Improved therapeutic strategies for patients with leukemia remain in great demand and beckon better understanding of the mechanisms underlying leukemic treatment resistance and relapse. Accordingly, discoveries in leukemic pathophysiology have been achieved in various animal models. Danio rerio—commonly known as the zebrafish—is a vertebrate organism well suited for the investigation of human leukemia. Zebrafish have a conserved hematopoietic program and unique experimental strengths. Recent technological advances in zebrafish research including efficient transgenesis, precise genome editing, and straightforward transplantation techniques have led to the generation of numerous zebrafish leukemia models. Additionally, improved imaging techniques, combined with the transparency of zebrafish, have revealed exquisite details of leukemic initiation, progression, and regression. Finally, advances in high-throughput drug screening in zebrafish are likely to hasten the discovery of novel anti-leukemic agents. Zebrafish provide a reliable experimental system for leukemic disease research and one in which investigators have accumulated knowledge concerning the genetic underpinnings of leukemic transformation and treatment resistance. Without doubt, zebrafish are rapidly expanding our understanding of disease mechanism and are helping to shape therapeutic strategy for improved patient outcomes.

With Athletes and individuals developing osteoarthritis and chondral defects at younger ages, long term treatments are in high demand. Total knee replacements only last for 10-15 years, so younger individuals would need to have multiple knee replacements within their lifetime. Allograft transplantation has shown to last long term and have high success rates, but the lack of donors and the possibility of damaging other areas of the knee to obtain tissue grafts has become a large concern. Xenografts derived from porcine cartilage is cost effective and the supply is abundant. Two antigen removal processes were examined: a short term antigen removal process to maintain the mechanical stability of the tissue, and a long antigen removal process to minimize the risk of triggering an immune response. The antigen removal processes were compared, and the future precautions were determined to enhance the probability of creating a viable osteochondral xenograft preparation technique.

O câncer primário de fígado (CPF) apresenta mau prognóstico, o que torna importante sua quimioprevenção. Nesse sentido, a tributirina (TB), um pró-fármaco do ácido butírico (AB), presente em laticínios e no mel, mostrou-se um agente quimiopreventivo promissor da hepatocarcinogênese experimental. Os efeitos inibitórios da TB têm sido relacionados à inibição do desenvolvimento de lesões pré-neoplásicas, bem como indução de apoptose e hiperacetilação de histonas. A quimioterapia é uma das abordagens mais comuns para o tratamento de diversos tipos de câncer, inclusive o CPF. Neste caso, o tratamento com sorafenibe (SO) é capaz de prolongar a sobrevida média dos pacientes com a doença em fases avançadas em aproximadamente apenas três meses. Em vista disso, são necessários estudos da associação do sorafenibe com outros compostos que possam aumentar a eficácia do tratamento quimioterápico. Desta forma, a associação de fármacos anti-neoplásicos com compostos bioativos dos alimentos pode consistir em uma estratégia potencial para aumentar a eficácia contra o câncer. No presente estudo, foi avaliada a atividade anticarcinogênica da TB e do SO, isoladamente ou em associação, na etapa de progressão da hepatocarcinogênese. Para tanto, foram realizados implantes singênicos no flanco de ratos Fischer-344 a partir de células da linhagem tumoral GP7TB. Quando as neoplasias atingiram 1 cm3, os animais foram aleatorizados em grupos experimentais: Grupo controle (CO), constituído por 10 ratos Fischer 344 que receberam Maltodextrina (300mg/ 100 g. p. c.), controle isocolarico e solução de etanol à 12,5% e Cremofor à 12,5% em agua estéril; Grupo Tributirina (TB), constituído por 9 ratos Fischer 344 que receberam TB (200mg/ 100 g. p. c.) e solução de etanol à 12,5% e Cremofor à 12,5% em água estéril; Grupo sorafenibe (SO) constituído por 9 ratos Fischer 344 que receberam Maltodextrina (300 mg/ 100 g. p. c.), controle isocalorico e tosilato de sorafenibe (3mg / 100 g. p. c. ) em água estéril; Grupo associação da tributirina com o sorafenibe (AS) constituído por 9 ratos Fischer 344 que receberam TB (20 mg/ 100 g. p. c.) e tosiliato de sorafenibe (3mg/ 100 g. p. c.); tratados por administração intragástrica (i.g) diariamente por 5 semanas consecutivas. As concentrações de AB e SO foram analisadas por cromatografia gasosa associada à espectrometria de massa e as neoplasias foram