Advances in Organ and Tissue Xenotransplantation

End-stage organ failure can result from various preexisting conditions and occurs in patients of all ages, and organ transplantation remains its only treatment. In recent years, extensive research has been done to explore the possibility of transplanting animal organs into humans, a process referred to as xenotransplantation. Due to their matching organ sizes and other anatomical and physiological similarities with humans, pigs are the preferred organ donor species. Organ rejection due to host immune response and possible interspecies infectious pathogen transmission have been the biggest hurdles to xenotransplantation's success. Use of genetically engineered pigs as tissue and organ donors for xenotransplantation has helped to address these hurdles. Although several preclinical trials have been conducted in nonhuman primates, some barriers still exist and demand further efforts. This review focuses on the recent advances and remaining challenges in organ and tissue xenotransplantation.

Critical diagnostic and cancer stem cell markers in neoplastic cells from canine primary and xenografted pulmonary adenocarcinoma

It is challenging to diagnose metastatic tumors whose cellular morphology is different from the primary. We characterized canine primary pulmonary adenocarcinoma (PAC) and its xenografted tumors by histological and immunohistochemical analyses for critical diagnostic and cancer stem cell (CSC) markers. To generate a tumor xenograft model, we subsequently transplanted the tissue pieces from the PAC into athymic nude mice. Immunohistochemical examination was performed for diagnostic (TTF-1, Napsin A, and SP-A) and CSC markers (CD44 and CD133). The use of CSC markers together with diagnostic markers can improve the detection and diagnosis of canine primary and metastatic adenocarcinomas.

Genome and transcriptome analyses providing insight into the immune response of pearl oysters after allograft and xenograft transplantations

The immune response after allograft or xenograft transplantation in the pearl oyster is a major factor that cause its nucleus rejection and death. To determine the mechanism underlying the immune response after allograft and xenograft transplantations in the pearl oyster Pinctada fucata martensii, we constructed two sets of transcriptomes of hemocytes at different times (6 and 12 h; 1, 3, 6, 12, and 30 d) after allograft and xenograft transplantations, in which the xenografted mantle tissue was from Pinctada maxima. The transcriptomic analysis reveals many genes are involved in the immune response to transplantation, such as transient receptor potential cation channel (TRP), calmodulin (CaM), DNA replication-related genes, and sugar and lipid metabolism-related genes. The expression of these identified genes was higher in the host pearl oyster transplanted with xenograft than that by allograft. The histological analysis of the pearl sac also confirmed that many hemocytes were still gathered around the transplanted nucleus, and no pearl sac was formed in the host pearl oysters at 30 d after xenograft transplantation. The genomic analysis indicated that pearl oysters evolved many copies of genes, such as TRP, CaM, and GST, to sense and cope with the immune response after transplantation. "Ribosome" and "Cytosolic DNA-sensing pathway" were specifically induced in the xenograft group, whereas "Notch signaling pathway" specifically responded to the allograft transplantation. These results can improve our understanding of the mechanism underlying the immune response of pearl oysters after allograft and xenograft transplantations.

Interspecific germ cell transplantation: a new light in the conservation of valuable Balkan trout genetic resources?

Interspecific transplantation of germ cells from the brown trout Salmo trutta m. fario and the European grayling Thymallus thymallus into rainbow trout Oncorhynchus mykiss recipients was carried out in order to improve current practices in conservation of genetic resources of endangered salmonid species in the Balkan Peninsula. Current conservation methods mainly include in situ efforts such as the maintenance of purebred individuals in isolated streams and restocking with purebred fingerlings; however, additional ex situ strategies such as surrogate production are needed. Steps required for transplantation such as isolation of high number of viable germ cells and fluorescent labeling of germ cells which are to be transplanted have been optimized. Isolated and labeled brown trout and grayling germ cells were intraperitoneally transplanted into 3 to 5 days post hatch rainbow trout larvae. Survival of the injected larvae was comparable to the controls. Sixty days after transplantation, fluorescently labeled donor cells were detected within the recipient gonads indicating successful incorporation of germ cells (brown trout spermatogonia and oogonia-27%; grayling spermatogonia-28%; grayling oogonia-23%). PCR amplification of donor mtDNA CR fragments within the recipient gonads additionally corroborated the success of incorporation. Overall, the transplantation method demonstrated in this study presents the first step and a possible onset of the application of the germ cell transplantation technology in conservation and revitalization of genetic resources of endangered and endemic species or populations of salmonid fish and thus give rise to new or improved management strategies for such species.

Xenotransfusion of anemic cats with blood compatibility issues: pre- and posttransfusion laboratory diagnostic and crossmatching studies

BACKGROUND

Finding compatible feline blood donors can be challenging. Canine blood has been occasionally used when compatible feline blood was not available in emergency situations.

OBJECTIVES

The study goals were to describe the effects of xenotransfusion in 2 anemic cats receiving canine blood because of discordant blood types and acute transfusion reaction, respectively, and to report in vitro heterotyping and crossmatching results between canine and feline blood samples.

MATERIAL AND METHODS

Blood samples from patients and other cats and dogs were typed, crossmatched, and assessed for alloantibodies using gel, card, and immunochromatographic strip techniques.

RESULTS

Cat 1 was found to have type AB blood. Cat 2, which experienced an acute transfusion reaction, had type A blood. Neither had detectable alloantibodies against feline RBC. Both cats transiently improved after transfusion with canine blood; however, acute intravascular hemolysis occurred and the PCV rapidly declined. Blood typing post xenotransfusion with DEA 1 strips revealed a positive control band that was absent in feline blood, thus allowing for the identification of transfused canine RBC. Longitudinal assessment revealed that canine RBC could no longer be detected 4 days after xenotransfusion. Major crossmatching (feline plasma with canine RBC) resulted in both positive and negative reactions, depending on the cat. Minor crossmatching results showed mostly incompatibility.

