Bone marrow-derived stem/progenitor cells: their use in clinical studies for the treatment of myocardial infarction

Research and application of hydrogel-encapsulated mesenchymal stem cells in the treatment of myocardial infarction

Myocardial infarction (MI) stands out as a highly lethal disease that poses a significant threat to global health. Worldwide, heart failure resulting from MI remains a leading cause of human mortality. Mesenchymal stem cell (MSC) therapy has emerged as a promising therapeutic approach, leveraging its intrinsic healing properties. Nevertheless, pervasive issues, including a low cell retention rate, suboptimal survival rate, and incomplete differentiation of MSCs, present formidable challenges for further research. The introduction and advancement of biomaterials have offered a novel avenue for the exploration of MSC therapy in MI, marking considerable progress thus far. Notably, hydrogels, among the representative biomaterials, have garnered extensive attention within the biomedical field. This review delves into recent advancements, specifically focusing on the application of hydrogels to augment MSC therapy for cardiac tissue regeneration in MI.

Investigating curcumin potential for diabetes cell therapy, in vitro and in vivo study

AIMS

An important obstacle on the way of cell-based therapy is the risk of tumorigenicity in the patients benefit from these transplanted cells due to undifferentiated cells which participate in transplantation. Curcumin, the main compound of spice turmeric -as one of the natural products-was demonstrated to possess effective anti-cancer properties, with no significant effect on normal cells in dose and/or time-dependent manner. Furthermore many studies have been accomplished using curcumin for diabetes treatment. Therefore in this study we examined the efficacy of IPCs treated with curcumin in vivo.

MAIN METHODS

Differentiation efficiency investigated by flowcytometry. RNA extraction and real-time PCR performed for important genes in IPC differentiation and tumorigenesis including Insulin, Nestin, Ngn3, Pdx1, P21, and P53. Finally we investigated the efficiency of these differentiated and treated cells in diabetic rats.

KEY FINDINGS

Our data indicates that nanocurcumin -in a specific dose-reduces the expression of Nestin with no significant effect on insulin expression in mRNA and protein level. Besides blood glucose level of diabetic rats which treated with DNC + cells, decreased from average 350 (mg/dI) to 100 (mg/dI). Checking out the pancreases of these rats, demonstrated that their endocrine segment was rebuilt. Moreover hematoxylin & eosin staining and IF results revealed that the Langerhans Islands were reformed.

SIGNIFICANCE

IPCs' which treated with DNC were able to efficiently control the blood glucose level in diabetic rats which these cells were transplanted to them. Hence Curcumin has the potential to be employed in this kind of cell therapy.

Mesenchymal stem cell therapy in the treatment of hip osteoarthritis

This study was performed to investigate the safety and efficacy of the intra-articular infusion of ex vivo expanded autologous bone marrow-derived mesenchymal stem cells (BM-MSC) to a cohort of patients with articular cartilage defects in the hip. The above rationale is sustained by the notion that MSCs express a chondrocyte differential potential and produce extracellular matrix molecules as well as regulatory signals, that may well contribute to cure the function of the damaged hip joint. A cohort of 10 patients with functional and radiological evidences of hip osteoarthritis, either in one or both legs, was included in the study. BM-MSC (the cell product) were prepared and infused into the damaged articulation(s) of each patient (60 × 10⁶ cells in 3 weekly/doses). Before and after completion of the cell infusion scheme, patients were evaluated (hip scores for pain, stiffness, physical function, range of motion), to assess whether the infusion of the respective cell product was beneficial. The intra-articular injection of three consecutive weekly doses of ex vivo expanded autologous BM-MSC to patients with articular cartilage defects in the hip and proved to be a safe and clinically effective treatment in the restoration of hip function and range of motion. In addition, the statistical significance of the above data is in line with the observation that the radiographic scores (Tönnis Classification of Osteoarthritis) of the damaged leg(s) remained without variation in 9 out of 10 patients, after the administration of the cell product.

Combined transplantation of mesenchymal stem cells and endothelial progenitor cells for tissue engineering: a systematic review and meta-analysis

BACKGROUND

Combined cell implantation has been widely applied in tissue engineering in recent years. In this meta-analysis, we aimed to establish whether the combined transplantation of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) promotes angiogenesis and tissue repair, compared with transplantation of a single cell type, following tissue injury or during tissue regeneration.