caracterizadas por imunoistoquímica. Em relação à evolução do tamanho das neoplasias o grupo AS apresentou menor (p=0,009) tamanho das mesmas em relação ao grupo CO. No entanto, estas diferenças não atingiram diferenças significativas (p>0,05) entre os grupos TB e CO, bem como entre os grupos SO e CO. Contudo, quando ajustados os valores do tamanho da neoplasia pela latência, observou-se alterações significativas (p<0,05) nos diversos grupos quando comparados ao grupo CO. O grupo SO aumentou a área necrótica das neoplasias, embora esta diferença não tenha atingido diferença significativa (p>0,05), enquanto que o grupo TB reduziu essa área necrótica em relação ao grupo CO (p=0,005). O grupo TB e AS apresentaram significativamente maiores (p<0,05) concentrações hepáticas e neoplásicas de AB em relação ao grupo CO. O grupo SO e AS apresentaram significativamente maiores (p<0,05) concentrações neoplásicas de SO em relação ao grupo CO. Os grupos SO e AS reduziram a expressão de PTEN, quando comparados ao grupo CO, embora esta diferença não tenha atingido diferença significativa (p>0,05). O grupo TB por sua vez expressou maiores niveis de PTEN, embora esta diferença não tenha atigindo significância estatística (p>0,05). Todos os grupos expressaram maiores niveis de caspase 3 clivada quando comparada ao grupo CO (p>0,05). OS grupos TB e SO reduziram a expressão de pERK &#189; quando comparados ao grupo CO. embora estas diferenças não tenham atingidos diferença estatística (p>0,05). O grupo AS apresentou maior expressão de pERK &#189; quando comparada ao grupo CO, embora esta diferença não tenha atingido diferença significativa (p>0,05). A caracterização das neoplasias do grupo CO foi padronizada por imunoistoquímica, apresentando-se positivas para CK 7, CK8, CK19 e Arginase e negativas para HepPar1 e CK18. Assim, os resultados sugerem que as neoplasias obtidas por implantes com células da linhagem GP7TB apresentam características de CPF oriundo de células tronco neoplásicas. Além disso, os grupos experimentais TB e AS apresentaram atividade anticarcinogênica promissora no modelo de implantes singênicos com células GP7TB, que eventualmente envolvem mecanismos de ação distintos da atividade quimioterápica apresentada pelo SO. / Primary liver cancer (PLC) presents poor prognosis, which makes its chemoprevention important. In this sense, tributyrin (TB), a prodrug of butyric acid (AB), present in dairy products and honey, has been shown to be a promising chemopreventive agent for experimental hepatocarcinogenesis. The inhibitory effects of TB have been related to inhibition of the development of pre-neoplastic lesions, as well as induction of apoptosis and hyperacetylation of histones. Chemotherapy is one of the most common approaches for treating various types of cancer, including PLC. In this case, treatment with sorafenib (SO) is able to prolong the average survival of patients with the disease in advanced stages in approximately three months. In view of this, studies of the association of sorafenib with other compounds that may increase the efficacy of chemotherapeutic treatment are necessary. Thus, the association of anti-neoplastic drugs with bioactive compounds in food may be a potential strategy to increase efficacy against cancer. In the present study, the anticarcinogenic activity of TB and SO was evaluated, alone or in combination, in the progression stage of hepatocarcinogenesis. For this purpose, syngenic implants were performed on the flank of Fischer-344 mice from GP7TB tumor cells. When the neoplasms reached 1 cm3, the animals were randomized into experimental groups: Control group (CO), consisting of 10 Fischer 344 rats receiving Maltodextrin (300mg / 100 g.p.c), isocaloric control and 12.5% ethanol solution, and Cremofor to 12.5% in sterile water; Tributyrin group (TB), consisting of 9 Fischer 344 rats that received TB (200mg / 100 g.p.c.) and 12.5% ethanol solution and Cremofor 12.5% in sterile water; Sorafenib group (SO) consisting of 9 Fischer 344 rats receiving maltodextrin (300 mg / 100 g, w / w), isocaloric control and sorafenib tosylate (3 mg / 100 g, w / w) in sterile water; The association group of tributyrin and sorafenib (AS) consisted of 9 Fischer 344 rats receiving TB (20 mg / 100 g p.o.) and sorafenib tosylate (3 mg / 100 g p.o.); treated intragastric (i.g) daily for 5 consecutive weeks. The concentrations of AB and SO were analyzed by gas chromatography associated with mass spectrometry and the neoplasms were characterized by immunohistochemistry. In relation to the evolution of the size of the neoplasias, the AS group presented smaller (p = 0.009) size of the same ones in relation to the CO group. However, these differences did not reach significant differences (p> 0.05) between the TB