Comparative Effects on Fetal Hematopoiesis and Placental Inflammation From Mesenchymal and Hematopoietic Stem Cells as Agents of Transamniotic Stem Cell Therapy (TRASCET) in a Syngeneic Model of Intrauterine Growth Restriction

PURPOSE

We compared transamniotic stem cell therapy (TRASCET) using either mesenchymal (MSCs) or hematopoietic (HSCs) stem cells on fetal hematopoiesis in a syngeneic model of intrauterine growth restriction (IUGR).

METHODS

Lewis dams exposed to cycling hypoxia (10.5% O2) in late gestation had their fetuses (n = 83) either receiving no intervention (untreated; n = 9), or intra-amniotic injections of either HSCs (HSC; n = 34), MSCs primed to an enhanced anti-inflammatory phenotype (primed-MSC; n = 28), or saline (sham; n = 12). Normal controls (n = 18) were also studied. Complete peripheral blood counts and placental ELISA for inflammation and angiogenesis markers were performed at term.

RESULTS

Overall survival from hypoxia was 41% (34/83). Red blood count (RBC), hematocrit (Hct) and hemoglobin levels (Hb) were all significantly decreased from normal in all hypoxia groups. TRASCET with primed-MSC had significantly higher RBC, Hct, and Hb levels than sham (p = 0.01-0.03, pairwise), though not than untreated (which had no surgical blood loss). The HSC group had only significantly higher Hb levels than sham (p = 0.005). TRASCET with primed-MSC had significantly lower levels of placental TNF-α than sham (p = 0.04), but not untreated.

CONCLUSIONS

MCSs seem more effective than HSCs in enhancing hematopoiesis when used as donor cells for TRASCET in a syngeneic model of IUGR.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Bidirectional Feto-Maternal Traffic of Donor Mesenchymal Stem Cells Following Transamniotic Stem Cell Therapy (TRASCET)

PURPOSE

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) has emerged experimentally as a potential treatment for different congenital diseases and maternal diseases of pregnancy. The broad applicability of TRASCET is predicated on hematogenous routing of donor MSCs via the placenta. We investigated whether donor MSC kinetics includes bidirectional traffic between the fetus and mother.

METHODS

Eight time-dated dams had their fetuses (n = 96) divided in 4 groups on gestational day 17 (E17, term = E21). Groups populating one uterine horn received intra-amniotic injections (50 μL) of either donor amniotic fluid-derived MSCs (2×106 cells/mL) labelled with a firefly luciferase reporter gene (MSC-injected, n = 32), or of acellular luciferase (luciferase-injected, n = 26). Contra-lateral (CL) horn fetuses received no injection (MSC-CL, n = 20 and luciferase-CL, n = 18). At term, samples from 11 fetal anatomical sites from CL fetuses, along with placentas from all fetuses and maternal blood were screened for luciferase activity via microplate luminometry.

RESULTS

Overall survival was 95 % (91/96). When controlled by the acellular injection, positive luciferase activity was observed in the placentas of all MSC-injected fetuses, confirming viability of the donor cells at term. When controlled by the acellular injection group, MSC-CL fetuses showed positive luciferase activity in the bone marrow, peripheral blood, brain and skin (p = <0.001-0.048). No luciferase activity was detected in any maternal blood sample.

CONCLUSION

Amniotic fluid-derived MSCs can traffic between the fetus and mother in both directions after simple intra-amniotic injection, in a healthy rat model. This phenomenon must be considered in TRASCET performed in twin/multiple pregnancies.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

A Digestive Cartridge Reduces Parenteral Nutrition Dependence and Increases Bowel Growth in a Piglet Short Bowel Model

OBJECTIVE

To determine whether the use of an immobilized lipase cartridge (ILC) to hydrolyze fats in enteral nutrition (EN) reduces parenteral nutrition (PN) dependence in a porcine model of short bowel syndrome with intestinal failure (SBS-IF).

BACKGROUND

SBS-IF occurs after intestinal loss resulting in malabsorption and PN dependence. Limited therapeutic options are available for achieving enteral autonomy.

METHODS

Eleven Yorkshire piglets underwent 75% jejunoileal resection and were randomized into control (n=6) and treatment (n = 5) groups. PN was initiated postoperatively and reduced as EN advanced if predefined clinical criteria were fulfilled. Animals were studied for 14 days and changes in PN/EN calories were assessed. Intestinal adaptation, absorption, and nutrition were evaluated at the end of the study (day 15). Comparisons between groups were performed using analysis of covariance adjusted for baseline.

