Pretreatment with adult progenitor cells improves recovery and decreases native myocardial proinflammatory signaling after ischemia

Deleterious effects of endogenous and exogenous testosterone on mesenchymal stem cell VEGF production

Modulating the paracrine effects of bone marrow mesenchymal stem cells (BMSCs) may be important for the treatment of ischemic myocardial tissue. In this regard, endogenous estrogen may enhance BMSC vascular endothelial growth factor (VEGF) production. However, little information exists regarding the effect of testosterone on stem cell function. We hypothesized that 1) endogenous or exogenous estrogen will enhance stem cell production of VEGF and 2) endogenous or exogenous testosterone will inhibit BMSC VEGF production. BMSCs were collected from adult male, female, castrated male, and ovariectomized female rats. One hundred thousand cells were incubated with testosterone (1, 10, or 100 nM) or estrogen (0.15, 1.5, or 15 nM) for 48 h. Cell supernatants were collected, and VEGF was measured by ELISA. BMSCs harvested from castrated males, normal females, and ovariectomized females produced more VEGF compared with normal males. Castration was associated with the highest level (1,018 ± 98.26 pg/ml) of VEGF production by BMSCs, which was significantly more than that produced by BMSCs harvested from normal male and normal female animals. Exogenous testosterone significantly reduced VEGF production in BMSCs harvested from ovariectomized females in a dose-dependent manner. Exogenous estrogen did not alter BMSC VEGF production. These findings suggest that testosterone may work on BMSCs to decrease protective growth factor production and that effective removal of testosterone's deleterious effects via castration may prove to be beneficial in terms of protective factor production. By manipulating the mechanisms that BMSCs use to produce growth factors, we may be able to engineer stem cells to produce maximum growth factors during therapeutic use.

Are neonatal stem cells as effective as adult stem cells in providing ischemic protection?

BACKGROUND

Bone marrow stem cells (BMSCs) may be a novel treatment modality for organ ischemia, possibly through beneficial paracrine mechanisms. However, stem cells from older hosts exhibit decreased function during stress. We therefore hypothesized that (1) BMSCs derived from neonatal hosts would provide protection to ischemic myocardium, and (2) neonatal stem cells would enhance postischemic myocardial recovery above that seen with adult stem cell therapy.

MATERIALS AND METHODS

Female adult Sprague Dawley rat hearts were subjected to an ischemia/reperfusion protocol via Langendorff isolated heart preparation (15 min equilibration, 25 min ischemia, and 60 min reperfusion). BMSCs were harvested from adult and neonatal mice and cultured through several passages under normal conditions (37 degrees C, 5% CO(2)/air). Immediately prior to ischemia, 1 million adult or neonatal BMSCs were infused into the coronary circulation. Cardiac functional parameters were continuously recorded.

RESULTS

Pretreatment with adult BMSCs significantly increased postischemic myocardial recovery as noted by improved left ventricular developed pressure, end diastolic pressure, contractility, and rate of relaxation. Neonatal stem cells, however, did not cause any noticeable improvement in myocardial functional parameters following ischemia.

CONCLUSION

Neonatal and adult BMSCs are distinctly different in the degree of beneficial tissue protection that they can provide. The data herein suggests that a critical age exists as to when stem cells become fully activated to provide their beneficial protective properties. Defining the genes that initiate these protective properties may allow for genetic amplification of beneficial signals, and the generation of "super stem cells" that provide maximum protection to ischemic tissues.

Long-term clinical results of autologous infusion of mobilized adult bone marrow derived CD34+ cells in patients with chronic liver disease

Evidence is growing in support of the role of stem cells as an attractive alternative in treatment of liver diseases. Recently, we have demonstrated the feasibility and safety of infusing CD34(+) adult stem cells; this was performed on five patients with chronic liver disease. Here, we present the results of long-term follow-up of these patients. Between 1 x 10(6) and 2 x 10(8) CD34(+) cells were isolated and injected into the portal vein or hepatic artery. The patients were monitored for side effects, toxicity and changes in clinical, haematological and biochemical parameters; they were followed up for 12-18 months. All patients tolerated the treatment protocol well without any complications or side effects related to the procedure, also there were no side effects noted on long-term follow-up. Four patients showed an initial improvement in serum bilirubin level, which was maintained for up to 6 months. There was marginal increase in serum bilirubin in three of the patients at 12 months, while the fourth patient's serum bilirubin increased only at 18 months post-infusion. Computed tomography scan and serum alpha-foetoprotein monitoring showed absence of focal lesions. The study indicated that the stem cell product used was safe in the short and over long term, by absence of tumour formation. The investigation also illustrated that the beneficial effect seemed to last for around 12 months. This trial shows that stem cell therapy may have potential as a possible future therapeutic protocol in liver regeneration.

