Athena Vale
Heart failure is the most common cause of death worldwide. This is because cardiac muscle cells do not divide and regenerate in humans and other mammals. However, this is not the case for zebrafish and amphibians, whose remaining cardiac muscle cells can reproduce and regenerate when damaged. Scientists have been trying to find a way to get human adult cells to divide and regenerate tissue in a similar way. A recent study has discovered that Lamin B2, a protein found on the outer layer of the cell nucleus, is a limiting factor in heart muscle cells' ability to regenerate.
| Characteristics | Values |
|---|---|
| Division of cardiac muscle cells | Cardiac muscle cells can divide and multiply during the embryo stage, but they lose their ability to divide shortly after birth. |
| Cardiac muscle cell regeneration | Unlike lower vertebrates, mammals, including humans, cannot repair their adult hearts after a heart attack. |
| Factors influencing regeneration | The ability of cardiac muscle cells to reproduce disappears due to the absence of a protein called Lamin B2, which is present in newborn mice but less so in adults. |
| Controlled regeneration | Temporally and spatially controlled reprogramming of cardiac muscle cells can lead to regeneration, but optimal strength and duration are critical to prevent tumor formation. |
| Impact of cell division | Division of cardiac muscle cells is rare and can disrupt the physiological process, causing the heart to become out of sync. |
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What You'll Learn
- Cardiac muscle cells in adult mammals cannot regenerate
- Heart failure is the most common cause of death worldwide
- Heart muscle cells can divide and multiply in embryos
- Heart muscle cells stop dividing due to a lack of Lamin B2 protein
- Zebrafish and amphibians can repair their adult hearts after a heart attack
Cardiac muscle cells in adult mammals cannot regenerate
The human heart has limited self-healing powers and a restricted ability to regenerate. When cardiac muscle cells are damaged, they die, which can lead to reduced heart function and death. This is a significant issue, as heart failure is the most common cause of death globally.
The ability of cardiac muscle cells to reproduce disappears in humans and other mammals shortly after birth. However, this is not the case for zebrafish or amphibians, whose remaining cardiac muscle cells can reproduce and allow the heart to regenerate if it becomes damaged. This difference is due to the presence of an intact centrosome in the cardiac muscle cells of zebrafish and amphibians, which is lacking in mammals.
Researchers are currently investigating methods to stimulate the reproduction of cardiac muscle cells in humans and restore the heart's function. One approach involves the controlled expression of regulatory factors, leading to the partial reprogramming of cardiac myocytes and temporary regeneration. Another method being explored is the forced temporary reprogramming of heart muscle cells, triggering dedifferentiation and cell division. These techniques hold potential for the development of new medical treatments for heart damage.
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Heart failure is the most common cause of death worldwide
In the event of a heart attack, for instance, the death of cardiac muscle cells due to insufficient oxygen and nutrient supply results in a gap in the heart's cell structure. Unlike the human heart, zebrafish and amphibians can regenerate their hearts as their cardiac muscle cells can reproduce. In contrast, mammals form a connective tissue scar to fill this gap, which can lead to further complications.
Scientists have been able to induce regeneration in damaged hearts in mice by employing controlled reprogramming of cardiac muscle cells. This involves the short-term, controlled expression of regulatory factors, causing cardiac muscle cells to rewind their developmental program and temporarily regain their ability to divide. However, the strength and duration of this reprogramming must be carefully managed to avoid regeneration failure or tumour formation.
Despite heart disease being the leading cause of death globally, with cardiovascular disease (CVD) accounting for approximately 19.91 million deaths worldwide in 2021, many people remain unaware of its significant impact. This lack of knowledge can be potentially deadly, as nearly half of all individuals in the US, for example, are estimated to have some form of CVD. Recognizing the prevalence of heart disease and its risk factors, such as high blood pressure, high cholesterol, and smoking, is crucial for reducing the chances of becoming a part of the alarming statistics.
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Heart muscle cells can divide and multiply in embryos
Heart muscle cells, or cardiomyocytes, can divide and multiply in embryos, allowing the heart to grow and develop. However, shortly after birth, these cells lose their ability to divide, a phenomenon also observed in other human cells such as those in the brain, spinal cord, and pancreas. This loss of proliferative capacity in adult cardiomyocytes is a significant challenge in regenerative medicine, as it limits the heart's ability to self-heal and regenerate after injuries like heart attacks.