RESULTS

ILC animals demonstrated a 19% greater reduction in PN calories ( P < 0.0001) and higher mean EN advancement (66% vs 47% of total calories, P < 0.0001) during the 14-day experiment. Treatment animals had increased intestinal length (19.5 vs 0.7%, P =0.03) and 1.9-fold higher crypt cell proliferation ( P =0.02) compared with controls. By day 15, ILC treatment resulted in higher plasma concentrations of glucagon-like peptide-2 ( P = 0.02), eicosapentaenoic acid ( P < 0.0001), docosahexaenoic acid ( P = 0.004), vitamin A ( P = 0.02), low-density lipoprotein ( P = 0.02), and high-density lipoprotein ( P = 0.04). There were no differences in liver enzymes or total bilirubin between the two groups.

CONCLUSIONS

ILC use in conjunction with enteral feeding reduced PN dependence, improved nutrient absorption, and increased bowel growth in a porcine SBS-IF model. These results support a potential role for the ILC in clinical SBS-IF.

Fetal Secretory IgA Delivery via Transamniotic Fetal Immunotherapy (TRAFIT) in a Rodent Model

PURPOSE

We sought to determine the feasibility and routing kinetics of transamniotic fetal delivery of secretory immunoglobulin-A (SIgA), in a rodent model.

METHODS

Fetuses (n = 94) from seven time-dated pregnant dams received intra-amniotic injections on gestational day 17 (E17, term = E21-22) of either saline (n = 15) or a solution of 1 mg/mL of ≥95% homogeneous human SIgA (n = 79). Animals were euthanized daily at E18-E21 for quantification of the IgA component by ELISA at gestational membranes, placenta, and select fetal anatomical sites against saline controls procured at term. Statistical analysis was by Mann-Whitney U-test.

RESULTS

None of the saline-injected animals had detectable human IgA. SIgA-injected fetuses showed human IgA in the stomach aspirate, intestinal wall, lungs, liver, and serum at all time points. IgA levels were significantly higher in the gastric aspirate and in the intestine than in all other sites (p < 0.001 for both), with intestinal levels remaining stable through E18-E21 (p = 0.09-0.62 pairwise). Serum and placental levels were consistently low throughout, reaching near zero levels by E21.

CONCLUSIONS

The chronology of exogenous secretory-IgA kinetics after intra-amniotic injection is suggestive of fetal uptake by ingestion, leading to consistent levels in the gastrointestinal tract. Transamniotic fetal immunotherapy (TRAFIT) with secretory-IgA may become a novel strategy for enhancing early mucosal immunity.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

TYPE OF STUDY

Animal and laboratory study.

A Medium-Chain Fatty Acid Analogue Prevents Intestinal Failure-Associated Liver Disease in Preterm Yorkshire Piglets

BACKGROUND & AIMS

At least 20%-30% of patients with intestinal failure receiving long-term parenteral nutrition will develop intestinal failure-associated liver disease (IFALD), for which there are few therapeutic options. SEFA-6179 is a first-in-class structurally engineered medium-chain fatty acid analogue that acts through GPR84, PPARα, and PPARγ agonism. We hypothesized that SEFA-6179 would prevent biochemical and histologic liver injury in a preterm piglet model of IFALD.

METHODS

Preterm Yorkshire piglets were delivered by cesarean section, and parenteral nutrition was provided for 14 days via implanted central venous catheters. Animals were treated with either medium-chain triglyceride vehicle control or SEFA-6179.

RESULTS

Compared to medium-chain triglyceride vehicle at day of life 15, SEFA-6179 prevented biochemical cholestasis (direct bilirubin: 1.9 vs <0.2 mg/dL, P = .01; total bilirubin: 2.7 vs 0.4 mg/dL, P = .02; gamma glutamyl transferase: 172 vs 30 U/L, P = .01). SEFA-6179 also prevented steatosis (45.6 vs 13.9 mg triglycerides/g liver tissue, P = .009), reduced bile duct proliferation (1.6% vs 0.5% area cytokeratin 7 positive, P = .009), and reduced fibrosis assessed by a masked pathologist (median Ishak score: 3 vs 1, P = 0.007). RNA sequencing of liver tissue demonstrated that SEFA-6179 broadly impacted inflammatory, metabolic, and fibrotic pathways, consistent with its in vitro receptor activity (GPR84/PPARα/PPARγ agonist).