METHODS

The electronic databases PubMed, EMBASE, MEDLINE, Chinese Biomedical Literature, and China National Knowledge Infrastructure were searched in this systematic review and meta-analysis. Eighteen controlled preclinical studies involving MSC and EPC transplantation in animal models of disease, or in coculture in vitro, were included in this review. The vessel density and other functional indexes, which were classified according to the organ source, were used to evaluate the efficiency of cotransplantation. Publication bias was assessed.

RESULTS

There was no obvious difference in angiogenesis following combined cell transplantation (EPCs and MSCs) and transplantation of EPCs alone; however, an improvement in the function of damaged organs was observed following cotransplantation. In addition, combined cell transplantation significantly promoted tissue recovery in cardiovascular disease, cerebrovascular disease, and during bone regeneration. Compared with combined transplantation (EPCs and MSCs) and transplantation of MSCs alone, cotransplantation significantly promoted angiogenesis and bone regeneration, as well as vessel revascularization and tissue repair in cerebrovascular disease; however, no obvious effects on cardiovascular disease were observed.

CONCLUSIONS

As an exploratory field in the discipline of tissue engineering, MSC and EPC cotransplantation offers advantages, although it is essential to assess the feasibility of this approach before clinical trials can be performed.

Infections and cardiovascular disease: is Bartonella henselae contributing to this matter?

Cardiovascular disease is still the major cause of death worldwide despite the remarkable progress in its prevention and treatment. Endothelial progenitor cells (EPCs) have recently emerged as key players of vascular repair and regenerative medicine applied to cardiovascular disease. A large amount of effort has been put into discovering the factors that could aid or impair the number and function of EPCs, and also into characterizing these cells at the molecular level in order to facilitate their therapeutic applications in vascular disease. Interestingly, the major cardiovascular risk factors have been associated with reduced number and function of EPCs. The bacterial contribution to cardiovascular disease represents a long-standing controversy. The discovery that Bartonella henselae can infect and damage EPCs revitalizes the enduring debate about the microbiological contribution to atherosclerosis, thus allowing the hypothesis that this infection could impair the cardiovascular regenerative potential and increase the risk for cardiovascular disease. In this review, we summarize the rationale suggesting that Bartonella henselae could favour atherogenesis by infecting and damaging EPCs, thus reducing their vascular repair potential. These mechanisms suggest a novel link between communicable and non-communicable human diseases, and put forward the possibility that Bartonella henselae could enhance the susceptibility and worsen the prognosis in cardiovascular disease.

Macrophages modulate the viability and growth of human mesenchymal stem cells

Following myocardial infarction, tissue repair is mediated by the recruitment of monocytes and their subsequent differentiation into macrophages. Recent findings have revealed the dynamic changes in the presence of polarized macrophages with pro-inflammatory (M1) and anti-inflammatory (M2) properties during the early (acute) and late (chronic) stages of cardiac ischemia. Mesenchymal stem cells (MSCs) delivered into the injured myocardium as reparative cells are subjected to the effects of polarized macrophages and the inflammatory milieu. The present study investigated how cytokines and polarized macrophages associated with pro-inflammatory (M1) and anti-inflammatory (M2) responses affect the survival of MSCs. Human MSCs were studied using an in vitro platform with individual and combined M1 and M2 cytokines: IL-1β, IL-6, TNF-α, and IFN-γ (for M1), and IL-10, TGF-β1, TGF-β3, and VEGF (for M2). In addition, polarization molecules (M1: LPS and IFN-γ; M2: IL-4 and IL-13) and common chemokines (SDF-1 and MCP-1) found during inflammation were also studied. Indirect and direct co-cultures were conducted using M1 and M2 polarized human THP-1 monocytes. M2 macrophages and their associated cytokines supported the growth of hMSCs, while M1 macrophages and their associated cytokines inhibited the growth of hMSCs in vitro under certain conditions. These data imply that an anti-inflammatory (M2) environment is more accommodating to the therapeutic hMSCs than a pro-inflammatory (M1) environment at specific concentrations.

