Heart of the matter-infection and xenotransplantation

In this clinicopathological conference, invited experts discussed a previously published case of a patient with nonischemic cardiomyopathy who underwent heart transplantation from a genetically modified pig source animal. His complex course included detection of porcine cytomegalovirus by plasma microbial cell-free DNA and eventual xenograft failure. The objectives of the session included discussion of selection of immunosuppressive regimens and prophylactic antimicrobials for human xenograft recipients, description of infectious disease risk assessment and mitigation in potential xenograft donors and understanding of screening and therapeutic strategies for potential xenograft-related infections.

A zebrafish xenotransplant model of anaplastic thyroid cancer to study the tumor microenvironment and innate immune cell interactions in vivo

Anaplastic thyroid cancer (ATC) is a rare malignant subtype of thyroid cancer. While ATC is rare it accounts for a disproportionately high number of thyroid cancer-related deaths. Here we developed an ATC xenotransplant model in zebrafish larvae, where we can study tumorigenesis and therapeutic response in vivo. Using both mouse (T4888M) and human (C643) derived fluorescently labeled ATC cell lines we show these cell lines display different engraftment rates, mass volume, proliferation, and angiogenic potential. Next, using a PIP-FUCCI reporter to track proliferation in-vivo we observed cells in each phase of the cell cycle. Additionally, we performed long-term non-invasive intravital microscopy over 48 hours to understand cellular dynamics in the tumor microenvironment at the single cell level. Lastly, we tested a well-known mTOR inhibitor to show our model could be used as an effective screening platform for new therapeutic compounds. Altogether, we show that zebrafish xenotransplants make a great model to study thyroid carcinogenesis and the tumor microenvironment, while also being a suitable model to test new therapeutics in vivo.

Unique problems for the design of the first trials of transplanting porcine kidneys into humans

Over the past year, 3 scientific teams conducted experiments of genetically edited porcine organs into human recipients, 3 of whom were deceased and 1 living. In this editorial, we describe challenges for the design of initial xenotransplantation clinical trials and focus on patient selection, consent, and requisite post-transplant follow-up. Given the uncertain clinical benefit of xenotransplantation, we propose that patient selection criteria might include novel elements, such as approaching patients who have a low quality of life and a strong aversion to continued dialysis therapy. We set expectations related to the importance of informing and protecting family members and medical teams who could be exposed to zoonotic viral infection from the donor organ and/or receive unwanted publicity. Meeting these challenges in trial design and oversight will require multidisciplinary expertise, a conceptual model that extends beyond the individual patient, and creative collaboration between scientists and regulatory agencies.

The Ultrastructural Analysis of Human Colorectal Cancer Stem Cell-Derived Spheroids and Their Mouse Xenograft Shows That the Same Cells Types Have Different Ratios

Spheroids from primary colorectal cancer cells and their mice xenografts have emerged as useful preclinical models for cancer research as they replicate tumor features more faithfully as compared to cell lines. While 3D models provide a reliable system for drug discovery and testing, their structural complexity represents a challenge and their structure-function relationships are only partly understood. Here, we present a comparative ultrastructural and flow citometric analysis of patient colorectal cancer-derived spheroids and their mice xenografts. Ultrastructural observations highlighted that multicellular spheroids and their xenografts contain the same cancer cell types but with different ratios, specifically multicellular spheroids were enriched in cells with a stem-like phenotype, while xenografts had an increased amount of lipid droplets-containing cells. The flow cytometric analysis for stem cell marker and activity showed enrichment of stem-like cells presence and activity in spheroids while xenografts had the inverse response. Our results evidence the effects on cancer cells of different in vitro and in vivo microenvironments. Those differences have to be paid into account in designing innovative experimental models for personalized drug testing.

The Use of Zebrafish Xenotransplant Assays to Analyze the Role of lncRNAs in Breast Cancer

Breast cancer represents a great challenge since it is the first cause of death by cancer in women worldwide. LncRNAs are a newly described class of non-coding RNAs that participate in cancer progression. Their use as cancer markers and possible therapeutic targets has recently gained strength. Animal xenotransplants allows for in vivo monitoring of disease development, molecular elucidation of pathogenesis and the design of new therapeutic strategies. Nevertheless, the cost and complexities of mice husbandry makes medium to high throughput assays difficult. Zebrafishes (Danio rerio) represent a novel model for these assays, given the ease with which xenotransplantation trials can be performed and the economic and experimental advantages it offers. In this review we propose the use of xenotransplants in zebrafish to study the role of breast cancer lncRNAs using low to medium high throughput assays.

