Lucian Beer

Intravenous and intramyocardial injection of apoptotic white blood cell suspensions prevents ventricular remodelling by increasing elastin expression in cardiac scar tissue after myocardial infarction

Congestive heart failure developing after acute myocardial infarction (AMI) is a major cause of morbidity and mortality. Clinical trials of cell-based therapy after AMI evidenced only a moderate benefit. We could show previously that suspensions of apoptotic peripheral blood mononuclear cells (PBMC) are able to reduce myocardial damage in a rat model of AMI. Here we experimentally examined the biochemical mechanisms involved in preventing ventricular remodelling and preserving cardiac function after AMI. Cell suspensions of apoptotic cells were injected intravenously or intramyocardially after experimental AMI induced by coronary artery ligation in rats. Administration of cell culture medium or viable PBMC served as controls. Immunohistological analysis was performed to analyse the cellular infiltrate in the ischaemic myocardium. Cardiac function was quantified by echocardiography. Planimetry of the infarcted hearts showed a significant reduction of infarction size and an improvement of post AMI remodelling in rats treated with suspensions of apoptotic PBMC (injected either intravenously or intramoycardially). Moreover, these hearts evidenced enhanced homing of macrophages and cells staining positive for c-kit, FLK-1, IGF-I and FGF-2 as compared to controls. A major finding in this study further was that the ratio of elastic and collagenous fibres within the scar tissue was altered in a favourable fashion in rats injected with apoptotic cells. Intravenous or intramyocardial injection of apoptotic cell suspensions results in attenuation of myocardial remodelling after experimental AMI, preserves left ventricular function, increases homing of regenerative cells and alters the composition of cardiac scar tissue. The higher expression of elastic fibres provides passive energy to the cardiac scar tissue and results in prevention of ventricular remodelling.

Analysis of the Secretome of Apoptotic Peripheral Blood Mononuclear Cells: Impact of Released Proteins and Exosomes for Tissue Regeneration

We previously showed that, when peripheral blood mononuclear cells (PBMCs) were stressed with ionizing radiation, they released paracrine factors that showed regenerative capacity in vitro and in vivo. This study aimed to characterize the secretome of PBMCs and to investigate its biologically active components in vitro and vivo. Bioinformatics analysis revealed that irradiated PBMCs differentially expressed genes that encoded secreted proteins. These genes were primarily involved in (a) pro-angiogenic and regenerative pathways and (b) the generation of oxidized phospholipids with known pro-angiogenic and inflammation-modulating properties. Subsequently, in vitro assays showed that the exosome and protein fractions of irradiated and non-irradiated PBMC secretome were the major biological components that enhanced cell mobility; conversely, secreted lipids and microparticles had no effects. We tested a viral-cleared PBMC secretome, prepared according to good manufacturing practice (GMP), in a porcine model of closed chest, acute myocardial infarction. We found that the potency for preventing ventricular remodeling was similar with the GMP-compliant and experimentally-prepared PBMC secretomes. Our results indicate that irradiation modulates the release of proteins, lipid-mediators and extracellular vesicles from human PBMCs. In addition our findings implicate the use of secretome fractions as valuable material for the development of cell-free therapies in regenerative medicine.

Peripheral blood mononuclear cell secretome for tissue repair.

For almost two decades, cell-based therapies have been tested in modern regenerative medicine to either replace or regenerate human cells, tissues, or organs and restore normal function. Secreted paracrine factors are increasingly accepted to exert beneficial biological effects that promote tissue regeneration. These factors are called the cell secretome and include a variety of proteins, lipids, microRNAs, and extracellular vesicles, such as exosomes and microparticles. The stem cell secretome has most commonly been investigated in pre-clinical settings. However, a growing body of evidence indicates that other cell types, such as peripheral blood mononuclear cells (PBMCs), are capable of releasing significant amounts of biologically active paracrine factors that exert beneficial regenerative effects. The apoptotic PBMC secretome has been successfully used pre-clinically for the treatment of acute myocardial infarction, chronic heart failure, spinal cord injury, stroke, and wound healing. In this review we describe the benefits of choosing PBMCs instead of stem cells in regenerative medicine and characterize the factors released from apoptotic PBMCs. We also discuss pre-clinical studies with apoptotic cell-based therapies and regulatory issues that have to be considered when conducting clinical trials using cell secretome-based products. This should allow the reader to envision PBMC secretome-based therapies as alternatives to all other forms of cell-based therapies.