[The role of adult bone marrow derived mesenchymal stem cells in the repair of tissue injuries]

Mesenchymal stem cells, which reside in adult bone marrow are multipotent, have an excellent regeneration potential for tissue repair. These cells are able to differentiate in cell culture not only into mesodermal lineages but also into other lineages of ectodermal and endodermal cells. This regenerative process is assisted by application of bioactive molecules, specific growth factors and biomaterials (scaffolds). The cell therapy is successfully used in the treatment of bone defects, nonunions, osteoblasts formed from the mesenchymal stem cells. At present, there are encouraging data in the clinical practice. The mesenchymal stem cell seems to be successful in the regeneration of articular cartilage. There are further promising data for the application of mesenchymal stem cells in the treatment of myocardial infarction, neurologic diseases, liver and kidney diseases and injuries and diabetes mellitus. The aim of this review is to survey the molecular characteristics of mesenchymal stem cells and specific growth factors using the data of preclinical investigations and to call attention to their possible clinical application.

Mesenchymal stem cells and the treatment of conditions and diseases: the less glittering side of a conspicuous stem cell for basic research

Not too long ago, several motivated and forward-looking articles were published describing the cellular and molecular properties of mesenchymal stem cells (MSCs), specially highlighting their potential for self-renewal, commitment, differentiation, and maturation into specific mesoderm-derived lineages. A very influential publication of that period entitled "Mesenchymal stem cells: No longer second class marrow citizens" [1] raised the point of view that "…challenges to harness MSC cell therapy to treat diseases … need to wait for the full comprehension that marrow is a rich source of mesenchyme-derived cells whose potential is still far from fully appreciated." Whether or not the prophecy of Gerson was fulfilled, in the last 8 years it has become evident that infusing MSCs into patients suffering a variety of disorders represents a viable option for medical treatment. Accordingly, a vast number of articles have explored the privileged cellular and molecular features of MSCs prepared from sources other than the canonical, represented by the bone marrow. This review will provide more information neither related to the biological attractiveness of MSCs nor to the success after their clinical use. Rather, we would like to underscore several "critical and tangential" issues, not always discussed in biomedical publications, but relevant to the clinical utilization of bone-marrow-derived MSCs.

Paracrine proangiopoietic effects of human umbilical cord blood-derived purified CD133+ cells--implications for stem cell therapies in regenerative medicine

CD133+ cells purified from hematopoietic tissues are enriched mostly for hematopoietic stem/progenitor cells, but also contain some endothelial progenitor cells and very small embryonic-like stem cells. CD133+ cells, which are akin to CD34+ cells, are a potential source of stem cells in regenerative medicine. However, the lack of convincing donor-derived chimerism in the damaged organs of patients treated with these cells suggests that the improvement in function involves mechanisms other than a direct contribution to the damaged tissues. We hypothesized that CD133+ cells secrete several paracrine factors that play a major role in the positive effects observed after treatment and tested supernatants derived from these cells for the presence of such factors. We observed that CD133+ cells and CD133+ cell-derived microvesicles (MVs) express mRNAs for several antiapoptotic and proangiopoietic factors, including kit ligand, insulin growth factor-1, vascular endothelial growth factor, basic fibroblast growth factor, and interleukin-8. These factors were also detected in a CD133+ cell-derived conditioned medium (CM). More important, the CD133+ cell-derived CM and MVs chemoattracted endothelial cells and display proangiopoietic activity both in vitro and in vivo assays. This observation should be taken into consideration when evaluating clinical outcomes from purified CD133+ cell therapies in regenerative medicine.