Anti-Müllerian Hormone (AMH) regulates BRCA1 and BRCA2 gene expression after ovarian cortex transplantation

OBJECTIVE

To test whether recombinant anti-Müllerian hormone (rAMH) could exert an inhibitory function on BRCA1/2 expression in human ovarian cortex.

METHODS

Pilot study on ovariectomized nude mice xenotransplanted with human vitrified/warmed ovarian cortex and treated with rAMH via infusion pump. Twelve nude mice were ovariectomized and Alzet pumps delivering 1.23 mcg rAMH/day to reach a serum concentration of 17.5 ng/mL, or placebo (controls), were inserted intraabdominally. Previously vitrified/warmed 2x2 mm ovarian cortex fragments were transplanted on day 7 and then harvested on day 14 after pump placement. PCR analyses determined mRNA levels for BRCA1 and BRCA2 in the human ovarian cortex.

RESULTS

In mice treated with rAMH, BRCA1 expression was significantly lower (0.196 fg/µg RNA, IQR 0.158, 0.236) than in controls (0.544 fg/µg RNA, IQR 0.458, 0.554; p = .030), while BRCA2 expression remained similar in rAMH mice (5.355 fg/µg RNA, IQR 4.479, 6.230) and in controls (4.011 fg/µg RNA, IQR 3.650, 4.182; p = .327).

CONCLUSION

Administration of rAMH in the peri-transplant period caused downregulation of BRCA1, but not of BRCA2 expression, in human ovarian cortex. These results help our understanding of DNA repair mechanism in the ovarian cortex and identify AMH's possible protective effect on ovarian reserve in BRCA1 mutation carriers.

Development of the Nude Rabbit Model

Loss-of-function mutations in the forkhead box N1 (FOXN1) gene lead to nude severe combined immunodeficiency, a rare inherited syndrome characterized by athymia, severe T cell immunodeficiency, congenital alopecia, and nail dystrophy. We recently produced FOXN1 mutant nude rabbits (NuRabbits) by using CRISPR-Cas9. Here we report the establishment and maintenance of the NuRabbit colony. NuRabbits, like nude mice, are hairless, lack thymic development, and are immunodeficient. To demonstrate the functional applications of NuRabbits in biomedical research, we show that they can successfully serve as the recipient animals in xenotransplantation experiments using human induced pluripotent stem cells or tissue-engineered blood vessels. Our work presents the NuRabbit as a new member of the immunodeficient animal model family. The relatively large size and long lifespan of NuRabbits offer unique applications in regenerative medicine, cancer research, and the study of a variety of other human conditions, including immunodeficiency.

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NuRabbit colony is established and available for the research community

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NuRabbits are nude and immunodeficient due to a mutation(s) in the FOXN1 gene

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NuRabbits support iPSC teratoma assay

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NuRabbits support xenotransplant of tissue-engineered blood vessels

Ultrasound-Targeted Microbubble Destruction-Mediated Downregulation of EZH2 Inhibits Stemness and Epithelial-Mesenchymal Transition of Liver Cancer Stem Cells

Background

Cancer cells could show the characteristics of cancer stem cells (CSCs) through epithelial-mesenchymal transition (EMT). EZH2 was associated with EMT. Ultrasound-targeted microbubble destruction (UTMD) could enhance gene transfection efficiency. Here, we explored the effect of UTMD-mediated shEZH2 on liver CSCs.

Methods

EZH2 expression in liver cancer and the overall survival of liver cancer patients were analyzed by bioinformatics. Liver CSCs (CD133⁺HuH7) were sorted by flow cytometry. After transfection of shEZH2 through UTMD (UTMD-shEZH2) or liposome (LIP-shEZH2), the viability, proliferation, sphere formation, migration, and invasion of CD133⁺HuH7 cells were detected by MTT, colony formation, tumor-sphere formation, wound healing, and transwell assays, respectively. A mice subcutaneous-xenotransplant tumor model was established by injecting CD133⁺HuH7 or CD133⁻HuH7 cells into the limbs of mice. Tumor weight and volume were documented. The expressions of EZH2, EMT-related factors, and STAT3/PI3K/AKT pathway-related factors in CD133⁺HuH7 cells or tumor tissues were detected by RT-qPCR, Western blot, or immunohistochemical.

