Characterization of slow cycling corneal limbal epithelial cells identifies putative stem cell markers

In order to identify reliable markers of corneal epithelial stem cells, we employed an inducible transgenic “pulse-chase” murine model (K5Tta × TRE-H2BGFP) to localize, purify, and characterize slow cycling cells in the cornea. The retention of GFP labeling in slowly dividing cells allowed for localization of these cells to the corneal limbus and their subsequent purification by FACS. Transcriptome analysis from slow cycling cells identified differentially expressed genes when comparing to GFP^- faster-dividing cells. RNA-Seq data from corneal epithelium were compared to epidermal hair follicle stem cell RNA-Seq to identify genes representing common putative stem cell markers or determinants, which included Sox9, Fzd7, Actn1, Anxa3 and Krt17. Overlapping retention of GFP and immunohistochemical expression of Krt15, ΔNp63, Sox9, Actn1, Fzd7 and Krt17 were observed in our transgenic model. Our analysis presents an array of novel genes as putative corneal stem cell markers.

Evaluation of Accessory Lacrimal Gland in Muller's Muscle Conjunctival Resection Specimens for Precursor Cell Markers and Biological Markers of Dry Eye Disease

PURPOSE

The accessory lacrimal glands (ALGs) are an understudied component of the tear functional unit, even though they are important in the development of dry eye syndrome (DES). To advance our understanding of aging changes, regenerative potential, and histologic correlates to human characteristics, we investigated human ALG tissue from surgical samples to determine the presence or absence of progenitor cell markers and lacrimal epithelial markers and to correlate marker expression to relevant patient characteristics.

MATERIALS AND METHODS

ALG tissues obtained from Muller's muscle conjunctival resection (MMCR) specimens were created using tissue microarrays (TMAs). Immunofluorescence staining of MMCR sections was performed using primary antibodies specific to cell protein markers. Cell marker localization in TMAs was then assessed by two blinded observers using a standardized scoring system. Patient characteristics including age, race, and status of ocular surface health were then compared against expression of stem cell markers.

RESULTS

Human ALG expressed a number of epithelial markers, and in particular, histatin-1 was well correlated with the expression of epithelial markers and was present in most acini. In addition, we noted the presence of precursor cell markers nestin, ABCG2, and CD90 in ALG tissue. There was a decrease in precursor cell marker expression with increasing age. Finally, we noted that a negative association was present between histatin-1 expression and DES.

CONCLUSIONS

Thus, we report for the first time that human ALG tissues contain precursor marker-positive cells and that this marker expression may decrease with increasing age. Moreover, histatin-1 expression may be decreased in DES. Future studies will be performed to use these cell markers to isolate and culture lacrimal epithelial cells from heterogeneous tissues, determine the relevance of histatin-1 expression to DES, and isolate candidate precursor cells from ALG tissue.

Heat shock improves Sca-1+ stem cell survival and directs ischemic cardiomyocytes toward a prosurvival phenotype via exosomal transfer: a critical role for HSF1/miR-34a/HSP70 pathway

Stem cell-based therapy is a promising intervention for ischemic heart diseases. However, the functional integrity of stem cells is impaired in an ischemic environment. Here, we report a novel finding that heat shock significantly improves Sca-1(+) stem cell survival in an ischemic environment by the regulation of the triangle: heat shock factor 1 (HSF1), HSF1/miR-34a, and heat shock protein 70 (HSP70). Initially we prove that HSP70 is the key chaperone-mediating cytoprotective effect of heat shock in Sca-1(+) cells and then we establish miR-34a as a direct repressor of HSP70. We found that miR-34a was downregulated in heat shocked Sca-11 stem cells (HSSca-11 cells) [corrected]. Intriguingly, we demonstrate that the downregulation of miR-34a is attributed to HSF1-mediated epigenetic repression through histone H3 Lys27 trimethylation (H3K27me3) on miR-34a promoter. Moreover, we show that heat shock induces exosomal transfer of HSF1 from Sca-1(+) cells, which directs ischemic cardiomyocytes toward a prosurvival phenotype by epigenetic repression of miR-34a. In addition, our in vivo study demonstrates that transplantation of (HS) Sca-1(+) cells significantly reduces apoptosis, attenuates fibrosis, and improves global heart functions in ischemic myocardium. Hence, our study provides not only novel insights into the effects of heat shock on stem cell survival and paracrine behavior but also may have therapeutic values for stem cell therapy in ischemic heart diseases.