and CO groups, as well as between the SO and CO groups. However, when adjusted for size of the neoplasm by latency, significant changes (p <0.05) were observed in the different groups when compared to the CO group. The SO group increased the necrotic area of the neoplasias, although this difference did not reach a significant difference (p> 0.05), while the TB group reduced this necrotic area in relation to the CO group (p = 0.005). The TB and AS groups presented significantly higher (p <0.05) hepatic and neoplastic AB concentrations than the CO group. The SO and AS groups presented significantly higher (p <0.05) neoplastic concentrations of SO in relation to the CO group. The SO and AS groups reduced the PTEN expression when compared to the CO group, although this difference did not reach a significant difference (p> 0.05). The TB group in turn expressed higher levels of PTEN, although this difference did not increase statistical significance (p> 0.05). All groups expressed higher levels of caspase 3 cleaved when compared to the CO group (p> 0.05). The TB and SO groups reduced the expression of pERK &#189; when compared to the CO group. although these differences did not reach statistical difference (p> 0.05). The AS group presented higher pERK &#189; expression when compared to the CO group, although this difference did not reach a significant difference (p> 0.05). Characterization of the neoplasias of the CO group was standardized by immunohistochemistry, presenting positive for CK 7, CK8, CK19 and Arginase and negative for HepPar1 and CK18. Thus, the results suggest that the neoplasias obtained by implants with GP7TB cells present CPF characteristics originating from neoplastic stem cells. In addition, the experimental groups TB and AS presented promising anticarcinogenic activity in the model of syngeneic implants with GP7TB cells, which eventually involve mechanisms of action distinct from the chemotherapy activity presented by SO.

Resistance to endocrine treatments in oestrogen receptor positive (ER+) breast cancer (BC) significantly contribute to patient morbidity and mortality. ER+ BC constitute 60% of all breast cancers although there is considerable clinico-pathological diversity within this group. Breast cancer initiating cells (BCICs) are implicated in tumour relapse and metastasis and are postulated to drive resistance to standard anti-cancer therapies. However little is known about the sensitivity of BCICs to endocrine therapies. We assessed the effect of tamoxifen treatment and acquired tamoxifen resistance on BCIC frequency in vitro and in vivo using breast cancer cell lines and, importantly, patient derived samples of early and metastatic ER+ breast cancer. In ER+ breast cancer, BCICs may be prospectively enriched in vitro by selecting cells by CD44+/CD24lo/ESA+ phenotype or by mammosphere initiating capacity (MIC). However the gold standard assay to determine BCIC frequency is limiting dilution transplantation in vivo. In the past it has been historically difficult to generate xenograft models of ER+ breast cancer using patient samples. In this thesis, using a novel experimental technique, patient-derived xenografts (PDX) of early and metastatic ER+ BC were generated with almost 85% efficiency in NOD/SCID IL2gammaR-/- (NSG) mice. PDX expressed ER and were able to undergo serial in vivo passage, matching the phenotype of the tumour from which they were derived. In this work, two patterns of response to tamoxifen treatment were observed in ER+ cell lines, patient derived breast cancer samples and xenografts during BCIC assays in vitro and in vivo; Limited Sensitivity (LS) or Resistance (R). In the LS group there was no change or a significant diminution in BCIC frequency in the presence of tamoxifen. In the R group, a significant increase in BCIC frequency was observed in the presence of tamoxifen. Furthermore BCIC activity was shown be enhanced by the acquisition of tamoxifen resistance using cell line models. Cellular populations enriched for BCICs in ER+ cell lines were shown to express low levels of ER compared to non-BCICs. Finally Notch (gamma-secretase inhibitor) and EGFR (gefitinib) pathway inhibitors were tested alone or in combination with tamoxifen against a panel of established and novel cell lines and ER+ patient-derived breast cancer samples for anti-BCIC activity. Tamoxifen treatment can increase BCIC frequency in vitro assays of cell lines and patient-derived samples and in vivo using patient-derived xenografts of ER+ breast cancer. However phenotypic diversity of BCIC may be present within the ER+ BC population. A pharmaceutical strategy to effectively treat BCICs alongside standard endocrine therapy is necessary for the effective future treatment of ER+ breast cancer.