CONCLUSION

While both cats survived xenotransfusion, the positive control band on the DEA 1 strip revealed that transfused canine RBC were short-lived and intravascular hemolysis occurred. Crossmatch results between cats and dogs showed varied incompatibilities and may not predict transfusion reactions.

Combined xeno/auto-grafting of a benign osteolytic lesion in a dog, using a novel bovine cancellous bone biomaterial

CASE HISTORY

A 4-year-old female Labrador Retriever was diagnosed with an osteolytic lesion of the right distal radius.

CLINICAL FINDINGS

Radiographs indicated a well-circumscribed radiolucent area 18 x 15 x 8 mm, centred on the distal radial physeal scar.

DIAGNOSIS

Histopathology, performed via Jamshidi needle biopsy and following surgical curettage, was inconclusive but suggested either an aneurysmal bone cyst or fibrous dysplasia.

CLINICAL RELEVANCE

A novel processed cancellous bovine bone xenograft was used in conjunction with autogenous cancellous bone (at a ratio of approximately 4:1) to fill the curetted defect. There were no observed complications associated with the use of this new biomaterial. Osteointegration of the bone graft was followed using conventional radiographs and peripheral quantitative computed tomography (pQCT) for 10 months post-operatively. Radiographically, the osteolytic lesion modelled to resemble metaphyseal trabeculation. The cross-sectional area and the average bone density of the grafted lesion determined using pQCT data increased over time, suggesting healthy osteoconduction and native bone production.

Xenogeneic transplantation of equine testicular cells into seminiferous tubules of immunocompetent rats

The objectives were to develop a transplantation assay for equine testicular cells using busulfan-treated prepubertal immunocompetent rats as recipients, and to determine if putative equine spermatogonial stem cells (SSCs) could be enriched by flow cytometric cell sorting (based on light scattering properties), thereby improving engraftment efficiency. Four weeks after transplantation of frozen/thawed PKH26-labeled equine testicular cells, 0.029 ± 0.045% (mean ± SD) of viable donor cells transplanted had engrafted. Donor cells were present in seminiferous tubules of all recipient rats forming chains, pairs, mesh structures, or clusters (with two to >30 cells/structure). Cells were localized to the basal compartment by the basement membrane. Although equine cells proliferated within rat seminiferous tubules, no donor-derived spermatogenesis was evident. Furthermore, there was no histologic evidence of acute cellular rejection. No fluorescent cells were present in control testes. When equine testicular cells were sorted based on light scattering properties, the percentage of transplanted donor cells that engrafted was higher after injection of cells from the small, low complexity fraction (II; 0.169 ± 0.099%) than from either the large, high complexity fraction (I; 0.046 ± 0.051%) or unsorted cells (0.009 ± 0.007%; P < 0.05). Seminiferous tubules of busulfan-treated prepubertal immunocompetent rats provided a suitable niche for engraftment and proliferation, but not differentiation, of equine testicular cells. Sorting equine testicular cells based on light scattering properties resulted in a 19-fold improvement in colonization efficiency by cells with high forward scatter and low side scatter, which may represent putative equine SSCs.

Analysis of Gene Expression in Bovine Testis Tissue Prior to Ectopic Testis Tissue Xenografting and During the Grafting Period1

The purpose of this study was to identify factors that contribute to bovine testis development and donor age-dependent differences in the abilities of bovine ectopic testis tissue grafts to produce elongated spermatids. We used real-time RT-PCR and microarrays to evaluate and to identify the expression of genes that are involved in Sertoli and germ cell development in bovine testis tissues. Testis tissues were obtained from 2-, 4-, and 8-wk-old bull calves and were grafted immediately. Grafted bovine testis tissue was removed from mice, RNA was isolated from the grafts, and real-time RT-PCR was used to evaluate gene expression during the grafting period. In addition, the gene expression in the donor tissue was analyzed using Affymetrix Bovine GeneChips, to identify differentially expressed genes. Examination of the testis tissue grafts indicated that Sertoli cell-specific gene expression was lower in 8-wk donor tissue grafts compared to the donors of other ages. Furthermore, the expression of KIT, which is a germ cell-specific gene, was low in testis tissue grafts. Microarray analysis of the donor tissue showed that several genes that are involved in angiogenesis or tissue growth were differentially expressed in 2-, 4-, and 8-wk-old bovine testes. The levels of expression of the genes for angiogenin, transgelin, thrombomodulin, early growth response 1, insulin-like growth factor 2, and insulin-like growth factor-binding protein 3 were lower in testis tissues from older animals. Using these data, it will be possible in the future to manipulate the testis xenograft microenvironment so as to improve the efficiency of sperm production within the graft.

Xenografting of adult mammalian testis tissue

Xenografting of testis tissue from immature males from several mammalian species to immunodeficient mouse hosts results in production of fertilization-competent sperm. However, the efficiency of testis tissue xenografting from adult donors has not been critically evaluated. Testis tissue xenografting from sexually mature animals could provide an option to preserve the genetic material from valuable males when semen for cryopreservation cannot be collected. To assess the potential use of this technique for adult individuals, testes from adult animals of six species (pig, goat, cattle, donkey, horse and rhesus monkey) were ectopically grafted to host mice. Grafts were recovered and analyzed at three time points: less than 12 weeks, between 12 and 24 weeks and more than 24 weeks after grafting. Histological analysis of the grafts revealed effects of species and donor tissue maturity: all grafts from species with greater daily sperm production (pig and goat) were found to have degenerated tubules or grafts were completely degenerated. None of the xenografts from mature adult bull and monkeys contained differentiated spermatogenic cells when examined more than 12 weeks post-grafting but tubules with Sertoli cells only remained. In grafts from a young adult bull, Sertoli cells persisted much longer than with the mature adult grafts. In grafts from a young adult horse, spermatogenesis proceeded to meiosis. In grafts from a young adult donkey and monkey, however, complete spermatogenesis was found in the grafts. These results show that testis tissue grafts from mature adult donors did not support germ cell differentiation but seminiferous tubules with Sertoli cells only survived in some species. The timing and progression of tubular degeneration after grafting of adult testis tissue appear to be related to the intensity of spermatogenesis at the time of grafting. Testis tissue from sub-adult donors survives better as xenograft than tissue from mature adult donors, and complete spermatogenesis can occur albeit with species-specific differences.

