3D bioprinted osteosarcoma model for experimental boron neutron capture therapy (BNCT) applications: Preliminary assessment

Osteosarcoma is the most frequently primary malignant bone tumor characterized by infiltrative growth responsible for relapses and metastases. Treatment options are limited, and a new therapeutic option is required. Boron neutron capture therapy (BNCT) is an experimental alternative radiotherapy able to kill infiltrative tumor cells spearing surrounding healthy tissues. BNCT studies are performed on 2D in vitro models that are not able to reproduce pathological tumor tissue organization or on in vivo animal models that are expensive, time-consuming and must follow the 3R's principles. A 3D in vitro model is a solution to better recapitulate the complexity of solid tumors meanwhile limiting the animal's use. Objective of this study is to optimize the technical assessment for developing a 3D in vitro osteosarcoma model as a platform for BNCT studies: printing protocol, biomaterial selection, cell density, and crosslinking process. The best parameters that allow a fully colonized 3D bioprinted construct by rat osteosarcoma cell line UMR-106 are 6 × 10⁶ cells/ml of hydrogel and 1% CaCl₂ as a crosslinking agent. The proposed model could be an alternative or a parallel approach to 2D in vitro culture and in vivo animal models for BNCT experimental study.

Characterization of a Bioink Combining Extracellular Matrix-like Hydrogel with Osteosarcoma Cells: Preliminary Results

Three-dimensional (3D) bioprinting allows the production of artificial 3D cellular microenvironments thanks to the controlled spatial deposition of bioinks. Proper bioink characterization is required to achieve the essential characteristics of printability and biocompatibility for 3D bioprinting. In this work, a protocol to standardize the experimental characterization of a new bioink is proposed. A functionalized hydrogel based on gelatin and chitosan was used. The protocol was divided into three steps: pre-printing, 3D bioprinting, and post-printing. For the pre-printing step, the hydrogel formulation and its repeatability were evaluated. For the 3D-bioprinting step, the hydrogel-printability performance was assessed through qualitative and quantitative tests. Finally, for the post-printing step, the hydrogel biocompatibility was investigated using UMR-106 cells. The hydrogel was suitable for printing grids with good resolution from 4 h after the cross-linker addition. To guarantee a constant printing pressure, it was necessary to set the extruder to 37 °C. Furthermore, the hydrogel was shown to be a valid biomaterial for the UMR-106 cells' growth. However, fragmentation of the constructs appeared after 14 days, probably due to the negative osteosarcoma-cell interference. The protocol that we describe here denotes a strong approach to bioink characterization to improve standardization for future biomaterial screening and development.

Comparison of Photon Isoeffective Dose Models Based on In Vitro and In Vivo Radiobiological Experiments for Head and Neck Cancer Treated with BNCT

Boron neutron capture therapy (BNCT) is a treatment modality for cancer that involves radiations of different qualities. A formalism that proved suitable to compute doses in photon-equivalent units is the photon isoeffective dose model. This study addresses the question whether considering in vitro or in vivo radiobiological studies to determine the parameters involved in photon isoeffective dose calculations affects the consistency of the model predictions. The analysis is focused on head and neck squamous cell carcinomas (HNSCC), a main target that proved to respond to BNCT. The photon isoeffective dose model for HNSCC with parameters from in vitro studies using the primary human cell line UT-SCC-16A was introduced and compared to the one previously reported with parameters from an in vivo oral cancer model in rodents. Both models were first compared in a simple scenario by means of tumor dose and control probability calculations. Then, the clinical impact of the different dose models was assessed from the analysis of a group of squamous cell carcinomas (SCC) patients treated with BNCT. Traditional dose calculations using the relative biological effectiveness factors derived from the SCC cell line were also analyzed. Predictions of tumor control from the evaluated models were compared to the patients' outcome. The quantification of the biological effectiveness of the different radiations revealed that relative biological effectiveness/compound biological effectiveness (RBE/CBE) factors for the SCC cell line are up to 20% higher than those assumed in clinical BNCT, highlighting the importance of using experimental data intimately linked to the tumor type to derive the model's parameters. The comparison of the different models showed that photon isoeffective doses based on in vitro data are generally greater than those from in vivo data (∼8-16% for total tumor absorbed doses of 10-15 Gy). However, the predictive power of the two models was not affected by these differences: both models fulfilled conditions to guarantee a good predictive performance and gave predictions statistically compatible with the clinical outcome. On the other hand, doses computed with the traditional model were substantially larger than those obtained with both photon isoeffective models. Moreover, the traditional model is statistically rejected, which reinforces the assertion that its inconsistencies are intrinsic and not due to the use of RBE/CBE factors obtained for a tumor type different from HN cancer. The results suggest that the nature of the radiobiological data would not affect the consistency of the photon isoeffective dose model in the studied cases of SCC head and neck cancer treated with BPA-based BNCT.

