Jean-Paul Dehoux

Assessment of hepatic perfusion parameters with dynamic MRI

Quantification of hepatic perfusion parameters greatly contributes to the assessment of liver function. The purpose of this study was to describe and validate the use of dynamic MRI for the noninvasive assessment of hepatic perfusion parameters. The signal from a fast T1‐weighted spoiled gradient‐echo sequence preceded by a nonslice‐selective 90° pulse and a spoiler gradient was calibrated in vitro with tubes filled with various gadolinium concentrations. Dynamic images of the liver were obtained after intravenous bolus administration of 0.05 mmol/kg of Gd‐DOTA in rabbits with normal liver function. Hepatic, aortic, and portal venous signal intensities were converted to Gd‐DOTA concentrations according to the in vitro calibration curve and fitted with a dual‐input one‐compartmental model. With MRI, hepatic blood flow was 100 ± 35 mL min‐1 100 mL‐1, the arterial fraction 24 ± 11%, the distribution volume 13.0 ± 3.7%, and the mean transit time 8.9 ± 4.1 sec. A linear relationship was observed between perfusion values obtained with MRI and with radiolabeled microspheres (r = 0.93 for hepatic blood flow [P < 0.001], r = 0.79 for arterial blood flow [P = 0.01], and r = 0.91 for portal blood flow [P < 0.001]). Our results indicate that hepatic perfusion parameters can be assessed with dynamic MRI and compartmental modeling. Magn Reson Med 47:135–142, 2002.

Glomerular filtration rate: assessment with dynamic contrast-enhanced MRI and a cortical-compartment model in the rabbit kidney.

To describe the use of MRI and a cortical‐compartment model to measure the glomerular filtration rate (GFR), and compare the results with those obtained with the Patlak‐Rutland model.

The importance of large animal models in transplantation.

Animal models have been extensively used in transplantation research. However, animal experimentation is contentious and subject to legal and ethical restrictions. Most experiments are carried out on rodents, but crucial prerequisites for the development of safe pre-clinical protocols in biomedical research are needed through suitable large animal models. In transplantation particularly, large animal models have developed dramatically. This article provides an overview of the large animal models commonly used to evaluate organ transplant experiments and analyzes the specificity of several models in various situations such as induction of allospecific tolerance and xenotransplantation. The key determination that remains be addressed is the most appropriate species and strains to model human immune and physiological systems. Because of their phylogenetic and physiologic similarities to man, non-human primates play an increasingly important role in pre-clinical testing. Nevertheless, a number of studies have shown the pig to be a reliable large animal model for transplantation research, and the availability of genetically defined or modified pigs establishes a stronger position for pigs as a large animal model.

Vitrification of non-human primate immature testicular tissue allows maintenance of proliferating spermatogonial cells after xenografting to recipient mice

This study demonstrates preservation of tissue integrity, maintenance of proliferating spermatogonia and Leydig cell functionality after vitrification and transplantation of non-human primate immature testicular tissue. The objective was to assess the potential of vitrification of non-human primate immature testicular tissue (ITT) in an in vivo xenotransplantation model. Testicular tissue was obtained from one immature rhesus monkey (Macaca mulatta) aged 4 years. Collection and vitrification of testicular tissue, followed by short-term xenografting (3 wks) to nude mice were performed to evaluate and compare vitrified/warmed and fresh tissue. Fresh ungrafted tissue was used for control purposes. Cell density and seminiferous tubule (ST) integrity were assessed by light microscopy. Presence of spermatogonia (SG) (MAGE-A4), proliferation (Ki-67) and Leydig cell (LC) functionality (3β-hydroxysteroid dehydrogenase; 3β-HSD) were evaluated by immunohistochemistry (IHC). Qualitative analysis revealed preservation of the histologic characteristics of SG and Sertoli cells (SCs), as well as cell-cell cohesion and cell adhesion to the basement membrane, in both vitrified and fresh grafted tissues. Survival of SG able to proliferate and functional LCs was confirmed by IHC in fresh and vitrified grafts. In conclusion, vitrification appears to be a promising approach, representing an alternative strategy to slow-freezing in the emerging field of ITT cryopreservation and cryobanking.

Effect of a bovine colostrum whey supplementation on growth performance, faecal Escherichia coli population and systemic immune response of piglets at weaning.