CONCLUSIONS

In a preterm piglet model of IFALD, SEFA-6179 treatment prevented biochemical cholestasis and steatosis and reduced bile duct proliferation and fibrosis. SEFA-6179 is a promising first-in-class therapy for the prevention and treatment of IFALD that will be investigated in an upcoming phase II clinical trial.

Morphometric, Developmental, and Anti-Inflammatory Effects of Transamniotic Stem Cell Therapy (TRASCET) on the Fetal Heart and Lungs in a Model of Intrauterine Growth Restriction

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) can attenuate placental inflammation and minimize intrauterine growth restriction (IUGR). We sought to determine whether MSC-based TRASCET could mitigate fetal cardiopulmonary effects of IUGR. Pregnant Sprague-Dawley dams were exposed to alternating 12-h hypoxia (10.5% O2) cycles in the last fourth of gestation. Their fetuses (n = 155) were divided into 4 groups. One group remained untreated (n = 42), while three groups received volume-matched intra-amniotic injections of either saline (sham; n = 34), or of syngeneic amniotic fluid-derived MSCs, either in their native state (TRASCET; n = 36) or "primed" by exposure to interferon-gamma and interleukin-1beta before administration in vivo (TRASCET-primed; n = 43). Normal fetuses served as additional controls (n = 30). Multiple morphometric and biochemical analyses were performed at term for select markers of cardiopulmonary development and inflammation previously shown to be affected by IUGR. Among survivors (75%; 117/155), fetal heart-to-body weight ratio was increased in both the sham and untreated groups (P < 0.001 for both) but normalized in the TRASCET and TRASCET-primed groups (P = 0.275, 0.069, respectively). Cardiac b-type natriuretic peptide levels were increased in all hypoxia groups compared with normal (P < 0.001), but significantly decreased from sham and untreated in both TRASCET groups (P < 0.0001-0.005). Heart tumor necrosis factor-alpha levels were significantly elevated in sham and TRASCET groups (P = 0.009, 0.002), but normalized in the untreated and TRASCET-primed groups (P = 0.256, 0.456). Lung transforming growth factor-beta levels were significantly increased in both sham and untreated groups (P < 0.001, 0.003), but normalized in both TRASCET groups (P = 0.567, 0.303). Similarly, lung endothelin-1 levels were elevated in sham and untreated groups (P < 0.001 for both), but normalized in both TRASCET groups (P = 0.367, 0.928). We conclude that TRASCET with MSCs decreases markers of fetal cardiac strain, insufficiency, and inflammation, as well as of pulmonary fibrosis and hypertension in the rodent model of IUGR.

Fetal Alloimmune Hemolytic Anemia (AHA) as a Potential Target for Transamniotic Fetal Immunotherapy (TRAFIT)

PURPOSE

Fetal alloimmune hemolytic anemia (AHA) resulting from maternal antibodies against fetal erythrocytes may require fetal administration of immunoglobulin-G (IgG) via invasive methods. IgG can reach the fetal circulation after transamniotic fetal immunotherapy (TRAFIT). We sought to both develop a model of AHA and to test TRAFIT as a potential treatment.

METHODS

Sprague-Dawley fetuses (n = 113) received intra-amniotic injections on gestational-day 18 (E18, term = E21) of either saline (control; n = 40), anti-rat-erythrocyte antibodies (AHA; n = 37), or anti-rat-erythrocyte antibodies plus IgG (AHA + IgG; n = 36). At term, blood was procured for red blood count (RBC), hematocrit, or ELISA for inflammatory markers.

RESULTS

There was no difference in survival [95% (107/113)] across groups (p = 0.87). Both hematocrit and RBC were significantly lower in the AHA group than controls (p < 0.001). Although still significantly lower than controls (p < 0.001), both hematocrit and RBC significantly increased in AHA + IgG group compared to AHA alone (p < 0.001). Pro-inflammatory TNF-α and IL1-β were significantly elevated from controls in the AHA group, but not in AHA + IgG (p < 0.001-0.159).

CONCLUSIONS

Intra-amniotic injection of anti-rat-erythrocyte antibodies can reproduce manifestations of fetal AHA, constituting a practical model of this disease. Transamniotic fetal immunotherapy with IgG reduces anemia in this model and may emerge as a new minimally invasive means of treatment.

TYPE OF STUDY

Animal and laboratory study.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Hematogenous Routing of Exogenous mRNA Delivered Into the Amniotic Fluid

INTRODUCTION

Therapies based on exogenous messenger RNA (mRNA) administration have emerged as a powerful novel strategy for the actual or potential treatment of an assortment of diseases, including congenital surgical pathologies. We sought to determine whether the minimally invasive transamniotic route could be an alternative for prenatal mRNA delivery.

