Clonal hematopoiesis of indeterminate potential (CHIP) and loss of the Y chromosome (LOY) represent heterogeneous, mutation-dependent contributors to atherosclerotic cardiovascular disease, with mechanistic insights beginning to inform genotype-guided anti-inflammatory prevention strategies.
Key Findings
Background
CHIP is defined as the expansion of hematopoietic clones carrying acquired mutations in genes recurrently mutated in myeloid hematological malignancies at a variant allele fraction ≥2%.
CHIP represents age-related somatic mosaicism in the hematopoietic system
The variant allele fraction threshold of ≥2% is used to define CHIP
Mutations occur in genes recurrently mutated in myeloid hematological malignancies
CHIP is increasingly recognized as a risk factor for atherosclerotic cardiovascular disease
Results
CHIP is associated with increased risk of coronary artery disease and other atherosclerosis-related outcomes across large human cohorts.
The association has been established across large human cohorts
The magnitude of the association varies substantially by mutated gene and clone size
The relationship between CHIP and atherosclerotic cardiovascular disease is gene-specific
Clone size is identified as a modulating factor in the strength of the association
Results
Experimental studies in hyperlipidemic mice support a causal contribution of several CHIP drivers to atherosclerosis through mutation-specific inflammatory mechanisms.
Complementary experimental studies were conducted in hyperlipidemic mouse models
Causal contribution to atherosclerosis was supported for several CHIP drivers
Each mutation was associated with distinct, mutation-specific inflammatory mechanisms
These mechanistic insights are beginning to inform genotype-guided, anti-inflammatory prevention strategies
Results
Loss of the Y chromosome (LOY) is the most frequent somatic chromosomal alteration detected in blood in aging men and has been associated with myocardial infarction and adverse cardiovascular outcomes.
LOY is described as the most frequent somatic chromosomal alteration detected in blood in aging men
LOY has been associated with myocardial infarction and adverse cardiovascular outcomes
Despite these associations, the causal role of LOY in atherosclerosis remains unproven
LOY is characterized as a heterogeneous, mutation-dependent contributor to atherosclerotic cardiovascular disease
Discussion
Methodological considerations substantially influence the observed associations between hematopoietic somatic mutations and atherosclerotic cardiovascular disease.
The paper specifically highlights methodological considerations that influence observed associations
Key knowledge gaps must be addressed to allow for clinical translation
The heterogeneous and mutation-dependent nature of CHIP and LOY contributions is emphasized
Genotype-guided prevention strategies are outlined as a future direction based on mechanistic insights
What This Means
This research summarizes the growing evidence that certain age-related changes in blood stem cells can increase the risk of heart disease caused by clogged arteries (atherosclerosis). The most studied phenomenon is called clonal hematopoiesis of indeterminate potential, or CHIP, which occurs when a blood stem cell acquires a genetic mutation and its descendants expand to make up a notable fraction of a person's blood cells. Studies in large groups of people have found that individuals with CHIP have a higher risk of coronary artery disease and related conditions, though the degree of risk depends heavily on which specific gene is mutated and how large the mutant cell population has grown. Studies in mice have helped demonstrate that these mutations likely cause heart disease — not just occur alongside it — and that they do so through inflammation-related processes that differ depending on which gene is affected.
The paper also reviews another age-related blood cell change in men: the loss of the Y chromosome (LOY) from blood cells over time. This is the most common large-scale chromosomal change seen in blood as men age, and it has been linked to heart attacks and other bad cardiovascular outcomes. However, unlike CHIP, it remains unclear whether LOY actually causes heart disease or is simply a marker of aging and vulnerability.
This research suggests that not all hematopoietic mutations carry the same cardiovascular risk, and that future prevention or treatment strategies may need to be tailored based on which specific mutation a person carries. The authors highlight that inconsistencies in how studies are conducted affect the results that are reported, and they point to important unanswered questions that will need to be resolved before these findings can be practically applied in clinical care.