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Purpose: Hydrogen sulfide (H2S) has many beneficial biological properties, including the ability to promote vasodilation. It has been shown to be released from stem cells and increased by hypoxia. Therefore, H2S may be an important paracrine factor in stem cell-mediated intestinal protection. We hypothesized that H2S created through conventional pathways would be a critical component of stem cell-mediated intestinal protection after ischemic injury., Methods: Human bone marrow-derived mesenchymal stem cells (BMSCs) were transfected with negative control siRNA (Scramble), or with siRNA to CBS, MPST, or CTH. Knockdown was confirmed with PCR and H2S gas assessed with AzMC fluorophore. Eight-week-old male mice then underwent intestinal ischemia for 60 min, after which time, perfusion was restored. BMSCs from each of the above groups were then placed into the mouse abdominal cavity before final closure. After 24 h, mice were reanesthetized and mesenteric perfusion was assessed by Laser Doppler Imaging (LDI). Animals were then sacrificed and intestines excised, placed in formalin, paraffin embedded, and stained with H & E. Intestines were then scored with a common mucosal injury grading scale., Results: PCR confirmed knockdown of conventional H2S-producing enzymes (CBS, MPST, CTH). H2S gas was decreased in MPST and CTH-transfected cells in normoxic conditions, but was not decreased compared with Scramble in any of the transfected groups in hypoxic conditions. BMSCs promoted increased mesenteric perfusion at 24 h postischemia compared with vehicle. Transfected stem cells provided equivalent protection. Histologic injury was improved with BMSCs compared with vehicle. CBS, MPST, and CTH knockdown cell lines did not have any worse histological injury compared with Scramble., Conclusions: Knocking down conventional H2S-producing enzymes only impacted gas production in normoxic conditions. When cells were transfected in hypoxic conditions, as would be expected in the ischemic intestines, H2S gas was not depressed. These data, along with unchanged perfusion and histological injury parameters with conventional enzyme knockdown, would indicate that alternative H2S production pathways may be initiated during hypoxic and/or ischemic events.

Hydrogen sulfide (H2S) is a novel signaling molecule most recently found to be of fundamental importance in cellular function as a regulator of apoptosis, inflammation, and perfusion. Mechanisms of endogenous H2S signaling are poorly understood; however, signal transmission is thought to occur via persulfidation at reactive cysteine residues on proteins. Although much has been discovered about how H2S is synthesized in the body, less is known about how it is metabolized. Recent studies have discovered a multitude of different targets for H2S therapy, including those related to protein modification, intracellular signaling, and ion channel depolarization. The most difficult part of studying hydrogen sulfide has been finding a way to accurately and reproducibly measure it. The purpose of this review is to: elaborate on the biosynthesis and catabolism of H2S in the human body, review current knowledge of the mechanisms of action of this gas in relation to ischemic injury, define strategies for physiological measurement of H2S in biological systems, and review potential novel therapies that use H2S for treatment.