METHODS

Pregnant Sprague-Dawley dams underwent laparotomy followed by volume-matched intra-amniotic injections in all their fetuses (n = 120) of either a suspension of a custom firefly luciferase mRNA encapsulated by a lipid- and synthetic cationic polymer-based composite, or of a suspension of the same encapsulation components without mRNA, on gestational day 17 (E17; term = E21-22). On E18, E19, E20, and E21, samples from 14 fetal anatomical sites and maternal serum were procured for the screening of mRNA incorporation by host cells by measurement of luciferase activity via microplate luminometry. Statistical analysis was by Mann-Whitney U-test, including Bonferroni-adjustment.

RESULTS

Overall survival was 87.5% (105/120). Controlled by the encapsulating composite without mRNA, luciferase activity was detected in the animals that received encapsulated mRNA in the following fetal annexes: amniotic fluid, amnion, chorion, umbilical cord, and placenta (P = 0.033 to <0.001), as well as in the following fetal sites: liver, stomach, intestines, and lungs (P = 0.043-0.002).

CONCLUSIONS

Packaged exogenous mRNA can be incorporated by the fetus at least at select anatomical sites after simple intra-amniotic administration in a rodent model. The pattern and chronology of mRNA incorporation are compatible with transplacental hematogenous routing, as well as with fetal swallowing/aspiration. Further study of transamniotic mRNA administration is warranted.

Transamniotic stem cell therapy (TRASCET): An emerging minimally invasive strategy for intrauterine stem cell delivery

Transamniotic stem cell therapy (TRASCET) is an emerging strategy for prenatal stem cell therapy involving the least invasive method described to date of delivering select stem cells to virtually any anatomical site in the fetus, including the blood and bone marrow, as well as to fetal annexes, including the placenta. Such broad therapeutic potential derives, to a large extent, from unique routing patterns following stem cell delivery into the amniotic fluid, which have commonalities with naturally occurring fetal cell kinetics. First reported experimentally only less than a decade ago, TRASCET has yet to be attempted clinically, though a first clinical trial appears imminent. Despite significant experimental advances, much promise and perhaps excessive publicity, most cell-based therapies have yet to deliver meaningful large-scale impact to patient care. The few exceptions typically consist of therapies based on the amplification of the normal biological role played by the given cells in their natural environment. Therein lays much of the appeal of TRASCET, in that it, too, is in essence a magnification of naturally occurring processes in the distinctive environment of the maternal-fetal unit. As much as fetal stem cells possess unique characteristics compared with other stem cells, so does the fetus when compared with any other age group, converging into a scenario that enables therapeutic paradigms exclusive to prenatal life. This review summarizes the diversity of applications and biological responses associated with the TRASCET principle.

Transamniotic stem cell therapy (TRASCET) for intrauterine growth restriction (IUGR): A comparison between placental and amniotic fluid donor mesenchymal stem cells

PURPOSE

Transamniotic stem cell therapy (TRASCET) with donor mesenchymal stem cells (MSCs) has been shown experimentally to reverse central effects of intrauterine growth restriction (IUGR). We sought to compare amniotic-fluid and placenta-derived MSCs (afMSCs and pMSCs, respectively) as TRASCET donor cells in a murine IUGR model.

METHODS

Pregnant Sprague-Dawley dams (n=8) were exposed to alternating 12-hour hypoxia (10.5% O₂) cycles, starting on gestational day 15 (E15; term=E21-22). On E17, fetuses (n=100) were divided into four groups. An untreated group had no further manipulations (n=24). Three groups received volume-matched intra-amniotic injections of either saline (sham; n=27), or suspensions of afMSCs (n=24), or pMSCs (n=25). Normal fetuses served as controls (n=21). All infused MSCs consisted of syngeneic Lewis rat cells phenotyped by flow cytometry and GFP-labeled. At term, fetal and placental morphometrics were calculated, and placental TNF-α levels were determined by ELISA. Statistical comparisons were by Fischer's T-test or Wilcoxon rank sum test (p≤0.05).

RESULTS

Overall survival of the hypoxic groups was 83% (83/100). Compared to normal, maternal-adjusted fetal weights were significantly decreased in all hypoxia groups (pairwise p<0.001), however only the afMSC group showed higher adjusted-fetal weights than sham (p<0.001). Placental efficiency was decreased in untreated, sham, and pMSC groups (p<0.001-0.056) but normalized in the afMSC group (p=0.205). Maternal-adjusted placental weights were lower than normal in all hypoxia groups (p<0.001-0.045), except for the pMSC group (p=0.387).