Results

EZH2 was high-expressed in liver cancer, and the patients with high expression of EZH2 had a poor survival. CD133⁺ HuH7 cells had higher EZH2 expression, higher viability, and stronger sphere-forming and tumor-forming abilities than CD133⁻ HuH7 cells. ShEZH2 inhibited the viability, proliferation, sphere formation, migration, and invasion of CD133⁺ HuH7 cells, decreased the weight and volume of the xenotransplant tumor, inhibited the expressions of EZH2, Vimentin, N-Cadherin, Twist-1, p-STAT3, p-PI3K, and p-AKT, and increased E-Cadherin expression. UTMD-shEZH2 caused a stronger effect on CD133⁺ HuH7 cells than LIP-shEZH2.

Conclusion

UTMD-mediated shEZH2 inhibited the stemness and EMT of liver CSCs in vitro and in vivo through regulating the STAT3/PI3K/AKT pathway.

Surgical Treatment of Pyoderma Gangrenosum with Negative Pressure Wound Therapy and Skin Grafting, Including Xenografts: Personal Experience and Comprehensive Review on 161 Cases

Significance: Pyoderma gangrenosum (PG) is a rare debilitating autoinflammatory ulcerative skin disease. No gold standard has been established for the treatment of PG. The role of surgical interventions and negative pressure wound therapy (NPWT) was discussed controversially until recently as these procedures might pose a trigger to further aggravate the condition. Recent Advances: Recent advances confirm the paradigm change that a surgical approach of PG with split thickness skin grafting (STSG) secured by NPWT is a safe and valuable treatment if performed under adequate immunosuppression. We elaborate this on the hand of a broad literature search retrieving 101 relevant articles describing 138 patients complemented with our personal experience on 23 patients, including 2 patients treated with a porcine xenodressing. Critical Issues: A wide range of surgical approaches have been reported, including xenografts. Treatment was finally successful in 86%, including the xenotransplant cases. Ten percent improved and failures were mainly reported without immunosuppression. Despite halting the inflammatory process, NPWT alone, without skin grafting, does not much accelerate healing time. The best surgical approach appears to be STSG fixed with NPWT as this leads to higher skin graft take. There remains the problem of the chronic nature of PG and the recurrence after tapering of immunosuppression or trauma; therefore, a sustained immunosuppressive treatment is suggested. Future Directions: While surgical treatment is supported by the published data, the exact immunosuppression is still evolving. Due to deeper insights into pathogenesis and growing clinical reports, a broader utilization of biologic treatments and a shift from tumor necrosis factor (TNF)-alpha to interleukin (IL)-12/23 or IL-23 antibodies alone are predictable, as IL-12/23 antibodies show good clinical responses with fewer side effects. The positive results with porcine xenodressings might be due to immunological effects of the xenomaterial; they appear promising, but are preliminary and should be confirmed in a larger patient collective.

Single xenotransplant of rat brown adipose tissue prolonged the ovarian lifespan of aging mice by improving follicle survival

Prolonging the ovarian lifespan is attractive and challenging. An optimal clinical strategy must be safe, long-acting, simple, and economical. Allotransplantation of brown adipose tissue (BAT), which is most abundant and robust in infants, has been utilized to treat various mouse models of human disease. Could we use BAT to prolong the ovarian lifespan of aging mice? Could we try BAT xenotransplantation to alleviate the clinical need for allogeneic BAT due to the lack of voluntary infant donors? In the current study, we found that a single rat-to-mouse (RTM) BAT xenotransplantation did not cause systemic immune rejection but did significantly increase the fertility of mice and was effective for more than 5 months (equivalent to 10 years in humans). Next, we did a series of analysis including follicle counting; AMH level; estrous cycle; mTOR activity; GDF9, BMP15, LHR, Sirt1, and Cyp19a level; ROS and annexin V level; IL6 and adiponectin level; biochemical blood indices; body temperature; transcriptome; and DNA methylation studies. From these, we proposed that rat BAT xenotransplantation rescued multiple indices indicative of follicle and oocyte quality; rat BAT also improved the metabolism and general health of the aging mice; and transcriptional and epigenetic (DNA methylation) improvement in F0 mice could benefit F1 mice; and multiple KEGG pathways and GO classified biological processes the differentially expressed genes (DEGs) or differentially methylated regions (DMRs) involved were identical between F0 and F1. This study could be a helpful reference for clinical BAT xenotransplantation from close human relatives to the woman.