Estradiol-treated mesenchymal stem cells improve myocardial recovery after ischemia

BACKGROUND

Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Our lab has recently shown that gender differences exist in mesenchymal stem cell (MSC) paracrine function. Estrogen is implicated in the cardioprotection found in females. It remains unknown whether 17beta-estradiol (E2) affects MSC paracrine function and whether E2-treated MSCs may better protect injured cardiac tissue. We hypothesize that E2-exposed MSCs infused into hearts prior to ischemia may demonstrate increased vascular endothelial growth factor (VEGF) production and greater protection of myocardial function compared to untreated MSCs.

MATERIALS AND METHODS

Untreated and E2-treated MSCs were isolated, cultured, and plated and supernatants were harvested for VEGF assay (enzyme-linked immunosorbent assay). Adult male Sprague-Dawley rat hearts (n = 13) were isolated and perfused via Langendorff model and subjected to 15 min equilibration, 25 min warm global ischemia, and 40 min reperfusion. Hearts were randomly assigned to perfusate vehicle, untreated male MSC, or E2-treated male MSC. Transcoronary delivery of 1 million MSCs was performed immediately prior to ischemia in experimental hearts.

RESULTS

E2-treated MSCs provoked significantly more VEGF production than untreated MSCs (933.2 +/- 64.9 versus 595.8 +/- 10.7 pg/mL). Postischemic recovery of left ventricular developed pressure was significantly greater in hearts infused with E2-treated MSCs (66.9 +/- 3.3%) than untreated MSCs (48.7 +/- 3.7%) and vehicle (28.9 +/- 4.6%) at end reperfusion. There was also greater recovery of the end diastolic pressure with E2-treated MSCs than untreated MSCs and vehicle.

CONCLUSIONS

Preischemic infusion of MSCs protects myocardial function and viability. E2-treated MSCs may enhance this paracrine protection, which suggests that ex vivo modification of MSCs may improve therapeutic outcome.

Intravenous infusion of bone marrow mesenchymal stem cells improves myocardial function in a rat model of myocardial ischemia

OBJECTIVE

We investigated the effects of three different sites for delivery of bone marrow mesenchymal stem cells (MSCs) in a rat model of myocardial ischemia.

DESIGN

Prospective, randomized, controlled study.

SETTING

University affiliated research institute.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

A thoracotomy was performed under general anesthesia. Myocardial ischemia was induced by ligation of the left anterior descending coronary artery. One month later, animals were randomized to receive 5 x 10(6) MSCs labeled with PKH26 in phosphate buffer solution or phosphate buffer solution alone as a placebo by injection into right femoral vein, directly into the left ventricular (LV) cavity, or into the ischemic zone in the anterior ventricular free wall.

MEASUREMENTS AND MAIN RESULTS

Echocardiographically measured myocardial function, including ejection fraction and fractional shortening, was quantitated 2 wks and 4 wks after administering MSCs or phosphate buffer solution. Hemodynamics, including cardiac index, LV dP/dt40, LV negative dP/dt, and LV diastolic pressure were measured 4 wks after administering MSCs or phosphate buffer solution. MSCs were counted in 5-microm sections obtained with cryostat from each harvested heart. Significant improvements in ejection fraction, fractional shortening, cardiac index, LV dP/dt40, LV negative dP/dt, and LV diastolic pressure followed injection of MSCs, regardless of the site of injection. However, the number of MSCs counted in the heart sections was significantly greater after direct myocardial injection.

CONCLUSIONS

Independently of the site of injection and regardless of the different concentration of bone marrow mesenchymal stem cells identified in the myocardium, myocardial function was comparably improved in all groups of animals treated with MSCs.