Background: Direct peritoneal resuscitation (DPR) has been shown to increase survival after intestinal ischemia and reperfusion injury (I/R). We have previously appreciated that minimum essential medium (MEM), a synthetic cell culture medium with bovine serum, glutamine, and antibiotics, contributes to these benefits. We hypothesized that (1) DPR using MEM as a dialysate would increase mesenteric perfusion, improve intestinal mucosal injury, and limit intestinal and hepatic inflammation after intestinal I/R and (2) these improvements would be dependent on endothelial nitric oxide pathways., Methods: Eight-week-old C57Bl6J wild-type (WT) and eNOS Knock Out (eNOS KO) male mice were anesthetized and intestinal ischemia was induced for 60 min. After ischemia, 1 mL of phosphate buffered saline vehicle or MEM was injected into the abdominal cavity. Intestinal perfusion was reassessed after 48 h. Animals were then euthanized, and intestines and livers explanted for histologic and molecular analyses., Results: DPR with MEM significantly improved mesenteric perfusion compared with vehicle (phosphate buffered saline) as measured by Laser Doppler Imaging (WT + MEM 91.58 ± 13.74%, WT + Vehicle 44.27 ± 11.93%, P < 0.05); however, these benefits were lost when endothelial nitric oxide signaling pathways were ablated (eNOS KO + MEM 21.72 ± 5.67 %, eNOS KO + Vehicle 45.24± 11.31%). WT mice treated with MEM also had significantly better preservation of their mucosal architecture (WT + MEM Mdn = 1.0, interquartile range [IQR] = 1.25, WT + Vehicle Mdn = 3.0, IQR = 2.0, P < 0.05). When we compared eNOS KO mice treated with either MEM or vehicle the protective effect of MEM disappeared (eNOS KO + MEM Mdn = 2.0, IQR = 2.25, eNOS KO + Vehicle Mdn = 2.0, IQR = 1.0 P > 0.05). Intestinal levels of interleukin (IL)-1β were increased in WT animals treated with MEM compared with eNOS KOs, whereas concentrations of intestinal IL-6 were similar between groups. Hepatic levels of both IL-1β and IL-6 were significantly elevated in eNOS KOs compared with WT treated with MEM., Conclusions: DPR with MEM has significant therapeutic potential for improving mesenteric perfusion, intestinal injury, and the local inflammatory response after intestinal I/R. These benefits appear to be dependent on nitric oxide signaling within the endothelium., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Vascular endothelial growth factor (VEGF) is a notable chemokine that plays critical roles in angiogenesis and vasculogenesis. The contemporary body of literature contains a substantial amount of information regarding its chemical properties as well as its fundamental role in vascular development. Studies strongly indicate its potential use as a therapeutic agent, especially in the vascular restoration of injured and ischemic tissues. VEGF therapy could be most beneficial for diseases whose pathologies revolve around tissue inflammation and necrosis, such as myocardial infarction and stroke, as well as ischemic bowel diseases such as acute mesenteric ischemia and necrotizing enterocolitis. However, a delicate balance exists between the therapeutic benefits of VEGF and the hazards of tumor growth and neo-angiogenesis. Effective future research surrounding VEGF may allow for the development of effective therapies for ischemia which simultaneously limit its more deleterious side effects. This review will: (1) summarize the current understanding of the molecular aspects and function of VEGF, (2) review potential benefits of its use in medical therapy, (3) denote its role in tumorigenesis and inflammation when overexpressed, and (4) elucidate the qualities which make it a viable compound of study for diagnostic and therapeutic applications., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Angiogenic factors have been the focus of a great deal of research for the treatment of ischemic diseases. Described just more than 10 years ago, angiopoietin 1 (Ang-1) has shown promising results in I/R models. Angiopoietin 1 is essential for both embryonic vasculogenesis and adult angiogenesis. Because of its role in maturation of vessels, it seems well suited to complement the angiogenic factor vascular endothelial growth factor (VEGF), which has been shown to induce vascular budding but in isolation produces nonfunctional vessels. This review will focus on (1) Ang-1 and its receptor, Tie-2, and the resultant intracellular signaling cascade; (2) the complex relationship of Ang-1 and VEGF; (3) the results of Ang-1 in I/R and sepsis models; (4) the results of combination (Ang-1 and VEGF) therapies in I/R and sepsis models; and (5) delivery mechanisms for angiogenic factors to ischemic heart.

Background Necrotizing enterocolitis (NEC) continues to be a morbid surgical condition among preterm infants. Novel therapies for this condition are desperately needed. Hydrogen sulfide (H 2 S) is an endogenous gasotransmitter that has been found to have beneficial properties. We therefore hypothesized that intraperitoneal injection of various H 2 S donors would improve clinical outcomes, increase intestinal perfusion, and reduce intestinal injury in an experimental mouse model of necrotizing enterocolitis. Methods NEC was induced in five-day-old mouse C57BL/6 mouse pups through maternal separation, formula feeding, and intermittent hypoxic and hypothermic stress. The control group (n = 10) remained with their mother and breastfed ad lib. Experimental groups (n = 10/group) received intraperitoneal injections of phosphate buffered saline (PBS) vehicle or one of the following H 2 S donors: (1) GYY4137, 50 mg/kg daily; (2) Sodium sulfide (Na 2 S), 20 mg/kg three times daily; (3) AP39, 0.16 mg/kg daily. Pups were monitored for weight gain, clinical status, and intestinal perfusion via transcutaneous Laser Doppler Imaging (LDI). After sacrifice on day nine, intestinal appearance and histology were scored and cytokines were measured in tissue homogenates of intestine, liver, and lung. Data were compared with Mann–Whitney and p < 0.05 was considered significant. Results Clinical score and weight gain were significantly improved in all three H 2 S-treated groups as compared to vehicle (p < 0.05 for all groups). Intestinal perfusion of the vehicle group was 22% of baseline while the GYY4137 group was 38.7% (p = 0.0103), Na 2 S was 47.0% (p = 0.0040), and AP39 was 43.0% (p = 0.0018). The vehicle group had a median histology score of 2.5, while the GYY4137 group's was 1 (p = 0.0013), Na 2 S was 0.5 (p = 0.0004), and AP39 was 0.5 (p = 0.0001). Cytokine analysis of the intestine of the H 2 S-treated groups revealed levels closer to breastfed pups as compared to vehicle (p < 0.05 for all groups). Conclusion Intraperitoneal administration of H 2 S protects against development of NEC by improving mesenteric perfusion, and by limiting mucosal injury and altering the tissue inflammatory response. Further experimentation is necessary to elucidate downstream mechanisms prior to clinical implementation. [ABSTRACT FROM AUTHOR]

