Aberrant Engagement of P-selectin Drives Hematopoietic Stem Cell Aging in Mice

Geriatrics Hematology Immunology Basic Medical Sciences Cell Biology Biochemistry Life Sciences Medicine
P-selectin hematopoietic stem cells aging gene expression erythropoiesis inflammation stem cell regeneration

1. Research Background and Scientific Problem

The health of the hematopoietic system is crucial to the proper functioning of the body, with hematopoietic stem cells (HSCs) at its core in maintaining normal blood system operation. HSCs possess self-renewal and multipotent differentiation abilities, capable of generating all types of blood cells, including red blood cells, white blood cells, and platelets. As age increases, the functions of HSCs gradually deteriorate, manifesting as reduced hematopoietic regenerative capacity, impaired erythropoiesis, and a bias towards myeloid differentiation (such as granulocytes, monocytes, and platelets). This aging of stem cells not only affects the body’s response capability to stressors like blood loss and infection, but also leads to various degenerative blood diseases and malignancies.

Previous studies have shown that HSC aging is related to a series of intracellular molecular changes, such as DNA damage, metabolic dysfunction, and epigenetic regulatory disorder. Moreover, extrinsic factors—such as remodeling of the bone marrow microenvironment and inflammatory response—exert significant effects on the HSC aging process as well. However, the specific functional molecular pathways, reversible aging mechanisms, and especially the molecular basis underlying the crosstalk between microenvironmental signaling and stem cell aging, have not been fully elucidated. Understanding these mechanisms not only helps extend healthy lifespan, but also provides a theoretical basis and potential interventional targets for treating age-related blood diseases.

Recently, P-selectin (encoded by selp) has attracted researchers’ attention in this field. P-selectin is a membrane-bound cell adhesion molecule, traditionally recognized for its important roles in endothelial cells and platelets, where it is a key regulator in inflammatory response and cell migration. Recent transcriptomic meta-analyses indicate markedly elevated expression of p-selectin in aged mice and human HSCs, but its specific functional role in HSC aging remains unclear. The present study, set against this background, aims to elucidate the pathogenic mechanism and reversibility of P-selectin in HSC aging.

2. Paper Source and Author Information

This research, titled “aberrant engagement of p-selectin drives hematopoietic stem cell aging in mice,” was published in June 2025 in the top academic journal Nature Aging (nature aging | volume 5 | june 2025 | 1010–1024). The corresponding authors are Britta Will and Gerald de Haan, with the author team hailing from the European Research Institute for the Biology of Ageing (ERIBA, University Medical Center Groningen, University of Groningen, the Netherlands), Albert Einstein College of Medicine (NY, USA), St. Jude Children’s Research Hospital, and other leading international research institutions. The team has profound experience in the field of hematopoietic stem cell and microenvironmental aging mechanisms, providing multidisciplinary perspectives and a solid foundation for this research.

3. Research Workflow and Experimental Methods

1. Initial Phenotypic and Molecular Characteristics Observation

The study first systematically analyzed age-related hematopoietic phenotypes in mice. The authors compared young (2-5 months old) and aged (>22 months old) mice, counting peripheral blood red blood cells (RBCs), platelets (PLT), and white blood cells. Results showed that aged mice had a significant decrease in RBC, hemoglobin, and hematocrit, but increased platelet counts. Additionally, the proportion of myeloid cells increased and B lymphocytes decreased, indicating a typical myeloid-biased differentiation.

At the HSC and progenitor cell levels, the proportions of long-term HSCs (LT-HSCs) and their downstream progenitors (MPPs, GMPs) were increased in aged mice, whereas erythroid progenitors and erythroid colony-forming units (CFU-Es) were decreased. Functional in vitro colony formation assays further confirmed the decline in the regenerative ability of aged HSCs. All these changes were accompanied by increased inter-individual variability, reflecting the heterogeneity of the aging process.

2. Analysis of P-selectin Expression and Identification of Cell Subpopulations

Using FACS, the team assessed and quantified p-selectin expression on various HSC and hematopoietic progenitor subpopulations. They found that only LT-HSCs significantly expressed p-selectin, and aging did not simply result in a uniform upregulation across all HSCs—instead, it led to a subdivision, with a fraction becoming p-selectin high (selphi), while the rest remained low-expressing (selplo).