Things we have learned from tilapia islet xenotransplantation

An islet xenotransplantation model has been developed using tilapia (Oreochromis niloticus) as the donors. Studies using this model for the treatment of experimental type 1 diabetes in mice have produced promising results including the maintenance of long-term normoglycemia and mammalian-like glucose tolerance profiles in islet graft recipients. Islet encapsulation has also provided a promising method for the prevention of graft rejection, and strains of transgenic tilapia expressing a [desThrB30] human insulin molecule have been produced. In addition to studying islet transplantation for the treatment of type 1 diabetes, these studies have also produced insights into piscine glucose homeostasis. Studies demonstrating the glucose responsiveness of tilapia islets are described. In addition, work performed by our group and by others pertaining to presence and nature of piscine glucose transporters is reviewed. Finally, studies addressing some of the broader challenges of islet xenotransplantation are discussed with particular attention paid to the post-transplantation fate of the various islet cell populations and the proteins they produce.

Pegylated liposomal doxorubicin as a chemotherapeutic agent for treatment of canine transmissible venereal tumor in murine models

The effectiveness of Doxil as a new chemotherapeutic agent against canine transmissible venereal tumor was evaluated, using NOD/ SCID and CD1-nu xenograft mouse models and the response between the two mouse strains was compared. Samples of xenografted venereal tumor were inoculated SC into 20 six week-old NOD/SCID mice and 20 six week-old CD1-nu mice. Seven weeks later, tumor-bearing mice were divided into treatment and control groups. Treatment group was injected with Doxil (6 mg/kg, IP, as a single injection). Control group was injected with buffered saline (0.75cc, IP). Tumor size was determined by caliper measurements and tumor response was assessed according to standard criteria. In both strains there was a significant decrease in tumor size in response to Doxil treatment (P<0.0001). In CD1-nu eight out of nine tumors (88%) responded to the treatment, and in 2 cases complete remission was observed. In NOD/SCID group response to the treatment was seen in eight out of ten tumors (80%) but none regressed fully. Response to the treatment was statistically equal in both strains even though the apoptotic rate, confirmed by TUNEL staining, was higher in NOD/SCID than in CD-1-nu (8.65% and 0.7%, respectively) and tumor infiltrating cells were different: eosinophils in NOD/SCID and CD45R-positive B lymphocytes, and plasma cells in CD-1-nu. In untreated CD1-nu mice, tumor progress was slower than in NOD/SCID. Our results indicate that Doxil is effective against CTVT in mouse xenograft models.

Evaluation of porcine ileum models of enterocyte infection by Lawsonia intracellularis

The early interaction of Lawsonia intracellularis with host cells was examined with the use of porcine ileum models. Two conventional swine were anesthetized, and ligated ileum loops were prepared during abdominal surgery. The loops were inoculated with 108 L. intracellularis or saline. After 60 min, samples of each loop were processed for routine histologic and electron microscopic study. Histologic and ultrathin sections of all the loops appeared normal, with no apposition of bacteria and host cells or bacterial entry events in any loop. Portions of ileum from a single gnotobiotic piglet were introduced as xenografts into the subcutis of each flank of 5 weaned mice with severe combined immunodeficiency disease. After 4 wk, 108 L. intracellularis were inoculated into each of 4 viable xenografts with a sterile needle; the other 3 viable xenografts received saline. Histologic and ultrathin sections of all the xenografts 3 wk after inoculation showed relatively normal porcine intestinal architecture, with normal crypts, crypt cell differentiation, and low villous structures; the xenografts treated with the bacteria also showed intracytoplasmic L. intracellularis within crypt and villous epithelial cells. Thus, entry of L. intracellularis into target epithelial cells and multiplication may not be sufficient alone to directly cause cell proliferation. A proliferative response may require active division of crypt cells and differentiation in conjunction with L. intracellularis growth.

Mosaicplasty with photooxidized, mushroom shaped, bovine, osteochondral xenografts in experimental sheep

The goal was to study the performance of mushroom shaped, photooxidized, osteochondral grafts in mosaicplasty focusing on graft stability and survival. Mushroom shaped, photooxidized grafts (6 mm for the cartilaginous head of the mushroom, 3 mm for the stem) were implanted in the medial femoral condyle of 10 sheep. Four transplants were inserted per condyle in an overlapping fashion using the pressfit technique (n=40 grafts in 10 condyles). The grafts were followed for 6 and 12 months. Semi-quantitative evaluation of graft performance was performed using a validated score system. All grafts were mechanically stable at 6 and 12 months with one exception, where the mushroom head broke off. The formation of cystic lesions in the subchondral bone area was minimal. Repopulation of the old photooxidized cartilage was noticed with cells invading the matrix from the subchondral bone area and also from the pannus on the surface. Fusion between host and graft cartilage was observed in some of the grafts at 12 months, while remodeling of the calcified cartilage zone and tidemark was noticed in all grafts. Results scored significantly better for the 6 months compared to the 12 months group if cartilage surface integrity was compared (p<0.05). In all other variables no significant differences were found between groups. Despite moderate graft recession in the 12 months group partial fusion of grafts and functional results were satisfactory. The photooxidized mushroom shaped osteochondral transplants may be a suitable type of graft for functional results in cartilage resurfacing if stable anchorage of the grafts can be achieved.

