Clonagem humana gera células-tronco embrionárias

Clonagem Humana

Cientistas afirmam ter criado células-tronco humanas por meio de clonagem.

Essencialmente, a técnica envolve pegar um óvulo humano e combiná-lo com uma célula de outra pessoa adulta, sem retirar o DNA original da célula.

Esta área de pesquisas é altamente controversa, não apenas por suas implicações éticas, mas também por causa de uma fraude científica recente.

Em 2004, o cientista sul-coreano Hwang Woo-suk ganhou fama meteórica ao anunciar que teria produzido uma linhagem de células-tronco geradas a partir do embrião de um clone humano.

Como todo bom meteoro, Hwang queimou-se na atmosfera quando se descobriu que ele tinha forjado resultados, além de ter obtido os óvulos de forma antiética e ilegal.

Preservando o DNA

Agora, Scott Noggle, Dieter Egli e seus colegas do Laboratório da Fundação de Células-Tronco de Nova Iorque (EUA), anunciaram, em um artigo publicado na revista Nature, ter alcançado resultados intermediários, mas por uma via diferente.

Eles usaram uma tecnologia de clonagem chamada transferência de núcleos de célula somática.

A técnica mais comum de clonagem consiste na remoção do núcleo de um óvulo e sua substituição pelo núcleo da célula do doador, cujo DNA é então inserido no óvulo inicial. Imerso em nutrientes, o óvulo se divide, passando então por uma reprogramação genética, assumindo o DNA do doador.

Na nova técnica, o DNA do óvulo é mantido, recebendo o material genético de células epiteliais de um doador adulto.

"Pode ser um bom momento para as Nações Unidas começarem a forjar regulamentações ou restrições sobre a clonagem, que têm estado paralisadas pelo debate político e religioso," afirma a revista Nature em editorial. "[E] pacientes desesperados vão encontrar médicos prontos a lhes dar tratamentos com células-tronco embrionárias não-comprovados e inseguros."[Imagem: Noggle et al./Nature]

Células-tronco embrionárias clonadas

O resultado é uma célula triploide, com três pares de cromossomos: 23 do óvulo original e 46 (dois pares de 23) da célula do doador - teoricamente um embrião inviável, embora ele não tenha sido deixado para se desenvolver.

O óvulo se desenvolveu até o estágio conhecido como blastocisto, composto por cerca de 100 células.

O blastocisto é usado como fonte de células-tronco embrionárias, usadas em inúmeras pesquisas e vistas como um recurso futuro para a cura de várias doenças.

Os cientistas afirmam ter visto nas células do embrião triploide indícios de células-tronco embrionárias normais, o que comprovaria a importância de se manter o DNA original do óvulo.

Isto também pode ser uma demonstração de que as chamadas "técnicas tradicionais" de clonagem não são eficientes como se acreditava.

Células-tronco personalizadas

A clonagem é um recurso idealizado para evitar o problema da rejeição que ocorre quando um paciente recebe células-tronco de um doador.

Neste caso, o sistema imunológico do receptor vê as células-tronco como invasoras, exigindo o uso de imunossupressores, o que complica e pode até inviabilizar o tratamento.

Com a clonagem, torna-se teoricamente possível criar "células-tronco personalizadas", criadas com o próprio DNA do receptor, evitando então o problema da rejeição.

Ética na clonagem

A pesquisa está em um passo bastante inicial. Um editorial da revista Nature, onde a pesquisa foi publicada, afirma que os embriões triploides são geneticamente anômalos e inviáveis.

Os pesquisadores vão precisar ainda produzir um embrião diploide, com 46 cromossomos, antes de pensar em usar terapeuticamente as células-tronco clonadas.

Se eles conseguirem, recomeçará então todo o debate ético sobre o que fazer com estes embriões, até que ponto eles poderão ser deixados crescer, e se será permitida a realização da clonagem reprodutiva.

"Pode ser um bom momento para as Nações Unidas começarem a forjar regulamentações ou restrições sobre a clonagem, que têm estado paralisadas pelo debate político e religioso," afirma a revista Nature em editorial. "[E] pacientes desesperados vão encontrar médicos prontos a lhes dar tratamentos com células-tronco embrionárias não-comprovados e inseguros."

Lipoaspiração sem exercícios pode ser perigosa

Gordura visceral

A realização da lipoaspiração não acompanhada de atividade física regular no pós-operatório pode acarretar um aumento significativo da gordura visceral, localizada na região entre os órgãos.