Human mesenchymal stem cells stimulated by TNF-alpha, LPS, or hypoxia produce growth factors by an NF kappa B- but not JNK-dependent mechanism

Understanding the mechanisms by which adult stem cells produce growth factors may represent an important way to optimize their beneficial paracrine and autocrine effects. Components of the wound milieu may stimulate growth factor production to promote stem cell-mediated repair. We hypothesized that tumor necrosis factor-alpha (TNF-alpha), endotoxin (LPS), or hypoxia may activate human mesenchymal stem cells (MSCs) to increase release of vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF-1), or hepatocyte growth factor (HGF) and that nuclear factor-kappa B (NF kappa B), c-Jun NH2-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) mediates growth factor production from human MSCs. To study this, human MSCs were harvested, passaged, divided into four groups (100,000 cells, triplicates) and treated as follows: 1) with vehicle; 2) with stimulant alone [24 h LPS (200 ng/ml), 24 h TNF-alpha (50 ng/ml), or 24 h hypoxia (1% O2)]; 3) with inhibitor alone [NF kappa B (PDTC, 1 mM), JNK (TI-JIP, 10 microM), or ERK (ERK Inhibitor II, 25 microM)]; and 4) with stimulant and the various inhibitors. After 24 h incubation, MSC activation was determined by measuring supernatants for VEGF, FGF2, IGF-1, or HGF (ELISA). TNF-alpha, LPS, and hypoxia significantly increased human MSC VEGF, FGF2, HGF, and IGF-1 production versus controls. Stem cells exposed to injury demonstrated increased activation of NF kappa B, ERK, and JNK. VEGF, FGF2, and HGF expression was significantly reduced by NF kappa B inhibition (50% decrease) but not ERK or JNK inhibition. Moreover, ERK, JNK, and NF kappa B inhibitor alone did not activate MSC VEGF expression over controls. Various stressors activate human MSCs to increase VEGF, FGF2, HGF, and IGF-1 expression, which depends on an NFkB mechanism.

Mesenchymal Stem Cells Attenuate Hypoxic Pulmonary Vasoconstriction by a Paracrine Mechanism

BACKGROUND

Hypoxic pulmonary vasoconstriction (HPV) may be an adaptive mechanism to correct ventilation-perfusion mismatch in the face of hypoxia. In chronic hypoxia, prolonged vasoconstriction may result in pulmonary hypertension and cor pulmonale. It has been shown that during chronic hypoxia, mesenchymal stem cells (MSCs) may contribute to pulmonary vascular remodeling, anti-inflammation, and vascular stability. Also, MSCs have been shown to release growth factors when stressed by hypoxia. We hypothesized that MSCs reduce HPV by a paracrine mechanism. To test this, MSCs were stressed by hypoxia in tissue culture and the cell-free media was then used to treat the pulmonary arteries subjected to HPV.

METHODS

Adult male (250-350 g) Sprague Dawley rat pulmonary arteries (n = 10/group) were isolated and suspended in physiological organ baths. Human MSCs were stressed with 60-min hypoxia and conditioned media was collected. Pulmonary artery rings were treated with vehicle or MSC-conditioned (cell-free) media prior to hypoxia. Force displacement was continuously recorded. Data (mean +/- SEM) were analyzed with two-way analysis of variance with post-hoc Bonferroni test.

RESULTS

Pulmonary arteries exposed to MSC-conditioned media experienced an augmented vasodilatory phase as compared to vehicle. Maximum vasodilation was 53.58 +/- 6.42% versus 39.76 +/- 4.05% for vehicle (P < 0.001). In addition, delayed, phase II vasoconstriction was significantly attenuated as compared to vehicle. Maximum phase II vasoconstriction was 28.51 +/- 12.42 versus 86.29 +/- 15.99% for vehicle (P < 0.001).

CONCLUSIONS

We conclude that acute hypoxia induces HPV and that MSC-conditioned media acutely attenuates this effect. Thus, in addition to a direct contribution to vessel remodeling in chronic hypoxia, MSCs may acutely protect and attenuate hypoxic pulmonary vasoreactivity through a paracrine mechanism.