Reversal of ischemic cardiomyopathy with Sca-1+ stem cells modified with multiple growth factors

Background

We hypothesized that bone marrow derived Sca-1⁺ stem cells (BM Sca-1⁺) transduced with multiple therapeutic cytokines with diverse effects will induce faster angiomyogenic differentiation in the infarcted myocardium.

Methods and Results

BM Sca-1⁺ were purified from transgenic male mice expressing GFP. Plasmids encoding for select quartet of growth factors, i.e., human IGF-1, VEGF, SDF-1α and HGF were prepared and used for genetic modification of Sca-1⁺ cells (^GFSca-1⁺). Scramble transfected cells (^ScSca-1⁺) were used as a control. RT-PCR and western blotting showed significantly higher expression of the growth factors in ^GFSca-1⁺. Besides the quartet of the therapeutic growth factors, PCR based growth factor array showed upregulation of multiple angiogenic and prosurvival factors such as Ang-1, Ang-2, MMP9, Cx43, BMP2, BMP5, FGF2, and NGF in ^GFSca-1⁺ (p<0.01 vs^ScSca-1⁺). LDH and TUNEL assays showed enhanced survival of ^GFSca-1⁺ under lethal anoxia (p<0.01 vs ^ScSca-1⁺). MTS assay showed significant increased cell proliferation in ^GFSca-1⁺ (p<0.05 vs^ScSca-1⁺). For in vivo study, female mice were grouped to receive the intramyocardial injection of 15 μl DMEM without cells (group-1) or containing 2.5×10^5ScSca-1⁺ (group-2) or ^GFSca-1⁺ (group-3) immediately after coronary artery ligation. As indicated by Sry gene, a higher survival of ^GFSca-1⁺ in group-3 on day4 (2.3 fold higher vs group-2) was observed with massive mobilization of stem and progenitor cells (cKit⁺, Mdr1⁺, Cxcr4⁺ cells). Heart tissue sections immunostained for actinin and Cx43 at 4 weeks post engraftment showed extensive myofiber formation and expression of gap junctions. Immunostaining for vWF showed increased blood vessel density in both peri-infarct and infarct regions in group-3. Infarct size was attenuated and the global heart function was improved in group-3 as compared to group-2.

Conclusions

Administration of BM Sca-1⁺ transduced with multiple genes is a novel approach to treat infarcted heart for its regeneration.

Cardiomyocyte protection by GATA-4 gene engineered mesenchymal stem cells is partially mediated by translocation of miR-221 in microvesicles

Introduction

microRNAs (miRs), a novel class of small non-coding RNAs, are involved in cell proliferation, differentiation, development, and death. In this study, we found that miR-221 translocation by microvesicles (MVs) plays an important role in cardioprotection mediated by GATA-4 overexpressed mesenchymal stem cells (MSC).