Multimodal evaluation of 19F-BPA internalization in pancreatic cancer cells for boron capture and proton therapy potential applications

PURPOSE

One of the obstacles to the application of Boron Neutron Capture Therapy (BNCT) and Proton Boron Fusion Therapy (PBFT) concerns the measurement of borated carriers' biodistribution. The objective of the present study was to evaluate the in vitro internalization of the ¹⁹F-labelled p-boronophenylalanine (¹⁹F-BPA) in the human cancer pancreatic cell line (PANC-1) for the potential application of BNCT and PBFT in pancreatic cancer. The ¹⁹F-BPA carrier has the advantage that its bio-distribution may be monitored in vivo using ¹⁹F-Nuclear Magnetic Resonance (¹⁹F NMR).

MATERIALS AND METHODS

The ¹⁹F-BPA internalization in PANC-1 cells was evaluated using three independent techniques on cellular samples left in contact with growing medium enriched with 13.6 mM ¹⁹F-BPA corresponding to a ¹¹B concentration of 120 ppm: neutron autoradiography, which quantifies boron; liquid chromatography hyphenated to tandem mass spectrometry and UV-Diode Array Detection (UV-DAD), which quantifies ¹⁹F-BPA molecule; and ¹⁹F NMR spectroscopy, which detects fluorine nuclei.

RESULTS

Our studies suggested that ¹⁹F-BPA is internalized by PANC-1 cells. The three methods provided consistent results of about 50% internalization fraction at 120 ppm of ¹¹B. Small variations (less than 15%) in internalization fraction are mainly dependent on the proliferation state of the cells.

CONCLUSIONS

The ability of ¹⁹F NMR spectroscopy to study ¹⁹F-BPA internalization was validated by well-established independent techniques. The multimodal approach we used suggests ¹⁹F-BPA as a promising BNCT/PBFT carrier for the treatment of pancreatic cancer. Since the quantification is performed at doses useful for BNCT/PBFT, ¹⁹F NMR can be envisaged to monitor ¹⁹F-BPA bio-distribution during the therapy.

Detailed dosimetry calculation for in-vitro experiments and its impact on clinical BNCT

PURPOSE

Boron Neutron Capture Therapy (BNCT) is a form of hadrontherapy based on the selective damage caused by the products of neutron capture in ¹⁰B to tumour cells. BNCT dosimetry strongly depends on the parameters of the dose calculation models derived from radiobiological experiments. This works aims at determining an adequate dosimetry for in-vitro experiments involving irradiation of monolayer-cultured cells with photons and BNCT and assessing its impact on clinical settings. M&M: Dose calculations for rat osteosarcoma UMR-106 and human metastatic melanoma Mel-J cell survival experiments were performed using MCNP, transporting uncharged particles for KERMA determinations, and secondary particles (electrons, protons, ¹⁴C, ⁴He and ⁷Li) to compute absorbed dose in cultures. Dose-survival curves were modified according to the dose correction factors determined from computational studies. New radiobiological parameters of the photon isoeffective dose models for osteosarcoma and metastatic melanoma tumours were obtained. Dosimetry implications considering cutaneous melanoma patients treated in Argentina with BNCT were assessed and discussed.

