FAP and macrophage changes in older muscle after six weeks of blood flow restricted exercise
In healthy older people, six weeks of blood flow restricted resistance exercise enlarged fibro-adipogenic progenitors and muscle stem cells, shifted the FAP pool toward a CD90 high phenotype, and raised the share of pro-inflammatory CD11c+ macrophages. These are cellular associations, not proof of cause. [1]
Automatic summary · not editorially reviewed
The key findings
Healthy older individuals did six weeks of blood flow restricted resistance exercise, and flow cytometry was used to characterise FAPs, muscle stem cells and immune cells in the muscle microenvironment. [1]
The exercise enlarged FAPs and muscle stem cells and shifted the FAP pool toward more CD90 high FAPs without altering total FAP abundance; CD90 high FAPs promoted myotube growth in vitro. [1]
The exercise increased the proportion of pro-inflammatory CD11c+ macrophages, and TNFα markedly reduced proliferation of human primary FAPs ex vivo. [1]
The source at a glance
- Study type / format
- Abstract of a human exercise study with cell and in vitro experiments
- Population / context
- Healthy older individuals doing six weeks of blood flow restricted resistance exercise.
- Summary based on
- Study abstract
- Publication status
- Preprint · peer-review status not confirmed
- Original publication
- September 28, 2026
Older adults, six weeks of restricted-flow resistance exercise
The abstract describes a study in healthy older individuals. Participants did six weeks of blood flow restricted resistance exercise (BFRRE), a form of resistance training with restricted blood flow. The researchers used flow cytometry to characterise changes in key cell populations in the skeletal muscle microenvironment: fibro-adipogenic progenitors (FAPs), muscle stem cells (MuSCs) and immune cells. The stated aim was to study cellular adaptations that accompany muscle hypertrophy, meaning muscle enlargement. The abstract does not report how many people took part, their exact ages, or whether a comparison group without BFRRE was included.
Supporting source [1]
Larger FAPs and MuSCs, more CD90 high FAPs
BFRRE led to significant enlargement of both FAPs and MuSCs, which the authors describe as consistent with cellular adaptation to exercise. Exercise also shifted the FAP pool toward more CD90 high FAPs, without changing total FAP abundance. In gene analysis, CD90 high FAPs showed enrichment of pro-myogenic factors among secretory protein genes, alongside matrix and collagen-related genes. In conditioned media experiments with freshly isolated FAPs, CD90 high FAPs promoted myotube growth in vitro compared with CD90 low FAPs. The authors suggest this phenotypic shift may facilitate muscle hypertrophy. These are in vitro and gene-expression findings, not demonstrated human muscle growth.
Supporting source [1]
More CD11c+ macrophages; TNFα reduced FAP proliferation ex vivo
In parallel, BFRRE increased the proportion of pro-inflammatory CD11c+ macrophages within the skeletal muscle niche, which the authors call a dynamic immune response during adaptation. The abstract also reports a possible link between these macrophages and FAPs: TNFα markedly reduced the proliferation of human primary FAPs ex vivo. The authors suggest macrophage-derived signals may attenuate excessive FAP expansion during tissue remodelling. The abstract states that CD11c+ macrophage expansion correlated with CD90 high FAP and MuSC responses. Correlation and ex vivo results do not establish that macrophages cause these FAP or stem cell changes in people.
Supporting source [1]
How to interpret this
This explainer is based only on the abstract; the full text was not reviewed. The abstract does not report sample size, exact ages, a comparison group, or measured human hypertrophy outcomes. Cell enlargement, gene expression, in vitro myotube growth and ex vivo TNFα effects are not proof that these cell changes cause muscle growth in older people.
Based on the study abstract; the full paper, tables and supplementary data were not reviewed.
Source & supporting passages
Wang J, Brorson J, Kuhdal S, Just J, Thybo FF, Bjerre M, de Paoli FV, Jessen N, Vissing K, Farup J. · europepmc.org · September 28, 2026