Establishment and Characterization of a Cell Line, MCO-Y4, Derived from Canine Mammary Gland Osteosarcoma

A cell line, MCO-Y4, was established from a mammary gland osteosarcoma of a 16-year-old female mongrel dog. Histopathologically the tumor was composed of osteoblastic cells with an osteoid meshwork and chondroid matrix. The mean doubling time of the cells at the 93rd passage was 32.39+/-4.66 hr. Immunohistochemically, the osteoblastic and chondroblastic cells were positive for bone morphogenetic protein (BMP)-2/4 and BMP receptor (BMPR) II. The cultured cells were spindle in shape during the growth and the confluent phases. No tumor matrix was detected in the culture dish by alcian blue staining or von-Kossa silver impregnation. MCO-Y4 cells on the chamber slides showed intense immunoreactivity for BMP-2/4 and BMPR II. Noggin, an antagonist for BMP-2/4, showed the growth inhibition on MCO-Y4 cells. In addition, fibronectin might be potential for stimulating growth of MCO-Y4 cells. When transplanted into severe combined immunodeficiency mice, the cells formed tumors consisting of solid proliferation of osteoblastic and fibroblastic cells with woven-bone trabeculae. These tumor cells were intensely positive for BMP-2/4 and BMPR II. Our results suggested that the cell line might be useful for studying the role of BMPs in canine osteosarcoma and the mechanism of ossification.

Discodermolide analogues as the chemical component of combination bacteriolytic therapy

The marine natural product (+)-discodermolide (1) and several simplified analogues of this microtubule-stabilizing agent have proven to be potent in vitro cell growth inhibitory agents in several human cancer cell lines. Here, we demonstrate the in vivo efficacy of discodermolide and several simplified congeners, both as stand-alone anti-tumor agents and, in the case of (+)-2,3-anhydrodiscodermolide (3), as a chemical component of the combination bacteriolytic therapy. A single intravenous injection of (+)-3 plus genetically modified Clostridium novyi-NT spores caused rapid and complete regressions of tumors in mice bearing HCT116 colorectal cancer xenografts.

Development of embryos reconstructed by interspecies nuclear transfer of adult fibroblasts between buffalo (Bubalus bubalis) and cattle (Bos indicus)

The objective of this study was to explore the feasibility of employing adult fibroblasts as donor cells in interspecies nuclear transfer (NT) between buffaloes and cattle. Buffalo and bovine oocytes matured in vitro for 22 h were enucleated by micromanipulation using the Spindle View system. An ear fibroblast, pretreated with 0.1 microg/mL aphidicolin for 24 h, followed by culture for 2-9 days in Dulbecco's Modified Eagle's Media+0.5% fetal bovine serum, was introduced into the cytoplast by microinjection. Reconstructed oocytes were activated by exposure to 5 microM ionomycin for 5 min and 2 mM 6-dimethylaminopurine for 3 h. When buffalo adult fibroblasts were used as donor cells, there were no differences (P < 0.75) in the cleavage rate (66.2% versus 64.0%) between bovine and buffalo recipient oocytes, but more embryos derived from bovine cytoplasts developed to blastocysts than from buffalo cytoplasts (13.3% versus 3.0%, P < 0.05). When bovine adult fibroblasts were used as donor nuclei, both cleavage rate (45.3%) and blastocyst yield (4.5%) of NT embryos derived from buffalo cytoplasts were lower than those of NT embryos derived from bovine cytoplasts (65.5 and 11.9%, P < 0.05). The proportion of parthenogenetic buffalo (29.1%) or bovine (35.6%) oocytes developing to blastocysts was higher than those of NT embryos (P < 0.01). Interspecies NT embryos were derived from the donor cells and 55.0-61.9% of them possessed a normal diploid karyotype. In conclusion, embryos reconstructed by interspecies NT of adult fibroblasts between buffaloes and cattle developed to blastocysts, but bovine cytoplasts may direct embryonic development more effectively than buffalo cytoplasts, regardless of donor cell species.

The use of porcine small intestinal submucosa for the repair of full-thickness corneal defects in dogs, cats and horses

OBJECTIVE

To evaluate the efficacy of using a porcine small intestinal submucosa (SIS) graft covered by a conjunctival flap for the surgical repair of full-thickness corneal wounds in dogs, cats and horses.

PROCEDURE

All records dating from August 1999 to February 2003 from Purdue University Veterinary Teaching Hospital of patients that had undergone ophthalmic surgical procedures and received a SIS corneal graft for a full-thickness lesion were reviewed. Fifteen cases were identified including six dogs, two cats and seven horses. Requirements for inclusion in this study were that SIS was used as a corneal graft in a full-thickness corneal defect and that the graft was completely covered with a conjunctival flap.

RESULTS

Of the 15 cases, one canine patient had received SIS following removal of an epibulbar melanocytoma. The remaining five canine patients had undergone this surgical procedure for the repair of corneal perforation. The two feline patients had been presented for corneal perforation following chronic ulceration. One equine patient had been presented for a deep melting ulcer, three for stromal corneal abscesses, and three for corneal perforations. Complications encountered postoperatively included aqueous leakage, conjunctival flap dehiscence, synechia, cataract and fibrin in the anterior chamber. Fourteen out of 15 patients were visual at the final re-evaluation.