Secretomes of apoptotic mononuclear cells ameliorate neurological damage in rats with focal ischemia

The pursuit of targeting multiple pathways in the ischemic cascade of cerebral stroke is a promising treatment option. We examined the regenerative potential of conditioned medium derived from rat and human apoptotic mononuclear cells (MNC), rMNC apo sec and hMNC apo sec, in experimental stroke. We performed middle cerebral artery occlusion on Wistar rats and administered apoptotic MNC-secretomes intraperitoneally in two experimental settings. Ischemic lesion volumes were determined 48 hours after cerebral ischemia. Neurological evaluations were performed after 6, 24 and 48 hours. Immunoblots were conducted to analyze neuroprotective signal-transduction in human primary glia cells and neurons. Neuronal sprouting assays were performed and neurotrophic factors in both hMNC apo sec and rat plasma were quantified using ELISA. Administration of rat as well as human apoptotic MNC-secretomes significantly reduced ischemic lesion volumes by 36% and 37%, respectively. Neurological examinations revealed improvement after stroke in both treatment groups. Co-incubation of human astrocytes, Schwann cells and neurons with hMNC apo sec resulted in activation of several signaling cascades associated with the regulation of cytoprotective gene products and enhanced neuronal sprouting in vitro. Analysis of neurotrophic factors in hMNC apo sec and rat plasma revealed high levels of brain derived neurotrophic factor (BDNF). Our data indicate that apoptotic MNC-secretomes elicit neuroprotective effects on rats that have undergone ischemic stroke.

Paracrine Factors from Irradiated Peripheral Blood Mononuclear Cells Improve Skin Regeneration and Angiogenesis in a Porcine Burn Model

Burn wounds pose a serious threat to patients and often require surgical treatment. Skin grafting aims to achieve wound closure but requires a well-vascularized wound bed. The secretome of peripheral blood mononuclear cells (PBMCs) has been shown to improve wound healing and angiogenesis. We hypothesized that topical application of the PBMC secretome would improve the quality of regenerating skin, increase angiogenesis, and reduce scar formation after burn injury and skin grafting in a porcine model. Full-thickness burn injuries were created on the back of female pigs. Necrotic areas were excised and the wounds were covered with split-thickness mesh skin grafts. Wounds were treated repeatedly with either the secretome of cultured PBMCs (SecPBMC), apoptotic PBMCs (Apo-SecPBMC), or controls. The wounds treated with Apo-SecPBMC had an increased epidermal thickness, higher number of rete ridges, and more advanced epidermal differentiation than controls. The samples treated with Apo-SecPBMC had a two-fold increase in CD31+ cells, indicating more angiogenesis. These data suggest that the repeated application of Apo-SecPBMC significantly improves epidermal thickness, angiogenesis, and skin quality in a porcine model of burn injury and skin grafting.

Low Tidal Volume Ventilation during Cardiopulmonary Bypass Reduces Postoperative Chemokine Serum Concentrations

BACKGROUND Open-heart surgery with cardiopulmonary bypass (CPB) is associated with a generalized immune response and postoperative lung dysfunction. Chemokines are involved in the pathogenesis of postoperative lung dysfunction. We investigated whether continued mechanical ventilation during CPB has an impact on chemokine serum concentrations. METHODS A total of 30 patients undergoing coronary artery bypass graft operation were randomized to either continuous ventilated group (n=15) or nonventilated group (n=15). Blood samples were drawn at the beginning and at the end of surgery and on the 5 consecutive days. Serum CCL2, CCL4, and CCL20 concentrations were measured and given as mean ± standard deviation. RESULTS Chemokine concentrations were elevated at the end of surgery in both groups. CCL2 and CCL4 levels returned to baseline on postoperative day (POD)-1 in the ventilation group and stayed elevated in the nonventilation group. CCL4 serum levels were significantly lower in ventilated-group patients on POD-1 (10.9 [39.0] vs. 153.2 [168.1]; p=0.005), POD-2 (16.8 [36.8] vs. 147.9 [165.4]; p=0.019), POD-3 (14.2 [24.0] vs. 97.9 [87.1]; p=0.005), and POD-5 (6.5 [25.0] vs. 33.6 [38.4]; p=0.045). CONCLUSION Continued mechanical ventilation during CPB results in reduced CCL4 concentrations on POD-1 to -5.