Background Necrotizing enterocolitis (NEC) continues to be a devastating condition among preterm infants. Nitric oxide, which is synthesized in the intestine by endothelial nitric oxide synthase (eNOS), acts as a potent vasodilator and antioxidant within the mesentery and may play a role in prevention of NEC. We hypothesized that loss of endothelial nitric oxide would worsen both intestinal and associated lung injury and increase local and systemic inflammation during experimental NEC. Methods NEC was induced in five-day-old wild type (WT) and eNOS-knockout (eNOSKO) mouse pups. Experimental groups (n = 10) were formula fed and subjected to intermittent hypoxic and hypothermic stress, while control groups (n = 10) remained with their mother to breastfeed. Pups were monitored by daily clinical assessment. After sacrifice on day nine, intestine and lung were assessed for injury, and cytokines were measured in tissue homogenates by ELISA. Data were compared with Mann–Whitney, and p < 0.05 was significant. Results Each NEC group was compared to its respective strain’s breastfed control to facilitate comparisons between the groups. Both NEC groups were significantly sicker than their breastfed controls. eNOSKO NEC animals had a median clinical assessment score of 3 (IQR = 1–5), and the WT NEC animal’s median score was 3 (IQR = 2–5). Despite similar clinical scores, intestinal injury was significantly worse in the eNOSKO NEC groups compared to WT NEC groups (median injury scores of 3.25 (IQR = 2.25–3.625) and 2 (IQR = 1–3), respectively (p = 0.0474). Associated lung injury was significantly worse in the eNOSKO NEC group as compared to the WT NEC group (median scores of 8.5 (IQR = 6.75–11.25) and 6.5 (IQR = 5–7.5), respectively, p = 0.0391). Interestingly, cytokines in both tissues were very different between the two groups, with varying effects noted for each cytokine (IL-6, IL-1β, VEGF, and IL-12) in both tissues. Conclusion Nitric oxide from eNOS plays a key role in preventing the development of NEC. Without eNOS function, both intestinal and lung injuries are more severe, and the inflammatory cascade is significantly altered. Further studies are needed to determine how eNOS-derived nitric oxide facilitates these beneficial effects. [ABSTRACT FROM AUTHOR]

Stem cell therapy is a promising treatment modality for necrotizing enterocolitis. Among the many promising stem cells identified to date, it is likely that mesenchymal stem cells will be the most useful and practical cell-based therapies for this condition. Using acellular components such as exosomes or other paracrine mediators are promising as well. Multiple mechanisms are likely at play in the positive effects provided by these cells, and further research is underway to further elucidate these effects. [ABSTRACT FROM AUTHOR]

Bone marrow mesenchymal stem cells (MSCs) may be a novel treatment modality for organ ischemia, possibly through the release of beneficial paracrine factors. However, an age threshold likely exists as to when MSCs gain their beneficial protective properties. We hypothesized that 1) VEGF would be a crucial stem cell paracrine mediator in providing postischemic myocardial protection and 2) small-interfering (si)RNA ablation of VEGF in adult MSCs (aMSCs) would equalize the differences observed between aMSC- and neonatal stem cell (nMSC)-mediated cardioprotection. Female adult Sprague-Dawley rat hearts were subjected to ischemia-reperfusion injury via Langendorff-isolated heart preparation (15 mm equilibration, 25 mm ischemia, and 60 mm reperfusion). MSCs were harvested from adult and 2.5-wk-old neonatal mice and cultured under normal conditions. VEGF was knocked down in both cell lines by VEGF siRNA. Immediately before ischemia, one million aMSCs or nMSCs with or without VEGF knockdown were infused into the coronary circulation. The cardiac functional parameters were recorded. VEGF in cell supernatants was measured via ELISA. aMSCs produced significantly more VEGF than nMSCs and were noted to increase postischemic myocardial recovery compared with nMSCs. The knockdown of VEGF significantly decreased VEGF production in both cell lines, and the pretreatment of these cells impaired stem cell-mediated myocardial function. The knockdown of VEGF in adult stem cells equalized the myocardial functional differ- ences observed between adult and neonatal stem cells. Therefore, VEGF is a critical paracrine mediator in facilitating postischemic myocardial recovery and likely plays a role in mediating the observed age threshold during stem cell therapy. [ABSTRACT FROM AUTHOR]