CONCLUSION

SIS is an inexpensive, easy-to-handle biomaterial that appears to be suitable for the repair of full-thickness corneal wounds in dogs, cats and horses. Results of our study support the conclusion that this relatively new product is an effective alternative to traditional implantation materials utilized in veterinary ophthalmology.

Prevalence of porcine endogenous retrovirus in domestic pigs in Japan and its potential infection in dogs xenotransplanted with porcine pancreatic islet cells

The prevalence of porcine endogenous retrovirus (PERV) proviral DNA among various pig breeds raised in Japan was investigated by polymerase chain reaction (PCR). Moreover, potential infection of PERV was investigated by PCR and reverse transcriptase-polymerase chain reaction (RT-PCR) in experimentally induced diabetic dogs (n=5) implanted with the diffusion chamber type bio-artificial endocrine pancreas (Bio-AEP) containing porcine pancreatic endocrine (PE) cells. No immunosuppressant was used after the transplantation. PERV gag, pol, env-A and env-B genes were detected in any pigs examined. In two of three Landrace breeds, env-C gene was absent. PERV proviral DNAs and viral RNAs were also detected from the cultured porcine PE-cells. In the peripheral blood mononuclear cells and the spleen obtained at 6, 30, 32, 36, 79 weeks of xenotransplantation in dogs, however, no evidence of microchimerism, infection and viremia were confirmed. These results suggested that the risk of PERV infection through xenotransplantation of Bio-AEP containing porcine islet cells without immunosuppressants may be quite low.

Biomedical and Agricultural Applications of Animal Transgenesis

Additive transgenesis by pronuclear injection of the mouse zygote has been in use for more than 20 yr and gene targeting in mouse embryonic stem cells for almost as long. Together, these techniques have revolutionized animal biology by helping to unravel much of what we now know about gene function. Both additive transgenics and targeting can also be performed in livestock species but the impact has not yet been substantial. In part, this has been the result of the inefficiency of the techniques but-at least in agriculture-also to a lack of obvious practicality. This review assesses the extent to which this situation is changing, with particular reference to applications in biopharming, xenotransplantation, and large animal models.

Xenotransplantation of porcine pancreatic endocrine cells to total pancreatectomized dogs

Xenotransplantation of porcine pancreatic endocrine (PE) cells in a diffusion chamber, a bioartificial endocrine pancreas (Bio-AEP), was conducted to total pancreatectomized dogs. Six pancreatectomized dogs were divided into two groups of 3 dogs each. In three dogs of the control group, exogenous insulin was administered twice a day for 30 weeks to maintain fasting blood glucose (FBG) levels within the normal range. The remaining three dogs were implanted with Bio-AEPs (implantation group), in addition to daily insulin administration. In the implantation group, Bio-AEPs containing 1.3 to 1.8 x 10(7) cells per kg of body weight of the recipient were implanted without fixation into the abdominal cavity. In the control group, exogenous insulin requirements did not decrease during the experimental period, whereas it significantly decreased for a certain period (3, 11, 17 weeks) after implantation in all implanted dogs. In the implantation group, laparotomy was performed after FBG and the exogenous insulin requirement increased again and Bio-AEPs were removed. Two Bio-AEPs were completely destroyed, and the remaining one was encapsulated by thin fibrous tissue. In this dog, effusion was present within the capsule, but the Bio-AEP was not destroyed. Histopathologically, the necrosis, presumably caused by hypoxia, of the PE-cells was observed on transmission electron microscopy. In conclusion, Bio-AEP could function for a certain period after implantation in this study. However, more preclinical researches should be needed to apply this technique for the treatment of diabetic dogs.

Incorporation of bovine bone marrow stromal cells into porcine foetal tissues after xenotransplantation

Bovine bone marrow stromal cells (BMSCs) were injected into the liver of foetal pigs at about 40 days of gestation to test whether these cells could populate developing tissue, and if so, which ones. Approximately 40 days after injection, the foetuses were harvested and tissue sections from many areas of the body were analysed for the presence of bovine cells using two different methods. First, using PCR, bovine repetitive DNA was found to be present in DNA extracted from foetal pig tissues. Secondly, using oligonucleotide primed in situ synthesis (PRINS), the in situ presence of bovine cells was found within porcine tissue sections. PRINS-labelled cells were found within cartilage, perichondrium, connective tissue and smooth muscle. These data suggest that bovine BMSCs integrate throughout the foetal pig.

An evaluation of combined immunosuppression with MNA 715 and microemulsified cyclosporine on renal allograft rejection in mismatched mongrel dogs

OBJECTIVE

To evaluate a combination of MNA 715 and microemulsifed cyclosporine for the prevention of renal allograft rejection in mismatched mongrel dogs.

STUDY DESIGN

Randomized, experimental study.

ANIMALS

Fourteen female mismatched mongrel dogs.

METHODS

Heterotopic renal transplantation and bilateral nephrectomy were performed in each dog. Dogs were randomly assigned to receive either MNA 715 and cyclosporine (n = 8) or cyclosporine alone (n = 6). Dogs were killed at 100 days after transplantation or when plasma creatinine exceeded 7 mg/dL.

RESULTS

In the cyclosporine and MNA 715 group: 4 dogs survived to 100 days with normal plasma creatinine concentrations; 2 dogs with intestinal intussusceptions were killed at 5 and 8 days, 1 dog with a wound infection and sepsis was killed at 14 days, and 1 dog with a serum creatinine concentration >7 mg/dL was killed at 51 days postoperatively. In the cyclosporine-alone group: 3 dogs with acute rejection were killed at 6 to 9 days and 3 dogs survived to 100 days. In dogs treated with cyclosporine and MNA 715, survival to histologically confirmed acute rejection was significantly longer (P =.044) and the degree of mononuclear cell infiltration was significantly reduced (P =.040), compared with dogs treated with cyclosporine alone.