RESULTS

KERMA values for the monolayer-cultured cells overestimate absorbed doses of radiation components of interest in BNCT. Detailed dose calculations for the osteosarcoma irradiation increased the relative biological effectiveness factor RBE_1% of the neutron component in more than 30%. The analysis based on melanoma cases reveals that the use of survival curves based on KERMA leads to an underestimation of the tumour doses delivered to patients.

CONCLUSIONS

Considering detailed dose calculation for in-vitro experiments significantly impact on the prediction of the tumor control in patients. Therefore, proposed methods are clinically relevant.

Potential Applications of Nanocellulose-Containing Materials in the Biomedical Field

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field.

Understanding the potentiality of accelerator based-boron neutron capture therapy for osteosarcoma: dosimetry assessment based on the reported clinical experience

BACKGROUND

Osteosarcoma is the most frequent primary malignant bone tumour, and its incidence is higher in children and adolescents, for whom it represents more than 10% of solid cancers. Despite the introduction of adjuvant and neo-adjuvant chemotherapy that markedly increased the success rate in the treatment, aggressive surgery is still needed and a considerable percentage of patients do not survive due to recurrences or early metastases. Boron Neutron Capture Therapy (BNCT), an experimental radiotherapy, was investigated as a treatment that could allow a less aggressive surgery by killing infiltrated tumour cells in the surrounding healthy tissues. BNCT requires an intense neutron beam to ensure irradiation times of the order of 1 h. In Italy, a Radio Frequency Quadrupole (RFQ) proton accelerator has been designed and constructed for BNCT, and a suitable neutron spectrum was tailored by means of Monte Carlo calculations. This paper explores the feasibility of BNCT to treat osteosarcoma using this neutron source based on accelerator.

METHODS

The therapeutic efficacy of BNCT was analysed evaluating the dose distribution obtained in a clinical case of femur osteosarcoma. Mixed field dosimetry was assessed with two different formalisms whose parameters were specifically derived from radiobiological experiments involving in vitro UMR-106 osteosarcoma cell survival assays and boron concentration assessments in an animal model of osteosarcoma. A clinical case of skull osteosarcoma treated with BNCT in Japan was re-evaluated from the point of view of dose calculation and used as a reference for comparison.

RESULTS

The results in the case of femur osteosarcoma show that the RFQ beam would ensure a suitable tumour dose painting in a total irradiation time of less than an hour. Comparing the dosimetry between the analysed case and the treated patient in Japan it turns out that doses obtained in the femur tumour are at least as good as the ones delivered in the skull osteosarcoma. The same is concluded when the comparison is carried out taking into account osteosarcoma irradiations with photon radiation therapy.

CONCLUSIONS

The possibility to apply BNCT to osteosarcoma would allow a multimodal treatment consisting in neo-adjuvant chemotherapy, high-LET selective radiation treatment and a more conservative surgery.

An improved neutron autoradiography set-up for (10)B concentration measurements in biological samples

AIM

Boron Neutron Capture Therapy (BNCT) is a binary hadrontherapy which exploits the neutron capture reaction in boron, together with a selective uptake of boronated substances by the neoplastic tissue. There is increasing evidence that future improvements in clinical BNCT will be triggered by the discovery of new boronated compounds, with higher selectivity for the tumor with respect to clinically used sodium borocaptate (BSH) and boronophenylalanine (BPA).

BACKGROUND

Therefore, a (10)B quantification technique for biological samples is needed in order to evaluate the performance of new boronated formulations.

MATERIALS AND METHODS

This article describes an improved neutron autoradiography set-up employing radiation sensitive films where the latent tracks are made visible by proper etching conditions.

RESULTS

Calibration curves for both liquid and tissue samples were obtained.

CONCLUSIONS

The obtained calibration curves were adopted to set-up a mechanism to point out boron concentration in the whole sample.