Methods and Results

Adult rat bone marrow MSC and neonatal rat ventricle cardiomyocytes (CM) were harvested as primary cultures. MSC were transduced with GATA-4 (MSC^GATA-4) using the murine stem cell virus (pMSCV) retroviral expression system. Empty vector transfection was used as a control (MSC^Null). The expression of miRs was assessed by real-time PCR and localized using in situ hybridization (ISH). MVs collected from MSC cultures were characterized by expression of CD9, CD63, and HSP70, and photographed with electron microscopy. Cardioprotection during hypoxia afforded by conditioned medium (CdM) from MSC cultures was evaluated by lactate dehydrogenase (LDH) release, MTS uptake by CM, and caspase 3/7 activity. Expression of miR-221/222 was significantly higher in MSC than in CM and miR-221 was upregulated in MSC^GATA-4. MSC overexpression of miR-221 significantly enhanced cardioprotection by reducing the expression of p53 upregulated modulator of apoptosis (PUMA). Moreover, expression of PUMA was significantly decreased in CM co-cultured with MSC. MVs derived from MSC expressed high levels of miR-221, and were internalized quickly by CM as documented in images obtained from a Time-Lapse Imaging System.

Conclusions

Our results demonstrate that cardioprotection by MSC^GATA-4 may be regulated in part by a transfer of anti-apoptotic miRs contained within MVs.

Protein kinase G1 α overexpression increases stem cell survival and cardiac function after myocardial infarction

BACKGROUND

We hypothesized that overexpression of cGMP-dependent protein kinase type 1α (PKG1α) could mimic the effect of tadalafil on the survival of bone marrow derived mesenchymal stem cells (MSCs) contributing to regeneration of the ischemic heart.

METHODS AND RESULTS

MSCs from male rats were transduced with adenoviral vector encoding for PKG1α ((PKG1α)MSCs).Controls included native MSCs ((Nat)MSCs) and MSCs transduced with an empty vector ((Null)MSCs). PKG1α activity was increased approximately 20, 5 and 16 fold respectively in (PKG1α)MSCs. (PKG1α)MSCs showed improved survival under oxygen and glucose deprivation (OGD) which was evidenced by lower LDH release, caspase-3/7 activity and number of positive TUNEL cells. Anti-apoptotic proteins pAkt, pGSK3β, and Bcl-2 were significantly increased in (PKG1α)MSCs compared to (Nat)MSCs and (Null)MSCs. Higher release of multiple prosurvival and angiogenic factors such as HGF, bFGF, SDF-1 and Ang-1 was observed in (PKG1α)MSCs before and after OGD. In a female rat model of acute myocardial infarction, (PKG1α)MSCs group showed higher survival compared with (Null)MSCs group at 3 and 7 days after transplantation as determined by TUNEL staining and sry-gene quantitation by real-time PCR. Increased anti-apoptotic proteins and paracrine factors in vitro were also identified. Immunostaining for cardiac troponin I combined with GFP showed increased myogenic differentiation of (PKG1α)MSCs. At 4 weeks after transplantation, compared to DMEM group and (Null)MSCs group, (PKG1α)MSCs group showed increased blood vessel density in infarct and peri-infarct areas (62.5±7.7; 68.8±7.3 per microscopic view, p<0.05) and attenuated infarct size (27.2±2.5%, p<0.01). Heart function indices including ejection fraction (52.1±2.2%, p<0.01) and fractional shortening (24.8%±1.3%, p<0.01) were improved significantly in (PKG1α)MSCs group.

CONCLUSION

Overexpression of PKG1α transgene could be a powerful approach to improve MSCs survival and their angiomyogenic potential in the infarcted heart.

Abstract 364: Valproic Acid Induced Reprogramming of Adult Somatic Cells for Cardiac Differentiation

Aims: Owing to the ethical concerns for use of embryonic stem cells (ESC), adult somatic cells are attractive stem cell sources for reprogramming to pluripotency. We report here non-viral approach for reprogramming of skeletal myoblasts (SM) using a small molecule.