Intra-Abdominal Heterotopic Cardiac Xenotransplantation: Pearls and Pitfalls

Heterotopic cardiac xenotransplantation in the intra-abdominal position has been studied extensively in a pig-to-baboon model to define the optimal donor genetics and immunosuppressive regimen to prevent xenograft rejection. Extensive investigation using this model is a necessary stepping stone toward the development of a life-supporting animal model, with the ultimate goal of demonstrating suitability for clinical cardiac xenotransplantation trials. Aspects of surgical technique, pre- and post-operative care, graft monitoring, and minimization of infectious risk have all required refinement and optimization of heterotopic cardiac xenotransplantation over time. This review details non-immunologic obstacles relevant to this model described by our group and in the literature, as well as strategies that have been developed to address these specific challenges.

Leukemia growth is inhibited by benzoxime without causing any harmful effect in rats bearing RBL-1 ×enotransplants

The present study aimed to investigate the effect of benzoxime on leukemia RBL-1 cell proliferation and a leukemic Sprague-Dawley rat model. Proliferation of RBL-1 cells was determined using an MTT assay. Sprague-Dawley rats were assigned randomly into three groups of 10 animals each, where the positive control group was administered an intravenous injection of normal saline, the negative control group was administered 1×10⁶ RBL-1 cells and the treatment group was administered with 1×10⁶ RBL-1 cells and then benzoxime (50 mg/kg/day) for 1 week. Increased dosage of benzoxime reduced RBL-1 cell viability from 92 at 2 µM to ٢١٪ at ١٢ µM after ٢٤ h. Benzoxime treatment prevented the loss of body weight in the rats with leukemia. Compared with the negative control rats, the body weight was determined to be significantly reduced (P<0.05) in the positive control rats. The weight of the spleen and liver was determined to be significantly increased (P<0.02) in the positive control rats and the benzoxime-treated rats compared with that in the negative control group on day 35 of RBL-1 cell implantation. Analysis of leukocytes in rats on day 35 demonstrated a significant reduction (P<0.05) in the cluster of differentiation (CD)11b and CD45 level in the positive control group compared with that in the negative control group. The level of CD11b and CD45 was determined to be similar in the rats in the benzoxime treatment and negative control groups. Analysis of the level of serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase and blood urea nitrogen indicated that all three components exhibited no significant changes in the rats following treatment with benzoxime compared with the component levels in the negative control group. The levels of these three components were in the normal range in rats treated with benzoxime on day 35 of cell implantation. These data demonstrated that the liver and kidneys are not influenced by benzoxime in rats with leukemia. In summary, the present study demonstrated that benzoxime efficiently prevents leukemia growth without inducing any harmful effects in rat models through targeting CD11b and CD45 level; thus, benzoxime should be evaluated further regarding its use in the treatment of leukemia.

Xenotransplantation of human intestine into mouse abdomen or subcutaneous tissue: Novel platforms for the study of the human enteric nervous system

BACKGROUND

Current efforts to develop stem cell therapy as a novel treatment for neurointestinal diseases are limited by the unavailability of a model system to study cell transplantation in the human intestine. We propose that xenograft models support enteric nervous system (ENS) development in the fetal human intestine when transplanted into mice subcutaneously or intra-abdominally.

METHODS

Fetal human small and large intestine were grafted onto the small intestinal mesentery and into the subcutaneous tissue of immunodeficient mice for up to 4 months. Intestinal cytoarchitecture and ENS development were studied using immunohistochemistry.

KEY RESULTS

In both abdominal and subcutaneous grafts, the intestine developed normally with formation of mature epithelial and mesenchymal layers. The ENS was patterned in two ganglionated plexuses containing enteric neurons and glia, including cholinergic and nitrergic neuronal subtypes. c-Kit-immunoreactive interstitial cells of Cajal were present in the gut wall.

CONCLUSIONS & INFERENCES

Abdominal xenografts represent a novel model that supports the growth and development of fetal human intestine. This in vivo approach will be a useful method to study maturation of the ENS, the pathophysiology of neurointestinal diseases, and the long-term survival and functional differentiation of neuronal stem cells for the treatment of enteric neuropathies.