CONCLUSIONS

Amniotic fluid-derived mesenchymal stem cells are superior to their placenta-derived counterparts in transamniotic stem cell therapy for intrauterine growth restriction in a rat model.

LEVEL OF EVIDENCE

Basic/Translational science.

Impact of bowel rotation and fixation on obstructive complications in congenital diaphragmatic hernia

AIM OF THE STUDY

Small bowel obstruction (SBO) is a known complication after congenital diaphragmatic hernia (CDH) repair, which can require surgery and even extensive bowel resection causing short bowel syndrome (SBS). We investigate whether specific bowel rotation and fixation can be used as a predictor for SBO including volvulus.

METHODS

A retrospective review of 256 CDH survivors following repair from 2003 to 2020 was performed. Operative notes and upper gastrointestinal series (UGI) were screened to determine the rotation and fixation of the bowel. Primary outcomes included SBO occurrence, SBO treated surgically, and volvulus. For statistical analysis Fisher's exact test was utilized.

RESULTS

Twenty-two (9%) patients presented with SBO and majority, 19 (86%), required surgery. Adhesion were observed in 10 (45%), recurrence in 5 (23%), and extensive volvulus leading to SBS in 3 (14%). Both rotation and fixation were recorded in 117 (46%). Presence of left CDH with malrotation and nonfixation was a significant predictor for SBO requiring surgery (P<0.05 vs all other groups). All 3 patients with extensive volvulus had left CDH with nonfixed bowel (100%), however only 1 had malrotation (33%).

CONCLUSIONS

Malrotation and nonfixation are associated with increased SBO in CDH. Normal rotation is not protective and patients are still at risk for volvulus resulting in SBS. SBO requiring surgical intervention is common in CDH. Bowel rotation and fixation are important determinants that, should be routinely documented and education about the risk of SBO should be included in family counseling.

LEVEL OF EVIDENCE

Level IV - Case Series.

A Novel Biological Strategy for Myocardial Protection by Intracoronary Delivery of Mitochondria: Safety and Efficacy

Mitochondrial dysfunction is the determinant insult of ischemia-reperfusion injury. Autologous mitochondrial transplantation involves supplying one's healthy mitochondria to the ischemic region harboring damaged mitochondria. The authors used in vivo swine to show that mitochondrial transplantation in the heart by intracoronary delivery is safe, with specific distribution to the heart, and results in significant increase in coronary blood flow, which requires intact mitochondrial viability, adenosine triphosphate production, and, in part, the activation of vascular K_IR channels. Intracoronary mitochondrial delivery after temporary regional ischemia significantly improved myocardial function, perfusion, and infarct size. The authors concluded that intracoronary delivery of mitochondria is safe and efficacious therapy for myocardial ischemia-reperfusion injury.

Mitochondrial transplantation enhances murine lung viability and recovery after ischemia-reperfusion injury

The most common cause of acute lung injury is ischemia-reperfusion injury (IRI), during which mitochondrial damage occurs. We have previously demonstrated that mitochondrial transplantation is an efficacious therapy to replace or augment mitochondria damaged by IRI, allowing for enhanced muscle viability and function in cardiac tissue. Here, we investigate the efficacy of mitochondrial transplantation in a murine lung IRI model using male C57BL/6J mice. Transient ischemia was induced by applying a microvascular clamp on the left hilum for 2 h. Upon reperfusion mice received either vehicle or vehicle-containing mitochondria either by vascular delivery (Mito V) through the pulmonary artery or by aerosol delivery (Mito Neb) via the trachea (nebulization). Sham control mice underwent thoracotomy without hilar clamping and were ventilated for 2 h before returning to the cage. After 24 h recovery, lung mechanics were assessed and lungs were collected for analysis. Our results demonstrated that at 24 h of reperfusion, dynamic compliance and inspiratory capacity were significantly increased and resistance, tissue damping, elastance, and peak inspiratory pressure (Mito V only) were significantly decreased (P < 0.05) in Mito groups as compared with their respective vehicle groups. Neutrophil infiltration, interstitial edema, and apoptosis were significantly decreased (P < 0.05) in Mito groups as compared with vehicles. No significant differences in cytokines and chemokines between groups were shown. All lung mechanics results in Mito groups except peak inspiratory pressure in Mito Neb showed no significant differences (P > 0.05) as compared with Sham. These results conclude that mitochondrial transplantation by vascular delivery or nebulization improves lung mechanics and decreases lung tissue injury.

