APOE ε4 Status in Healthy Older African Americans is Associated with Deficits in Pattern Separation and Hippocampal Hyperactivation


African Americans are 1.4 times more likely than European Americans to carry the APOE ε4 allele, a risk factor for Alzheimer’s disease (AD). However, little is known about the neural correlates of cognitive function in older African Americans and how they relate to genetic risk for AD. In particular, no past study on African Americans has examined the effect of APOE ε4 status on pattern separation—mnemonic discrimination performance and its corresponding neural computations in the hippocampus. Previous work using the mnemonic discrimination paradigm has localized increased activation in the DG/CA3 hippocampal sub-regions as being correlated with discrimination deficits.📍

APOE ε4 Status in Healthy Older African Americans is Associated with Deficits in Pattern Separation and Hippocampal Hyperactivation


African Americans are 1.4 times more likely than European Americans to carry the APOE ε4 allele, a risk factor for Alzheimer’s disease (AD). However, little is known about the neural correlates of cognitive function in older African Americans and how they relate to genetic risk for AD. In particular, no past study on African Americans has examined the effect of APOE ε4 status on pattern separation—mnemonic discrimination performance and its corresponding neural computations in the hippocampus. Previous work using the mnemonic discrimination paradigm has localized increased activation in the DG/CA3 hippocampal sub-regions as being correlated with discrimination deficits.📍

APOE ε4 Status in Healthy Older African Americans is Associated with Deficits in Pattern Separation and Hippocampal Hyperactivation


African Americans are 1.4 times more likely than European Americans to carry the APOE ε4 allele, a risk factor for Alzheimer’s disease (AD). However, little is known about the neural correlates of cognitive function in older African Americans and how they relate to genetic risk for AD. In particular, no past study on African Americans has examined the effect of APOE ε4 status on pattern separation—mnemonic discrimination performance and its corresponding neural computations in the hippocampus. Previous work using the mnemonic discrimination paradigm has localized increased activation in the DG/CA3 hippocampal sub-regions as being correlated with discrimination deficits.📍

Does Malformed Lamin A Produce Enough Cellular Senescence to Contribute Meaningfully to the Progression of Aging?

Progeria is one of the better known accelerated aging conditions. It isn’t actually accelerated aging, but rather one specific runaway form of cell damage that gives rise to general dysfunction in cells throughout the body. Since degenerative aging is also a matter of general dysfunction in cells throughout the body, there is some overlap in the observed results, even though the root causes are completely different. So progeria patients appear, superficially at least, to be prematurely aged, and die from heart disease early in life.

The cause of progeria was discovered to be a mutation in the Lamin A (LMNA) gene, resulting in a malformed protein now called progerin. This protein is an important structural component of the cell nucleus. If it doesn’t function correctly, the nucleus becomes misshapen, and near all processes involving nuclear DNA maintenance and gene expression – the production of needed proteins at the right time from their genetic blueprints – cease to work correctly. The cell becomes dysfunctional. When near all cells are in this state, the prognosis for the individual is dire. Interestingly, in the years since this discovery, it has become clear that progerin is also present in small amounts in genetically normal older individuals. There is some debate over whether or not this is important in the progression of aging. Does it cause enough damage, or is it insignificant in comparison to other harmful processes?

In this context, we can consider cellular senescence, a mechanism closely connected to DNA damage, by which a small number of problem cells can cause outsized amounts of harm. Another possibility is damage to stem cells, as they are also small in number but highly influential on tissue function. Cells become senescent in response to internal damage, including that produced by progerin, and then either self-destruct or linger to secrete a potent mix of inflammatory and other signals. It is these signals, the senescence-associated secretory phenotype, that allows a comparatively small number of cells to produce comparatively large problems. It is known that senescent cells are important in many age-related conditions, particular those with a strong inflammatory component. Is generation of progerin significant as a cause of cellular senescence in normal aging, however? In this open access paper, researchers consider some of the mechanisms involved.