Primate Primordial Germ Cells Acquire Transplantation Potential by Carnegie Stage 23

Primordial germ cells (PGCs) are the earliest embryonic progenitors in the germline. Correct formation of PGCs is critical to reproductive health as an adult. Recent work has shown that primate PGCs can be differentiated from pluripotent stem cells; however, a bioassay that supports their identity as transplantable germ cells has not been reported. Here, we adopted a xenotransplantation assay by transplanting single-cell suspensions of human and nonhuman primate embryonic Macaca mulatta (rhesus macaque) testes containing PGCs into the seminiferous tubules of adult busulfan-treated nude mice. We discovered that both human and nonhuman primate embryonic testis are xenotransplantable, generating colonies while not generating tumors. Taken together, this work provides two critical references (molecular and functional) for defining transplantable primate PGCs. These results provide a blueprint for differentiating pluripotent stem cells to transplantable PGC-like cells in a species that is amenable to transplantation and fertility studies.

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Rhesus PGCs in Carnegie stage 23 correspond to human PGCs at 8–10 weeks

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Carnegie stage 23 PGCs co-express cKIT, OCT4, TFAP2C, BLIMP1, SOX17, and VASA

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Carnegie stage 23 PGCs generate colonies following xenotransplantation

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Carnegie stage 23 PGCs do not yield tumors following xenotransplantation

Human Schwann cells exhibit long-term cell survival, are not tumorigenic and promote repair when transplanted into the contused spinal cord

The transplantation of rodent Schwann cells (SCs) provides anatomical and functional restitution in a variety of spinal cord injury (SCI) models, supporting the recent translation of SCs to phase 1 clinical trials for human SCI. Whereas human (Hu)SCs have been examined experimentally in a complete SCI transection paradigm, to date the reported behavior of SCs when transplanted after a clinically relevant contusive SCI has been restricted to the use of rodent SCs. Here, in a xenotransplant, contusive SCI paradigm, the survival, biodistribution, proliferation and tumorgenicity as well as host responses to HuSCs, cultured according to a protocol analogous to that developed for clinical application, were investigated. HuSCs persisted within the contused nude rat spinal cord through 6 months after transplantation (longest time examined), exhibited low cell proliferation, displayed no evidence of tumorigenicity and showed a restricted biodistribution to the lesion. Neuropathological examination of the CNS revealed no adverse effects of HuSCs. Animals exhibiting higher numbers of surviving HuSCs within the lesion showed greater volumes of preserved white matter and host rat SC and astrocyte ingress as well as axon ingrowth and myelination. These results demonstrate the safety of HuSCs when employed in a clinically relevant experimental SCI paradigm. Further, signs of a potentially positive influence of HuSC transplants on host tissue pathology were observed. These findings show that HuSCs exhibit a favorable toxicity profile for up to 6 months after transplantation into the contused rat spinal cord, an important outcome for FDA consideration of their use in human clinical trials.

Postnatal xenogeneic B-cell tolerance in swine following in utero intraportal antigen exposure

BACKGROUND

The objective of this study was to investigate the humoral immune response to xenogeneic antigens administered during the fetal state utilizing a baboon-to-pig model.

METHODS

Nine fetuses from an alpha-1,3-galactosyltransferase gene knockout (GalT-KO) MGH-miniature swine sow underwent transuterine ultrasound-guided intraportal injection of T-cell depleted baboon bone marrow (B-BM) at mid-gestation. Two juvenile GalT-KO swine undergoing direct B-BM intraportal injection were used as controls.

RESULTS

Postnatal humoral tolerance was induced in the long-term surviving piglets as demonstrated by the absence of any antibody response to baboon donor cells. In addition, a second intraportal B-BM administration at 2.5 months post-birth led to no antibody formation despite re-exposure to xenogeneic antigens. This B-cell unresponsiveness was abrogated only when the animal was exposed subcutaneously to third-party xenogeneic and allogeneic antigens, suggesting that the previously achieved humoral non-responsiveness was donor specific. In comparison, the two juvenile GalT-KO control swine demonstrated increasing anti-baboon IgM and IgG levels following intraportal injection.

CONCLUSIONS

In summary, xenogeneic B-cell tolerance was induced through in utero intraportal exposure to donor cells and this tolerance persisted following postnatal rechallenge with donor B-BM, but was lost on exposure to third-party antigen, possibly as a result of cross-reactive antibody formation.