Essa gordura é extremamente danosa para a saúde por estar associada ao aumento do risco cardiovascular.

Os exercícios físicos inibem o aumento dessa gordura entre os órgãos - veja Gordura abdominal interna é a mais perigosa para doenças do coração.

A conclusão é de um estudo realizado na Escola de Educação Física e Esporte (EEFE) da Universidade de São Paulo (USP).

Treinadas e sedentárias

A pesquisadora Fabiana Braga Benatti recrutou 36 mulheres com Índice de Massa Corporal (IMC) abaixo de 30, que fariam lipoaspiração na região abdominal, para participar da pesquisa.

O IMC é calculado a partir do peso da pessoa em quilogramas, dividido pela sua altura em metros elevada ao quadrado.

O grupo foi igualmente dividido em "mulheres treinadas" e "mulheres sedentárias".

Dois meses depois da cirurgia, o primeiro grupo foi submetido à uma série de exercícios de força e aeróbicos, por três vezes semanais, durante quatro meses, enquanto o segundo grupo permaneceu sem fazer atividades físicas regulares.

Uma bateria de exames foi feita antes e depois do processo e serviu de base para toda a pesquisa.

Aumento de gordura sem perceber

No grupo das mulheres sedentárias, o ganho da massa visceral chegou a 10%.

O fato não foi percebido pelas pacientes, pois o aumento desta gordura interna do corpo dificilmente é identificado no dia-a-dia, já que não representa grandes proporções em termos visuais.

Isso aumenta a importância do estudo, já que dificilmente estes dados seriam alcançados a não ser por um acompanhamento detalhado durante o pós-operatório.

Já no grupo de mulheres treinadas não houve aumento da gordura visceral. O treinamento físico preveniu este aumento.

Uma possível explicação para isso é o fato deste tipo de gordura ser metabolicamente ativo e mais responsivo ao aumento das concentrações de adrenalina que ocorrem durante o exercício físico.

Além disso, o treinamento físico preservou o gasto energético das mulheres treinadas, o que pode ter contribuído para seus efeitos benéficos observados.

Lipoaspiração não é para perder peso

O peso perdido na cirurgia de lipoaspiração foi recuperado em ambos os grupos.

"A cirurgia não tem como objetivo a redução de peso, que diminui em média 1%. A pretensão da lipoaspiração é retirar a gordura localizada e modelar o corpo do paciente", diz Fabiana.

No caso das mulheres sedentárias, contudo, o peso retornou possivelmente pelo novo ganho de massa gorda, favorecida pelo estilo de vida levado. O metabolismo se esforça para manter uma constante e isso inclui o peso.

Perda de massa gorda

A diminuição do gasto energético durante dietas restritivas normalmente é atribuída à perda de massa magra.

"Como não se percebeu perda de massa magra durante o estudo, este resultado foi considerado inesperado. "Acreditamos que tenha a ver com a perda de massa gorda", diz Fabiana.

A retirada de massa gorda ocasiona, ainda, a queda nos níveis do hormônio adiponectina, que tem efeito benéfico no corpo. Ele regula a sensibilidade da insulina que, quando alterada, pode gerar uma série de consequências danosas para o corpo, a mais conhecida delas sendo a diabetes.

Puramente estético

Ao contrabalancear os efeitos da lipoaspiração, Fabiana diz que o que deve ser feito é um esclarecimento sobre os efeitos colaterais causados pela cirurgia.

"Metabolicamente falando, não vimos nada de benéfico na cirurgia. Ela é um procedimento puramente estético", conclui.

O aumento da gordura visceral e dos riscos que isso traz podem ser evitados, mas para isso é preciso atentar e esclarecer, tanto para médicos quanto para pacientes, a real necessidade de fixação de uma série de exercícios na rotina do pós-operatório.

• Suplemento alimentar só reduz peso se acompanhado de exercício

MVA-B Spanish HIV Vaccine Shows 90 Percent Immune Response in Humans

ScienceDaily (Oct. 6, 2011) — Phase I clinical trials developed by Spanish Superior Scientific Research Council (CSIC) together with Gregorio Marañón Hospital in Madrid and Clínic Hospital in Barcelona, reveals MVA-B preventive vaccine's immune efficiency against human immunodeficiency virus (HIV). 90% of the volunteers who went through the tests developed an immunological response against the virus and 85% has kept this response for at least one year. Safety and efficiency of this treatment have been described in articles for Vaccine and theJournal of Virology.