Role of p38 mitogen-activated protein kinase on cardiac dysfunction after hemorrhagic shock in rats

Cardiac dysfunction is a well-known complication of hemorrhagic shock as a consequence of local inflammatory response. Several studies have indicated that p38 mitogen-activated protein kinase (MAPK) is a key mediator in organ dysfunction that is associated with the inflammatory state through the activation of proinflammatory cytokines such as TNF-alpha and IL-1beta. Whether the same applies to cardiac dysfunction after hemorrhagic shock has not been clearly determined. Therefore, in this study, the role of p38 MAPK on cardiac dysfunction after hemorrhagic shock was studied up to 5 h after a hemorrhage using FR167653, a specific inhibitor of p38 MAPK phosphorylation. The p38 MAPK phosphorylation, the cardiac mRNA expressions of TNF-alpha and IL-1beta, and intracardiac serum concentrations of each cytokine and creatine phosphokinase-MB isozyme increased after a hemorrhage. Activated neutrophil accumulation in the heart, histological inflammation-related injuries, and frequent ventricular arrhythmia were observed in the late phase after hemorrhagic shock. FR167653 inhibited these hemorrhagic changes except the induction of the primary hypotensive state. These results demonstrate that p38 MAPK phosphorylation in hemorrhagic shock plays an important role in the cardiac expression of the proinflammatory cytokines and in the development of cardiac dysfunction relative to the inflammatory responses.

STEM CELL MECHANISMS AND PARACRINE EFFECTS

Heart disease remains the leading cause of death in the industrialized world. Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Cardiac surgery represents the unique situation where preischemia and postischemia treatment modalities exist that may use stem cell paracrine protection. This review (1) recalls the history of stem cells in cardiac disease and the unraveling of its mechanistic basis for protection, (2) outlines the pathways for stem cell-mediated paracrine protection, (3) highlights the signaling factors expressed, (4) explores the potential of using stem cells clinically in cardiac surgery, and (5) summarizes all human stem cell studies in cardiac disease to date.

The critical role of vascular endothelial growth factor in pulmonary vascular remodeling after lung injury

The pulmonary vascular endothelial cell plays a crucial role in the regulation of the pulmonary vascular tone and in the maintenance of the barrier function and integrity of the alveolar-capillary membrane. It also plays a major role in coagulation, fibrinolysis, and angiogenesis and participates in inflammatory reactions. Vascular endothelial growth factor (VEGF) is a central growth and survival factor for the endothelial cell. Particularly high levels of VEGF are expressed in the lungs, reflecting the critical role of VEGF for lung development and structural integrity of the adult lung. Vascular endothelial growth factor exerts a variety of physiological and pathophysiological actions in the lung. Recent evidence suggests its involvement in the pathogenesis of lung diseases such as bronchopulmonary dysplasia, acute lung injury, emphysema, and pulmonary hypertension. To summarize the critical effects of VEGF on the pulmonary endothelial cell in the pathogenesis of these diseases, the purposes of this review are to (1) discuss the biological activities and intracellular signaling pathways of VEGF in the lung; (2) summarize the regulatory mechanisms involved in VEGF expression; (3)address the effects of VEGF on endothelial cells in hyperoxia-induced and other forms of lung injury; (4) highlight the endothelial effects of VEGF in the pathogenesis of emphysema; and (5) explore the role of VEGF in the pathogenesis of pulmonary arterial hypertension.

In the adult mesenchymal stem cell population, source gender is a biologically relevant aspect of protective power

BACKGROUND

Acute treatment with bone marrow mesenchymal stem cells (MSC) reduces myocardial infarct size by multiple mechanisms, including the paracrine release of protective growth factors. Female MSCs produce more growth factor when stressed; therefore, we hypothesized that myocardial protection provoked by female MSCs would be greater than that elicited by male MSCs.

METHODS

Hearts were subjected to 25 min of warm global ischemia, 40 min of reperfusion, and randomly assigned into one of three groups: (1) vehicle treated; (2) male MSC treated; and (3) female MSC treated. Myocardial function was continuously recorded and in separate experiments, male and female MSC growth factor production was assessed by ELISA.

RESULTS

All indices of functional recovery were significantly higher in the stem cell infused rat heart compared with control hearts. Interestingly, female MSC treated rat hearts demonstrated significantly greater recovery of left ventricular developed pressure, +dP/dT, and -dP/dT than male MSC treated hearts at end reperfusion. In addition, male MSCs produced significantly greater tumor necrosis factor alpha, and significantly less vascular endothelial growth factor than female MSCs.