Acute myeloid leukemia does not deplete normal hematopoietic stem cells but induces cytopenias by impeding their differentiation. Proc Natl Acad Sci U S A. 2013;110:13576-13581. [PMID: 23901108 DOI: 10.1073/pnas.1301891110]

Acute myeloid leukemia (AML) induces bone marrow (BM) failure in patients, predisposing them to life-threatening infections and bleeding. The mechanism by which AML mediates this complication is unknown but one widely accepted explanation is that AML depletes the BM of hematopoietic stem cells (HSCs) through displacement. We sought to investigate how AML affects hematopoiesis by quantifying residual normal hematopoietic subpopulations in the BM of immunodeficient mice transplanted with human AML cells with a range of genetic lesions. The numbers of normal mouse HSCs were preserved whereas normal progenitors and other downstream hematopoietic cells were reduced following transplantation of primary AMLs, findings consistent with a differentiation block at the HSC-progenitor transition, rather than displacement. Once removed from the leukemic environment, residual normal hematopoietic cells differentiated normally and outcompeted steady-state hematopoietic cells, indicating that this effect is reversible. We confirmed the clinical significance of this by ex vivo analysis of normal hematopoietic subpopulations from BM of 16 patients with AML. This analysis demonstrated that the numbers of normal CD34(+)CD38(-) stem-progenitor cells were similar in the BM of AML patients and controls, whereas normal CD34(+)CD38(+) progenitors were reduced. Residual normal CD34(+) cells from patients with AML were enriched in long-term culture, initiating cells and repopulating cells compared with controls. In conclusion the data do not support the idea that BM failure in AML is due to HSC depletion. Rather, AML inhibits production of downstream hematopoietic cells by impeding differentiation at the HSC-progenitor transition.

Human Vγ2Vδ2 T cells limit breast cancer growth by modulating cell survival-, apoptosis-related molecules and microenvironment in tumors

Innate immune system has been known to play an important role in inhibiting the malignant transformation, tumor progression and invasion. However, the mechanistic basis remains ambiguous. Despite polyclonality of human γδ T cells, Vγ2Vδ2 T cell subset was shown to recognize and limit the growth of various tumors at various degrees. The differential recognition of the tumor cells by Vγ2Vδ2 T cells are yet to be defined. Our study reveals that γδ T cells limit in vitro growth of most breast tumor cells, such as SkBr7 (HER2+), MCF7 (ER+) and MDA-MB-231 (ER-) by inhibiting their survival and inducing apoptosis, except BrCa-MZ01 (PR+) cells. To investigate detail mechanisms of antineoplastic effects, we found that cell death was associated with the surface expression levels of MICA/B and ICAM1. Molecular signaling analysis demonstrated that inhibition of cell growth by γδ T cells was associated with the lower expression levels of cell survival-related molecules such as AKT, ERK and concomitant upregulation of apoptosis-related molecules, such as PARP, cleaved caspase 3 and tumor suppressor genes PTEN and P53. However, opposite molecular signaling was observed in the resistant cell line after coculture with γδ T cells. In vivo, antineoplastic effects of γδ T cells were also documented, where tumor growth was inhibited due to the downregulation of survival signals, strong induction of apoptotic molecules, disruption of microvasculature and increased infiltration of tumor associated macrophages. These findings reveal that a complex molecular signaling is involved in γδ T cell-mediated antineoplastic effects.

Human fetal testis xenografts are resistant to phthalate-induced endocrine disruption

BACKGROUND

In utero exposure to endocrine-disrupting chemicals may contribute to testicular dysgenesis syndrome (TDS), a proposed constellation of increasingly common male reproductive tract abnormalities (including hypospadias, cryptorchidism, hypospermatogenesis, and testicular cancer). Male rats exposed in utero to certain phthalate plasticizers exhibit multinucleated germ cell (MNG) induction and suppressed steroidogenic gene expression and testosterone production in the fetal testis, causing TDS-consistent effects of hypospadias and cryptorchidism. Mice exposed to phthalates in utero exhibit MNG induction only. This disparity in response demonstrates a species-specific sensitivity to phthalate-induced suppression of fetal Leydig cell steroidogenesis. Importantly, ex vivo phthalate exposure of the fetal testis does not recapitulate the species-specific endocrine disruption, demonstrating the need for a new bioassay to assess the human response to phthalates.