Three-dimensional model of an HIV particle. 

The success of this vaccine, CSIC's patent, is based on the capability of human's immune system to learn how to react over time against virus particles and infected cells. "MVA-B vaccine has proven to be as powerful as any other vaccine currently being studied, or even more," says Mariano Esteban, head researcher from CSIC's National Biotech Centre.

In 2008, MVA-B already showed very high efficiency in mice as well as macaque monkeys against Simian's immunodeficiency virus (SIV). Due to it's high immunological response in humans, Phase I clinic trials will be conducted with HIV infected volunteers, to test its efficiency as a therapeutic vaccine.

Weapon's origins

Back in 1999, Esteban's research team began to work in the development and preclinical studies of MVA-B, which name comes from its composition, based in Modified Ankara Vaccinia virus. MVA-B is an attenuated virus, which has already been used in the past to eradicate smallpox, and also as a model in the research of many other vaccines. The "B" stands for the HIV subtype it is meant to work against, the most common in Europe.

Development of MVA-B is based in the insertion of four HIV genes (Gag, Pol, Nef & Env) in Vaccina's genetic sequence. A healthy immunitary system is able to react against MVA.

On the other hand, the inserted HIV genes in its DNA are not able to self-replicate, which guarantees the safety of the clinical trial.

30 healthy volunteers participated in this clinical trial. 24 of them were treated with MVA-B, while the other 6 were treated with a placebo, following a double-blind testing method. 3 doses of the vaccine were given via intramuscular route in weeks 0, 4 and 16. The effects were studied in peripheral blood until the trial ended on week 48.

Combat battalion

Inoculating the vaccine in a healthy volunteer is intended to train it's immune system to detect and learn how to combat those virus components. According to Esteban " it is like showing a picture of the HIV so that it is able to recognise it if it sees it again in the future."

Lymphocytes T and B are the main cells in this experiment, the soldiers in charge of detecting the foreign substances in the body and sending the right coordinates to destroy them.

"Our body is full of lymphocytes, each of them programmed to fight against a different pathogen" says Esteban. For that reason "Training is needed when it involves a pathogen, like the HIV one, which cannot be naturally defeated."

Lymphocytes B are responsible for the humoral immune response, producing antibodies which attack the HIV particles before they penetrate and infect the cell, anchoring themselves to the external structure and blocking it. 48th week blood tests reveal 72,7% of the treated volunteers hold specific antibodies against HIV.

On the other side, lymphocytes T control cell's immune response, in charge of detecting and destroying HIV infected cells. In order to verify their defence response to the vaccine, production of interferon gamma immunitary protein was measured.

Tests performed on the 48th week, 32 weeks after the last inoculation of the vaccine, show the production of lymphocytes T CD4+ and CD8+ of the vaccinated group is 38,5% and 69,2%, respectively, while it stays at 0% in the control group.

Action in several fronts

Besides interferon gamma, other immune proteins (cytokines and chemokines) are produced by the body when the presence of a pathogen is detected. Each of these proteins tends to attack a different enemy front. When T lymphocytes' defence action is able to generate several of these proteins it is called a polyfunctional action. CSIC's researcher adds "The importance of polyfunctionality has to do with the capability of pathogens to develop resistance to the immune systems attacks. The higher the polyfunctionality, the lower the resistance."

The defence spectrum of T lymphocytes in vaccinated subjects was measured based on the production of 3 other immunitary proteins. Tests indicate the vaccine generates up to 15 types of lymphocyte T CD4+ and CD8+ populations. 25% of CD4+ type and 45% of CD8+ type are able to produce two or more different proteins, proving their polyfunctionality.

War veterans

For a vaccine to become really effective, besides its immune system's defence capability, generating a long lasting response against future attacks is the key. For this purpose, the body needs to be able to keep a basic level of memory T lymphocytes. These lymphocytes, generated after a first pathogen attack, are veteran soldiers, which can circulate the body for years, prepared to respond to a new enemy's incursion.

48th week blood tests ran on vaccinated subjects show over 50% of CD4+ and CD8+ lymphocytes were memory T lymphocytes in the 85% of the patients who kept an immune response at this point of the trials.