GATA4-dependent regulation of the secretory phenotype via MCP-1 underlies lamin A-mediated human mesenchymal stem cell aging

The LMNA gene encodes lamin and lamin C, which are major components of the nuclear lamina. Mutations in the LMNA gene have been implicated in premature aging disorders, including Hutchinson-Gilford progeria syndrome (HGPS). HGPS is caused by splicing defect and consequent generation of progerin, mutant-truncated lamin protein. Cells of HGPS patients exhibit an abnormal nuclear structure, increased DNA damage and premature senescence. In addition to the effects of progerin, accumulation of prelamin A, precursor of lamin A, induces defects in nuclear structures. ZMPSTE24 is an enzyme that produces mature lamin by cleavage of amino acids in prelamin A.

Zmpste24 knock-out mice have been widely used to study the mechanisms of aging and progeria. Depletion of Zmpste24 causes premature senescence in mice, including decreases in life span and bone density. Increased prelamin expression caused by ZMPSTE24 deficiency causes defective DNA repair. Zmpste24 knock-out mice have been extensively studied because of their impaired DNA damage response (DDR). Lamin also functions as a structural barrier to DDR. Altogether, these findings indicate that defects in the nuclear structure induced by progerin or prelamin lead to the accumulation of DNA damage, which results in accelerated aging.

It has been reported that exogenous expression of progerin in human mesenchymal stem cells (hMSCs) can impair their differentiation potential. Furthermore, production of induced pluripotent stem cells (iPSCs) from HGPS patients has revealed that the progerin expression levels are the highest in MSCs, vascular smooth muscle cells, and fibroblasts. These results indicate that MSCs are a specific target cell type of progerin-induced senescence. Like progerin, excessive accumulation of prelamin induces premature senescence in MSCs, including wrinkled nuclei. Downregulation of ZMPSTE24 in hMSCs also induces the senescence phenotype. These investigations imply that both progerin and prelamin can induce senescence in hMSCs with change in nuclear morphology.

Senescent cells secrete a group of factors that induce senescence in neighboring cells, a phenomenon termed senescence-associated secretory phenotype (SASP). The secreted inflammatory factors propagate senescence and recruit immune cells to senescent tissues by the generation of a pro-inflammatory environment. Among the factors reported to regulate the SASP, GATA4 has been recently identified as a regulator of senescence and inflammation. GATA4 is expressed during oncogene– and irradiation-induced senescence in fibroblasts in response to DNA damage. During the process of cellular senescence, GATA4 has a regulatory role in the SASP of fibroblasts. Because GATA4-dependent cellular senescence is closely associated with DDR, the role of GATA4 in other senescence models and other cell types may reveal a new mechanism.

Senescent hMSCs also induce senescence in neighboring cells. Monocyte chemoattractant protein-1 (MCP-1) secreted from senescent human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) induces premature senescence in neighboring cells. Insulin-like growth factor binding proteins are also produced by senescent hMSCs, and they trigger senescence in adjacent normal cells. These studies investigated the mechanisms of the SASP by inducing senescence in hMSCs through prolonged passaging. However, cellular senescence of MSCs can be regulated by various factors other than passaging. In our previous report, we have demonstrated that depletion of ZMPSTE24 and introduction of progerin induce premature senescence in hUCB-MSCs. It remains to be determined whether defective lamin triggers paracrine senescence via inflammatory factors in hMSCs.

In this study, we identified that paracrine senescence is triggered in senescent hMSCs with abnormal nuclear structures by increasing the expression of MCP-1 and that inhibition of MCP-1 decreases the SASP. Furthermore, we found that GATA4 mediates the senescence of hMSCs induced by defective lamin A. We assessed whether down-regulation of GATA4 disturbs the progerin- or prelamin A-dependent senescence phenotype. Elucidating how GATA4 regulates senescence in hMSCs with nuclear defects may aid in understanding the etiology of complex aging disorders. We show that inhibition of GATA4 expression protects hMSCs from cellular senescence, implying unique therapeutic opportunity against progeroid syndromes and physiological aging.