Comparative study of the radiobiological effects induced on adherent vs suspended cells by BNCT, neutrons and gamma rays treatments

The present work is part of a preclinical in vitro study to assess the efficacy of BNCT applied to liver or lung coloncarcinoma metastases and to limb osteosarcoma. Adherent growing cell lines can be irradiated as adherent to the culture flasks or as cell suspensions, differences in radio-sensitivity of the two modalities of radiation exposure have been investigated. Dose related cell survival and cell cycle perturbation results evidenced that the radiosensitivity of adherent cells is higher than that of the suspended ones.

Water-soluble carboranyl-phthalocyanines for BNCT. Synthesis, characterization, and in vitro tests of the Zn(ii)-nido-carboranyl-hexylthiophthalocyanine

Nido-[ZnMCHESPc]Cs₈ increases boron concentration in selected cancerous cell lines.

Biocompatibility of functionalized boron phosphate (BPO4) nanoparticles for boron neutron capture therapy (BNCT) application

Boron neutron capture therapy (BNCT) is a radiotherapy treatment based on the accumulation in the tumor of a (10)B-containing drug and subsequent irradiation with low energy neutrons, which bring about the decay of (10)B to (7)Li and an α particle, causing the death of the neoplastic cell. The effectiveness of BNCT is limited by the low delivery and accumulation of the used boron-containing compounds. Here we report the development and the characterization of BPO4 nanoparticles (NPs) as a novel possible alternative drug for BNCT. An extensive analysis of BPO4 NP biocompatibility was performed using both mature blood cells (erythrocytes, neutrophils and platelets) and a model of hematopoietic progenitor cells. A time- and concentration-dependent cytotoxicity study was performed on neoplastic coloncarcinoma and osteosarcoma cell lines. BPO4 functionalization with folic acid, introduced to improve the uptake by tumor cells, appeared to effectively limit the unwanted effects of NPs on the analyzed blood components.

FROM THE CLINICAL EDITOR

Boron neutron capture therapy (BNCT) is a radiotherapy treatment modality based on the accumulation of a (10)B-containing drug and subsequent irradiation with low energy neutrons, inducing the decay of (10)B to (7)Li and an α particle, causing neoplastic cell death. This team of authors reports on a folic acid functionalized BPO4 nanoparticle with improved characteristics compared with conventional BNCT approaches, as demonstrated in tumor cell lines, and hopefully to be followed by translational human studies.

Rational design of gold nanoparticles functionalized with carboranes for application in Boron Neutron Capture Therapy

In this paper we propose a bottom-up approach to obtain new boron carriers built with ortho-carborane functionalized gold nanoparticles (GNPs) for applications in Boron Neutron Capture Therapy. The interaction between carboranes and the gold surface was assured by one or two SH-groups directly linked to the boron atoms of the B10C2 cage. This allowed obtaining stable, nontoxic systems, though optimal biological performance was hampered by low solubility in aqueous media. To improve cell uptake, the hydrophilic character of carborane functionalized GNPs was enhanced by further coverage with an appropriately tailored diblock copolymer (PEO-b-PCL). This polymer also contained pendant carboranes to provide anchoring to the pre-functionalized GNPs. In vitro tests, carried out on osteosarcoma cells, showed that the final vectors possessed excellent biocompatibility joint to the capacity of concentrating boron atoms in the target, which is encouraging evidenced to pursue applications in vivo.

Design, development and characterization of multi-functionalized gold nanoparticles for biodetection and targeted boron delivery in BNCT applications

The aim of this study is to optimize targeted boron delivery to cancer cells and its tracking down to the cellular level. To this end, we describe the design and synthesis of novel nanovectors that double as targeted boron delivery agents and fluorescent imaging probes. Gold nanoparticles were coated with multilayers of polyelectrolytes functionalized with the fluorescent dye (FITC), boronophenylalanine and folic acid. In vitro confocal fluorescence microscopy demonstrated significant uptake of the nanoparticles in cancer cells that are known to overexpress folate receptors.