Bone marrow mesenchymal stem cells can differentiate and assume corneal keratocyte phenotype

It remains elusive as to what bone marrow (BM) cell types infiltrate into injured and/or diseased tissues and subsequently differentiate to assume the phenotype of residential cells, for example, neurons, cardiac myocytes, keratocytes, etc., to repair damaged tissue. Here, we examined the possibility of whether BM cell invasion via circulation into uninjured and injured corneas could assume a keratocyte phenotype, using chimeric mice generated by transplantation of enhanced green fluorescent protein (EGFP)⁺ BM cells into keratocan null (Kera^−/−) and lumican null (Lum^−/−) mice. EGFP⁺ BM cells assumed dendritic cell morphology, but failed to synthesize corneal-specific keratan sulfate proteoglycans, that is KS-lumican and KS-keratocan. In contrast, some EGFP⁺ BM cells introduced by intrastromal transplantation assumed keratocyte phenotypes. Furthermore, BM cells were isolated from Kera-Cre/ZEG mice, a double transgenic mouse line in which cells expressing keratocan become EGFP⁺ due to the synthesis of Cre driven by keratocan promoter. Three days after corneal and conjunctival transplantations of such BM cells into Kera^−/− mice, green keratocan positive cells were found in the cornea, but not in conjunctiva. It is worthy to note that transplanted BM cells were rejected in 4 weeks. MSC isolated from BM were used to examine if BM mesenchymal stem cells (BM-MSC) could assume keratocyte phenotype. When BM-MSC were intrastromal-transplanted into Kera^−/− mice, they survived in the cornea without any immune and inflammatory responses and expressed keratocan in Kera^−/− mice. These observations suggest that corneal intrastromal transplantation of BM-MSC may be an effective treatment regimen for corneal diseases involving dysfunction of keratocytes.

Ensheathing cell-conditioned medium directs the differentiation of human umbilical cord blood cells into aldynoglial phenotype cells

Despite their similarities to bone marrow precursor cells (PC), human umbilical cord blood (HUCB) PCs are more immature and, thus, they exhibit greater plasticity. This plasticity is evident by their ability to proliferate and spontaneously differentiate into almost any cell type, depending on their environment. Moreover, HUCB-PCs yield an accessible cell population that can be grown in culture and differentiated into glial, neuronal and other cell phenotypes. HUCB-PCs offer many potential therapeutic benefits, particularly in the area of neural replacement. We sought to induce the differentiation of HUCB-PCs into glial cells, known as aldynoglia. These cells can promote neuronal regeneration after lesion and they can be transplanted into areas affected by several pathologies, which represents an important therapeutic strategy to treat central nervous system damage. To induce differentiation to the aldynoglia phenotype, HUCB-PCs were exposed to different culture media. Mononuclear cells from HUCB were isolated and purified by identification of CD34 and CD133 antigens, and after 12 days in culture, differentiation of CD34+ HUCB-PCs to an aldynoglia phenotypic, but not that of CD133+ cells, was induced in ensheathing cell (EC)-conditioned medium. Thus, we demonstrate that the differentiation of HUCB-PCs into aldynoglia cells in EC-conditioned medium can provide a new source of aldynoglial cells for use in transplants to treat injuries or neurodegenerative diseases.

Bone marrow-derived mesenchymal stem cells enhance cryopreserved trachea allograft epithelium regeneration and vascular endothelial growth factor expression

BACKGROUND

Epithelium regeneration and revascularization of tracheal implants are challenging issues to be solved in tracheal transplantation research. Bone marrow-derived mesenchymal stem cells (BMSCs) can migrate to the damaged tissue and promote functional restoration. Here, we applied intravenous transplantation of BMSCs combined with a cryopreserved allograft to investigate the role of BMSCs in enhancing implant survival, tracheal epithelium regeneration and revascularization.

METHODS

After transplantation with cryopreserved allografts, PKH-26 labeled 3 to 5 passage BMSCs were injected into recipient rats through the tail vein. Rats in the control groups were injected with a comparable amount of phosphate-buffered saline. We observed the histology of the tracheal allograft and measured vascular endothelial growth factor (VEGF) protein levels in the epithelium to evaluate the effect of BMSCs on epithelium regeneration and revascularization.

RESULTS

Histologic observation of the rats from the BMSCs injection groups showed that the tracheal lumen was covered by pseudostriated ciliated columnar epithelium. The cartilage structure was intact. There were no signs of denaturation or necrosis. PKH-26 labeled BMSCs migrated to the implant site and exhibited red fluorescence, with the brightest red fluorescence at the anastomotic site. VEGF protein levels in the allograft epithelium of the BMSCs injection group were higher than the levels in the phosphate-buffered saline injection group.