📍

Does Malformed Lamin A Produce Enough Cellular Senescence to Contribute Meaningfully to the Progression of Aging?

Progeria is one of the better known accelerated aging conditions. It isn’t actually accelerated aging, but rather one specific runaway form of cell damage that gives rise to general dysfunction in cells throughout the body. Since degenerative aging is also a matter of general dysfunction in cells throughout the body, there is some overlap in the observed results, even though the root causes are completely different. So progeria patients appear, superficially at least, to be prematurely aged, and die from heart disease early in life.

The cause of progeria was discovered to be a mutation in the Lamin A (LMNA) gene, resulting in a malformed protein now called progerin. This protein is an important structural component of the cell nucleus. If it doesn’t function correctly, the nucleus becomes misshapen, and near all processes involving nuclear DNA maintenance and gene expression – the production of needed proteins at the right time from their genetic blueprints – cease to work correctly. The cell becomes dysfunctional. When near all cells are in this state, the prognosis for the individual is dire. Interestingly, in the years since this discovery, it has become clear that progerin is also present in small amounts in genetically normal older individuals. There is some debate over whether or not this is important in the progression of aging. Does it cause enough damage, or is it insignificant in comparison to other harmful processes?

In this context, we can consider cellular senescence, a mechanism closely connected to DNA damage, by which a small number of problem cells can cause outsized amounts of harm. Another possibility is damage to stem cells, as they are also small in number but highly influential on tissue function. Cells become senescent in response to internal damage, including that produced by progerin, and then either self-destruct or linger to secrete a potent mix of inflammatory and other signals. It is these signals, the senescence-associated secretory phenotype, that allows a comparatively small number of cells to produce comparatively large problems. It is known that senescent cells are important in many age-related conditions, particular those with a strong inflammatory component. Is generation of progerin significant as a cause of cellular senescence in normal aging, however? In this open access paper, researchers consider some of the mechanisms involved.

GATA4-dependent regulation of the secretory phenotype via MCP-1 underlies lamin A-mediated human mesenchymal stem cell aging

The LMNA gene encodes lamin and lamin C, which are major components of the nuclear lamina. Mutations in the LMNA gene have been implicated in premature aging disorders, including Hutchinson-Gilford progeria syndrome (HGPS). HGPS is caused by splicing defect and consequent generation of progerin, mutant-truncated lamin protein. Cells of HGPS patients exhibit an abnormal nuclear structure, increased DNA damage and premature senescence. In addition to the effects of progerin, accumulation of prelamin A, precursor of lamin A, induces defects in nuclear structures. ZMPSTE24 is an enzyme that produces mature lamin by cleavage of amino acids in prelamin A.

Zmpste24 knock-out mice have been widely used to study the mechanisms of aging and progeria. Depletion of Zmpste24 causes premature senescence in mice, including decreases in life span and bone density. Increased prelamin expression caused by ZMPSTE24 deficiency causes defective DNA repair. Zmpste24 knock-out mice have been extensively studied because of their impaired DNA damage response (DDR). Lamin also functions as a structural barrier to DDR. Altogether, these findings indicate that defects in the nuclear structure induced by progerin or prelamin lead to the accumulation of DNA damage, which results in accelerated aging.

It has been reported that exogenous expression of progerin in human mesenchymal stem cells (hMSCs) can impair their differentiation potential. Furthermore, production of induced pluripotent stem cells (iPSCs) from HGPS patients has revealed that the progerin expression levels are the highest in MSCs, vascular smooth muscle cells, and fibroblasts. These results indicate that MSCs are a specific target cell type of progerin-induced senescence. Like progerin, excessive accumulation of prelamin induces premature senescence in MSCs, including wrinkled nuclei. Downregulation of ZMPSTE24 in hMSCs also induces the senescence phenotype. These investigations imply that both progerin and prelamin can induce senescence in hMSCs with change in nuclear morphology.

