The perfused swine uterus model: long-term perfusion

Observations and findings during the development of a subnormothermic/normothermic long-term ex vivo liver perfusion machine

BACKGROUND

Ex situliver machine perfusion at subnormothermic/normothermic temperature isincreasingly applied in the field of transplantation to store and evaluateorgans on the machine prior transplantation. Currently, various perfusionconcepts are in clinical and preclinical applications. Over the last 6 years ina multidisciplinary team, a novel blood based perfusion technology wasdeveloped to keep a liver alive and metabolically active outside of the bodyfor at least one week.

METHODS

Within thismanuscript, we present and compare three scenarios (Group 1, 2 and 3) we werefacing during our research and development (R&D) process, mainly linked tothe measurement of free hemoglobin and lactate in the blood based perfusate. Apartfrom their proven value in liver viability assessment (ex situ), these twoparameters are also helpful in R&D of a long-term liver perfusion machine and moreover supportive in the biomedical engineering process.

RESULTS

Group 1 ("good" liver on the perfusion machine) represents the best liver clearance capacity for lactate and free hemoglobin wehave observed. In contrast to Group 2 ("poor" liver on the perfusion machine), that has shown the worst clearance capacity for free hemoglobin. Astonishingly,also for Group 2, lactate is cleared till the first day of perfusion andafterwards, rising lactate values are detected due to the poor quality of theliver. These two perfusate parametersclearly highlight the impact of the organ quality/viability on the perfusion process. Whereas Group 3 is a perfusion utilizing a blood loop only (without a liver).

CONCLUSION

Knowing the feasible ranges (upper- and lower bound) and the courseover time of free hemoglobin and lactate is helpful to evaluate the quality ofthe organ perfusion itself and the maturity of the developed perfusion device. Freehemoglobin in the perfusate is linked to the rate of hemolysis that indicates how optimizing (gentle blood handling, minimizing hemolysis) the perfusion machine actually is. Generally, a reduced lactate clearancecapacity can be an indication for technical problems linked to the blood supplyof the liver and therefore helps to monitor the perfusion experiments.Moreover, the possibility is given to compare, evaluate and optimize developed liverperfusion systems based on the given ranges for these two parameters. Otherresearch groups can compare/quantify their perfusate (blood) parameters withthe ones in this manuscript. The presented data, findings and recommendations willfinally support other researchers in developing their own perfusion machine ormodifying commercially availableperfusion devices according to their needs.

Scorpio D, Scozzoli M, Bettini G, Forni M, Bacci ML. Preliminary Assessment of the Mucosal Toxicity of Tea Tree (Melaleuca alternifolia) and Rosemary (Rosmarinus officinalis) Essential Oils on Novel Porcine Uterus Models

Antimicrobial resistance, an ever-growing global crisis, is strongly linked to the swine production industry. In previous studies, Melaleucaalternifolia and Rosmarinusofficinalis essential oils have been evaluated for toxicity on porcine spermatozoa and for antimicrobial capabilities in artificial insemination doses, with the future perspective of their use as antibiotic alternatives. The aim of the present research was to develop and validate in vitro and ex vivo models of porcine uterine mucosa for the evaluation of mucosal toxicity of essential oils. The in vitro model assessed the toxicity of a wider range of concentrations of both essential oils (from 0.2 to 500 mg/mL) on sections of uterine tissue, while the ex vivo model was achieved by filling the uterine horns. The damage induced by the oils was assessed by Evans Blue (EB) permeability assay and histologically. The expression of ZO-1, a protein involved in the composition of tight junctions, was assessed through immunohistochemical and immunofluorescence analysis. The results showed that low concentrations (0.2–0.4 mg/mL) of both essential oils, already identified as non-spermicidal but still antimicrobial, did not alter the structure and permeability of the swine uterine mucosa. Overall, these findings strengthen the hypothesis of a safe use of essential oils in inseminating doses of boar to replace antibiotics.

The development of an extended normothermic ex vivo reperfusion model of the sheep uterus to evaluate organ quality after cold ischemia in relation to uterus transplantation

INTRODUCTION

Uterus transplantation has recently proved that infertility in women with uterine factor infertility can be cured. It is still an experimental procedure with numerous critical details remaining to be established, including tolerance to warm and cold ischemic insults. In preparation for human uterus transplantation trials, most teams use the sheep as a model system for research and team training, since the vasculature and the uterus is of similar size as in the human. We, therefore, aimed to develop an ex vivo sheep uterus reperfusion platform that mimics the reperfusion situation so that initial assessments and comparisons can be performed without the need for costly and labor-intensive in vivo transplantation experiments.

MATERIAL AND METHODS

Isolated sheep uteri were perfused with the preservation solution IGL-1 and were then exposed to cold ischemia for either 4 (n = 6) or 48 hours (n = 7). Uteri were then reperfused for 48 hours under normothermic conditions with an oxygenated recirculating perfusate containing growth factors and synthetic oxygen carriers. Histological and biochemical analysis of the perfusate was conducted to assess reperfusion injury.

RESULTS

Quantification of cell density indicated no significant edema in the myometrium or in the endometrium of uteri exposed to 4 hours cold ischemia and then a normothermic ex vivo reperfusion for 48 hours. Only the outer serosa layer and the inner columnar luminal epithelial cells were affected by the reperfusion. However, a much faster and severe reperfusion damage of all uterine layers were evident during the reperfusion experiment following 48 hours of cold ischemia. This was indicated by major accumulation of extracellular fluid, presence of apoptotic-labeled glandular epithelial layer and vascular endothelium. A significant accumulation of lactate was measured in the perfusate with a subsequent decrease in pH.