CONCLUSIONS

Our results indicate that given systemic administration, BMSCs may enhance epithelium regeneration and revascularization by upregulating VEGF expression.

Dual-modal tracking of transplanted mesenchymal stem cells after myocardial infarction

PURPOSE

Results for implantation efficiency and effective improvement of cardiac function in the field of mesenchymal stem cells (MSCs) are controversial. To attempt to clarify this debate, we utilized magnetic resonance imaging (MRI) and near-infrared optical imaging (OI) to explore the effects of different delivery modes of mesenchymal stem cells on cell retention time and cardiac function after myocardial infarction (MI).

METHODS

Rat MSCs were labeled with superparamagnetic iron oxide nanoparticles and 1, 1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt (DiD) for noninvasive cell tracking in a rat MI model. Rats underwent coronary artery ligation and were randomized into three experimental groups: intravenous (IV), intramyocardial (IM), and a control group. The first two groups referred to the route of delivery of the transplanted dual-labeled MSCs; whereas the control group was given an IV injection of serum-free medium one day post-MI. Cellular engraftment was determined 1 day and 7 days post cell delivery by measuring the iron and optical signals in explanted organs. Prussian blue staining and fluorescent microscopy were performed on histological sections for iron and DiD, respectively. Cardiac function was measured by echocardiography on day 7.

RESULTS

The cardiac function of the IM group increased significantly compared to the IV and control groups at day 7. In the IM group, labeled cells were visualized in the infracted heart by serial MRI, and the intensity by OI was significantly higher on day 1. In the IV group, the heart signals were significantly attenuated by dual-modal tracking at two time points, but the lung signals in OI were significantly stronger than the IM group at both time points.

CONCLUSION

IM injection of MSCs increased cell engraftment within infarcted hearts and improved cardiac function after MI. However, IV infusion has a low efficacy due to the cell trapping in the lung. Therefore, direct injection may provide an advantage over IV, with regard to retention of stem cells and protection of cardiac function.

Risk factors in the development of stem cell therapy

Stem cell therapy holds the promise to treat degenerative diseases, cancer and repair of damaged tissues for which there are currently no or limited therapeutic options. The potential of stem cell therapies has long been recognised and the creation of induced pluripotent stem cells (iPSC) has boosted the stem cell field leading to increasing development and scientific knowledge. Despite the clinical potential of stem cell based medicinal products there are also potential and unanticipated risks. These risks deserve a thorough discussion within the perspective of current scientific knowledge and experience. Evaluation of potential risks should be a prerequisite step before clinical use of stem cell based medicinal products.

The risk profile of stem cell based medicinal products depends on many risk factors, which include the type of stem cells, their differentiation status and proliferation capacity, the route of administration, the intended location, in vitro culture and/or other manipulation steps, irreversibility of treatment, need/possibility for concurrent tissue regeneration in case of irreversible tissue loss, and long-term survival of engrafted cells. Together these factors determine the risk profile associated with a stem cell based medicinal product. The identified risks (i.e. risks identified in clinical experience) or potential/theoretical risks (i.e. risks observed in animal studies) include tumour formation, unwanted immune responses and the transmission of adventitious agents.

Currently, there is no clinical experience with pluripotent stem cells (i.e. embryonal stem cells and iPSC). Based on their characteristics of unlimited self-renewal and high proliferation rate the risks associated with a product containing these cells (e.g. risk on tumour formation) are considered high, if not perceived to be unacceptable. In contrast, the vast majority of small-sized clinical trials conducted with mesenchymal stem/stromal cells (MSC) in regenerative medicine applications has not reported major health concerns, suggesting that MSC therapies could be relatively safe. However, in some clinical trials serious adverse events have been reported, which emphasizes the need for additional knowledge, particularly with regard to biological mechanisms and long term safety.

Myocardial implantation of a combination stem cell product by using a transendocardial MYOSTAR injection catheter: A technical assessment

AIM

Different types of progenitor cells have been used to improve cardiac conditions after myocardial infarction (MI). Results have shown that while the infusion of a single cell type is safe and feasible, efficacy is modest. Recently, the use of a combination, rather than a single, stem cell product has emerged as an attractive option to improve cardiac outcome after a MI. Before initiating a phase II clinical trial to assess safety and efficacy after the transendocardial infusion of a combination stem cell product, a bench testing assay was designed to validate that delivery through the injection catheter is not associated with cell loss/damage. The latter is important since mesenchymal stem cells (MSC), a component of the cell product, consist of large cells expressing matrix molecules and adhesive receptors.