The inability of adult cardiomyocytes to divide is due to the suppression of mitotic activity during early fetal growth. While the exact mechanism remains unclear, researchers are exploring ways to reactivate cell division in these specialized cells. One approach involves blocking the proteins that halt the cell cycle, essentially reverting cardiomyocytes to their primitive state when they were actively dividing. However, this strategy must be carefully controlled to avoid excessive or unwanted cell division, which could lead to tumor formation.
In contrast to mammals, lower vertebrates like zebrafish, amphibians, and salamanders possess remarkable cardiac regenerative abilities. For instance, in the event of heart damage, the remaining cardiac muscle cells in these organisms can reproduce, facilitating heart regeneration. This difference between mammals and lower vertebrates presents a compelling area of investigation, with the potential to unlock new avenues for heart regeneration in humans.
Despite the challenges, recent advancements in regenerative medicine offer a glimmer of hope. Researchers from the Gladstone Institute of Cardiovascular Disease have identified key factors and cell types responsible for cardiomyocyte proliferation, providing insights into the differences between adult and embryonic cell behavior. Additionally, scientists from the Max Planck Institute for Heart and Lung Research have successfully regenerated damaged hearts in mice through the temporally and spatially controlled reprogramming of heart muscle cells, demonstrating the potential for future therapeutic interventions in humans.
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Heart muscle cells stop dividing due to a lack of Lamin B2 protein
Heart muscle cells, also known as cardiomyocytes, are highly differentiated cells that have a limited ability to regenerate. This is because they lose their ability to divide shortly after birth. The loss of this ability is not fully understood, but recent studies have identified a key factor: the Lamin B2 protein.
Lamin B2 is an intermediate filament protein that resides on the outer layer of the nucleus of heart muscle cells. It plays a critical role in maintaining the structural integrity of the nucleus and facilitating cell division. In a study on mice, researchers found that heart muscle cells stopped dividing in adults due to a lack of Lamin B2 protein expression. Conversely, when mice were genetically engineered to express more Lamin B2, their heart muscle cells began to replicate and regenerate heart tissue.
The Lamin B2 protein is highly expressed in newborn mice, whose heart cells are actively dividing and proliferating. However, as mice age into adulthood, the expression of Lamin B2 decreases, leading to a reduced capacity for heart muscle cell division. This discovery was further validated by experiments on cardiomyocytes derived from human stem cells, which exhibited similar cell division problems when Lamin B2 was eliminated.
The loss of Lamin B2 in heart muscle cells causes them to get stuck together during cell division attempts, resulting in the presence of extra copies of the cell's DNA-containing chromosomes in each nucleus. This accumulation of extra chromosomes further complicates the process of cell division. Therefore, the presence of Lamin B2 is crucial for heart muscle cells to complete their cycles of cell division successfully.
Understanding the role of Lamin B2 in heart muscle cell division provides valuable insights into the potential regeneration of the heart after damage. By manipulating the expression of Lamin B2, researchers aim to stimulate the reproduction of cardiac muscle cells, offering new possibilities for medical treatments and organ transplants.
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Zebrafish and amphibians can repair their adult hearts after a heart attack
Unlike humans, zebrafish and amphibians can repair their hearts after a heart attack. This is because, in the event of damage to the heart, the remaining cardiac muscle cells in these organisms can reproduce, allowing the heart to regenerate.
In humans, when cardiac muscle cells die due to a lack of oxygen and nutrients caused by blocked coronary arteries, a connective tissue scar forms to fill the gap in the cell structure. This results in reduced heart function and can lead to death. However, zebrafish and amphibians can clear this scar tissue and replace it with functional myocardium, avoiding the loss of heart function.
Zebrafish, in particular, have become a popular model organism for studying heart regeneration. They possess a thin layer of primordial cardiomyocytes, which resemble embryonic heart cells and are suspected to be important for regeneration. Additionally, their distinctive horizontal stripes and ease of propagation in labs have made them a well-characterized and accessible subject for research.
By studying the differences between zebrafish and other fish species that cannot regenerate heart tissue, scientists hope to gain insights into why mammals cannot regenerate as adults. This knowledge may inform the development of therapies to heal human hearts after a heart attack or other injuries.
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Frequently asked questions
Cardiac muscle cells in adult mammals lose their ability to divide shortly after birth. However, in a recent study, scientists have found a way to make adult cells divide and repair hearts damaged by heart attacks in animal models.
The human heart has a limited self-healing capacity because cardiac muscle cells in adult humans have largely lost their ability to divide. This is due to the lack of the Lamin B2 protein, which is necessary for heart muscle cells to complete their cycles of cell division.
Yes, lower vertebrates like zebrafish, amphibians, and salamanders have a remarkable ability to repair their own injured organs by regenerating dead muscle tissue.