Senescent cells secrete a group of factors that induce senescence in neighboring cells, a phenomenon termed senescence-associated secretory phenotype (SASP). The secreted inflammatory factors propagate senescence and recruit immune cells to senescent tissues by the generation of a pro-inflammatory environment. Among the factors reported to regulate the SASP, GATA4 has been recently identified as a regulator of senescence and inflammation. GATA4 is expressed during oncogene– and irradiation-induced senescence in fibroblasts in response to DNA damage. During the process of cellular senescence, GATA4 has a regulatory role in the SASP of fibroblasts. Because GATA4-dependent cellular senescence is closely associated with DDR, the role of GATA4 in other senescence models and other cell types may reveal a new mechanism.

Senescent hMSCs also induce senescence in neighboring cells. Monocyte chemoattractant protein-1 (MCP-1) secreted from senescent human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) induces premature senescence in neighboring cells. Insulin-like growth factor binding proteins are also produced by senescent hMSCs, and they trigger senescence in adjacent normal cells. These studies investigated the mechanisms of the SASP by inducing senescence in hMSCs through prolonged passaging. However, cellular senescence of MSCs can be regulated by various factors other than passaging. In our previous report, we have demonstrated that depletion of ZMPSTE24 and introduction of progerin induce premature senescence in hUCB-MSCs. It remains to be determined whether defective lamin triggers paracrine senescence via inflammatory factors in hMSCs.

In this study, we identified that paracrine senescence is triggered in senescent hMSCs with abnormal nuclear structures by increasing the expression of MCP-1 and that inhibition of MCP-1 decreases the SASP. Furthermore, we found that GATA4 mediates the senescence of hMSCs induced by defective lamin A. We assessed whether down-regulation of GATA4 disturbs the progerin- or prelamin A-dependent senescence phenotype. Elucidating how GATA4 regulates senescence in hMSCs with nuclear defects may aid in understanding the etiology of complex aging disorders. We show that inhibition of GATA4 expression protects hMSCs from cellular senescence, implying unique therapeutic opportunity against progeroid syndromes and physiological aging.

📍

Does Malformed Lamin A Produce Enough Cellular Senescence to Contribute Meaningfully to the Progression of Aging?

Progeria is one of the better known accelerated aging conditions. It isn’t actually accelerated aging, but rather one specific runaway form of cell damage that gives rise to general dysfunction in cells throughout the body. Since degenerative aging is also a matter of general dysfunction in cells throughout the body, there is some overlap in the observed results, even though the root causes are completely different. So progeria patients appear, superficially at least, to be prematurely aged, and die from heart disease early in life.

The cause of progeria was discovered to be a mutation in the Lamin A (LMNA) gene, resulting in a malformed protein now called progerin. This protein is an important structural component of the cell nucleus. If it doesn’t function correctly, the nucleus becomes misshapen, and near all processes involving nuclear DNA maintenance and gene expression – the production of needed proteins at the right time from their genetic blueprints – cease to work correctly. The cell becomes dysfunctional. When near all cells are in this state, the prognosis for the individual is dire. Interestingly, in the years since this discovery, it has become clear that progerin is also present in small amounts in genetically normal older individuals. There is some debate over whether or not this is important in the progression of aging. Does it cause enough damage, or is it insignificant in comparison to other harmful processes?

In this context, we can consider cellular senescence, a mechanism closely connected to DNA damage, by which a small number of problem cells can cause outsized amounts of harm. Another possibility is damage to stem cells, as they are also small in number but highly influential on tissue function. Cells become senescent in response to internal damage, including that produced by progerin, and then either self-destruct or linger to secrete a potent mix of inflammatory and other signals. It is these signals, the senescence-associated secretory phenotype, that allows a comparatively small number of cells to produce comparatively large problems. It is known that senescent cells are important in many age-related conditions, particular those with a strong inflammatory component. Is generation of progerin significant as a cause of cellular senescence in normal aging, however? In this open access paper, researchers consider some of the mechanisms involved.