Methods and Results: SM purified from young male Oct3/4-GFP+ transgenic mouse were treated for 5 days with valproic acid (VPA), a histone deacetylase (HDAC) inhibitor. Three weeks later, GFP+ colonies of SM derived iPSC (Sk-iPS) resembling with mouse embryonic stem cells were observed and propagated in vitro. SiPS were positive for alkaline phosphatase, had normal karyotype, expressed SSEA1, and induced teratomas in nude mice containing tissue comprising all three germ layers. RT PCR analysis showed that Sk-iPS cells expressed Oct4, Sox2, KLF4, c-Myc, Nanog and ESC specific pluripotency genes. HDAC1 activity was significantly reduced in Sk-iPs generated with valproic acid treatment as compared to ES cells. Sk-iPS derived embryoid bodies (EBs) yielded spontaneously contracting cardiomyocytes with morphological, molecular, and ultrastructural features of developing cardiomyocytes. These cells were also positive for early and late cardiac markers such as myosin heavy chain, Gata4, Mef-2c and Nkx2.5, Connexin-43 (P<0.01vs native SM). Micro RNA (miR) profiling showed abolition of let-7 family in Sk-iPS whereas ESC specific family of miR-290-295 was upregulated which indicated that Sk-iPS possessed miR profile similar to ESC. However muscle specific miRNAs (miR -133, -206) were identified in Sk-iPS cells as compared to ES cells indicating that the Sk-iPS retained the epigenetic memory of myogenic origin.

Conclusions: We conclude that SM with endogenous expression of Sox2, KLF4, and cMyc are suitable candidates to generate iPS cells without viral vectors using a single small molecule.

GATA-4 promotes myocardial transdifferentiation of mesenchymal stromal cells via up-regulating IGFBP-4

BACKGROUND AIMS

GATA-4 is a cardiac transcription factor and plays an important role in cell lineage differentiation during development. We investigated whether overexpression of GATA-4 increases adult mesenchymal stromal cell (MSC) transdifferentiation into a cardiac phenotype in vitro.

METHODS

MSC were harvested from rat bone marrow (BM) and transduced with GATA-4 (MSC(GATA-4)) using a murine stem cell virus (pMSCV) retroviral expression system. Gene expression in MSC(GATA-4) was analyzed using quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. Native cardiomyocytes (CM) were isolated from ventricles of neonatal rats. Myocardial transdifferentiation of MSC was determined by immunostaining and electrophysiologic recording. The transdifferentiation rate was calculated directly from flow cytometery.

RESULTS

The expression of cardiac genes, including brain natriuretic peptide (BNP), Islet-1 and α-sarcomeric actinin (α-SA), was up-regulated in MSC(GATA-4) compared with control cells that were transfected with Green Fluorescent Protein (GFP) only (MSC(Null)). At the same time, insulin-like growth factor-binding protein (IGFBP)-4 was significantly up-regulated in MSC(GATA-4). A synchronous beating of MSC with native CM was detected and an action potential was recorded. Some GFP (+) cells were positive for α-SA staining after MSC were co-cultured with native CM for 7 days. The transdifferentiation rate was significantly higher in MSC(GATA-4). Functional studies indicated that the differentiation potential of MSC(GATA-4) was decreased by knockdown of IGFBP-4.

CONCLUSIONS

Overexpression of GATA-4 significantly increases MSC differentiation into a myocardial phenotype, which might be associated with the up-regulation of IGFBP-4.

Paracrine effect of Wnt11-overexpressing mesenchymal stem cells on ischemic injury