This study examined the effect of a bovine colostrum whey supplementation on growth performance, feed intake, faecal Escherichia coli population and systemic immune response of piglets at weaning. A total of 96 piglets weaned at 26 ± 2 days of age were assigned for 4 weeks to one of the two treatments: (1) the control (commercial diet with bovine milk whey powder) and (2) the colostrum (commercial diet with freeze-dried bovine colostrum whey) treatments. The two supplements were incorporated in the diet at a level of 20 g/kg during the first 2 weeks after weaning and lowered to a level of 10 g/kg for the next 2 weeks. BW and feed intake were measured weekly. Faecal E. coli counts were determined weekly on specific culture media. Blood samples were collected weekly and submitted to a cell counter analyser for their main components (red and white blood cells, platelets) and flow cytometry was used to determine the lymphocyte population (B, T, Th and Tc). Finally, total seric immunoglobulin (IgM, IgG and IgA) concentrations were determined by the ELISA method. During the first week of the trial, the piglets from the colostrum treatment had improved average daily gain (170 g/day v. 81 g/day, P < 0.001), average daily feed intake (346 g/day v. 256 g/day, P = 0.03) and feed efficiency (BW gain/feed intake) (0.48 v. 0.31, P = 0.04). The pigs fed the colostrum treatment had also a 25% increase in circulating IgA (P = 0.03) compared with the control treatment the first week. It is concluded that a distribution of bovine colostrum whey (20 g/kg diet) during the first week post-weaning induces a systemic IgA response and has a beneficial action on growth performances and feed efficiency.

Characterization of baboon anti-porcine IgG antibodies during acute vascular rejection of porcine kidney xenograft

In the pig‐to‐baboon model, the removal of anti‐porcine natural antibodies abrogates hyperacute vascular rejection (HAVR), but the xenograft then undergoes an acute vascular rejection (AVR) concomitantly to the appearance of newly formed anti‐porcine antibodies. The use of anti‐IgM monoclonal antibody (mAb) in baboons allowed to avoid HAVR of pig‐to‐baboon renal xenografts, but, at post‐operative day 6, AVR occurred because of a rapid return of anti‐porcine antibodies. The aim of this work was to characterize the anti‐porcine antibodies during AVR. Sera from anti‐IgM‐treated animals were assessed prior to the graft and at the time of AVR by enzyme linked immunosorbent assay (ELISA) to determine anti‐porcine antibodies concentration as well as the IgG subtypes. The same sera were tested on confluent cultures of porcine aortic endothelial cells (PAECs) to assess (i) the cytolytic complement‐dependent activity and (ii) the E‐selectin expression. The K affinity of anti‐Gal IgG antibodies was measured by ELISA. Anti‐porcine (Gal and non‐Gal) IgG antibodies were tested on PAECs by flow cytometry to discriminate the presence of Gal epitopes from the recognition of other porcine epitopes. We found that both anti‐porcine IgM and IgG antibodies presented a significantly increased cytolytic activity and E‐selectin expression on PAECs during AVR. These characteristics are related to an important increase of the antibody (Ab) titer (especially anti‐galactosyl) and a switch to anti‐galactosyl IgG1 subclass production, whereas the K affinity remained unchanged. The deleterious effects of both IgM and IgG antibodies observed during AVR showed the crucial need for treatment controlling the cells producing anti‐porcine antibodies.

Specific depletion of preformed IgM natural antibodies by administration of anti-mu monoclonal antibody suppresses hyperacute rejection of pig to baboon renal xenografts.

Background. The elimination of circulating anti-porcine preformed antibodies is crucial for avoiding hyperacute vascular rejection (HAVR) of primarily vascularized xenograft in discordant pig to baboon model.Previously described methods used for eliminating natural antibodies, however, constantly removed both anti-porcine IgM and IgG antibodies, as well as often complement proteins. To study specifically the role of preformed anti-porcine IgM antibodies, a specific anti-IgM monoclonal antibody (mAb) has been designed and evaluated in vivo. Methods. Iterative injections of anti-IgM mAb (LO-BM2) at high dose (20 mg/kg) depleted to undetectable level the circulating IgM and therefore anti-porcine IgM antibodies but did not change the concentration of anti-pig IgG antibodies. The serum concentration of IgM and IgG antibodies was assessed by ELISA and the level of anti-pig natural IgM and IgG antibodies by flow cytometry (FC). Anti-rat sensitization was assessed by specific ELISA as well as the serum concentration of LO-BM2. Results. Iterative injections of LO-BM2 allowed to specifically eliminate the anti-porcine IgM antibodies to undetectable levels at ELISA. Despite a normal serum level of anti-porcine IgG and complement proteins, HAVR was avoided. Without immunosuppression, the specific elimination of preformed anti-porcine IgM prolonged the survival of a renal xenograft in baboon up to 6 days, whereas without IgM antibody elimination, the renal xenografts were hyperacutely rejected within hours. The lost of activity of LO-BM2 after 10 days was concomitant to an IgM and IgG antibody rebound, which caused an acute vascular rejection of the xenograft. Conclusion. Specific elimination of natural anti-porcine IgM antibodies allows to avoid HAVR of a pig to baboon renal xenograft, whereas anti-porcine IgG antibodies and complement proteins were present in the serum. This result confirms previous in vitro reports and demonstrates for the first time in vivo that preformed IgM antibodies alone are responsible for HAVR, while preformed anti-porcine IgG antibodies are unable alone to cause HAVR. Anti-IgM therapy appears as an important tool to transiently but completely eliminates xeno-IgM antibodies in vivo.