CONCLUSIONS

MNA 715 combined with cyclosporine prolonged allograft survival and reduced the severity of histologic rejection in a clinically relevant renal transplant model.

CLINICAL RELEVANCE

An immunosuppressive regimen consisting of MNA715 and microemulsified cyclosporine may be effective in preventing allograft rejection in canine renal transplant patients.

Progress in reproductive biotechnology in swine

This article summarizes recent progress in reproductive biotechnology in swine with special reference to in vitro production of embryos, generation of identical multiples, and transgenic pigs useful for xenotransplantation. In vitro production (in vitro maturation, in vitro fertilization, and in vitro culture) of viable porcine embryos is possible, although with much lower success rates than in cattle. The main problems are insufficient cytoplasmic maturation of porcine oocytes, a high proportion of polyspermic fertilization and a low proportion of blastocysts that, in addition, are characterized by a low number of cells, hampering their development in vivo upon transfer to recipients. Microsurgical bisection of morula and blastocyst stage embryos leads to a 2 to 3% monozygotic twinning rate of the transferred demiembryos, which is similar to that in rabbits and mice but considerably lower than in ruminants. It was found that with decreasing quality an increasing proportion of demi-embryos did not possess an inner cell mass. Porcine individual blastomeres derived from 4- and 8-cell embryos can be cultured in defined medium to the blastocyst stage. Leukemia inhibitory factor has been shown to be effective at defined embryonic stages and supports the formation of the inner cell mass in cultured isolated blastomeres in a concentration-dependent manner. For maintaining pregnancies with micromanipulated porcine embryos, it is not necessary to transfer extraordinarily high numbers of embryos. Porcine nuclear transfer is still struggling from the inefficiency of producing normally functioning blastocysts. Blastomeres, blastocyst-derived cells, fibroblasts and granulosa cells have been employed as donor cells in porcine nuclear transfer and have yielded blastocysts. Recently, the generation of the first piglets from somatic cell nuclear transfer has been achieved. DNA-microinjection into pronuclei of porcine zygotes has reliably resulted in the generation of transgenic pigs, which have special importance for the production of valuable pharmaceutical proteins in milk and xenotransplantation. It has been demonstrated that by expression of human complement regulatory proteins in transgenic pigs the hyperacute rejection response occurring after xenotransplantation can be overcome in a clinically relevant manner. Although biotechnological procedures in swine have recently undergone tremendous progress, the development is still lagging behind that in cattle and sheep. With regard to genetic engineering, considerable progress will originate from the possibility of employing homologous recombination in somatic cell lines and their subsequent use in nuclear transfer. In combination with the increasing knowledge in gene sequences this will allow in the foreseeable future widespread use in the pig industry either for agricultural or biomedical purposes.

Refinement of an orthotopic lung cancer model in the nude rat

Over 85% of people with lung cancer eventually succumb to this disease, largely because current chemotherapies are ineffective. The testing and validation of promising new approaches generally rely on achieving responses with cell lines in vitro or in tumor xenografts in nude mice. However, quite often the results seen with these models are not recapitulated in the clinic, thus necessitating the need for better animal models of lung cancer for preclinical testing of new therapies. One promising model is that of orthotopic lung cancer, where xenografts of human lung cancer are established in lungs of immunodeficient rodents. The problems associated with this model include poor rates of engraftment, limited tumor multiplicity, and a heightened risk for surgical trauma. The purpose of our study was to develop an efficient approach to engraftment of orthotopic tumors throughout the lungs of the Rowett nude rat. Initially, we augmented immunosuppression in the rats with whole-body X-irradiation and then used orotracheal cannulas to intratracheally instill human cancer cells from the Calu-6 cell line. This protocol produced a low rate of engraftment and low tumor multiplicity. The hypothesis that slight disruption of the pulmonary epithelium or the surfactant layer would allow better tumor engraftment was tested by coadministration of either pancreatic elastase or ethylenediaminetetraacetic acid (EDTA) along with the cell instillations. Lung tumor engraftment was evaluated 8 weeks after instillation. The inclusion of elastase or EDTA with the Calu-6 cells resulted in an 80-100% engraftment rate, respectively. Coadministration of EDTA resulted in significantly larger and greater numbers of tumors/lung than those in elastase-treated animals. Temporal studies demonstrated that small nodules were scattered throughout the lung parenchyma 5 weeks after instilling Calu-6 cells and EDTA. These nodules grew to coalesce and form large masses that effaced >75% of the parenchyma at 9 weeks postinstillation. The refinements made through our studies have led to the development of an orthotopic lung cancer model that should facilitate the evaluation of novel therapies designed to treat or impede lung cancer development.

Xenotransplantation: regulatory challenges

During 1999-2000, the US government published three xenotransplantation policy/guidance documents, one by the Public Health Service and two by the Food and Drug Administration (FDA). The FDA also held two public meetings of the xenotransplantation subcommittee of the Biological Response Modifiers Advisory Committee to discuss particular issues in xenotransplantation.

Use of a murine xenograft model for canine transmissible venereal tumor

OBJECTIVE

To develop a murine model for canine transmissible venereal tumor (CTVT).

ANIMALS

Thirty-three 6-week-old NOD/LtSz-scid (NOD/SCID) mice and seven 6-week-old C57BL/6J mice.

PROCEDURE

Samples of CTVT were excised from a 3-year-old dog and inoculated SC into ten 6-week-old NOD/SCID mice to induce growth of xenograft transmissible venereal tumor (XTVT). To establish mouse-to-mouse transmission, samples of XTVT were removed and inoculated SC into 4 groups of 6-week-old NOD/SCID mice and into a control group. Samples of CTVT were also inoculated into immunocompetent C57BL/6J mice for a mouse antibody production (MAP) test. The canine and xenografted tumors were evaluated cytologically and histologically, and polymerase chain reaction was performed for detection of the rearranged LINE/c-MYC junction.