Xenotransplantation is the final frontier of using vascularised organs or cellular grafts to treat end-organ disease and offers a potential solution to the worldwide shortage of human tissue available for transplantation. The main immunological barrier to xenografting from pig-to-primate is the antigen, Galactose-α1,3-Galactose (Gal) which is found in all species except humans and other higher primates. Even with the major advancement of deleting Gal from the potential pig donor species with the aid of cloning technology, complete elimination may be elusive as alternative genes yet to be fully characterised, may still produce Gal at low levels. Thus, the human immune response against Gal may continue to be a barrier to successful xenotransplantation. The aim of this project was to develop small animal models of the important components of xenograft rejection that largely relate to the anti-Gal immune response. These include models of hyperacute, acute vascular and chronic xenograft-like rejection that in turn, provide new insights in the immune mechanisms of the rejection processes. The role of antibody and both innate and cognate cellular immunity are explored. Both vascularised heart grafts and non-vascularised skin graft models are examined as rejection of solid organs may differ from cellular transplantation. The project also provides a platform for future studies in testing genetic and pharmacotherapeutic strategies to overcome the rejection processes uncovered.

Xenotransplantation is the final frontier of using vascularised organs or cellular grafts to treat end-organ disease and offers a potential solution to the worldwide shortage of human tissue available for transplantation. The main immunological barrier to xenografting from pig-to-primate is the antigen, Galactose-α1,3-Galactose (Gal) which is found in all species except humans and other higher primates. Even with the major advancement of deleting Gal from the potential pig donor species with the aid of cloning technology, complete elimination may be elusive as alternative genes yet to be fully characterised, may still produce Gal at low levels. Thus, the human immune response against Gal may continue to be a barrier to successful xenotransplantation. The aim of this project was to develop small animal models of the important components of xenograft rejection that largely relate to the anti-Gal immune response. These include models of hyperacute, acute vascular and chronic xenograft-like rejection that in turn, provide new insights in the immune mechanisms of the rejection processes. The role of antibody and both innate and cognate cellular immunity are explored. Both vascularised heart grafts and non-vascularised skin graft models are examined as rejection of solid organs may differ from cellular transplantation. The project also provides a platform for future studies in testing genetic and pharmacotherapeutic strategies to overcome the rejection processes uncovered.

