatory, and wound-healing effects of MNC-QQ therapy in both in vitro and in vivo models. This system addresses the low efficiency and efficacy of the current naïve MNC therapy for wound-healing in diabetic patients. As this technique requires a simple blood draw, isolation, and peripheral blood MNC suspension culture for only a week, it can be used as a simple and effective outpatient-based vascular and regenerative therapy for patients with diabetes mellitus.

Promise of autologous CD34+ stem/progenitor cell therapy for treatment of cardiovascular disease

CD34+ cells are haematopoietic stem cells used therapeutically in patients undergoing radiation or chemotherapy due to their regenerative potential and ability to restore the haematopoietic system. In animal models, CD34+ cells have been associated with therapeutic angiogenesis in response to ischaemia. Several trials have shown the potential safety and efficacy of CD34+ cell delivery in various cardiovascular diseases. Moreover, Phase III trials have now begun to explore the potential role of CD34+ cells in treatment of both myocardial and peripheral ischaemia. CD34+ cells have been shown to be safe and well-tolerated in the acute myocardial infarction (AMI), heart failure, and angina models. Several studies have suggested potential benefit of CD34+ cell therapy in patients with coronary microvascular disease as well. In this review, we will discuss the therapeutic potential of CD34+ cells, and describe the pertinent trials that have used autologous CD34+ cells in no-options refractory angina, AMI, and heart failure. Lastly, we will review the potential utility of autologous CD34+ cells in coronary endothelial and microvascular dysfunction.

Therapeutic Approaches for the No-Option Refractory Angina Patient

The combination of an aging population and improved survival rates among patients with coronary artery disease has resulted in an increase in the number of patients with refractory angina or anginal equivalent symptoms despite maximal medical therapy. Patients with refractory angina are often referred to the cardiac catheterization laboratory; however, they have often exhausted conventional revascularization options; thus, this population is often deemed as having "no options." We review the definition, prevalence, outcomes, therapeutic options, and treatment considerations for no-option refractory angina patients and focus on novel therapies for this complex and challenging population. We propose a multidisciplinary team approach for the evaluation and management of patients with refractory angina, ideally in a designated clinic. The severe limitations and symptomatology experienced by these patients highlight the need for additional research into the development of innovative treatments.

Current Status of Cell-Based Therapy in Patients with Critical Limb Ischemia

(1) Background: The treatment of peripheral arterial disease (PAD) is focused on improving perfusion and oxygenation in the affected limb. Standard revascularization methods include bypass surgery, endovascular interventional procedures, or hybrid revascularization. Cell-based therapy can be an alternative strategy for patients with no-option critical limb ischemia who are not eligible for endovascular or surgical procedures. (2) Aims: The aim of this narrative review was to provide an up-to-date critical overview of the knowledge and evidence-based medicine data on the position of cell therapy in the treatment of PAD. The current evidence on the cell-based therapy is summarized and future perspectives outlined, emphasizing the potential of exosomal cell-free approaches in patients with critical limb ischemia. (3) Methods: Cochrane and PubMed databases were searched for keywords “critical limb ischemia and cell therapy”. In total, 589 papers were identified, 11 of which were reviews and 11 were meta-analyses. These were used as the primary source of information, using cross-referencing for identification of additional papers. (4) Results: Meta-analyses focusing on cell therapy in PAD treatment confirm significantly greater odds of limb salvage in the first year after the cell therapy administration. Reported odds ratio estimates of preventing amputation being mostly in the region 1.6–3, although with a prolonged observation period, it seems that the odds ratio can grow even further. The odds of wound healing were at least two times higher when compared with the standard conservative therapy. Secondary endpoints of the available meta-analyses are also included in this review. Improvement of perfusion and oxygenation parameters in the affected limb, pain regression, and claudication interval prolongation are discussed. (5) Conclusions: The available evidence-based medicine data show that this technique is safe, associated with minimum complications or adverse events, and effective.