RESULTS

8 of 10 NOD/SCID mice that were inoculated with CTVT developed tumors 3 to 10 weeks after inoculation. In the second-generation xenograft, all mice developed tumors by postinoculation day 47; 1 X 10(6) of XTVT cells were enough to create a xenograft. Metastases developed in 4 of 20 mice. Xenografted and metastatic tumors retained cytologic, histologic, and molecular characteristics of CTVT. Results of the MAP test were negative for all pathogens.

CONCLUSION

We established an NOD/SCID murine model for XTVT and metastasis of CTVT. This model should facilitate study of tumor transplantation, progression, and metastasis and should decrease or eliminate the need for maintaining allogenic transfer in dogs.

Anaesthetic management of baboons undergoing heterotopic porcine cardiac xenotransplantation

A detailed anaesthetic technique for baboons (Papio anubis) undergoing heterotopic abdominal cardiac xenotransplantation is described. Twenty-two baboons served as transplant recipients. Donors were either crossbred farm pigs (Sus scrofa) (n = 4) or transgenic pigs (Sus scroefa) (n = 18) expressing human complement regulatory proteins on the endothelium. Intra-operative management was complicated by the physiological consequences of infrarenal. abdominal aortic cross-clamping, in addition to the immunological sequelae related to cross-species transplantation. In choosing anaesthetics for this procedure, we considered the need for maximal cardiac stability throughout a long surgical procedure that required abdominal aortic cross-clamping to facilitate the implantation of an oversized porcine cardiac graft. Baboons received a balanced anaesthetic consisting of inhaled isoflurane in oxygen, intravenous fentanyl and intravenous pancuronium. The pharmacological techniques employed were found to be safe and reliable and were well tolerated by our recipients without any significant side-effects.

Follicular development in cryopreserved Common Wombat ovarian tissue xenografted to Nude rats

The Northern Hairy-nosed Wombat (Lasiorhinus krefftii) is a highly endangered marsupial species and every possible option for sustaining the species needs to be explored. One important approach may be the development of assisted reproductive technologies in the non-endangered Common Wombat (Vombatus ursinus) and Southern Hairy-nosed Wombat (Lasiorhinus latifrons) for application in breeding the Northern Hairy-nosed Wombat. In this study, it was examined whether cryopreserved Wombat ovarian tissue would develop following xenografting to immunologically deficient rats. Ovarian tissue was collected from Common Wombats (n = 3) and cryopreserved as small cortical pieces. After thawing the cortical pieces were grafted underneath the kidney capsule of Nude rats (n = 16). The grafts were recovered at 2, 4, and 10 weeks after transplantation and their gross and histological appearance investigated. Two weeks after grafting (n = 2), the tissue was revascularized and healthy primordial follicles were present. At week 4 (n = 2), some follicular development was present. At week 10, six rats received human chorionic gonadotrophin (hCG) to trigger follicle and oocyte maturation while another six rats were not given any treatment. The administration of hCG did not induce preovulatory follicles and oocyte maturation although type 5 follicles were present in ovarian tissue collected 10 weeks posttransplantation in both treated and untreated groups. This study demonstrates for the first time that Wombat ovarian tissue can survive and function when grafted into immunocompromized rats and that Wombat ovarian follicles can be recruited to growth and development in an ovarian xenograft. This model system has the potential to produce mature oocytes from endangered species for use in assisted reproductive technologies such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and mature oocytes from non-endangered species for nuclear transfer which may be necessary for the preservation of critically endangered species.

Fracture healing after stabilization with intramedullary xenograft cortical bone pins: a study in pigeons

OBJECTIVE

To investigate the effectiveness of intramedullary xenograft cortical bone pins compared with stainless steel Kirschner wire for the repair of a standardized avian humeral fracture.

STUDY DESIGN

Prospective randomized study.

SAMPLE POPULATION

Thirty mature pigeons (Columba livia).

METHODS

Birds were randomly assigned to 3 groups. Transverse mid-diaphyseal humeral fractures were created in 1 humerus in each bird. Fractures were stabilized with intramedullary ostrich or canine xenograft cortical bone pins or Kirschner wire. Radiographic, histological, and biomechanical assessments were used to compare fracture healing 6 weeks after fracture stabilization. The contralateral humerus of each bird was used as a control.

RESULTS

All fractures healed regardless of intramedullary pin type. There were no statistically significant biomechanical differences among groups or within groups. Xenograft cortical bone pins induced a mononuclear inflammatory reaction that did not impair bone healing. Bones stabilized with intramedullary cortical bone pins had more periosteal callus and inflammation at the fracture site than bones stabilized with stainless steel Kirschner wires.

CONCLUSIONS

Intramedullary xenograft cortical bone pins, derived from mammalian or avian sources, appear to represent an alternative for the repair of avian humeral fractures.

CLINICAL RELEVANCE

Intramedullary xenograft cortical bone pins are biodegradable and may reduce the need for additional surgery to remove implants after fracture healing.

Chest roentgenographic techniques for demonstrating human lung tumour xenografts in nude rats

Roentgenographic techniques were investigated for imaging orthotopic lung tumours in anaesthetized nude rats endobronchially implanted with human lung cancer cells. A conventional radiographic unit with a dual-screen, double-emulsion film mammographic receptor produced images preferable to those from a mammographic unit because of superior resolution. Typical exposure factors were 300 mA, 29 kVp, and 17 ms at a focus-film distance of 76 cm with a 2.11 by 2.41 mm effective focal spot and inherent filtration of 1.2 mm aluminium. Sensitivity for tumour detection was 0.93 for 59 animals with pathologically proved tumours and 0.96 for 54 animals with tumours larger than 4 mm or 50 mg. For 24 pathologically tumour-free animals, specificity was 1.00. For 55 animals radiographically judged to have tumours, positive predictive value was 1.00. For all 83 animals, accuracy was 0.95. This technique effectively demonstrates orthotopic human lung tumours in nude rats and should be useful for noninvasive monitoring of tumour presence, location, size, and changes in size.