GATA4-dependent regulation of the secretory phenotype via MCP-1 underlies lamin A-mediated human mesenchymal stem cell aging

The LMNA gene encodes lamin and lamin C, which are major components of the nuclear lamina. Mutations in the LMNA gene have been implicated in premature aging disorders, including Hutchinson-Gilford progeria syndrome (HGPS). HGPS is caused by splicing defect and consequent generation of progerin, mutant-truncated lamin protein. Cells of HGPS patients exhibit an abnormal nuclear structure, increased DNA damage and premature senescence. In addition to the effects of progerin, accumulation of prelamin A, precursor of lamin A, induces defects in nuclear structures. ZMPSTE24 is an enzyme that produces mature lamin by cleavage of amino acids in prelamin A.

Zmpste24 knock-out mice have been widely used to study the mechanisms of aging and progeria. Depletion of Zmpste24 causes premature senescence in mice, including decreases in life span and bone density. Increased prelamin expression caused by ZMPSTE24 deficiency causes defective DNA repair. Zmpste24 knock-out mice have been extensively studied because of their impaired DNA damage response (DDR). Lamin also functions as a structural barrier to DDR. Altogether, these findings indicate that defects in the nuclear structure induced by progerin or prelamin lead to the accumulation of DNA damage, which results in accelerated aging.

It has been reported that exogenous expression of progerin in human mesenchymal stem cells (hMSCs) can impair their differentiation potential. Furthermore, production of induced pluripotent stem cells (iPSCs) from HGPS patients has revealed that the progerin expression levels are the highest in MSCs, vascular smooth muscle cells, and fibroblasts. These results indicate that MSCs are a specific target cell type of progerin-induced senescence. Like progerin, excessive accumulation of prelamin induces premature senescence in MSCs, including wrinkled nuclei. Downregulation of ZMPSTE24 in hMSCs also induces the senescence phenotype. These investigations imply that both progerin and prelamin can induce senescence in hMSCs with change in nuclear morphology.

Senescent cells secrete a group of factors that induce senescence in neighboring cells, a phenomenon termed senescence-associated secretory phenotype (SASP). The secreted inflammatory factors propagate senescence and recruit immune cells to senescent tissues by the generation of a pro-inflammatory environment. Among the factors reported to regulate the SASP, GATA4 has been recently identified as a regulator of senescence and inflammation. GATA4 is expressed during oncogene– and irradiation-induced senescence in fibroblasts in response to DNA damage. During the process of cellular senescence, GATA4 has a regulatory role in the SASP of fibroblasts. Because GATA4-dependent cellular senescence is closely associated with DDR, the role of GATA4 in other senescence models and other cell types may reveal a new mechanism.

Senescent hMSCs also induce senescence in neighboring cells. Monocyte chemoattractant protein-1 (MCP-1) secreted from senescent human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) induces premature senescence in neighboring cells. Insulin-like growth factor binding proteins are also produced by senescent hMSCs, and they trigger senescence in adjacent normal cells. These studies investigated the mechanisms of the SASP by inducing senescence in hMSCs through prolonged passaging. However, cellular senescence of MSCs can be regulated by various factors other than passaging. In our previous report, we have demonstrated that depletion of ZMPSTE24 and introduction of progerin induce premature senescence in hUCB-MSCs. It remains to be determined whether defective lamin triggers paracrine senescence via inflammatory factors in hMSCs.

In this study, we identified that paracrine senescence is triggered in senescent hMSCs with abnormal nuclear structures by increasing the expression of MCP-1 and that inhibition of MCP-1 decreases the SASP. Furthermore, we found that GATA4 mediates the senescence of hMSCs induced by defective lamin A. We assessed whether down-regulation of GATA4 disturbs the progerin- or prelamin A-dependent senescence phenotype. Elucidating how GATA4 regulates senescence in hMSCs with nuclear defects may aid in understanding the etiology of complex aging disorders. We show that inhibition of GATA4 expression protects hMSCs from cellular senescence, implying unique therapeutic opportunity against progeroid syndromes and physiological aging.