Further immunofluorescence staining and whole-bone marrow imaging indicated that selphi HSCs were primarily localized in sinusoidal niches of the bone marrow, distinct from the megakaryocyte (MK) microenvironment typically occupied by young HSCs. This spatial distribution difference is closely related to microenvironmental remodeling during HSC aging.

3. Functional Analysis of High P-selectin HSCs

The team compared the functions of selphi and selplo HSCs from aged mice: in vitro myeloid colony assays first demonstrated that selphi HSCs had lower colony formation efficiency than selplo. Subsequent competitive serial transplantation experiments showed that selphi HSCs had significantly diminished in vivo repopulating ability, despite similar myeloid engraftment efficiency. Notably, after transplantation, the surface expression of p-selectin on selphi HSCs returned to low levels, suggesting that this expression is reversible.

4. SELP Overexpression Animal Model Analysis

To test whether p-selectin expression has a direct functional impact on HSCs, the authors enforced selp gene expression (selpoe) in young mouse HSCs via viral transduction and performed competitive in vivo transplantation. Even with super-physiological levels of p-selectin expression, differentiation into white blood cells and platelets did not change significantly, but long-term repopulation capacity was persistently impaired, and there was almost no generation of red blood cells. Further FACS analysis revealed a marked block in the differentiation of poly- and late-stage erythroid progenitors. The data suggest that p-selectin overexpression not only impairs functional repopulation but also selectively inhibits erythropoiesis, which may be relevant to the clinical mechanisms of age-associated anemia.

5. Molecular and Transcriptomic Characterization of Selphi HSCs

Using RNA sequencing, the team systematically compared the transcriptomic features of selplo and selphi HSCs isolated from aged mice. They identified 162 significantly differentially expressed genes; key proliferation regulators such as cebpb and foxm1 were repressed in selphi HSCs, and downstream pathways were less active. Cell cycle and DNA replication genes were lowly expressed, indicating that selphi HSCs were more quiescent. The erythroid master transcription factor gata1 and its target genes were significantly downregulated in selphi HSCs, while myeloid-differentiation and innate immunity pathways were activated. Molecular signals associated with aged HSCs were enriched in the selphi population, confirming that it is a “molecularly older” subpopulation.

6. Analysis of the Relationship Between Inflammatory Factors and P-selectin Expression

Utilizing public databases and original experiments, the team further found that proinflammatory pathways, especially IL-1β signaling activation, were highly correlated with the selphi HSC identity. In vivo injection of IL-1β or TNF in animals rapidly increased p-selectin expression on HSC surfaces, and IL-1β concentrations in aged bone marrow interstitial fluid were elevated. Although prolonged IL-1β stimulation could drive p-selectin expression, simply blocking the IL-1R1 pathway was insufficient to fully restore molecular characteristics in aged HSCs, suggesting that other inflammatory pathways also participate in regulation. Further, by transplanting aged HSCs into young mice, the team observed downregulation of inflammatory genes and normalized p-selectin levels post-transplant, indicating that the microenvironment plays an important, reversible regulatory role in HSC aging.

7. Mechanistic Analysis of P-selectin Ligand PSGL-1 Signal Transduction

PSGL-1 is the primary physiological ligand of p-selectin, expressed on various immune cells. The study found that DCs, monocytes, granulocytes, and CD4+ T cells exhibited decreased PSGL-1 expression in aged bone marrow. In vitro, the addition of PSGL-1 protein to HSC culture significantly downregulated inflammation- and aging-related genes in the presence of wild-type p-selectin, involving ERK1/2 and STAT3 signaling pathways. Single-cell division experiments showed that PSGL-1 stimulation enhanced the proliferative activity of high p-selectin HSCs, suggesting its regulatory function depends on p-selectin expression levels.

8. Phenotypic and Functional Analysis of selp-deficient HSCs

Utilizing a selp gene knockout (selpko) mouse model, the team compared its HSC functions and aging phenotypes. Transcriptomic analysis showed that selpko HSCs extensively activated aging-upregulated gene signatures, with elevated expression of inflammatory factors (IL-6, IL-1β). Functionally, despite little change in total peripheral blood cell counts, selpko mice displayed myeloid bias and increased CD150-high LT-HSCs. Competitive in vivo transplantation revealed that selpko HSCs had difficulty in reconstituting recipient hematopoiesis, indicating that the lack of p-selectin leads to premature HSC aging and functional loss.