Toxicity of anticancer agents, growth and chemosensitivity of human tumour xenografts in a segregating stock of AF nude mice

An investigation of the usefulness of a segregating stock of nude mice [AF nude mice (AF-nu)] for screening anticancer agents was undertaken. The toxicity of anticancer agents, takes and growth rates of human tumour xenografts and chemosensitivities of xenografts in AF-nu were studied and compared with those in BALB/cA nude mice (BALB/cA-nu). The results showed differences in the pattern of mortalities of AF-nu and BALB/cA-nu administered a range of anticancer agents. Body weight changes in the two nude mouse strains differed in the case of 5-fluorouracil, but not for nimustine, adriamycin and vincristine. All tumours transplanted in AF-nu grew as in BALB/cA-nu. Growth rates of 2 xenografts (gastric cancer and glioblastoma) were not significantly different between the 2 nude mouse strains, but those of 2 lung tumour xenografts were significantly greater in AF-nu than those in BALB/cA-nu. There were no significant differences in chemosensitivities of human tumours in AF-nu and BALB/cA-nu (consistency rate as evaluated by our criteria was 88%). From these results, it is suggested that AF-nu are more suitable for anticancer agent screening and experimental chemotherapy of human tumour xenografts than BALB/cA-nu because of lower costs and high reproductive rate. Although they are genetically heterogeneous, sets of experimental animals sharing the same gene pool can be produced routinely.

Oestrogen production by the preimplantation donkey conceptus compared with that of the horse and the effect of between-species embryo transfer

Aromatase distribution in membranes of preimplantation horse and donkey conceptuses was compared by measuring the incorporation of [3H]androstenedione into oestrone and oestradiol-17 beta. In the donkey conceptus, aromatase activity was similar in all the tissues examined (yolk sac, chorionic girdle and allantochorion), whereas in the horse it was generally lower and showed the relationship chorionic girdle greater than yolk sac greater than allantochorion. A higher proportion of labelled precursor was incorporated into oestradiol-17 beta by extra-embryonic tissues of the donkey compared with those of the horse. In contrast to previous results, aromatase in the chorionic girdle did not decline progressively before its migration into the endometrium on Day 36 to form the endometrial cups. The chorionic girdle of a donkey conceptus carried in the uterus of a mare failed to invade the surrogate horse endometrium and aromatase activity was still high in this tissue at Day 42. Aromatase distribution in 2 transferred donkey-in-horse conceptuses resembled that of the fetal, rather than the maternal, genotype indicating a lack of effect of the maternal environment.

Host response to bovine ocular squamous cell carcinoma

Specific humoral and cellular immunologic responses to autologous and heterologous tumors were evaluated in 35 Hereford cows with ocular squamous cell tumors and in 6 healthy cows. Sera from 5 healthy cows and 23 ocular tumor-bearing cows were evaluated for antibody to tumor, using radioimmunoassay, passive hemagglutination, agglutination, and microagglutination assays with various soluble tumor antigen and whole tumor cell preparations. Antibody to tumor was detected in only 2 cows. Using the microagglutination assay, antibody to autologous and heterologous tumor cells was found in the sera of 2 cows inoculated intraocularly with purified, viable autologous tumor cells. Twenty-eight tumor-bearing cows and 3 healthy cows were evaluated for delayed-type hypersensitivity responses, using 5 tumor preparations; positive skin test responses were not observed.

Cervical vertebral interbody fusion in the horse: a comparative study of bovine xenografts and autografts supported by stainless steel baskets

A modified form of the Cloward technique for anterior cervical fusion in human beings was used in the application of different grafts for evaluation of their effectiveness in stabilizing equine cervical vertebrae. Results of bovine xenograft implants in 8 horses were compared with results of stainless steel baskets (SSB) packed with cancellous autogenous bone in 8 horses. Graft material was incorporated in all cases. Evidence of graft rejection was not present. Both forms of implants decreased the mobility of the intervertebral space in which they were implanted. A fibrous connective tissue union was prevalent after xenograft implantation. Osseous union was prevalent after implantation of the SSB. Reduction in range of motion was greatest at those sites with the SSB.

Xenografts of articular chondrocytes in the nude mouse

Subcutaneous transplantation of articular chondrocytes isolated enzymatically from immature rabbits and dogs into athymic (nu/nu) mice resulted in the formation of hyaline cartilaginous nodules. Graft rejection was seen when the cells were injected into heterozygous (nu/+) mice. Radiosulfate-labeled proteoglycan extracted from the xenografts had a high buoyant density and was digested by chondroitinase ABC. A monomeric preparation of proteoglycan (A1-D1) contained a small quantity of aggregate as assessed by gel chromatography and gel electrophoresis. Almost no incorporation of 3H-thymidine was found by autoradiography. The matrix did not become calcified over the course of 42 days. The nude mouse system lends itself to testing a variety of problems in the biology of cartilage. These include the redifferentiation of chondrocytes following dedifferentiation in vitro. Species differences were found in this regard. The nodules formed by rabbit articular chondrocytes, grown in monolayer culture for up to 14 days, had a hyaline chondroid character. Dog chondrocytes that had "dedifferentiated" during 14 days of culture prior to transplantation, formed a graft that had a sparse fibrous rather than hyaline matrix.