Abstract: All surgical disciplines encounter planned and unplanned ischemic events that may ultimately lead to cellular dysfunction and death. Stem cell therapy has shown promise for the treatment of a variety of ischemic and inflammatory disorders where tissue damage has occurred. As stem cells have proven beneficial in many disease processes, important opportunities in the future treatment of gastrointestinal disorders may exist. Therefore, this article will serve to review the different types of stem cells that may be applicable to the treatment of gastrointestinal disorders, review the mechanisms suggesting that stem cells may work for these conditions, discuss current practices for harvesting and purifying stem cells, and provide a concise summary of a few of the pediatric intestinal disorders that could be treated with cellular therapy. [Copyright &y& Elsevier]

Abstract: Stem cells have shown promise for the treatment of end organ ischemia. NFkB has been demonstrated to regulate growth factor secretion in human adult bone marrow stem cells (aBMSCs). We hypothesized that: (1) NFkB is an important mediator in aBMSC and neonatal BMSC (nBMSC) VEGF and IL-6 secretion; and (2) inhibition of NFkB will result in a decrease of VEGF and IL-6 in nBMSCs. BMSCs were plated and exposed to TNF (50ng/ml) or LPS (100ng/ml), with or without NFkB or IKK inhibition. VEGF and IL-6 were measured via ELISA in 24-h supernatants. Inhibition of NFkB and IKK both demonstrated a decrease in VEGF (p <0.05) in aBMSCs but not nBMSCs. The LPS-stimulated nBMSC with IKK inhibition group was the only exception which demonstrated a decrease in VEGF secretion. However, both NFkB inhibition caused both aBMSCs and nBMSCs to produced less IL-6 after LPS stimulation (p <0.05). Only aBMSCs’ secretion of IL-6 decreased with NFkB and IKK inhibition when stimulated with TNF (p <0.05) differing only when TNF-stimulated nBMSCs were inhibited with IKK. VEGF and IL-6 secretion in aBMSCs is dependent on the classic NFkB pathway. However, neonatal BMSC VEGF and IL-6 secretion is stimulant-specific and utilization of the NFkB pathway is more complex. [Copyright &y& Elsevier]

Background: Gender differences have been noted in acute ischemia/reperfusion injury. Estrogen and the estrogen receptors (ER) appear to play a critical role in cardiovascular gender differences, given that females have improved myocardial functional recovery associated with decreased tissue inflammation. It has been suggested that ER beta plays a part in decreasing myocardial inflammation following hemorrhage. It remains unknown, however, whether ER beta also may be protective following the more severe insult of complete global, normothermic ischemia/reperfusion injury in the isolated mouse heart. Methods: Adult male and female wild-type (WT) and ER beta knockout (ERbKO) mouse hearts were subjected to 20 minutes ischemia and 60 minutes reperfusion (Langendorff model). Myocardial contractile function (±dP/dt) was continuously recorded. Heart tissue was analyzed for tumor necrosis factor, interleukin (IL)-1β, IL-6, and IL-10 levels as determined by enzyme-linked immunosorbent assay. Results: Females had markedly improved functional recovery compared with males following ischemia/reperfusion. This recovery was associated with lower levels of myocardial tumor necrosis factor, IL-1β, and IL-6 in females. However, ERbKO females exhibited significantly less postischemic functional recovery than WT females and were similar to WT males. Interestingly, increased myocardial production of tumor necrosis factor, IL-1β, and IL-6 was noted in ERbKO female hearts in response to ischemia/reperfusion. No significant differences were found between male WT and male ERbKO in postischemic functional recovery and proinflammatory cytokine production. Conclusion: ER beta plays a role in the protective effects of estrogen following global, warm ischemia/reperfusion of the isolated mouse heart. This understanding ultimately may enable the development of pharmaceutical agents that harness such protection with minimal collateral sex hormone effects. [Copyright &y& Elsevier]