METHODS

The cell product (a mixture of mononuclear cells and MSC) was sequentially injected through a Myostar injection catheter. Exiting fractions were assessed for cell number, viability, capability to restart cell growth and immunophenotype.

RESULTS

Cell recovery and viability were high. In turn, exiting cells preserved their biological properties and immunophenotype.

CONCLUSIONS

Delivery of cells through a Myostar catheter is safe and not associated with changes in cell survival and/or properties.

Endothelial progenitor cells as factors in neovascularization and endothelial repair

Endothelial progenitor cells (EPCs) are a heterogeneous population of cells that are provided by the bone marrow and other adult tissue in both animals and humans. They express both hematopoietic and endothelial surface markers, which challenge the classic dogma that the presumed differentiation of cells into angioblasts and subsequent endothelial and vascular differentiation occurred exclusively in embryonic development. This breakthrough stimulated research to understand the mechanism(s) underlying their physiologic function to allow development of new therapeutic options. One focus has been on their ability to form new vessels in injured tissues, and another has been on their ability to repair endothelial damage and restore both monolayer integrity and endothelial function in denuded vessels. Moreover, measures of their density have been shown to be a better predictor of cardiovascular events, both in healthy and coronary artery disease populations than the classical tools used in the clinic to evaluate the risk stratification. In the present paper we review the effects of EPCs on revascularization and endothelial repair in animal models and human studies, in an attempt to better understand their function, which may lead to potential advancement in clinical management.

Combination stem cell therapy for the treatment of medically refractory coronary ischemia: a Phase I study

PURPOSE

Infusion of a source of endothelial progenitor cells (EPC) into the ischemic myocardium is emerging as a promising therapy for coronary ischemia, probably mediated by the formation of new blood vessels. Studies have shown that while the procedure is safe and feasible, efficacy results are contentious. The investigators hypothesized that the infusion of a combination cell product consisting of a source of EPC and mesenchymal stem cells (MSC) is safe and promotes the formation of more stable and mature blood vessels resulting in improved clinical outcomes.

METHODS

Ten patients with stable angina pectoris (class III to IV) on maximal medical therapy were included. All patients had ≥ 70% stenosis in at least one coronary artery, and none was considered a candidate for percutaneous coronary intervention or coronary artery bypass graft. End points were feasibility and safety of intracoronary infusion of the combination cell product and assessment of myocardial ischemia, left ventricular ejection fraction (LVEF), and quality of life at 6 months postinfusion.

RESULTS

Six months after cell infusion there were no adverse clinical events. Functional cardiac evaluation during the same period showed significant improvements in LVEF (average increase: 11%, P = .02) and myocardial ischemia (average decrease: 1.8 fold, P = .02). Additionally, all patients described significant improvements in quality of life.

CONCLUSIONS

Despite the inherent limitations associated with a Phase I clinical trial, this study demonstrates that the intracoronary infusion of the combination cell product is feasible and safe and also insinuates that this form of therapy may be beneficial.

Hypoxic preconditioning induces the expression of prosurvival and proangiogenic markers in mesenchymal stem cells