Our previous studies have suggested that transduction of Wnt11 directly increases bone marrow-derived mesenchymal stem cells (MSCs) differentiation into cardiac phenotypes. In this study, we investigated whether Wnt11 enhances MSC-mediated cardioprotection via paracrine fashion after acute ischemia. MSCs were harvested from male rat bone marrow and transduced with Wnt11 (MSC(Wnt11)). An acute myocardial infarction model in rats was developed by ligation of the left anterior descending coronary artery. MSC(Wnt11) were transplanted into the peri-infarct region after acute myocardial infarction. To mimic ischemic injury, cultured cardiomyocytes (CMs) isolated from neonatal ventricles were exposed to hypoxia. ELISA studies indicated that the release of Wnt11 (3.45-fold) as well as transforming growth factor-β2 (TGFβ2) (1.5-fold) was significantly increased from MSC(Wnt11) compared with transduced control MSC (MSC(Null)). Hypoxia-induced apoptosis and cell death was significantly reduced when CM were co-cultured with MSC(Wnt11) in a dual chamber system. The cell protection mediated by MSC(Wnt11) was mimicked by treating CM with conditioned medium obtained from MSC(Wnt11) and abrogated by Wnt11- and TGFβ2 neutralizing antibodies. Further, animals receiving MSC(Wnt11) showed a significant improvement in cardiac contractile function as assessed by echocardiography. Masson trichrome and TUNEL staining showed a significant reduction in infarct size and apoptosis of CM in MSC(Wnt11)-treated animals. Transplantation of MSC(Wnt11) improved cardiac function. The release of Wnt11 and other factors from transplanted MSC(Wnt11) is more likely responsible for protection of native CM at risk.

Modified Turkish delight: morcellized polyethylene dorsal graft for rhinoplasty

Rhinoplasty is one of the most challenging facial aesthetic procedures. Achieving a desirable result depends on correct planning and execution and the tissue characteristics of the patient. Dorsal augmentation has been performed extensively using cartilage grafts harvested from the septum, alar cartilage, conchal artilage and costal cartilages as well as from bone harvested from the ilium or tibia. Carved or crushed cartilage used as a graft might be perceptible through the nasal skin when tissue resolution is complete. Graft warpage and displacement are potential complications. The use of finely diced cartilage wrapped in one layer of Surgicel mixed with 1 ml of the patient's blood, popularly known as Turkish delight, was suggested by Erol in 2000. The use of cartilage from the septum and ala might not suffice and conchal and costal cartilage harvesting requires a second surgical site. Also, considering the increasing demand for revision rhinoplasty, it might not always be feasible to harvest an adequate quantity of graft. The authors suggest the use of finely diced Medpor implant material wrapped in Surgicel, mixed with 1 ml of the patient's blood for dorsal augmentation during rhinoplasty. Preliminary results are encouraging.

Transduction of Wnt11 promotes mesenchymal stem cell transdifferentiation into cardiac phenotypes

Transplantation of mesenchymal stem cells (MSCs) has emerged as a potential treatment for ischemic heart repair. Previous studies have suggested that Wnt11 plays a critical role in cardiac specification and morphogenesis. In this study, we examined whether transduction of Wnt11 directly increases MSC differentiation into cardiac phenotypes. MSCs harvested from rat bone marrow were transduced with both Wnt11 and green fluorescent protein (GFP) (MSC(Wnt11)) using the murine stem cell virus (pMSCV) retroviral expression system; control cells were only GFP-transfected (MSC(Null)). Compared with control cells, MSC(Wnt11) was shown to have higher expression of Wnt11 by immunofluorescence, real-time polymerase chain reaction, and western blotting. MSC(Wnt11) shows a higher expression of cardiac-specific genes, including GATA-4, brain natriuretic peptide (BNP), islet-1, and α-actinin, after being cultured with cardiomyocytes (CMs) isolated from ventricles of neonatal (1-3 day) SD rats. Some MSC(Wnt11) were positive for α-actinin when MSCs were cocultured with native CMs for 7 days. Electron microscopy further confirmed the appearance of sarcomeres in MSC(Wnt11). Connexin 43 was found between GFP-positive MSCs and neonatal rat CMs labeled with red fluorescent probe PKH26. The transdifferentiation rate was significantly higher in MSC(Wnt11) than in MSC(Null), as assessed by flow cytometry. Functional studies indicated that the differentiation of MSC(Wnt11) was diminished by knockdown of GATA-4 with GATA-4-siRNA. Transduction of Wnt11 into MSCs increases their differentiation into CMs by upregulating GATA-4.