Stem cells may be a novel treatment modality for organ ischemia, possibly through beneficial paracrine mechanisms. Stem cells from older hosts have been shown to exhibit decreased function during stress. We therefore hypothesized that I) neonatal bone marrow mesenchymal stem cells (nBMSCs) would produce different levels of IL-6, VEGF, and IGF- I compared with adults (aBMSCs) when stimulated with TNF or LPS; 2) differences in cytokines would be due to distinct cellular charac- teristics, such as proliferation or pluripotent potential; and 3) differences in cytokines would be associated with differences in p38 MAPK and ERK signaling within nBMSCs. BMSCs were isolated from adult and neonatal mice. Cells were exposed to TNF or LPS with or without p38 or ERK inhibition. Growth factors were measured via ELISA, proliferation via daily cell counts, cell surface markers via flow cytometry, and pluripotent potential via alkaline phosphatase activity. nBMSCs produced lower levels of IL-6 and VEGF, but higher levels of IGF-1 under basal conditions, as well as after stimulation with TNF, but not LPS. Neonatal and adult BMSCs had similar pluripotent potentials and cell surface markers, but nBMSCs proliferated faster. Furthermore, p38 and ERK appeared to play a more substantial role in nBMSC cytokine and growth factor production. Neonatal stem cells may aid in decreasing the local inflammatory response during ischemia, and could possibly be expanded more rapidly than adult cells prior to therapeutic use. [ABSTRACT FROM AUTHOR]

Background: Females demonstrate improved cardiac recovery after ischemia/reperfusion injury compared with males. Attenuation of myocardial dysfunction with preischemic estradiol suggests that estrogen may be an important mediator of this cardioprotection. However, it remains unclear whether post-injury estradiol may have clinical potential in the treatment of acute myocardial infarction. We hypothesize that postischemic administration of 17β-estradiol will decrease myocardial ischemia/reperfusion injury and improve left ventricular cardiac function. Materials and methods: Adult male Sprague Dawley rat hearts (n = 20) (Harlan, Indianapolis, IN) were isolated, perfused with Krebs-Henseleit solution via Langendorff model, and subjected to 15 min of equilibration, 25 min of warm ischemia, and 40 min reperfusion. Experimental hearts received postischemic 17β-estradiol infusion, 1 nm (n = 4), 10 nm (n = 4), 25 nm (n = 4), or 50 nm (n = 4), throughout reperfusion. Control hearts (n = 4) were infused with perfusate vehicle. Results: Postischemic recovery of left ventricular developed pressure was significantly greater with 1 nm (51.6% ± 7.4%) and 10 nm estradiol (47.7% ± 8.6%) than with vehicle (37.8% ± 9.7%) at end reperfusion. There was also greater recovery of the end diastolic pressure with 1 nm (47.8 ± 4.0 mmHg) and 10 nm estradiol (54.0 ± 4.0) compared with vehicle (75.3 ± 7.5). Further, 1 nm and 10 nm estrogen preserved coronary flow after ischemia and decreased coronary effluent lactated dehydrogenase compared with controls. Estrogen at 25 nm and 50 nm did not provide additional benefit in terms of functional recovery. Estrogen at all concentrations increased extracellular signal-regulated protein kinase phosphorylation. Conclusions: Postischemic infusion of 17β-estradiol protects myocardial function and viability. The attractive potential for the clinical application of postischemic estrogen therapy warrants further study to elucidate the mechanistic pathways and differences between males and females. [Copyright &y& Elsevier]