Native and bioengineered extracellular vesicles for cardiovascular therapeutics

Extracellular vesicles (EVs) are a heterogeneous group of natural particles that are relevant to the treatment of cardiovascular diseases. These endogenous vesicles have certain properties that allow them to survive in the extracellular space, bypass biological barriers and deliver their biologically active molecular cargo to recipient cells. Moreover, EVs can be bioengineered to increase their stability, bioactivity, presentation to acceptor cells and capacity for on-target binding at both cell-type-specific and tissue-specific levels. Bioengineering of EVs involves the modification of the donor cell before EV isolation or direct modification of the EV properties after isolation. The therapeutic potential of native EVs and bioengineered EVs has been only minimally explored in the context of cardiovascular diseases. Efforts to harness the therapeutic potential of EVs will require innovative approaches and a comprehensive integration of knowledge gathered from decades of research into molecular-compound delivery. In this Review, we outline the endogenous properties of EVs that make them natural delivery agents as well as the features that can be improved by bioengineering. We also discuss the therapeutic applications of native and bioengineered EVs to cardiovascular diseases and examine the opportunities and challenges that need to be addressed to advance this research area, with an emphasis on clinical translation.

Refractory Angina: From Pathophysiology to New Therapeutic Nonpharmacological Technologies

Despite optimal combination of guideline-directed anti-ischemic therapies and myocardial revascularization, a substantial proportion of patients with stable coronary artery disease continues to experience disabling symptoms and is often referred as "no-option." The appraisal of the pathways linking ischemia to symptom perception indicates a complex model of heart-brain interactions in the generation of the subjective anginal experience and inspired novel approaches that may be clinically effective in alleviating the angina burden of this population. Conversely, the prevailing ischemia-centered view of angina, with the focus on traditional myocardial revascularization as the sole option to address ischemia on top of medical therapy, hinders the experimental characterization and broad-scale clinical implementation of strongly needed therapeutic options. The interventionist, often the first physician to establish the diagnosis of refractory angina pectoris (RAP) following coronary angiography, should be aware of the numerous emerging technologies with the potential to improve quality of life in the growing population of RAP patients. This review describes the current landscape and the future perspectives on nonpharmacological treatment technologies for patients with RAP, with a view on the underlying physiopathological rationale and current clinical evidence.

[Problems and prospects of cell therapy for critical ischaemia of lower limbs]

BACKGROUND

Cell therapy was proposed as a procedure of indirect revascularization for patients with critical ischaemia of lower extremities for whom endovascular and surgical revascularization is impossible. We present herein a review of the state of the art of studies in the field of cell therapy of this cohort of patients.

BASIC PROVISIONS

Cell therapy has proved safe, however, the results of studies of efficacy are relatively ambiguous and unconvincing. The number of patients in separately taken clinical trials is minimal. The reviewed studies differed not only by heterogeneity of the cell types used but by the routes of administration of cells (cells were delivered either intramuscularly (predominantly) or intraarterially) and the duration of follow up (time of assessment and duration of follow up varied from 1 month to 2 years). One of the problems became the lack of the routine study of the angiogenic potential of stem cells prior to their clinical application. It is known that the angiogenic activity of multipotent cells of apparently healthy patients may differ from that of patients suffering from atherosclerosis, chronic renal failure, diabetes.

CONCLUSIONS

It is supposed that treatment with stem cells or precursor cells is more efficient as compared to protein or gene therapy not only owing to direct vasculogenic properties but a paracrine action through excretion of proangiogenic biologically active substances. More studies with larger cohorts are necessary to provide stronger safety and efficacy data on cell therapy. Besides, a promising trend in the field of cellular approaches is modulation of regenerative capability of stem cells, which may help overcome difficulties in understanding the place of cell therapy in therapeutic angiogenesis.

Non-pharmacological Treatment of Refractory Angina and Microvascular Angina

Refractory angina (RA) is defined as debilitating anginal symptoms despite the optimal guideline-directed combination of medical, percutaneous, and surgical therapies. Often referred to as “no option”, these patients represent a significant unmet clinical need for healthcare institutions. Due to the ageing of the population, and increased survival from coronary artery disease, the number of patients with RA is expected to rise exponentially. Despite the developments of novel technologies for the treatment of RA, none of them found wide clinical application (to date). Microvascular dysfunction, alone or in combination with epicardial coronary disease, is thought to contribute significantly to refractory angina. However, most of the techniques developed to improve RA symptoms have not been tested specifically on patients with microvascular dysfunction. This review discusses the recent developments in the treatment of RA, and gives some perspectives on the future of these techniques.