OBJECTIVES

In this study, we aimed to develop and validate a rat and mouse testis xenograft bioassay of phthalate exposure and examine the human fetal testis response.

METHODS

Fetal rat, mouse, and human testes were xenografted into immunodeficient rodent hosts, and hosts were gavaged with a range of phthalate doses over multiple days. Xenografts were harvested and assessed for histopathology and steroidogenic end points.

RESULTS

Consistent with the in utero response, phthalate exposure induced MNG formation in rat and mouse xenografts, but only rats exhibited suppressed steroidogenesis. Across a range of doses, human fetal testis xenografts exhibited MNG induction but were resistant to suppression of steroidogenic gene expression.

CONCLUSIONS

Phthalate exposure of grafted human fetal testis altered fetal germ cells but did not reduce expression of genes that regulate fetal testosterone biosynthesis.

Human fallopian tube mesenchymal stromal cells enhance bone regeneration in a xenotransplanted model

We have recently reported that human fallopian tubes, which are discarded during surgical procedures of women submitted to sterilization or hysterectomies, are a rich source of human fallopian tube mesenchymal stromal cells (htMSCs). It has been previously shown that human mesenchymal stromal cells may be useful in enhancing the speed of bone regeneration. This prompted us to investigate whether htMSCs might be useful for the treatment of osteoporosis or other bone diseases, since they present a pronounced capacity for osteogenic differentiation in vitro. Based on this prior knowledge, our aim was to evaluate, in vivo, the osteogenic capacity of htMSCs to regenerate bone through an already described xenotransplantation model: nonimmunosuppressed (NIS) rats with cranial defects. htMSCs were obtained from five 30-50 years old healthy women and characterized by flow cytometry and for their multipotenciality in vitro capacity (osteogenic, chondrogenic and adipogenic differentiations). Two symmetric full-thickness cranial defects on each parietal region of seven NIS rats were performed. The left side (LS) of six animals was covered with CellCeram (Scaffdex)-a bioabsorbable ceramic composite scaffold that contains 60% hydroxyapatite and 40% β-tricalciumphosphate-only, and the right side (RS) with the CellCeram and htMSCs (10(6) cells/scaffold). The animals were euthanized at 30, 60 and 90 days postoperatively and cranial tissue samples were taken for histological analysis. After 90 days we observed neobone formation in both sides. However, in animals euthanized 30 and 60 days after the procedure, a mature bone was observed only on the side with htMSCs. PCR and immunofluorescence analysis confirmed the presence of human DNA and thus that human cells were not rejected, which further supports the imunomodulatory property of htMSCs. In conclusion, htMSCs can be used successfully to enhance bone regeneration in vivo, opening a new field for future treatments of osteoporosis and bone reconstruction.

Comparison of Gal and non-Gal-mediated cardiac xenograft rejection

BACKGROUND

This study compares the pathologic condition of delayed xenograft rejection in Gal-positive and Gal-knockout cardiac xenografts after pig-to-baboon heterotopic cardiac xenotransplantation when the induced anti-Gal antibody response is unregulated, blocked, or absent.

METHODS

Baboon recipients of Gal-positive, CD46 pig hearts were treated with an αGal polymer (group 1; n=11) or Gal-specific immunoapheresis (group 2; n=8) to block anti-Gal antibody. Gal-knockout cardiac xenografts recipients (group 3; n=5) received no anti-Gal therapy. Perioperative and interim biopsies were examined and antibody responses were determined.

RESULTS

No hyperacute rejection was seen and histologic findings were similar across the groups. All groups showed vascular antibody deposition in perioperative and interim biopsies and in explant samples. A prominent antibody response was detected only in group 2. Complement activation was evident by C3d deposition but deposition of C5b and C5b-9 was limited. Earliest evidence of myocardial injury was myocyte vacuolization in the absence of microvascular thrombosis or coagulative necrosis that developed later. Histology of explanted hearts exhibited mainly microvascular thrombosis and coagulative necrosis with little evidence of interstitial hemorrhage or edema.

CONCLUSIONS

The histology of rejection seemed independent of the anti-Gal or non-Gal immune response. Myocyte vacuolization seems to be an early feature of delayed xenograft rejection presaging more classic pathologic features.