Interleukin-6 (IL6) has both proinflammatory and anti-inflammatory pathways, but its effects on intestinal recovery following ischemia are unknown. We hypothesized that administration of IL6 following intestinal ischemia would improve mesenteric perfusion and mucosal injury. Adult male C57Bl6J mice were anesthetized, and a laparotomy was performed. Baseline intestinal perfusion was assessed by laser Doppler imaging. Intestinal ischemia was induced for 60 min by temporarily occluding the superior mesenteric artery. After ischemia, treatments were administered intraperitoneally before closure (Vehicle: 250 μL phosphate-buffered-saline, IL6 low dose (20 ng), IL6 medium dose (200 ng), or IL6 high dose (2 μg)). Animals were allowed to recover for 24 h, were reanesthetized, and their mesenteric perfusion was reassessed. Perfusion was expressed as percentage of baseline. Animals were then sacrificed, and the intestines were explanted for histological analysis. Separate frozen samples were homogenized and analyzed by ELISA for vascular endothelial growth factor (VEGF) and interferon gamma-induced protein 10. IL6 increased mesenteric perfusion in low dose groups only, whereas it improved postischemic mucosal injury scores in both low and medium dose groups. No differences in perfusion or histology were seen when high dose IL6 was utilized. Intestinal VEGF was higher in the low dose IL6 group compared to vehicle, whereas IP-10 levels were lower in low and medium dose groups compared to vehicle. No differences were noted compared to vehicle in intestinal VEGF and IP-10 with high dose IL6 therapy. Lower doses of IL6 may serve as effective therapy to decrease intestinal injury after ischemia. Further studies are needed to elucidate the downstream mechanisms before widespread clinical use. [ABSTRACT FROM AUTHOR]

Background Transplantation of mesenchymal stromal cells (MSCs) may be a novel treatment for intestinal ischemia. The optimal stromal cell source that could yield maximal protection after injury, however, has not been identified. We hypothesized that (1) MSCs would increase survival and mesenteric perfusion, preserve intestinal histologic architecture, and limit inflammation after intestinal ischemia and reperfusion (I/R) injury, and (2) MSCs harvested from different sources of tissue would have equivalent protective properties to the intestine after I/R inury. Methods Adult male mice were anesthetized, and a midline laparotomy was performed. The intestines were eviscerated, the small bowel mesenteric root was identified, and baseline intestinal perfusion was determined using laser Doppler imaging. Intestinal ischemia was established by temporarily occluding the superior mesenteric artery for 60 min with a noncrushing clamp. After ischemia, the clamp was removed and the intestines were allowed to recover. Before abdominal closure, 2 × 10 6 human umbilical cord–derived MSCs, bone marrow–derived MSCs, or keratinocytes in 250 μL of phosphate-buffered saline vehicle were injected into the peritoneum. Animals were allowed to recover for 12 or 24 h (perfusion, histology, and inflammatory studies) or 7 d (survival studies). Survival data was analyzed using the log-rank test. Perfusion was expressed as a percentage of the baseline, and 12- and 24-h data was analyzed using one-way analysis of variance and the Student t -test. Nonparametric data was compared using the Mann–Whitney U -test. A P value of <0.05 was considered statistically significant. Results All MSCs increased 7-d survival after I/R injury and were superior to vehicle and keratinocytes ( P < 0.05). All MSCs increased mesenteric perfusion more than vehicle at 12 and 24 h after injury ( P < 0.05). All MSCs provided superior perfusion compared with keratinocytes at 24 h after injury ( P < 0.05). Administration of each MSC line improved intestinal histology after I/R injury ( P < 0.05). Multiple proinflammatory chemokines were downregulated after the application of MSCs, suggesting a decreased inflammatory response after MSC therapy. Conclusions Transplantation of MSCs after intestinal I/R injury, irrespective of a tissue source, significantly increases survival and mesenteric perfusion and at the same time limits intestinal damage and inflammation. Further studies are needed to identify the mechanism that these cells use to promote improved outcomes after injury. [ABSTRACT FROM AUTHOR]

Background: Stem cell transplantation is one of the next great frontiers for surgery. Stem cells, which are undifferentiated and self-renewing, have shown the ability to differentiate into cardiomyocytes, as well as many other cell types for potential therapeutic use by surgeons. Materials and methods: As a result, stem cells have the potential to undo irreversible cellular damage, something traditional therapies could not cure. However, numerous issues must be resolved to permit safe and effective clinical application of stem cell therapy. These include the interpretation of cellular labeling, the origin of replicating myocytes, the homing mechanism of stem cells, and the differentiation process. Results: Successful translational research will depend on precise delivery of these cells in real time to the area of interest, e.g., the spinal cord, liver, or heart. Surgeons will be better able to excise and replace/regrow, rather than excise alone. As such, a basic understanding of stem cell biology will benefit the surgeon scientist and clinical surgeon. Conclusions: The review: 1) discusses myocardial regeneration; 2) defines and categorizes stem cells; 3) presents evidence of stem cell transdifferentiation into cardiomyocytes; and, 4) delineates the therapeutic potential of stem cells in the treatment of ischemic heart disease. [Copyright &y& Elsevier]