CONCLUSIONS

This study is the first to demonstrate that, in the adult mesenchymal population, source gender is a biologically relevant aspect of ultimate stem cell function in the heart.

Stem Cells Improve Right Ventricular Functional Recovery After Acute Pressure Overload and Ischemia Reperfusion Injury

BACKGROUND

In many clinical scenarios, a relatively untrained right ventricle may be subjected to acute elevations in pulmonary artery and right ventricular pressures. The right and left heart are distinctly different in this regard and there is currently no in vivo model to study right ventricular ischemia in the setting of acute pressure overload. In acute injury, cardiomyocytes produce tumor necrosis factor, which mediates a proinflammatory pathway, eventually leading to myocardial dysfunction. Stem cells have been shown to reduce the production of proinflammatory mediators by the ischemic myocardium and protect the myocardium. Pretreatment with stem cells has been shown to protect the left ventricle. The effect of acute pressure overload to the untrained right ventricle is still not well understood. Furthermore, it is unclear whether pretreatment with stem cells would protect the right ventricle when it is subjected to acute pressure overload and concomitant ischemia reperfusion injury. The purpose of this study was (1) to create a simple model of acute pressure overload for the study of concomitant right ventricular ischemia and reperfusion, and (2) to evaluate the effect of pretreatment with stem cells prior to ischemia reperfusion injury.

MATERIALS AND METHODS

Isolated rat hearts were perfused with the modified Langendorff technique with the latex balloon in the right ventricle instead of the left, with a pressure-transduced balloon being used to create an acute elevation in right ventricular pressure before ischemia. In the first of a two-series experiment, there were two experimental groups (N = 8 per group): one with right ventricular balloon end-diastolic pressure (EDP) of 5 mmHg (physiological), and the other with an EDP of 40 mmHg (pathologic). In the second series, the hearts with the higher balloon pressure (EDP 40 mmHg) were divided into two experimental groups (N = 5 per group). The control group was not pretreated. One group was pretreated with human mesenchymal stem cells 5 min immediately prior to ischemia reperfusion injury. Right ventricular developed pressure (RVDP), contractility (+dP/dt), and compliance (-dP/dt) were continuously assessed. Additionally, mesenchymal stem cells (MSCs) in culture were stressed by hypoxia and activation was determined by measuring vascular endothelial growth factor-A (VEGF) and hepatocyte growth factor (HGF) production by enzyme-linked immunosorbent assay.

RESULTS

Recovery of RVDP, +dP/dt, and -dP/dt was significantly higher (P < 0.001) in the group with lower EDP compared to the group with the higher EDP [RVDP: 79.53 +/- 6.34 versus 54.28 +/- 10.76%; +dP/dt: 76.54 +/- 8.79 versus 38.75 +/- 19.74%; -dP/dt: 72.29 +/- 7.02 versus 30.54 +/- 12.44%]. In the higher EDP groups, pretreatment with human mesenchymal stem cells significantly improved myocardial function recovery (P < 0.01) when compared to controls [RVDP: 75.76 +/- 7.97 versus 59.10 +/- 11.18%; +dP/dt: 71.78 +/- 10.36 versus 54.93 +/- 12.64%; -dP/dt: 77.38 +/- 11.09 versus 59.30 +/- 15.20%]. Further, hypoxic MSCs demonstrated significantly greater VEGF and HGF release than controls.

CONCLUSION

This compounded injury model allowed the study of right ventricular dysfunction in the setting of acute pressure overload and ischemia. Additionally, we have also demonstrated that pretreatment with stem cells of an acutely pressure overloaded right ventricle prior to ischemia reperfusion injury improves functional recovery. This is the first report of a modified Langendorff technique to study right ventricular function in the setting of acute pressure overload and ischemia and the effect of pretreatment with stem cells.