Cell death following BNCT: a theoretical approach based on Monte Carlo simulations

In parallel to boron measurements and animal studies, investigations on radiation-induced cell death are also in progress in Pavia, with the aim of better characterisation of the effects of a BNCT treatment down to the cellular level. Such studies are being carried out not only experimentally but also theoretically, based on a mechanistic model and a Monte Carlo code. Such model assumes that: (1) only clustered DNA strand breaks can lead to chromosome aberrations; (2) only chromosome fragments within a certain threshold distance can undergo misrejoining; (3) the so-called "lethal aberrations" (dicentrics, rings and large deletions) lead to cell death. After applying the model to normal cells exposed to monochromatic fields of different radiation types, the irradiation section of the code was purposely extended to mimic the cell exposure to a mixed radiation field produced by the (10)B(n,α) (7)Li reaction, which gives rise to alpha particles and Li ions of short range and high biological effectiveness, and by the (14)N(n,p)(14)C reaction, which produces 0.58 MeV protons. Very good agreement between model predictions and literature data was found for human and animal cells exposed to X- or gamma-rays, protons and alpha particles, thus allowing to validate the model for cell death induced by monochromatic radiation fields. The model predictions showed good agreement also with experimental data obtained by our group exposing DHD cells to thermal neutrons in the TRIGA Mark II reactor of the University of Pavia; this allowed to validate the model also for a BNCT exposure scenario, providing a useful predictive tool to bridge the gap between irradiation and cell death.

1H and 10B NMR and MRI investigation of boron- and gadolinium-boron compounds in boron neutron capture therapy

(10)B molecular compounds suitable for Boron Neutron Capture Therapy (BNCT) are tagged with a Gd(III) paramagnetic ion. The newly synthesized molecule, Gd-BPA, is investigated as contrast agent in Magnetic Resonance Imaging (MRI) with the final aim of mapping the boron distribution in tissues. Preliminary Nuclear Magnetic Resonance (NMR) measurements, which include (1)H and (10)B relaxometry in animal tissues, proton relaxivity of the paramagnetic Gd-BPA molecule in water and its absorption in tumoral living cells, are reported.

In vitro and in vivo studies of boron neutron capture therapy: boron uptake/washout and cell death

Boron neutron capture therapy (BNCT) is a binary radiotherapy based on thermal-neutron irradiation of cells enriched with (10)B, which produces α particles and (7)Li ions of short range and high biological effectiveness. The selective uptake of boron by tumor cells is a crucial issue for BNCT, and studies of boron uptake and washout associated with cell survival studies can be of great help in developing clinical applications. In this work, boron uptake and washout were characterized both in vitro for the DHDK12TRb (DHD) rat colon carcinoma cell line and in vivo using rats bearing liver metastases from DHD cells. Despite a remarkable uptake, a large boron release was observed after removal of the boron-enriched medium from in vitro cell cultures. However, analysis of boron washout after rat liver perfusion in vivo did not show a significant boron release, suggesting that organ perfusion does not limit the therapeutic effectiveness of the treatment. The survival of boron-loaded cells exposed to thermal neutrons was also assessed; the results indicated that the removal of extracellular boron does not limit treatment effectiveness if adequate amounts of boron are delivered and if the cells are kept at low temperature. Cell survival was also investigated theoretically using a mechanistic model/Monte Carlo code originally developed for radiation-induced chromosome aberrations and extended here to cell death; good agreement between simulation outcomes and experimental data was obtained.

Isolation and ex vivo expansion of bone marrow-derived porcine mesenchymal stromal cells: potential for application in an experimental model of solid organ transplantation in large animals

Pharmacological aspecific immunosuppression, despite being widely used in solid organ transplantation recipients, is unable to completely prevent allograft rejection. It promotes the occurrence of sometimes life-threatening infections. Due to their immunosuppressive and anti- inflammatory properties, there is great interest in the therapeutic use of bone marrow (BM)-derived mesenchymal stromal cells (MSC). Large animal models play a crucial role to investigate the biological and functional properties of MSCs as novel cellular therapy. In the current study we sought to isolate expand ex vivo, and phenotypically characterize MSC derived from BM of 4 Large White 6-month-old piglets. Porcine MSC (pMSC) were characterized for their in vitro differentiation capacity. pMSC were successfully isolated from all BM samples. They showed spindle-shaped morphology and a stable doubling time on culture. They were positive for CD90, CD29, CD105, and negative for CD45 and CD11b. Furthermore, they differentiated, upon specific in vitro conditions toward adipogenic and osteogenic lineages. The optimization of methods for the isolation and characterization of pMSC may be useful to elucidate their biological and functional properties. The anatomy and physiology of the pig, which is similar to humans, make this animal model more attractive than small animals to test the safety and efficacy of MSC in the context of solid organ transplantation.