In Esteban's opinión "MVA-B immune profile meets, initially, the requirements for a promising HIV vaccine." MVA-B is not capable of removing the virus from the body as once a cell is infected, virus' genetic data is integrated and replicated with the cell. However, the immune response induced by the vaccine could keep the virus under control, "if the virus enters the body and tries to develop in a cell, the immune system is ready to inactivate the virus and destroy the infected cell."

According to CSIC's researcher: "If this genetic cocktail passes Phase II and Phase III future clinic trials, and makes it into production, in the future HIV could be compared to herpes virus nowadays." Virus would not cause a disease anymore and would become a minor chronic infection, which would only show its effects in a low defence scenario, with a much lower contagious profile.

Evidence Found for the Genetic Basis of Autism: Models of Autism Show That Gene Copy Number Controls Brain Structure and Behavior

ScienceDaily (Oct. 6, 2011) — Scientists at Cold Spring Harbor Laboratory (CSHL) have discovered that one of the most common genetic alterations in autism -- deletion of a 27-gene cluster on chromosome 16 -- causes autism-like features. By generating mouse models of autism using a technique known as chromosome engineering, CSHL Professor Alea Mills and colleagues provide the first functional evidence that inheriting fewer copies of these genes leads to features resembling those used to diagnose children with autism.

This three-dimensional representation of the mouse brain highlights eight regions (shown with different colors) affected by 16.p11.2 deletion. 

The study appears in theProceedings of the National Academy of Sciences in the early online edition during the week of October 3.

"Children normally inherit one copy of a gene from each parent. We had the tools to see whether copy number changes found in kids with autism were causing the syndrome," explains Mills. In 2007, Professor Michael Wigler, also at CSHL, revealed that some children with autism have a small deletion on chromosome 16, affecting 27 genes in a region of our genomes referred to as 16p11.2. The deletion -- which causes children to inherit only a single copy of the 27-gene cluster -- is one of the most common copy number variations (CNVs) associated with autism.

"The idea that this deletion might be causing autism was exciting," says Mills. "So we asked whether clipping out the same set of genes in mice would have any effect."

After engineering mice that had a chromosome defect corresponding to the human 16p11.2 deletion found in autism, Mills and her team analyzed these models for a variety of behaviors, as the clinical features of autism often vary widely from patient to patient, even within the same family.

"Mice with the deletion acted completely different from normal mice," explains Guy Horev, a Postdoctoral Fellow in the Mills laboratory and first author of the study. These mice had a number of behaviors characteristic of autism: hyperactivity, difficulty adapting to a new environment, sleeping deficits, and restricted, repetitive behaviors.

Interestingly, mice that had been engineered to carry an extra copy, or duplication, of the 16p11.2 region did not have these characteristics, but instead, had the reciprocal behaviors. For each behavior, the deletion had a more dire consequence than the duplication, indicating that gene loss was more severe. This might explain why 16p11.2 duplications are detected much more frequently than deletions within the human population, and why patients with 16p11.2 deletions tend to be diagnosed earlier than those with duplications.

The mouse models also revealed a potential link between 16p11.2 deletion and survival, as about half the mice died following birth. Whether these findings extend to the human population might be answered by future studies that investigate the link between this deletion and unexplained cases of infant death.

The researchers also used MRI to identify specific regions of the brain that were altered in the autism models, revealing that eight different parts of the brain were affected. The group is now working to identify which gene or group of genes among the 27 that are located within the deleted region is responsible for the behaviors and brain alterations observed.

"Alea Mills has created a valuable resource for everyone engaged in autism research. The technical skill is extraordinary in creating mouse models bearing a human genetic variant that has been associated with autism," says Dr. Gerald Fischbach, Director of Life Sciences and Simons Foundation Autism Research Initiative (SFARI).

These mice will be invaluable for pinpointing the genetic basis of autism and for elucidating how these alterations affect the brain. They could also be used for inventing ways to diagnose children with autism before they develop the full-blown syndrome, as well as for designing clinical interventions.

Collaborators on this work include a group of MRI specialists led by Dr. Mark Henkelman at the Hospital of Sick Children in Toronto. This study was funded by the Simons Foundation Autism Research Initiative (SFARI).

Patient-Specific Stem Cells: Major Step Toward Cell-Based Therapies for Life-Threatening Diseases

ScienceDaily (Oct. 6, 2011) — A team of scientists led by Dieter Egli and Scott Noggle at The New York Stem Cell Foundation (NYSCF) Laboratory in New York City has made an important advance in the development of patient-specific stem cells that could impact the study and treatment of diseases such as diabetes, Parkinson's, and Alzheimer's.