STAT3 mediates bone marrow mesenchymal stem cell VEGF production

The mechanisms by which mesenchymal stem cells (MSCs) may protect native tissue are incompletely understood. Understanding the mechanisms by which these cells release factors such as vascular endothelial growth factor (VEGF), may lead to enhanced protection. We hypothesized that stress, in the form of hypoxia or TNF, activates MSCs to release VEGF by STAT3 and p38 MAPK dependent mechanisms. Mouse MSCs from wild type (WT) and STAT3 knockout mice (STAT3KO) were harvested and purified by a single-step method using adhesion. The release of VEGF was analyzed by using MSC conditioned media under hypoxia or TNF stimulation with or without p38 MAPK inhibition. Activation of STAT3 and p38 MAPK was determined by analysis of cell lysates. MSCs released VEGF under normoxia, which was associated with constitutive STAT3 activity. STAT3 deficiency resulted in decreased MSC production of VEGF. In response to hypoxia or TNF, MSCs produced more VEGF, which was correlated with hypoxia or TNF activated p38 MAPK and STAT3. The p38 MAPK inhibitor significantly decreased hypoxia-induced or TNF-stimulated VEGF production in WT. Additionally, STAT3 ablation neutralized hypoxia-induced MSC release of VEGF. No effect of p38 MAPK inhibitor alone was observed on MSC release of VEGF in WT. However, inhibition of p38 MAPK blocked release of VEGF in STAT3KO MSCs. MSCs are a potent source of VEGF, the production of which is mediated by STAT3 under normoxia partly; however, following hypoxia or TNF exposure, MSC release of VEGF is mediated by both STAT3 and p38 MAPK.

High passage number of stem cells adversely affects stem cell activation and myocardial protection

Progenitor cell plasticity enhances positive remodeling of damaged tissue. We and others have previously shown that progenitor cells may limit apoptosis and modulate inflammation in part by the production of growth factors. However, recent studies suggest that progenitor cells senesce and lose their differentiation potential with increasing time in culture and passage. We hypothesize that murine bone marrow mesenchymal stem cells (MSCs) are cardioprotective against ischemia/reperfusion injury in the isolated perfused rat heart, and that passage number has an adverse effect on MSC activation and cardioprotection. Adult male and female Sprague-Dawley rat hearts were isolated, perfused via Langendorff model, and subjected to ischemia/reperfusion. Mouse MSCs were harvested, cultured, suspended in perfusate, and infused before global index ischemia. Hearts were assigned to controls or infusion with passage 3, 5, or 10 MSCs. In addition, MSCs in culture were stressed by hypoxia and increasing doses of endotoxin (lipopolysaccharide). Mesenchymal stem cell activation was determined by measuring vascular endothelial growth factor production with enzyme-linked immunosorbent assay. All data are reported as mean +/- SEM and were analyzed with 2-way analysis of variance. Differences are considered significant if P < 0.05. Passage 3 murine MSC infusion in hearts before ischemia reduced the depression of left ventricular developed pressure, attenuated the increase of end-diastolic pressure, and reduced the depression of +dP/dT and -dP/dT. However, the MSC protective effect disappeared in hearts infused with passage 5 and passage 10 MSCs. Although hypoxia and lipopolysaccharide resulted in significant activation of MSCs, passage 3 MSCs demonstrated significantly greater vascular endothelial growth factor release than passage 5 and 10 MSCs. Acute murine MSC infusion confers protection in isolated rat hearts. However, high passage number has an adverse effect on MSC activation and protection. This portends limited ex vivo expansion before possible therapeutic use.

Sex dimorphisms in activated mesenchymal stem cell function

The plasticity of bone marrow-derived stem cells (BMSCs) has resulted in positive remodeling and the regeneration of viable tissues. However, BMSC release of growth factors, which limit apoptosis and inflammation, may play an important role in conferring organ protection. Recent studies also indicate that those patients with higher circulating BMSC counts may be more resistant to septic and traumatic insults. There are clear sex differences in response to such insults. Within the population of BMSC, mesenchymal stem cells (MSCs) may have clinical advantages. Therefore, we hypothesize that sex differences in the MSC paracrine response to acute injury exist. Mesenchymal stem cells were obtained from male and female mice. One million MSCs per well (triplicate wells per group) were stressed by hypoxia and increasing doses of endotoxin (lipopolysaccharide [LPS]) and hydrogen peroxide. Mesenchymal stem cell activation was determined by measuring vascular endothelial growth factor (VEGF) and tumor necrosis factor alpha production by enzyme-linked immunosorbent assay. Differences were considered significant if P < 0.05.