📍

Does Malformed Lamin A Produce Enough Cellular Senescence to Contribute Meaningfully to the Progression of Aging?

Progeria is one of the better known accelerated aging conditions. It isn’t actually accelerated aging, but rather one specific runaway form of cell damage that gives rise to general dysfunction in cells throughout the body. Since degenerative aging is also a matter of general dysfunction in cells throughout the body, there is some overlap in the observed results, even though the root causes are completely different. So progeria patients appear, superficially at least, to be prematurely aged, and die from heart disease early in life.

The cause of progeria was discovered to be a mutation in the Lamin A (LMNA) gene, resulting in a malformed protein now called progerin. This protein is an important structural component of the cell nucleus. If it doesn’t function correctly, the nucleus becomes misshapen, and near all processes involving nuclear DNA maintenance and gene expression – the production of needed proteins at the right time from their genetic blueprints – cease to work correctly. The cell becomes dysfunctional. When near all cells are in this state, the prognosis for the individual is dire. Interestingly, in the years since this discovery, it has become clear that progerin is also present in small amounts in genetically normal older individuals. There is some debate over whether or not this is important in the progression of aging. Does it cause enough damage, or is it insignificant in comparison to other harmful processes?

In this context, we can consider cellular senescence, a mechanism closely connected to DNA damage, by which a small number of problem cells can cause outsized amounts of harm. Another possibility is damage to stem cells, as they are also small in number but highly influential on tissue function. Cells become senescent in response to internal damage, including that produced by progerin, and then either self-destruct or linger to secrete a potent mix of inflammatory and other signals. It is these signals, the senescence-associated secretory phenotype, that allows a comparatively small number of cells to produce comparatively large problems. It is known that senescent cells are important in many age-related conditions, particular those with a strong inflammatory component. Is generation of progerin significant as a cause of cellular senescence in normal aging, however? In this open access paper, researchers consider some of the mechanisms involved.

GATA4-dependent regulation of the secretory phenotype via MCP-1 underlies lamin A-mediated human mesenchymal stem cell aging

The LMNA gene encodes lamin and lamin C, which are major components of the nuclear lamina. Mutations in the LMNA gene have been implicated in premature aging disorders, including Hutchinson-Gilford progeria syndrome (HGPS). HGPS is caused by splicing defect and consequent generation of progerin, mutant-truncated lamin protein. Cells of HGPS patients exhibit an abnormal nuclear structure, increased DNA damage and premature senescence. In addition to the effects of progerin, accumulation of prelamin A, precursor of lamin A, induces defects in nuclear structures. ZMPSTE24 is an enzyme that produces mature lamin by cleavage of amino acids in prelamin A.

Zmpste24 knock-out mice have been widely used to study the mechanisms of aging and progeria. Depletion of Zmpste24 causes premature senescence in mice, including decreases in life span and bone density. Increased prelamin expression caused by ZMPSTE24 deficiency causes defective DNA repair. Zmpste24 knock-out mice have been extensively studied because of their impaired DNA damage response (DDR). Lamin also functions as a structural barrier to DDR. Altogether, these findings indicate that defects in the nuclear structure induced by progerin or prelamin lead to the accumulation of DNA damage, which results in accelerated aging.

It has been reported that exogenous expression of progerin in human mesenchymal stem cells (hMSCs) can impair their differentiation potential. Furthermore, production of induced pluripotent stem cells (iPSCs) from HGPS patients has revealed that the progerin expression levels are the highest in MSCs, vascular smooth muscle cells, and fibroblasts. These results indicate that MSCs are a specific target cell type of progerin-induced senescence. Like progerin, excessive accumulation of prelamin induces premature senescence in MSCs, including wrinkled nuclei. Downregulation of ZMPSTE24 in hMSCs also induces the senescence phenotype. These investigations imply that both progerin and prelamin can induce senescence in hMSCs with change in nuclear morphology.