Bioinformatics approach for choosing the correct reference genes when studying gene expression in human keratinocytes.

Reverse transcription polymerase chain reaction (qRT‐PCR) has become a mainstay in many areas of skin research. To enable quantitative analysis, it is necessary to analyse expression of reference genes (RGs) for normalization of target gene expression. The selection of reliable RGs therefore has an important impact on the experimental outcome. In this study, we aimed to identify and validate the best suited RGs for qRT‐PCR in human primary keratinocytes (KCs) over a broad range of experimental conditions using the novel bioinformatics tool ‘RefGenes’, which is based on a manually curated database of published microarray data. Expression of 6 RGs identified by RefGenes software and 12 commonly used RGs were validated by qRT‐PCR. We assessed whether these 18 markers fulfilled the requirements for a valid RG by the comprehensive ranking of four bioinformatics tools and the coefficient of variation (CV). In an overall ranking, we found GUSB to be the most stably expressed RG, whereas the expression values of the commonly used RGs, GAPDH and B2M were significantly affected by varying experimental conditions. Our results identify RefGenes as a powerful tool for the identification of valid RGs and suggest GUSB as the most reliable RG for KCs.

Continued mechanical ventilation during coronary artery bypass graft operation attenuates the systemic immune response

OBJECTIVES Cardiopulmonary bypass (CPB) is known to induce a short pro- and long-lasting anti-inflammatory immune response. The anti-inflammatory protein soluble ST2 (sST2) may be involved in the pathogenesis of postoperative immune dysfunction. We investigated whether continued mechanical ventilation during CPB has an impact on postoperative serum sST2 and cytokine release. METHODS Thirty patients undergoing conventional coronary artery bypass graft (CABG) operation were randomized into a ventilated on CPB (VG; n = 15) and non-ventilated on CPB group (NVG; n = 15). Blood samples were drawn at the beginning and at the end of surgery, and at the 5 consecutive days. sST2, IL-4, IL-10, IgM, IgG, IL-6 and endotoxin were measured by ELISA. Data are given as mean standard deviation (SD). A Mann-Whitney U-test was used for statistical analysis. RESULTS Serum levels of sST2 and IL-10 were significantly higher in the NVG when compared with the VG at the first postoperative day (POD-1) [sST2 pg/ml: 1366.4 (433) (VG) vs 2296.3 (1795.5) (NVG) P = 0.029; IL-10 pg/ml: 10.7 (4.0) (VG) vs 15.4 (6.8) (NVG) P = 0.038]. In addition, the secretion of proinflammatory IL-6 was slightly reduced in the VG at POD-1 [IL-6 pg/ml: 83.1 (52.5) (VG) vs 110.2 (42.3) (NVG) P = 0.033]. IL-4, endotoxin, IgM and IgG showed no differences between groups. CONCLUSION These data suggest that continued mechanical ventilation during CABG attenuates inflammatory and anti-inflammatory immune responses after CPB. Continued mechanical ventilation may have beneficial effects in the attenuation of the CPB-induced immune activation.

Anti-Thymocyte Globulin Induces Neoangiogenesis and Preserves Cardiac Function after Experimental Myocardial Infarction

Rationale Acute myocardial infarction (AMI) followed by ventricular remodeling is the major cause of congestive heart failure and death in western world countries. Objective Of relevance are reports showing that infusion of apoptotic leucocytes or anti-lymphocyte serum after AMI reduces myocardial necrosis and preserves cardiac function. In order to corroborate this therapeutic mechanism, the utilization of an immunosuppressive agent with a comparable mechanism, such as anti-thymocyte globulin (ATG) was evaluated in this study. Methods and Results AMI was induced in rats by ligation of the left anterior descending artery. Initially after the onset of ischemia, rabbit ATG (10 mg/rat) was injected intravenously. In vitro and in vivo experiments showed that ATG induced a pronounced release of pro-angiogenic and chemotactic factors. Moreover, paracrine factors released from ATG co-incubated cell cultures conferred a down-regulation of p53 in cardiac myocytes. Rats that were injected with ATG evidenced higher numbers of CD68+ macrophages in the ischemic myocardium. Animals injected with ATG evidenced less myocardial necrosis, showed a significant reduction of infarct dimension and an improvement of post-AMI remodeling after six weeks (infarct dimension 24.9% vs. 11.4%, p<0.01). Moreover, a higher vessel density in the peri-infarct region indicated a better collateralization in rats that were injected with ATG. Conclusions These data indicate that ATG, a therapeutic agent successfully applied in clinical transplant immunology, triggered cardioprotective effects after AMI that salvaged ischemic myocardium by down-regulation of p53. This might have raised the resistance against apoptotic cell death during ischemia. The combination of these mechanisms seems to be causative for improved cardiac function and less ventricular remodeling after experimental AMI.