Paracrine factors released by GATA-4 overexpressed mesenchymal stem cells increase angiogenesis and cell survival

Transplanted mesenchymal stem cells (MSC) release soluble factors that contribute to cardiac repair and vascular regeneration. We hypothesized that overexpression of GATA-4 enhances the MSC secretome, thereby increasing cell survival and promoting postinfarction cardiac angiogenesis. MSCs harvested from male rat bone marrow were transduced with GATA-4 (MSC(GATA-4)) using the murine stem cell virus retroviral expression system; control cells were either nontransduced (MSC(bas)) or transduced with empty vector (MSC(Null)). Compared with these control cells, MSC(GATA-4) were shown by immunofluorescence, real-time PCR, and Western blotting to have higher expression of GATA-4. An increased expression of angiogenic factors in MSC(GATA-4) and higher MSC resistance against hypoxia were observed. Human umbilical vein endothelial cells (HUVEC) treated with MSC(GATA-4) conditioned medium exhibited increased formation of capillary-like structures and promoted migration, compared with HUVECs treated with MSC(Null) conditioned medium. MSC(GATA-4) were injected into the peri-infarct region in an acute myocardial infarction model in Sprague-Dawley rats developed by ligation of the left anterior descending coronary artery. Survival of MSC(GATA-4), determined by Sry expression, was increased at 4 days postengraftment. MSC(GATA-4)-treated animals showed significantly improved cardiac function as assessed by echocardiography. Furthermore, fluorescent microsphere and histological studies revealed increased blood flow and blood vessel density and reduced infarction size in MSC(GATA-4)-treated animals. We conclude that GATA-4 overexpression in MSCs increased both MSC survival and angiogenic potential in ischemic myocardium and may therefore represent a novel and efficient therapeutic approach for postinfarct remodeling.

Over-expression of CXCR4 on mesenchymal stem cells augments myoangiogenesis in the infarcted myocardium

Bone marrow mesenchymal stem cells (MSCs) participate in myocardial repair following myocardial infarction. However, their in vivo reparative capability is limited due to lack of their survival in the infarcted myocardium. To overcome this limitation, we genetically engineered male rat MSCs overexpressing CXCR4 in order to maximize the effect of stromal cell-derived factor-1alpha (SDF-1alpha) for cell migration and regeneration. MSCs were isolated from adult male rats and cultured. Adenoviral transduction was carried out to over-express either CXCR4/green fluorescent protein (Ad-CXCR4/GFP) or Ad-null/GFP alone (control). Flow cytometry was used to identify and isolate GFP/CXCR4 over-expressing MSCs for transplantation. Female rats were assigned to one of four groups (n=8 each) to receive GFP-transduced male MSCs (2 x 10(6)) via tail vein injection 3 days after ligation of the left anterior descending (LAD) coronary artery: GFP-transduced MSCs (Ad-null/GFP-MSCs, group 1) or MSCs over-expressing CXCR4/GFP (Ad-CXCR4/GFP-MSCs, group 2), or Ad-CXCR4/GFP-MSCs plus SDF-1alpha (50 ng/microl) (Ad-CXCR4/GFP-MSCs/SDF-1alpha, group 3), or Ad-miRNA targeting CXCR4 plus SDF-1alpha (Ad-miRNA/GFP-MSCs+SDF-1alpha treatment, group 4). Cardiodynamic data were obtained 4 weeks after induction of regional myocardial infarction (MI) using echocardiography after which hearts were harvested for immunohistochemical studies. The migration of GFP and Y-chromosome positive cells increased significantly in the peri- and infarct areas of groups 2 and 3 compared to control group (p<0.05), or miRNA-CXCR4 group (p<0.01). The number of CXCR4 positive cells in groups 2, 3 was intimately associated with angiogenesis and myogenesis. MSCs engraftment was blocked by pretreatment with miRNA (group 4). Cardiac function was significantly improved in rats receiving MSCs over-expressing CXCR4 alone or with SDF-1alpha. The up-regulation of matrix metalloproteinases (MMPs) by CXCR4 overexpressing MSCs perhaps facilitated their engraftment in the collagenous tissue of the infarcted area. CXCR4 over-expression led to enhance in vivo mobilization and engraftment of MSCs into ischemic area where these cells promoted neomyoangiogenesis and alleviated early signs of left ventricular remodeling.