4. Main Research Results and Conclusions

This study systematically reveals, from cellular, molecular, and physiological perspectives, that: - P-selectin expression in aged HSCs is significantly stratified and is strongly associated—both molecularly and functionally—with “aging” phenotypes; - An inflammatory microenvironment (especially IL-1β) can acutely induce p-selectin surface expression on HSCs; certain inflammatory pathways (like IL-1β, TNF-α) are key but redundant mechanisms jointly participate in regulation; - Overexpression of selp (p-selectin) alone is sufficient to drive functional decline in HSCs, as shown by reduced regenerative ability and impaired erythroid differentiation, partially mimicking clinical age-related anemia; - Transplanting aged HSCs into young bone marrow “rejuvenates” their molecular phenotype, with normalized p-selectin expression, further confirming the decisive role of the microenvironment; - Expression of the P-selectin ligand PSGL-1 decreases in the microenvironment; supplementing PSGL-1 can downregulate aging and inflammatory genes and enhance HSC proliferative capacity; - selp-deficient HSCs display premature aging, upregulation of aging gene signatures, increased myeloid bias, and severely compromised function.

In conclusion, abnormal overexpression of p-selectin is not just a marker of HSC aging, but a functionally pro-aging molecule. Aberrant inflammatory signals in the microenvironment drive HSC functional decline by modulating the p-selectin/PSGL-1 axis, indicating that p-selectin and its signaling network could serve as promising targets for anti-aging interventions.

5. Research Significance and Academic Value

This work systematically establishes the determinative role of p-selectin in HSC aging, revealing the reversibility of its expression and activation. The study provides an important theoretical basis for understanding HSC aging mechanisms and for using inflammation-microenvironment axes to intervene in age-related hematological diseases. The functional study of p-selectin transcends the traditional view of it as merely an adhesion molecule and redefines it as a molecular hub for functional regulation of aging. PSGL-1, as the rate-limiting regulator of p-selectin, may provide a novel strategy for prolonging HSC health and restoring their function through exogenous supplementation in the niche.

Furthermore, through multi-dimensional experimental approaches such as HSC transplantation and p-selectin signaling modulation, this study offers technical standards for identifying and sorting “young-like” stem cell subpopulations, which facilitates optimization of hematopoietic stem cell transplantation and regenerative medicine protocols.

6. Research Highlights and Innovations

  • Revealed the heterogeneity of p-selectin expression and functional stratification in HSC aging;
  • Established a new perspective on the interplay between inflammatory microenvironment and adhesion molecules in controlling stem cell fate;
  • Employed transplantation-rejuvenation experiments to directly demonstrate the reversibility of stem cell functional decline by the microenvironment;
  • Built a complete causal chain from molecular mechanism to physiological function to interventional potential;
  • Innovatively demonstrated that the decline of PSGL-1 in the microenvironment is a key factor in the aging process, broadening the research field of adhesion molecule regulation;
  • Organically integrated multiple high-throughput omics (transcriptomics, single-cell RNA-Seq), functional reconstitution assays, and cell biological techniques to provide a paradigm for analyzing complex phenotypes.

7. Prospects and Further Considerations

The study further suggests that p-selectin expression and function are dynamically reversible. Although p-selectin high-expressing cells are functionally inferior to low-expressing ones, they do not completely lose regenerative ability, pointing towards directions for selectively “rejuvenating” or removing aged HSC subpopulations. It is necessary to further explore why PSGL-1 is suppressed in aged bone marrow and whether its supplementation is clinically feasible. In addition, it remains to be further investigated whether the p-selectin/PSGL-1 axis participates in broader functions such as HSC homing and engraftment.

8. Conclusion

This high-level original research published in Nature Aging provides a new explanatory framework for hematopoietic stem cell aging, elucidates the key regulatory role of p-selectin and its microenvironmental dependence, and opens up new molecular targets for intervention in age-related hematological diseases and for maintaining HSC function. Its research paradigm, technical system, and scientific insights possess significant academic and practical value.