O câncer primário de fígado (CPF) apresenta mau prognóstico, o que torna importante sua quimioprevenção. Nesse sentido, a tributirina (TB), um pró-fármaco do ácido butírico (AB), presente em laticínios e no mel, mostrou-se um agente quimiopreventivo promissor da hepatocarcinogênese experimental. Os efeitos inibitórios da TB têm sido relacionados à inibição do desenvolvimento de lesões pré-neoplásicas, bem como indução de apoptose e hiperacetilação de histonas. A quimioterapia é uma das abordagens mais comuns para o tratamento de diversos tipos de câncer, inclusive o CPF. Neste caso, o tratamento com sorafenibe (SO) é capaz de prolongar a sobrevida média dos pacientes com a doença em fases avançadas em aproximadamente apenas três meses. Em vista disso, são necessários estudos da associação do sorafenibe com outros compostos que possam aumentar a eficácia do tratamento quimioterápico. Desta forma, a associação de fármacos anti-neoplásicos com compostos bioativos dos alimentos pode consistir em uma estratégia potencial para aumentar a eficácia contra o câncer. No presente estudo, foi avaliada a atividade anticarcinogênica da TB e do SO, isoladamente ou em associação, na etapa de progressão da hepatocarcinogênese. Para tanto, foram realizados implantes singênicos no flanco de ratos Fischer-344 a partir de células da linhagem tumoral GP7TB. Quando as neoplasias atingiram 1 cm3, os animais foram aleatorizados em grupos experimentais: Grupo controle (CO), constituído por 10 ratos Fischer 344 que receberam Maltodextrina (300mg/ 100 g. p. c.), controle isocolarico e solução de etanol à 12,5% e Cremofor à 12,5% em agua estéril; Grupo Tributirina (TB), constituído por 9 ratos Fischer 344 que receberam TB (200mg/ 100 g. p. c.) e solução de etanol à 12,5% e Cremofor à 12,5% em água estéril; Grupo sorafenibe (SO) constituído por 9 ratos Fischer 344 que receberam Maltodextrina (300 mg/ 100 g. p. c.), controle isocalorico e tosilato de sorafenibe (3mg / 100 g. p. c. ) em água estéril; Grupo associação da tributirina com o sorafenibe (AS) constituído por 9 ratos Fischer 344 que receberam TB (20 mg/ 100 g. p. c.) e tosiliato de sorafenibe (3mg/ 100 g. p. c.); tratados por administração intragástrica (i.g) diariamente por 5 semanas consecutivas. As concentrações de AB e SO foram analisadas por cromatografia gasosa associada à espectrometria de massa e as neoplasias foram caracterizadas por imunoistoquímica. Em relação à evolução do tamanho das neoplasias o grupo AS apresentou menor (p=0,009) tamanho das mesmas em relação ao grupo CO. No entanto, estas diferenças não atingiram diferenças significativas (p>0,05) entre os grupos TB e CO, bem como entre os grupos SO e CO. Contudo, quando ajustados os valores do tamanho da neoplasia pela latência, observou-se alterações significativas (p<0,05) nos diversos grupos quando comparados ao grupo CO. O grupo SO aumentou a área necrótica das neoplasias, embora esta diferença não tenha atingido diferença significativa (p>0,05), enquanto que o grupo TB reduziu essa área necrótica em relação ao grupo CO (p=0,005). O grupo TB e AS apresentaram significativamente maiores (p<0,05) concentrações hepáticas e neoplásicas de AB em relação ao grupo CO. O grupo SO e AS apresentaram significativamente maiores (p<0,05) concentrações neoplásicas de SO em relação ao grupo CO. Os grupos SO e AS reduziram a expressão de PTEN, quando comparados ao grupo CO, embora esta diferença não tenha atingido diferença significativa (p>0,05). O grupo TB por sua vez expressou maiores niveis de PTEN, embora esta diferença não tenha atigindo significância estatística (p>0,05). Todos os grupos expressaram maiores niveis de caspase 3 clivada quando comparada ao grupo CO (p>0,05). OS grupos TB e SO reduziram a expressão de pERK &#189; quando comparados ao grupo CO. embora estas diferenças não tenham atingidos diferença estatística (p>0,05). O grupo AS apresentou maior expressão de pERK &#189; quando comparada ao grupo CO, embora esta diferença não tenha atingido diferença significativa (p>0,05). A caracterização das neoplasias do grupo CO foi padronizada por imunoistoquímica, apresentando-se positivas para CK 7, CK8, CK19 e Arginase e negativas para HepPar1 e CK18. Assim, os resultados sugerem que as neoplasias obtidas por implantes com células da linhagem GP7TB apresentam características de CPF oriundo de células tronco neoplásicas. Além disso, os grupos experimentais TB e AS apresentaram atividade anticarcinogênica promissora no modelo de implantes singênicos com células GP7TB, que eventualmente envolvem mecanismos