Preconditioning enhances cell survival and differentiation of stem cells during transplantation in infarcted myocardium

AIMS

We hypothesized that preconditioning (PC) with stromal-derived factor 1 alpha (SDF-1) significantly enhances cell survival, proliferation, and engraftment of bone marrow-derived mesenchymal stem cells (MSCs) via SDF-1/CXCR4 signaling.

METHODS AND RESULTS

MSCs were cultured and then incubated in medium for 60 min without SDF-1 (control group) or with SDF-1 0.05 microg/mL (SDF-1 group) or CXCR4-selective antagonist, AMD 3100 (AMD) (5 microg/mL, AMD group) or SDF-1 and AMD (0.05 microg/mL, 5 microg/mL, respectively, SDF-1+AMD group). MSCs were treated for 60 min, washed in normal medium, and then exposed to H2O2 (100 micromol/L) for 60 min to determine the effects of various treatments on cell injury, viability, and proliferation. For in vivo studies, rats were grouped (n = 6) after left anterior descending coronary artery ligation to receive 20 microL Dulbecco's modified Eagle's medium without cells or with 5 x 10(5) non-preconditioned MSCs (control group), SDF-1 preconditioned MSCs (SDF-1 group), AMD (AMD group), or MSCs treated with SDF-1 plus AMD (SDF-1+AMD group). Heart function, infarct size, fibrosis, and MSC proliferation and differentiation in infarcted myocardium were determined after 4 weeks. In vitro data showed a marked increase in cell viability and proliferation following SDF-1 PC. In vivo data in preconditioned group showed a robust cell proliferation, reduction in infarct size and fibrosis, and significant improvement in cardiac function. Effects of SDF-1 PC were abrogated by CXCR4 antagonist.

CONCLUSION

We conclude that PC with the chemokine SDF-1 suppresses MSCs apoptosis, enhances their survival, engraftment, and vascular density, and improves myocardial function via SDF/CXCR4 signaling. Chemokine PC is a novel approach for enhancing stem cell survival and regeneration of infarcted myocardium.

HIF-1alpha induced-VEGF overexpression in bone marrow stem cells protects cardiomyocytes against ischemia

Hypoxia inducible factor-1alpha (HIF-1alpha) is a proangiogenic transcription factor stabilized and activated under hypoxia. It regulates the expression of numerous target genes, including vascular endothelial growth factor (VEGF) and other cytoprotective proteins. In this study, we hypothesized that bone marrow stem cells (BMSCs) secrete growth factors which protect cardiomyocytes via HIF-1alpha pathway. BMSCs were obtained from transgenic mice overexpressing green fluorescent protein (GFP). The study was carried out in vitro using co-culture of BMSCs with cardiomyocytes. LDH release, MTT uptake, DNA fragmentation and annexin-V positive cells were used as cell injury markers. The level of HIF-1alpha protein as well as its activated form and VEGF were measured by ELISA. The expression of HIF-1alpha and VEGF in BMSCs was analyzed by quantitative PCR and cellular localization was determined by immunohistochemistry. LDH release was increased and MTT uptake was decreased after exposure of cardiomyocytes to hypoxia for 30 h, which were prevented by co-culturing cardiomyocytes with BMSCs. Cardiomyocyte apoptosis induced by hypoxia and H(2)O(2) was also reduced by co-culture with BMSCs. VEGF release from BMSCs was significantly increased in parallel with high level of HIF-1alpha in BMSCs following anoxia or hypoxia in a time-dependent manner. Although no significant up-regulation could be seen in HIF-1alpha mRNA, HIF-1alpha protein and its activated form were markedly increased and translocated to the nucleus or peri-nuclear area. The increase and translocation of HIF-1alpha in BMSCs were completely blocked by 2-methoxyestradiol (2-ME2; 5 mumol), a HIF-1alpha inhibitor. Moreover, the protection of cardiomyocytes by BMSC and VEGF secretion was abolished by neutralizing HIF-1alpha antibody in a concentration dependent manner (200-3200 ng/ml). Bone marrow stem cells protect cardiomyocytes by up-regulation of VEGF via activating HIF-1alpha.