Senescent cells secrete a group of factors that induce senescence in neighboring cells, a phenomenon termed senescence-associated secretory phenotype (SASP). The secreted inflammatory factors propagate senescence and recruit immune cells to senescent tissues by the generation of a pro-inflammatory environment. Among the factors reported to regulate the SASP, GATA4 has been recently identified as a regulator of senescence and inflammation. GATA4 is expressed during oncogene– and irradiation-induced senescence in fibroblasts in response to DNA damage. During the process of cellular senescence, GATA4 has a regulatory role in the SASP of fibroblasts. Because GATA4-dependent cellular senescence is closely associated with DDR, the role of GATA4 in other senescence models and other cell types may reveal a new mechanism.

Senescent hMSCs also induce senescence in neighboring cells. Monocyte chemoattractant protein-1 (MCP-1) secreted from senescent human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) induces premature senescence in neighboring cells. Insulin-like growth factor binding proteins are also produced by senescent hMSCs, and they trigger senescence in adjacent normal cells. These studies investigated the mechanisms of the SASP by inducing senescence in hMSCs through prolonged passaging. However, cellular senescence of MSCs can be regulated by various factors other than passaging. In our previous report, we have demonstrated that depletion of ZMPSTE24 and introduction of progerin induce premature senescence in hUCB-MSCs. It remains to be determined whether defective lamin triggers paracrine senescence via inflammatory factors in hMSCs.

In this study, we identified that paracrine senescence is triggered in senescent hMSCs with abnormal nuclear structures by increasing the expression of MCP-1 and that inhibition of MCP-1 decreases the SASP. Furthermore, we found that GATA4 mediates the senescence of hMSCs induced by defective lamin A. We assessed whether down-regulation of GATA4 disturbs the progerin- or prelamin A-dependent senescence phenotype. Elucidating how GATA4 regulates senescence in hMSCs with nuclear defects may aid in understanding the etiology of complex aging disorders. We show that inhibition of GATA4 expression protects hMSCs from cellular senescence, implying unique therapeutic opportunity against progeroid syndromes and physiological aging.

📍

What Makes A Difference?

I’ve been dwelling with this question for a while. Like any good, real, question it is taking me for a ride. What makes a difference? Before I get into my response to this compelling question, I just want to extoll the value of a good question.  A really good question, such as this one, doesn’t […]

The post What Makes A Difference? appeared first on ChangingAging.

Progress Towards Ways to Make Old Stem Cells More Effective for Heart Repair

Stem cells in old tissues are less active than stem cells in young tissues, meaning a lesser supply of cells to maintain the tissue, and a consequent slow loss of function. The evidence to date suggest that a sizable part of this decline is a reaction to rising levels of tissue damage and the changing balance of cell signaling that results from that damage. There is certainly damage occurring to stem cells themselves, but that doesn’t appear to contribute to as great a degree until very late in life. This means that it is feasible to think about ways to force stem cells to get back to work, to rejuvenate their behavior if not their level of intrinsic damage, and assess the benefits against the potential risks, such as a higher rate of cancer. The stem cell therapies of the past few decades suggest that this cancer risk is lower than was expected, that evolution has left us more wiggle room for therapeutic enhancement of stem cell activity in the old than it might have done.

Ischemic heart disease affects a majority of people, especially elderly patients. Recent studies have utilized autologous adult stem cells and progenitor cells as a treatment option to heal cardiac tissue after myocardial infarction. However, donor cells from aging patients are more likely to be in a senescent stage. Rejuvenation is required to reverse the damage levied by aging and promote a youthful phenotype. This review aims to discuss current strategies that are effective in rejuvenating aging cardiac stem cells and represent novel therapeutic methods to treat the aging heart.