Stem cells transplanted to the ischemic myocardium usually encounter massive cell death within a few days of therapy. Hypoxic preconditioning (HPC) is currently employed as a strategy to prepare stem cells for increased survival and engraftment in the heart. However, HPC of stem cells has provided varying results, supposedly due to the differences in the oxygen concentration, duration of exposure, and passage conditions. In the present study, we determined the effect of HPC on rat mesenchymal stem cells (MSCs) exposed to 0.5% oxygen concentration for 24, 48, or 72 h. We evaluated the expression of prosurvival, proangiogenic, and functional markers such as hypoxia-inducible factor-1α, VEGF, phosphorylated Akt, survivin, p21, cytochrome c, caspase-3, caspase-7, CXCR4, and c-Met. MSCs exposed to 24-h hypoxia showed reduced apoptosis on being subjected to severe hypoxic conditions. They also had significantly higher levels of prosurvival, proangiogenic, and prodifferentiation proteins when compared with longer exposure (72 h). Cells taken directly from the cryopreserved state did not respond effectively to the 24-h HPC as those that were cultured under normoxia before HPC. Cells cultured under normoxia before HPC showed decreased apoptosis, enhanced expression of connexin-43, cardiac myosin heavy chain, and CD31. The preconditioned cells were able to differentiate into the cardiovascular lineage. The results suggest that MSCs cultured under normoxia before 24-h HPC are in a state of optimal expression of prosurvival, proangiogenic, and functional proteins that may increase the survival and engraftment in the infarct heart. These results could provide further insights into optimal preparation of MSCs which would greatly influence the effectiveness of cell therapy in vivo.

Improved heart function follows enhanced inflammatory cell recruitment and angiogenesis in 11betaHSD1-deficient mice post-MI

AIMS

Mice unable to locally regenerate corticosterone due to deficiency of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) have enhanced angiogenesis during acute myocardial infarct healing. The present study investigates the hypotheses that in these mice (i) inflammation and angiogenic signalling are promoted and (ii) longer-term remodelling and function are improved.

METHODS AND RESULTS

Myocardial infarction (MI) was induced by coronary artery ligation in 11βHSD1(-/-) and wild-type (C57BL/6) mice. Studies were terminated 2, 4, 7, and 28 days post-surgery. Increased vessel density (CD31 immunoreactivity) on the infarct border was confirmed 7 days after MI in 11βHSD1(-/-) hearts (P < 0.05) and was accompanied by improved ejection fraction (ultrasound) compared with C57BL/6. During wound healing, recruitment of neutrophils (at 2 days after MI) and macrophages (from 4 days after MI) and expression of monocyte-chemoattractant protein-1 was increased in 11βHSD1(-/-) compared with C57BL/6 hearts (P < 0.05). Recruitment of alternatively activated YM1-positive macrophages was particularly enhanced in the period preceding increased vessel density and was accompanied by increased expression of pro-angiogenic IL-8. By 28 days post-MI, when the infarct scar had matured, higher vessel density was maintained in 11βHSD1(-/-) hearts and vessels were smooth-muscle coated. Infarct scars were thicker (P < 0.001) in 11βHSD1(-/-) compared with C57BL/6 hearts and ejection fraction was higher (P < 0.05).

CONCLUSION

Increased vessel density in healing infarcts of mice deficient in 11(-/-)HSD1 follows recruitment of pro-reparative macrophages and increased pro-angiogenic signalling. Mature infarcts show less thinning and cardiac function is improved relative to wild-type mice, suggesting that 11βHSD1 may be a novel therapeutic target after MI.

Cell therapy of congenital corneal diseases with umbilical mesenchymal stem cells: lumican null mice

BACKGROUND

Keratoplasty is the most effective treatment for corneal blindness, but suboptimal medical conditions and lack of qualified medical personnel and donated cornea often prevent the performance of corneal transplantation in developing countries. Our study aims to develop alternative treatment regimens for congenital corneal diseases of genetic mutation.

METHODOLOGY/PRINCIPAL FINDINGS

Human mesenchymal stem cells isolated from neonatal umbilical cords were transplanted to treat thin and cloudy corneas of lumican null mice. Transplantation of umbilical mesenchymal stem cells significantly improved corneal transparency and increased stromal thickness of lumican null mice, but human umbilical hematopoietic stem cells failed to do the same. Further studies revealed that collagen lamellae were re-organized in corneal stroma of lumican null mice after mesenchymal stem cell transplantation. Transplanted umbilical mesenchymal stem cells survived in the mouse corneal stroma for more than 3 months with little or no graft rejection. In addition, these cells assumed a keratocyte phenotype, e.g., dendritic morphology, quiescence, expression of keratocyte unique keratan sulfated keratocan and lumican, and CD34. Moreover, umbilical mesenchymal stem cell transplantation improved host keratocyte functions, which was verified by enhanced expression of keratocan and aldehyde dehydrogenase class 3A1 in lumican null mice.