de ação distintos da atividade quimioterápica apresentada pelo SO. / Primary liver cancer (PLC) presents poor prognosis, which makes its chemoprevention important. In this sense, tributyrin (TB), a prodrug of butyric acid (AB), present in dairy products and honey, has been shown to be a promising chemopreventive agent for experimental hepatocarcinogenesis. The inhibitory effects of TB have been related to inhibition of the development of pre-neoplastic lesions, as well as induction of apoptosis and hyperacetylation of histones. Chemotherapy is one of the most common approaches for treating various types of cancer, including PLC. In this case, treatment with sorafenib (SO) is able to prolong the average survival of patients with the disease in advanced stages in approximately three months. In view of this, studies of the association of sorafenib with other compounds that may increase the efficacy of chemotherapeutic treatment are necessary. Thus, the association of anti-neoplastic drugs with bioactive compounds in food may be a potential strategy to increase efficacy against cancer. In the present study, the anticarcinogenic activity of TB and SO was evaluated, alone or in combination, in the progression stage of hepatocarcinogenesis. For this purpose, syngenic implants were performed on the flank of Fischer-344 mice from GP7TB tumor cells. When the neoplasms reached 1 cm3, the animals were randomized into experimental groups: Control group (CO), consisting of 10 Fischer 344 rats receiving Maltodextrin (300mg / 100 g.p.c), isocaloric control and 12.5% ethanol solution, and Cremofor to 12.5% in sterile water; Tributyrin group (TB), consisting of 9 Fischer 344 rats that received TB (200mg / 100 g.p.c.) and 12.5% ethanol solution and Cremofor 12.5% in sterile water; Sorafenib group (SO) consisting of 9 Fischer 344 rats receiving maltodextrin (300 mg / 100 g, w / w), isocaloric control and sorafenib tosylate (3 mg / 100 g, w / w) in sterile water; The association group of tributyrin and sorafenib (AS) consisted of 9 Fischer 344 rats receiving TB (20 mg / 100 g p.o.) and sorafenib tosylate (3 mg / 100 g p.o.); treated intragastric (i.g) daily for 5 consecutive weeks. The concentrations of AB and SO were analyzed by gas chromatography associated with mass spectrometry and the neoplasms were characterized by immunohistochemistry. In relation to the evolution of the size of the neoplasias, the AS group presented smaller (p = 0.009) size of the same ones in relation to the CO group. However, these differences did not reach significant differences (p> 0.05) between the TB and CO groups, as well as between the SO and CO groups. However, when adjusted for size of the neoplasm by latency, significant changes (p <0.05) were observed in the different groups when compared to the CO group. The SO group increased the necrotic area of the neoplasias, although this difference did not reach a significant difference (p> 0.05), while the TB group reduced this necrotic area in relation to the CO group (p = 0.005). The TB and AS groups presented significantly higher (p <0.05) hepatic and neoplastic AB concentrations than the CO group. The SO and AS groups presented significantly higher (p <0.05) neoplastic concentrations of SO in relation to the CO group. The SO and AS groups reduced the PTEN expression when compared to the CO group, although this difference did not reach a significant difference (p> 0.05). The TB group in turn expressed higher levels of PTEN, although this difference did not increase statistical significance (p> 0.05). All groups expressed higher levels of caspase 3 cleaved when compared to the CO group (p> 0.05). The TB and SO groups reduced the expression of pERK &#189; when compared to the CO group. although these differences did not reach statistical difference (p> 0.05). The AS group presented higher pERK &#189; expression when compared to the CO group, although this difference did not reach a significant difference (p> 0.05). Characterization of the neoplasias of the CO group was standardized by immunohistochemistry, presenting positive for CK 7, CK8, CK19 and Arginase and negative for HepPar1 and CK18. Thus, the results suggest that the neoplasias obtained by implants with GP7TB cells present CPF characteristics originating from neoplastic stem cells. In addition, the experimental groups TB and AS presented promising anticarcinogenic activity in the model of syngeneic implants with GP7TB cells, which eventually involve mechanisms of action distinct from the chemotherapy activity presented by SO.