High levels of lung resident CD4+CD28null cells in COPD: implications of autoimmunity

SummaryChronic obstructive pulmonary disease (COPD) is a worldwide burden and a major cause of death. Pathogenetic mechanisms underlying the disease are still largely unknown. However, a continuous toxic injury due to tobacco smoking leading to a self-maintaining inflammatory process is considered a key factor in the pathophysiology of the disease. Evidence that autoimmunity might be involved in the maintenance of COPD has been recently noticed with great interest.During the chronic phase of an autoimmune response, lymphocytes lose their costimulatory signals. Previously, CD4+CD28null cells were reported to be systemically heightened in COPD patients. However, a direct role of CD4+CD28null cells in the pathogenesis of COPD is still under discussion, since there is no evidence that CD4+CD28null cells originate from the lungs of diseased patients. Therefore, we evaluated lungs from end-stage COPD patients and compared the levels of tissue infiltrating CD4+CD28null cells to systemic levels. We could show that CD4+CD28null cells are present in high amounts in lung tissue obtained from COPD GOLD IV patients suggesting a direct involvement of those cells in the pathophysiology of COPD. Furthermore, purified lung-resident CD4+ cells showed a stable proliferative response to lung specific elastin and collagen.These results further corroborate the role of autoreactive CD4+ cells in the maintenance of the inflammatory destruction in COPD. Modulating CD4+ cell function might be a new promising tool for future therapeutic approaches.ZusammenfassungDie chronisch obstruktive Lungenerkrankung (COPD) zählt zu den häufigsten Todesursachen weltweit. Die der Erkrankung zu Grunde liegenden, pathogenetischen Mechanismen sind noch immer großteils unbekannt. Allerdings zählt eine kontinuierliche toxische Schädigung durch Rauchen, welche letztlich zu einer sich selbst-erhaltenden, entzündliche Reaktion führt, als pathophysiologischer Schlüsselfaktor. Hinweise, dass Autoimmunität beim Krankheitsprozess eine Rolle spielen könnte, haben kürzlich großes Aufsehen erregt.Während der chronischen Phase einer Autoimmunreaktion verlieren Lymphozyten ihre kostimulatorischen Signale. In früheren Studien konnte eine erhöhte Zahl von CD4+CD28null Zellen in der Zirkulation von COPD Patienten nachgewiesen werden. Allerdings ist eine direkte Beteiligung dieser CD4+CD28null Zellen an der Pathogenese der COPD umstritten, da es bis dato keinen Nachweis gibt, ob CD4+CD28null Zellen unmittelbar in der Lunge erkrankter Patienten entstehen. Im Rahmen dieser Studie wurden Lunge von Stadium IV COPD Patienten untersucht und die Zahl von Lungen-infiltrierenden CD4+CD28null Zellen mit der Anzahl an zirkulierenden CD4+CD28null Zellen verglichen.Es konnte gezeigt werden, dass CD4+CD28null Zellen in hoher Konzentration im Lungengewebe von COPD Patienten vorhanden sind. Dies lässt auf eine direkte Beteiligung dieser Zellen an der Pathophysiologie der COPD schließen. Zusätzlich zeigten aus dem Lungengewebe aufgereinigte CD4+ Zellen eine stabile proliferative Antwort auf lungenspezifisches Elastin und Kollagen.Diese Ergebnisse unterstützen die Autoimmunhypothese und die Rolle von autoreaktiven CD4+ Zellen in der COPD. Eine Modulation der CD4+ Zellfunktion könnte zukünftig therapeutisch genutzt werden.