Selective uptake of p-boronophenylalanine by osteosarcoma cells for boron neutron capture therapy

Osteosarcoma is the most common non-hematologic primary cancer type that develops in bone. Current osteosarcoma treatments combine multiagent chemotherapy with extensive surgical resection, which in some cases makes necessary the amputation of the entire limb. Nevertheless its infiltrative growth leads to a high incidence of local and distant recurrences that reduce the percentage of cured patients to less than 60%. These poor data required to set up a new therapeutic approach aimed to restrict the surgical removal meanwhile performing a radical treatment. Boron neutron capture therapy (BNCT), a particular radiotherapy based on the nuclear capture and fission reactions by atoms of (10)B, when irradiated with thermal neutrons, could be a valid alternative or integrative option in case of osteosarcoma management, thanks to its peculiarity in selectively destroying neoplastic cells without damaging normal tissues. Aim of the present work is to investigate the feasibility of employing BNCT to treat the limb osteosarcoma. Boronophenylalanine (BPA) is used to carry (10)B inside the neoplastic cells. As a first step the endocellular BPA uptake is tested in vitro on the UMR-106 osteosarcoma cell line. The results show an adequate accumulation capability. For the in vivo experiments, an animal tumor model is developed in Sprague-Dawley rats by means of an intrafemoral injection of UMR-106 cells at the condyle site. The absolute amounts of boron loading and the tumor to normal tissue (10)B ratio are evaluated 2 h after the i.v. administration of BPA. The boron uptake by the neoplastic tissue is almost twice the normal one. However, higher values of boron concentration in tumor are requested before upholding BNCT as a valid therapeutic option in the treatment of osteosarcoma.

Short-term cyclosporine therapy and cotransplantation of donor splenocytes: effects on graft rejection and survival rates in pigs subjected to renal transplantation

BACKGROUND

Donor-specific allogeneic loading can prolong the survival of solid organ transplants by inducing a state known as acceptance. Several populations of cells are known to be involved in this process, but their exact roles have yet to be defined. The aim of this study was to assess the effects of portal-vein transfusion of donor-specific splenocytes (DST) after short-term cyclosporine A (CyA) therapy in pigs subjected to renal transplantation.

METHODS

Four groups of unrelated swine underwent renal transplantation with removal of the native kidneys. Antirejection protocols consisted in portal-vein DST (3 x 10(8) cells/kg) (Group 2, n = 7); intravenous CyA (9 mg/kg/d) on postoperative days 1-12 (Group 3, n = 14); and DST + CyA (as described above) (Group 4, n = 13). Results (through postoperative day 90) were compared with those obtained in untreated control recipients (Group 1, n = 7).

RESULTS

Compared with animals of Groups 1, 2, and 3, Group 4 recipients presented significantly longer survival (mean: 90 days, P < 0.01 in Kaplan-Meier analysis) and better renal function (P < 0.05). Graft histology revealed preserved parenchyma.

CONCLUSION

The role of spleen cells in the immune response has probably been underestimated. Cotransplantation of donor splenocytes seems to induce a certain degree of acceptance toward the renal allograft. The route of administration (portal-vein infusion in this study) may be crucial for developing favorable mechanisms of recognition.

[Liver transplantation in swine: a model for tolerance induction]

AIM

The liver as a solid graft has a known immunological privilege. Its tolerogenic property has been demonstrated in rodents. In humans the onset of chronic rejection and the severity of such complication is less frequent after liver transplantation compared to other organs. The underlying events whose effect is graft acceptance instead of rejection should be further investigated. Their control could open new ways to decrease the need for long-term immunosuppression after transplantation of other organs. Aim of this study is to evaluate a model of liver transplantation in swine as a preliminary step for immunological studies.