CONCLUSIONS

We developed a novel ex vivo sheep uterus model for prolonged perfusion. This model proved to be able to distinguish reperfusion injury-related differences associated to organ preservation. The experimental setup is a platform that can be used to conduct further studies on uterine ischemia- and reperfusion injury that may lead to improved human uterus transplantation protocols.

Bioengineering strategies of the uterus towards improving current investigative models and female reproductive health

Ever since the inception of artificial reproductive technologies (ART), new advances have been developed in the lab and translated to the clinic to improve the reproductive outcome of patients. Tissue engineering (TE) adopts ideas and concepts from biology, bioengineering and material science amongst others, resulting in a promising and burgeoning multidisciplinary field of investigation within regenerative medicine. The main objective of the work presented in this thesis was to use TE based approaches to create different types of natural biomaterials obtained from decellularized porcine or rabbit uteri. We investigated if these different bioscaffolds could improve current investigative in vitro models while also showing potential to be used as therapeutic solutions. Decellularized whole organs are acellular vascularized scaffolds that could be used to create tissue-engineered, transplantable organs. However, they can also be processed further into thin sections, ECM hydrogels and coatings, and were used as biocompatible tissue-specific substrates for cell and embryo culture. Two animal models were used, the pig model demonstrated that our perfusion-based protocol (with or without a freeze/thaw step) successfully decellularizes large uteri, yielding a biocompatible material. Secondly, we adapted this protocol for the rabbit uterus and converted the acellular endometrium into tissue-specific ECM hydrogels and coatings. After characterization of these substrates their effect on in vitro embryo development was also examined. While DC organs could one day be used to resolve the main issues plaguing transplantations, endometrial ECM sections, hydrogels and coatings have shown the potential to become a platform used in the culture of stem/progenitor cells and primary culture cells to better maintain their tissue-specific phenotype, improving in vitro models. Furthermore, ECM hydrogels could possibly be used in the future in vivo, as part of a treatment of Asherman's syndrome and endometrial atrophy.

Effect of porcine uterus as ex vivo model of fertilizing ability and gene expression pattern on blastocysts

The success of in vitro embryo production demonstrates that the oviduct can be bypassed during early embryonic development. Using an ex vivo model of porcine uterus is one of the strategies used to investigate fertilization within the oviductal environment. In this study, in vitro-matured porcine oocytes (MII) were fertilized with 7.5 × 10⁷, 15 × 10⁷, or 30 × 10⁷ sperm cells for 20 min in the oviduct of a porcine uterine ex vivo model. MII oocytes used for in vitro fertilization (IVF) served as control 1; those cultured in the oviduct of the ex vivo model for 20 min before IVF served as control 2. In present study, the penetration rate, polyspermy, and fertilization efficiency, and accumulated reactive oxygen species (ROS) levels in the treatment groups were significantly decreased compared to those in the control 1 group. During embryonic development, the cleavage rates in the treatment groups were significantly lower than those in the control groups. The cleavage rate in the 30 × 10⁷ sperm cell-treated group was higher than that in the 7.5 × 10⁷ sperm cell-treated group. The blastocyst formation rate in control 1 and 2, and 30 × 10⁷ sperm cell-treated groups increased compared to that in the 7.5 and 15 × 10⁷ sperm cell-treated groups. PCNA, HSP70.2, and GLUT1 were upregulated in the treatment groups and POU5F1, BAX, GPX1 were upregulated in the treatment and control 2 groups, compared to the control 1 group. These results suggest that an ex vivo model may decrease the penetration rate and fertilization efficiency by increasing the accumulated ROS levels and inducing the expression of apoptosis- and stress-related genes. However, the model improved the monospermy rate and expression of embryo developmental competence genes. This is the first study that evaluates the effect of an ex vivo model of porcine uterus on fertilization parameters, and the development of porcine embryos.

GPR119 Agonism Increases Glucagon Secretion During Insulin-Induced Hypoglycemia

Insulin-induced hypoglycemia in diabetes is associated with impaired glucagon secretion. In this study, we tested whether stimulation of GPR119, a G-protein-coupled receptor expressed in pancreatic islet as well as enteroendocrine cells and previously shown to stimulate insulin and incretin secretion, might enhance glucagon secretion during hypoglycemia. In the study, GPR119 agonists were applied to isolated islets or perfused pancreata to assess insulin and glucagon secretion during hypoglycemic or hyperglycemic conditions. Insulin infusion hypoglycemic clamps were performed with or without GPR119 agonist pretreatment to assess glucagon counterregulation in healthy and streptozotocin (STZ)-induced diabetic rats, including those exposed to recurrent bouts of insulin-induced hypoglycemia that leads to suppression of hypoglycemia-induced glucagon release. Hypoglycemic clamp studies were also conducted in GPR119 knockout (KO) mice to evaluate whether the pharmacological stimulatory actions of GPR119 agonists on glucagon secretion during hypoglycemia were an on-target effect. The results revealed that GPR119 agonist-treated pancreata or cultured islets had increased glucagon secretion during low glucose perfusion. In vivo, GPR119 agonists also significantly increased glucagon secretion during hypoglycemia in healthy and STZ-diabetic rats, a response that was absent in GPR119 KO mice. In addition, impaired glucagon counterregulatory responses were restored by a GPR119 agonist in STZ-diabetic rats that were exposed to antecedent bouts of hypoglycemia. Thus, GPR119 agonists have the ability to pharmacologically augment glucagon secretion, specifically in response to hypoglycemia in diabetic rodents. Whether this effect might serve to diminish the occurrence and severity of iatrogenic hypoglycemia during intensive insulin therapy in patients with diabetes remains to be established.