Preischemic autologous mitochondrial transplantation by intracoronary injection for myocardial protection

OBJECTIVE

To investigate preischemic intracoronary autologous mitochondrial transplantation (MT) as a therapeutic strategy for prophylactic myocardial protection in a porcine model of regional ischemia-reperfusion injury (IRI).

METHODS

The left coronary artery was cannulated in Yorkshire pigs (n = 26). Mitochondria (1 × 10⁹) or buffer (vehicle [Veh]) were delivered as a single bolus (MT_S) or serially (10 injections over 60 minutes; MT_SS). At 15 minutes after injection, the heart was subjected to temporary regional ischemia (RI) by snaring the left anterior descending artery. After 30 minutes of RI, the snare was released, and the heart was reperfused for 120 minutes.

RESULTS

Coronary blood flow (CBF) and myocardial function were increased temporarily during the pre-RI period. Following 30 minutes of RI, MT_S and MT_SS hearts had significantly increased CBF that persisted throughout reperfusion (Veh vs MT_S and MT_SS; P = .04). MT_S and MT_SS showed a significantly enhanced ejection fraction (Veh vs MT_S, P < .001; Veh vs MT_SS, P = .04) and developed pressure (Veh vs MT_S, P < .001; Veh vs MT_SS, P = .03). Regional function, assessed through segmental shortening (Veh vs MT_S, P = .03; Veh vs MT_SS, P < .001), fractional shortening (Veh vs MT_S, P < .001; Veh vs MT_SS, P = .04), and strain analysis (Veh vs MT_S, P = .002; Veh vs MT_SS, P = .003), was also significantly improved. Although there was no difference in the area at risk between treatment groups, infarct size was significantly reduced in both MT groups (Veh vs MT_S and MT_SS, P < .001).

CONCLUSIONS

Preischemic MT by single or serial intracoronary injections provides prophylactic myocardial protection from IRI, significantly decreasing infarct size and enhancing global and regional function.

Mitochondrial transplantation prolongs cold ischemia time in murine heart transplantation

BACKGROUND

Cold ischemia time (CIT) causes ischemia‒reperfusion injury to the mitochondria and detrimentally effects myocardial function and tissue viability. Mitochondrial transplantation replaces damaged mitochondria and enhances myocardial function and tissue viability. Herein we investigated the efficacy of mitochondrial transplantation in enhancing graft function and viability after prolonged CIT.

METHODS

Heterotopic heart transplantation was performed in C57BL/6J mice. Upon heart harvesting from C57BL/6J donors, 0.5 ml of either mitochondria (1 × 10⁸ in respiration buffer; mitochondria group) or respiration buffer (vehicle group) was delivered antegrade to the coronary arteries via injection to the coronary ostium. The hearts were excised and preserved for 29 ± 0.3 hours in cold saline (4°C). The hearts were then heterotopically transplanted. A second injection of either mitochondria (1 × 10⁸) or respiration buffer (vehicle) was delivered antegrade to the coronary arteries 5 minutes after transplantation. Grafts were analyzed for 24 hours. Beating score, graft function, and tissue injury were measured.

RESULTS

Beating score, calculated ejection fraction, and shortening fraction were significantly enhanced (p < 0.05), whereas necrosis and neutrophil infiltration were significantly decreased (p < 0.05) in the mitochondria group as compared with the vehicle group at 24 hours of reperfusion. Transmission electron microscopy showed the presence of contraction bands in vehicle but not in mitochondria grafts.

CONCLUSIONS

Mitochondrial transplantation prolongs CIT to 29 hours in the murine heart transplantation model, significantly enhances graft function, and decreases graft tissue injury. Mitochondrial transplantation may provide a means to reduce graft failure and improve transplantation outcomes after prolonged CIT.

Alloreactivity and allorecognition of syngeneic and allogeneic mitochondria

Previously, we have demonstrated that the transplantation of autologous mitochondria is cardioprotective. No immune or autoimmune response was detectable following the single injection of autologous mitochondria. To expand the therapeutic potential and safety of mitochondrial transplantation, we now investigate the immune response to single and serial injections of syngeneic and allogeneic mitochondria delivered by intraperitoneal injection. Our results demonstrate that there is no direct or indirect, acute or chronic alloreactivity, allorecognition or damage-associated molecular pattern molecules (DAMPs) reaction to single or serial injections of either syngeneic or allogeneic mitochondria.