Au-delà de l’intérêt cognitif de la démarche, la compréhension des mécanismes qui régissent le développement pancréatique humain reste la clé pour décrypter les acteurs physiopathologiques des maladies du pancréas et pour développer des approches thérapeutiques innovantes. En outre, alors que la cellule bêta de rongeurs et la cellule bêta humaine partagent un grand nombre de similitudes, certaines données indiquent également des différences marquées entre les espèces. L'absence de systèmes expérimentaux robustes , à partir de matériel humain, n'a pas permis un examen détaillé du développement pancréatique humain jusqu’à présent. Dans le laboratoire, il a été précédemment validé un modèle de xénogreffe de pancréas immature humain sous la capsule rénale de souris immuno-incompétentes SCID. Il a été démontré que celui-ci permettait de récapituler l’ensemble des étapes du développement endocrine humain. Néanmoins le site de greffe limitait les possibilités de modifier ce développement, notamment par infection virale. Dans ce travail, nous avons développé et validé un nouveau site de greffe dans le muscle squelettique, plus simple et plus superficiel. En outre, nous démontrons qu’il est possible de créer un pancréas humain partiellement transgénique in vivo en réalisant du transfert de gènes médié par des lentivirus, après injection directe de la solution virale dans le greffon. Ce modèle de greffe dans le muscle est une nouvelle approche permettant d’envisager des études longitudinales, dans lesquelles il serait possible d’étudier la régulation de certains gènes ou le devenir de certaines lignées marquées par des gènes rapporteurs apportés par le virus à différents stades de développement. / Whilst sporadic human genetic studies have permitted some comparisons between rodent and human pancreatic development, the lack of a robust experimental system has not permitted detailed examination of human pancreatic development. We previously developed a xenograft model of immature human fetal pancreas grafted under the kidney capsule of immune-incompetent mice, which allowed the development of human pancreatic beta cells. Here, we compared the development of human and murine fetal pancreatic grafts either under skeletal muscle epimysium or under the renal capsule. We demonstrated that human pancreatic beta cell development occurs) both by differentiation of pancreatic progenitors and by proliferation of developing beta cells. The superficial location of the skeletal muscle graft and its easier access permitted in vivo lentivirus-mediated gene transfer which targeted specific cells. This model of engraftment under the skeletal muscle epimysium is a new approach for longitudinal studies, which allows localized manipulation to determine the regulation of human pancreatic development.

Heterogeneity within tumors has long been studied as a potential confounding factor for effective therapies, with recent studies pointing to heterogeneity resulting in distinct clonal subtypes, each with varying degrees of fitness and metastatic potential. Studies of heterogeneity have previously been limited to microscopy observations, immunohistochemistry, and flow cytometry. Recently, however, it has become possible to examine heterogeneity at a previously unexplored level: the transcriptome of individual cells. Osteosarcomas have been known to be highly heterogeneous, so we have selected osteosarcoma as our primary tumor to study as a proof-of-concept. Additionally, we have elected to create a murine patient derived xenograft (PDX) model from a primary osteosarcoma tumor and examine differences between the primary tumor and resulting xenograft at the single-cell level. Through this, we hope to better understand tumor heterogeneity and add to the current discussion in the scientific community regarding the relevance of PDX models for testing promising new therapies and personalized medicine. Through our examination of single-cell heterogeneity in osteosarcomas, we have confirmed the extensive heterogeneity previously reported, but this time at the level of mRNA. The osteosarcomas were so hetereogeneous that our resulting dataset of over 1,000 cells still did not have enough resolution to generate highly differentiated and separate groupings of cells. Upon examining inter-tumor heterogeneity, we observed the cells from different tumors to generally cluster separately. However, there were certain populations of cells from all tumors that clustered together. We also generated a PDX model and sequenced the resulting tumor, observing markedly reduced heterogeneity as compared to the original primary tumor. Importantly, the cells from the PDX model clustered within the larger group of cells from the original tumor, lending credence to the theory of clonal selection. This work presents evidence of extensive intra- and inter-tumor heterogeneity at the mRNA level within osteosarcoma tumors. This heterogeneity requires further single cell sampling to shed light on the biology of tumor diversity. Further, this heterogeneity is significantly reduced in a generated murine PDX model. This difference should serve as a potential warning about additional factors to take into account when evaluating therapies in PDX models, and suggests that further studies examining cause and effect of this observed heterogeneity are warranted.

No description available.