Is the baboon model appropriate for endometriosis studies

OBJECTIVE To determinethe prevalence of spontaneous endometriosis andthe incidence of induced endometriosis after endocervical canal resection in baboons. DESIGN Induction and follow-up of endometriosis in baboons, which is one of the primate species that develop spontaneous endometriosis. Forty-one baboons were checked for the presence of spontaneous endometriosis. We then attempted to induce endometriosis in 30 of them by endocervical canal resection. SETTING Institute of Primate Research, Nairobi, Kenya, and Catholic University of Louvain, Brussels, Belgium. ANIMAL(S) Forty-one baboons were checked for spontaneous endometriosis and 30 of them were used to develop a model of induced endometriosis. INTERVENTION(S) A total of 41 baboons underwent diagnostic laparoscopy for 10 months. In a first step, 30 of this number subsequently underwent endocervical canal resection. In a second step, 20 of the 30 underwent uterine horn resection. MAIN OUTCOME MEASURE(S) Follow-up by laparoscopy. RESULT(S) Two of the 41 baboons were diagnosed with spontaneous endometriosis (4.8%). Twelve months after the surgical procedure to induce endometriosis, 8 of 29 animals presented with endometriotic lesions diagnosed by using laparoscopy and confirmed by histologic examination. The incidence of induced endometriosis in our model was thus 27.6%. In 2 baboons, endometriosis disappeared over time, resulting in a final rate of 20.7% (6/29). CONCLUSION(S) The rate of spontaneous endometriosis is very low (4.8%). Endometriosis can be induced (with a rate of just 27.6%) by endocervical canal resection to stimulate retrograde menstruation.

Induction of endometriotic nodules in an experimental baboon model mimicking human deep nodular lesions

OBJECTIVE To establish an experimental model for the study of deep nodular endometriosis. DESIGN Induction of nodular endometriosis in baboons by grafting different uterine specimens to the peritoneal cavity. SETTING Research and university facilities. ANIMAL(S) Ten baboons, to develop a model of induced deep nodular endometriosis. INTERVENTION(S) Biopsies of endometrium, and endometrium plus the junctional zone (JZ), full uterine thickness, and myometrium grafted to the peritoneum. MAIN OUTCOME MEASURE(S) Macroscopic descriptions recorded for observed induced lesions; staining with hematoxylin and eosin for histological evaluation and specific antibodies (CK22, CD10) for immunohistochemical studies; and analysis of surface area and volume of lesions, glandular density, and invasion of surrounding organs. RESULT(S) The incidence of induced nodular endometriosis was 100%, but the extent depended on the tissue grafted. Lesions induced after grafting specimens containing the JZ were statistically significantly larger than those not containing the JZ. Surrounding organ invasion was reported in more than 40% of lesions after grafting specimens containing the JZ. CONCLUSION(S) The first experimental model of nodular endometriosis allows investigation of deeper nodular lesions as well as invasion phenomena associated with nodular lesions.

In vivo biocompatibility of three potential intraperitoneal implants.

The intraperitoneal biocompatibility of PDMS, polyHEMA and pEVA was investigated in rats, rabbits and rhesus monkeys. No inflammation was evidenced by hematological analyses and measurement of inflammatory markers throughout the experiment and by post-mortem examination of the pelvic cavity. After 3 or 6 months, histological analysis revealed fibrous tissue encapsulating PDMS and PEVA implants in all species and polyHEMA implants in rabbits and monkeys. Calcium deposits were observed inside polyHEMA implants. The intraperitoneal biocompatibility of all 3 polymers makes them suitable for the design of drug delivery systems, which may be of great interest for pathologies confined to the pelvic cavity.