Recent literature mainly focuses on three approaches that aim to reverse cardiac aging: genetic modification, pharmaceutical administration, and optimization of extracellular factors. In vitro genetic modification can be used to overexpress or knock down certain genes and allow for reversal of the aging phenotype. Pharmaceutical administration is another approach that allows for manipulation of signaling pathways related to cell proliferation and cell senescence. Since the stem cell niche can contribute to the age-related decline in stem cell function, rejuvenation strategies also include optimization of extracellular factors.

Overall, improving the intrinsic properties of aging stem cells as well as the surrounding environment allows these cells to adopt a phenotype similar to their younger counterparts. Recent studies show promising results of the ability of these techniques to rejuvenate the aging heart. However, more understanding of the combinatorial effects of these interventions and fine-tuning of these techniques is required to evaluate the translational potential of these methods. Each strategy has its own advantages and disadvantages. The success of myocardial regenerative treatment will require teamwork across various disciplines to make stem cell therapy a reliable method for cardiac repair.

Link: https://doi.org/10.1155/2018/9308301

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Senescent T Cells as a Contributing Cause of Age-Related Autoimmunity

The more familiar autoimmune conditions, such as rheumatoid arthritis, are not all that age-related. Like cancer in young adults, they are a rare and unlucky happenstance, a form of most likely random cellular malfunction that spreads far enough to cause major problems. In later life, however, there occur a wide range of less familiar, less categorized, and comparatively poorly understood autoimmune conditions. It is an area of active research and many unknowns – look at just how recently type 4 diabetes was identified, for example.

These age-related autoimmunities arise from the chaotic failure of the immune system in late life. Cells fall into a variety of unhealthy states, malfunctioning cells dominate over useful cells, the immune system as a whole flails, producing chronic inflammation while failing at its primary tasks, and the supply of new competent immune cells diminishes dramatically. The publication here considers just one type of problem immune cell, those that have become senescent. This, fortunately, is an area in which solutions lie just around the corner. There is every reason to believe that senescent immune cells will just as vulnerable to destruction by senolytic therapies as any other kind of cell. If they are destroyed, they will cause no further harm, and the patient will be in a better position.

Immune aging (immunosenescence) is characterized by the reduced competence of acquired immunity, leading to increased susceptibility to infection as well as decreased vaccination efficiency. Recent accumulating evidence indicates that immunosenescence underlies an increased proinflammatory trait with age, including various chronic inflammatory and metabolic disorders, such as atherosclerosis and diabetes mellitus, as well as an increased risk for autoimmunity. Cellular senescence is characterized by irreversible arrest of proliferation, grossly altered gene expression, and relative resistance to apoptosis. Notably, senescent cells are often metabolically active and may become foci of host reactions in tissues by secreting various inflammatory factors. The features and consequences of cellular senescence in T cells in the immune system, however, remain elusive.

One of the most prominent changes occurring in the immune organs with age is an early involution of the thymus. The thymus is a central immune organ to support T cell development and establish T cell self-tolerance. T cell generation in the thymus sharply declines after the juvenile stage, eventually replaced almost entirely by fat tissues at later stages of life. In concordance with the decrease of T cell genesis, the peripheral naïve T cells are gradually reduced with age. Although the peripheral T cell pool is well maintained in aged individuals, the population shows a steady increase in the proportions of memory phenotype (MP) T cells.

We reported that a unique PD-1+ MP CD4+ T cell population is increased with age, now termed senescence-associated (SA-) T cells. The SA-T cells show characteristic signs and features of cellular senescence and emerge as follicular T cells in spontaneous germinal centers (GCs) that occur in aged mice. Spontaneous development of GCs is a hallmark of systemic autoimmune diseases, and among a number of changes in immune function with age is an increasing risk for autoimmunity.

Link: https://www.ncbi.nlm.nih.gov/books/NBK500331/

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