RESULTS

Lipopolysaccharide resulted in significant activation of both male and female MSCs. However, LPS provoked significantly more VEGF production in female MSCs versus male MSCs at all LPS doses. Hypoxia of 1 h and hydrogen pyroxide exposure also caused significantly more VEGF production in female MSCs versus male MSCs. Female MSCs expressed significantly less tumor necrosis factor alpha than male MSCs after acute LPS and hypoxia.

CONCLUSION

This study constitutes the first demonstration that sex differences exist in activated MSC function. Sex differences in progenitor cell function may have important implications in understanding the observed sex differences in the host's response to injury.

Gender differences in injury induced mesenchymal stem cell apoptosis and VEGF, TNF, IL-6 expression: role of the 55 kDa TNF receptor (TNFR1)

Concomitant pro- and anti-inflammatory properties of bone marrow stem cells (BMSC) may be an important aspect of their ability to heal injured tissue. However, very few studies have examined whether gender differences exist in BMSC function. Indeed, it remains unknown whether gender differences exist in BMSC function and ability to resist apoptosis, and if so, whether TNF receptor 1 (TNFR1) plays a role in these differences. We hypothesized that TNFR1 ablation equalizes gender differences in bone marrow mesenchymal stem cell (MSC) apoptosis, as well as expression of vascular endothelial growth factor (VEGF), TNF and interleukin (IL)-6. Mouse MSCs from male wild type (WT), female WT, male TNFR1 knockouts (TNFR1KO) and female TNFR1KO were stressed by endotoxin 200 ng/ml or 1 h hypoxia. MSC activation was determined by measuring VEGF, TNF and IL-6 production (ELISA). Differences considered significant if p<0.05. LPS and hypoxia resulted in significant activation in all experimental groups compared to controls. Male WT demonstrated significantly greater TNF and IL-6 and significantly less VEGF release than female WT MSCs. However, release of TNF, IL-6 and VEGF in male TNFR1 knockouts differed from male WT, but was not different from female WT MSCs. Similarly apoptosis in hypoxic male TNFRIKO differed from male WT, but it was not different from apoptosis from WT female. Female WT did not differ in TNF, IL-6 and VEGF release compared to female TNFR1KO. Gender differences exist in injury induced BMSC VEGF, TNF and IL-6 expression. TNFR1 may autoregulate VEGF, TNF and IL-6 expression in males more than females. MSCs are novel therapeutic agents for organ protection, but further study of the disparate expression of VEGF, TNF and IL-6 in males and females as well as the role of TNFR1 in these gender differences is necessary to maximize this protection.

Human progenitor cells from bone marrow or adipose tissue produce VEGF, HGF, and IGF-I in response to TNF by a p38 MAPK-dependent mechanism

Accumulating evidence suggests that progenitor cells may decrease destructive inflammation and reduce tissue loss by antiapoptotic mechanisms. However, they remain poorly characterized, and many questions remain regarding the mechanisms by which they may positively affect wound healing, tissue remodeling, or tissue regeneration. It has been speculated that various growth factors are responsible, but what components of the wound milieu stimulate progenitor cell production of growth factors and by what mechanisms? We hypothesized that tumor necrosis factor-alpha (TNF-alpha) stimulated progenitor cell secretion of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and insulin-like growth factor I (IGF-I) by a p38 mitogen-activated protein kinase (MAPK)-dependent mechanism. Human mesenchymal stem cells (hMSCs) and human adipose progenitor cells (hAPCs) were divided into four groups: control, p38 MAPK inhibitor (p38MKI), TNF, and TNF + p38MKI. After 24 h of incubation, supernatants were harvested for ELISA of VEGF, HGF, and IGF-I. Cells were collected for Western blot analysis of p38 MAPK activation. Secretion of VEGF, HGF, and IGF-I in hMSCs and hAPCs was significantly increased by stimulation with TNF and was associated with increased activation of p38 MAPK. The p38 MAPK inhibitor decreased production of TNF-stimulated VEGF, HGF, and IGF-I in hMSCs and hAPCs. However, p38 MAPK inhibitor alone had no effect on production of growth factors. These data demonstrate that progenitor cells are potent sources of VEGF, HGF, and IGF-I. TNF, a prominent tissue cytokine, strongly stimulated production of growth factors by hMSCs and hAPCs via a p38 MAPK-dependent mechanism.