METHODS

Ten outbred Landrace/Large White mismatched swine underwent to liver transplantation with a simple passive portocaval jugular bypass. The onset of rejection was monitored daily by liver function test. After death or sacrifice the liver parenchyma was studied to evaluate tissue damage and inflammatory infiltrate.

RESULTS

The postoperative liver function showed a critical period for organ rejection about postoperative day 5. The animals that survived longer were sacrificed with a normal biochemical hepatic function. However, histology consistently showed a pattern of mild rejection in a still preserved architecture.

CONCLUSIONS

The evidence of a prolonged liver function in a rejecting model of liver transplantation makes this model suitable for studies of tolerance induction.

[Immunomodulation after combined spleen and kidney transplantation in swine]

AIM

Organ transplantation is the most effective treatment for several degenerative end-stage diseases. While the mainstream immunosuppression can achieve satisfactory results, the therapy has either side effects and flaws. The golden target to reach should be a stable tolerance with the transplanted organ accepted without a long term drug administration. Recent studies demonstrated a tolerogenic effect of spleen cells. Aim of this study is to evaluate a model of combined spleen and whole organ transplantation in a significant preclinical setting in swine.

METHODS

Twenty-five outbred Landrace/Large-White swine underwent combined spleen/kidney transplantation (SKTx). The experiments were stratified into 3 groups per randomization. Group 1 (N=7) received kidney transplantation (KTx) alone with no immunosuppressive treatment. Group 2 (N=9) had a combined KTx and whole graft spleen Tx. Group 3 (N=9) had KTx and spleen cells (DST), injected through the portal vein. Renal lab tests were collected to evaluate the onset of rejection. Survivals were evaluated as well. The end-point of the study was at onset of kidney failure or at the limit of 60 postoperative day (POD) in non-rejecting animals. Tissue samples were collected to evaluate grade and severity of rejection.

RESULTS

Controls died from kidney failure within 10(th) POD. Group 2 and 3, had a delayed renal graft rejection and an overall prolonged graft survival. Whole graft and spleen cells injection share this effect, while spleen administration through the portal route proved a superior effect, which is significant compared to controls (Kaplan Meier survival analysis P<0.05).

CONCLUSIONS

These results, from a non immunosuppressed setting, suggest that spleen plays a key role as an immunomodulatory organ.

[Blockade of B7:CD28 costimulatory pathway reduces the vascular damage in an experimental model of chronic rejection]

AIM

Costimulatory blockade and donor specific transfusion (DST) can catalyze tolerance of transplanted organs through a multistep adaptation between the recipient and donor immune systems. Such an in vivo process may prolong graft survival. Aim of this study was to evaluate the outcome of aortic transplantation under CTLA4Ig and DST in a mismatched model in rats.

METHODS

Orthotopic aortic transplantation was performed in recipients Lewis from Wistar-Furth rats. The animals were stratified into 3 groups, according to the postoperative treatment. Group 1 had aortic transplantation only (controls, n=6), while group 2 (n=7) had a load of donor splenocytes (DST). Group 3 was treated with DST and CTLA4Ig. All the animals were sacrificed at the 60th postoperative day and the aortic specimens were prepared for histology. Intimal cells, muscular cells and lymphocyte cell infiltration were evaluated by serial counts.

RESULTS

In Group 1 there was a severe chronic rejection, while group 2 showed a slower onset of chronic rejection with less inflammatory infiltrate than group 1 (P<0.05). Group 3 had the best overall outcome with lower infiltration and minimal alterations compared with groups 1 and 2.

CONCLUSIONS

Costimulatory blockade and DST load can prevent the onset of chronic rejection in this experimental setting. Despite the wide availability of immunosuppressors, which makes transplantation a today's clinical routine, the solution to chronic rejection is still elusive. The synergistic role of splenocytes and costimulatory blockade raises interesting perspectives about the immunomodulatory role of spleen in tolerance induction.