For the first time, scientists have derived embryonic stem cells from individual patients by adding the nuclei of adult skin cells from patients with type 1 diabetes to unfertilized donor oocytes

As reported in the journal Nature, for the first time the scientists have derived embryonic stem cells from individual patients by adding the nuclei of adult skin cells from patients with type 1 diabetes to unfertilized donor oocytes.

The achievement is significant because such patient-specific cells potentially can be transplanted to replace damaged or diseased cells in persons with diabetes and other diseases without rejection by the patient's immune system. The scientists report further work is necessary before such cells can be used in cell-replacement medicine.

The research was conducted in The NYSCF Laboratory in Manhattan in collaboration with clinicians and researchers at Columbia University Medical Center. DNA analysis was provided by scientists at the University of California, San Diego.

"The specialized cells of the adult human body have an insufficient ability to regenerate missing or damaged cells caused by many diseases and injuries," said Dr. Egli, NYSCF senior scientist in the study. "But if we can reprogram cells to a pluripotent state, they can give rise to the very cell types affected by disease, providing great potential to effectively treat and even cure these diseases. In this three-year study, we successfully reprogrammed skin cells to the pluripotent state. Our hope is that we can eventually overcome the remaining hurdles and use patient-specific stem cells to treat and cure people who have diabetes and other diseases."

"The ultimate goal of this study is to save and enhance lives by finding better treatments and eventually cures for diabetes, Alzheimer's, Parkinson's and other debilitating diseases and injuries affecting millions of people across the US and the globe," said NYSCF CEO Susan L. Solomon. "This research brings us an important step closer to creating new healthy cells for patients to replace their cells that are damaged or lost through injury."

The scientists demonstrate for the first time that the transfer of the nucleus from an adult skin cell of a patient into an oocyte without removing the oocyte nucleus results in reprogramming of the adult nucleus to the pluripotent state. Embryonic stem cell lines were then derived from the oocyte containing the patient's genetic material.

Since these pluripotent stem cells also have a copy of the chromosome from the oocyte, resulting in an abnormal number of chromosomes, these cells are not ready for therapeutic use. Future work will focus on understanding the role of the oocyte chromosome so that patient- specific stem cells can be made that contain only the patient's DNA.

In the study, skin cells from patients with type 1 diabetes and healthy patients (control group) were reprogrammed, allowing the derivation of pluripotent stem cells, cells that have the capacity for universal tissue production. Such cells potentially could be used to create beta cells that produce insulin.

Patients with type 1 diabetes lack insulin-producing beta cells, resulting in insulin deficiency and high blood sugar levels. Producing beta cells from stem cells for transplantation holds promise for the treatment and potential cure of type 1 diabetes.

"This is an important step toward generating stem cells for disease modeling and drug discovery, as well as for ultimately creating patient-specific cell-replacement therapies for people with diabetes or other degenerative diseases or injuries," said Rudolph L. Leibel, MD, co-director of Columbia's Naomi Berrie Diabetes Center and a collaborator in the study.

The study raises the possibility of using somatic cell reprogramming to create banks of stem cells that could be used for a wide range of patients, noted another collaborator, Robin Goland, MD, co-director of the Naomi Berrie Diabetes Center. "In theory, stem cell lines could be matched to a particular patient, much as we do now when we screen an individual for compatibility with a kidney transplant," she said.

"This project is a great example of how enormous strides can be achieved when investigators in basic science and clinical medicine collaborate," said Mark V. Sauer, MD, a coauthor of the paper and Vice Chairman of the Department of Obstetrics and Gynecology and chief of reproductive endocrinology at Columbia University Medical Center. Dr. Sauer is also program director of assisted reproduction at the Center for Women's Reproductive Care. "I feel fortunate to have been able to participate in this important project."

Zach W. Hall, PhD, former Director of the NIH's National Institute of Neurological Disorders and Stroke and former President of the California Institute for Regenerative Medicine said, "This work represents a major advance toward the production of patient-specific stem cells for therapeutic use by demonstrating that the nucleated oocyte has the ability to completely reprogram the nucleus of an adult human cell."

The study was funded solely with private funding and adhered to ethical guidelines adopted by the American Society for Reproductive Medicine and the International Society for Stem Cell Research, as well as protocols reviewed and approved by the institutional review board and stem cell committees of Columbia University.