In vitro and in vivo effects of bone marrow stem cells on cardiac structure and function

It is hypothesized that the protection of bone marrow stem cells (BMSCs) on ischemic myocardium might be related to the anti-apoptotic effect via paracrine mechanisms. In this study, a wide array of cytokines including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), stromal cell-derived factor-1 (SDF-1) and insulin growth factor-1 (IGF-1) were detected in the BMSCs cultured medium by ELISA. Myocyte apoptosis was assayed by DNA fragmentation and annexin-V staining. Myocardial infarction model was produced by ligation of mouse left anterior descending coronary artery (LAD). Before LAD ligation, mice were myoablated by irradiation and transplanted with bone marrow cells from transgenic mice expressing green fluorescent protein (GFP). After LAD ligation, animals were administered stem cell factor (SCF, 200 mug/day/kg, i.p.) or saline for 6 days. Animals were sacrificed at 4 weeks after SCF treatment. Apoptotic cardiomyocytes were analyzed by TUNEL. Myocardial function was analyzed by echocardiography and pressure-volume system. Bcl-2 protein was analyzed by Western blotting. Our results showed that cultured BMSCs released VEGF, bFGF, SDF-1 and IGF-1. Hypoxia-induced cell apoptosis was diminished in cardiomyocytes co-cultured with BMSCs. Smaller LV dimension and increased LV ejection fraction were seen in SCF-treated animals. SCF significantly reduced cardiomyocytes apoptosis within peri-infarct area and increased up-regulation expression of Bcl-2 in ischemic area. Moreover, conditioned medium from cultured BMSCs also induced up-regulation of Bcl-2 protein in cardiomyocytes. It is concluded that paracrine mediators secreted by BMSCs might be involved in early repair of ischemic heart by preventing cardiomyocytes apoptosis and improving cardiac function.

Cardiac protection by mitoKATP channels is dependent on Akt translocation from cytosol to mitochondria during late preconditioning

This investigation elucidates the Akt/mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channel signaling pathway in late pharmacological preconditioning, using the mitoK(ATP) channel openers BMS-191095 (BMS) and diazoxide (DE). BMS (1 mg/kg ip) and DE (7 mg/kg ip) alone or BMS plus wortmannin (WTN, 15 microg/kg ip), an inhibitor of phosphatidylinositol 3-kinase, and BMS plus 5-hydroxydecanoic acid (5-HD, 5 mg/kg ip), an inhibitor of mitoK(ATP) channels, were administered to male mice. Twenty-four hours later, hearts were isolated and subjected to 40 min of ischemia and 120 min of reperfusion via Langendorff's apparatus. Both BMS and DE reduced left ventricular end-diastolic pressure and increased left ventricular developed pressure as well as reduced LDH release. Coadministration of BMS and WTN abolished the beneficial effects of BMS on cardiac function. Moreover, BMS and DE accelerated Akt phosphorylation in cardiac tissue as determined by Western blot analysis and also significantly reduced apoptosis compared with ischemic control. WTN significantly suppressed BMS-induced Akt phosphorylation, whereas 5-HD had no effect on Akt phosphorylation in cytosol, and the effect of BMS on apoptosis was abolished. It is concluded that the cardioprotective effect by mitoK(ATP) channels is attributed to the translocation of phosphorylated Akt from cytosol to mitochondria.