CONCLUSIONS/SIGNIFICANCE

Umbilical mesenchymal stem cell transplantation is a promising treatment for congenital corneal diseases involving keratocyte dysfunction. Unlike donated corneas, umbilical mesenchymal stem cells are easily isolated, expanded, stored, and can be quickly recovered from liquid nitrogen when a patient is in urgent need.

Clinical potential of adult vascular progenitor cells

Cell therapy to treat vascular and cardiovascular diseases has evolved over the past decade with improved understanding of progenitor cell mobilization, recruitment, and differentiation. The beneficial effects seen in several preclinical studies have prompted translation of adult vascular progenitor therapy to clinical trials. To date, progenitor cells isolated from bone marrow and peripheral blood have been tested in the context of acute myocardial infarction and chronic ischemic cardiomyopathy, with moderate benefit. This therapeutic effect occurs despite a relatively small number of injected progenitor cells and short-term residence in the target zone. Thus, indirect benefits, such as paracrine factors released from these cells, have been suggested as significant contributors to therapeutic efficacy. Several additional vascular progenitors of endothelial, smooth muscle, mesenchymal, and cardiac origin have been identified that may contribute to vasculogenesis. Indeed, a unifying paradigm for the most effective cell therapy strategies to date appears to be robust support of angiogenesis. Here we discuss a number of progenitor cells that currently show potential as cardiovascular therapeutics, either singly or in combination. We look at emerging cell types and disease targets that may be exploited for therapeutic benefit and future strategies that may maximize clinical efficacy.

Stem cell therapy in acute myocardial infarction: a review of clinical trials

Stem cells (SCs) possess the ability to differentiate into cells of various tissues. Although the differentiation of SCs into functional cardiomyocytes has been difficult to demonstrate in humans, clinical trials using SCs in the setting of acute myocardial infarction (AMI) have demonstrated variable results. Interpretation of these trials has been difficult because of multiple variables, which include differences in trial design, cell type, timing of cell delivery, and outcome measurements. Herein, a summary of all clinical trials in subgroups of direct injection, indirect mobilization, and combination approaches of SC therapy in AMI is provided with significant findings in each group.

Stem cell-like human endothelial progenitors show enhanced colony-forming capacity after brief sevoflurane exposure: preconditioning of angiogenic cells by volatile anesthetics

BACKGROUND

Endothelial progenitor cells play a pivotal role in tissue repair, and thus are used for cell replacement therapies in "regenerative medicine." We tested whether the anesthetic sevoflurane would modulate growth or mobilization of these angiogenic cells.

METHODS

In an in vitro model, mononuclear cells isolated from peripheral blood of healthy donors were preconditioned with sevoflurane (3 times 30 min at 2 vol% interspersed by 30 min of air). Colony-forming units were determined after 9 days in culture and compared with time-matched untreated control. Using magnetic cell sorting, CD133+/CD34+ endothelial progenitors were enriched from human umbilical cord blood, and vascular endothelial growth factor (VEGF), VEGFR2 (KDR), granulocyte colony-stimulating factor (G-CSF), STAT3, c-kit, and CXCR4 expressions were determined in sevoflurane-treated and untreated cells by real-time reverse transcriptase polymerase chain reaction. In a volunteer study with crossover design, we tested whether sevoflurane inhalation (<1 vol% end-tidal concentration) would mobilize endothelial progenitor cells from the bone marrow niche into the circulation using flow cytometry of peripheral blood samples. VEGF and G-CSF plasma levels were also measured.

RESULTS

In vitro sevoflurane exposure of mononuclear cells enhanced colony-forming capacity and increased VEGF mRNA levels in CD133+/CD34+ cord blood cells (P = 0.017). Sevoflurane inhalation in healthy volunteers did not alter the number of CD133+/CD34+ or KDR+/CD34+ endothelial progenitors in the circulation, but increased the number of colony-forming units (P = 0.034), whereas VEGF and G-CSF plasma levels remained unchanged.

CONCLUSIONS

Sevoflurane preconditioning promotes growth and proliferation of stem cell-like human endothelial progenitors. Hence, it may be used to promote perioperative vascular healing and to support cell replacement therapies.