Chronic Limb Ischemia: A Non-Surgical Breakthrough Using G-CSF and Compression Therapy

Proofreaded by Dr. Darwin Eton, MD, FACS, DFSVS

In this review, I describe a therapeutic concept developed from clinical observation and molecular insight, aimed at treating chronic limb-threatening ischemia (CLTI) also called chronic limb ischemia through biological rather than mechanical means. The central element is the use of granulocyte colony-stimulating factor (G-CSF), not merely as a hematopoietic agent, but as a catalyst for neovascularization and physiologic fibrinolysis in ischemic tissue.

Traditional surgical and endovascular interventions, while often providing short-term benefit, tend to fall short in restoring durable perfusion. They are costly, invasive, and – perhaps most importantly – they fail to engage the body’s intrinsic capacity for vascular repair. What is proposed here is not an alternative to intervention, but a shift in focus: from revascularization as a technical achievement to revascularization as a biologic process – reinitiated and sustained from within the tissue itself.

The purpose of this article is to trace, in detail, the cellular, molecular, and hemodynamic events that support neovascularization and intrinsic fibrinolysis in chronically ischemic tissue. These observations are grounded in proteomic and cytometric findings from patients with CLTI who responded favorably to a novel G-CSF protocol.

Of particular interest – and contrary to longstanding assumptions – is the role of neutrophils. Once regarded primarily as pro-thrombotic and inhibitory to vascular growth, they demonstrated, under this regimen, a robust capacity to support angiogenesis and promote fibrin clearance. This unexpected behavior invites a necessary reappraisal of their function within the ischemic microenvironment.

Mechanisms of Neovascularization (NV)

NV, essential in overcoming arterial occlusion, occurs via:

• Arteriogenesis: growth of collateral arteries triggered by shear stress.
• Angiogenesis: formation of capillaries and smaller vessels in response to hypoxia.

Successful NV depends not only on progenitor cell mobilization (particularly endothelial progenitor cells [EPCs] and hematopoietic stem/progenitor cells [HSPCs]) and critical growth factors like VEGF, but also on the optimization of the biosynthetic microenvironment within ischemic tissue. This is a vital prerequisite that prior clinical trials often neglected. The hypoxic environment of chronic ischemia drives anaerobic glycolysis, which lowers tissue pH and leads to enzyme denaturation – compromising key reparative processes.

Additionally, toxic metabolic byproducts must be effectively cleared, and nutritive, oxygenated inflow is essential to restore homeostasis. Without these corrections, even mobilized progenitor cells may fail to engraft or differentiate effectively. Thus, both biochemical conditions and structural support are required for angiogenesis and arteriogenesis to proceed.

Key obstacles to NV include:

• Low progenitor cell availability due to age, diabetes, or cardiovascular disease.
• Unfavorable microenvironments, including inflammation and oxidative stress.
• Impaired endothelial shear stress in occluded vessels.

Overcoming Progenitor Cell Deficit with G-CSF at Chronic Limb Ischemia

G-CSF facilitates progenitor cell mobilization from bone marrow to blood. The novel regimen – filgrastim 7–10 µg/kg every 72 hours for up to 10 doses – demonstrated:

• Significant increases in circulating CPCs.
• Enhanced proangiogenic protein levels.
• 10-fold increases in plasmin (fibrinolytic enzyme) and elevated fibrin degradation products.

These findings suggest that G-CSF can effectively stimulate both vascular regeneration and fibrinolysis, countering old assumptions about neutrophil roles.

Hemodynamic Barriers and Compression Therapy for Chronic Limb Ischemia

One of the less appreciated, but fundamental, issues in chronic ischemia is the near-complete absence of adequate endothelial shear stress. Without that mechanical signal, endothelial cells remain inactive.

They don’t respond, they don’t remodel, they don’t recruit. Shear stress isn’t just a flow parameter – it’s the trigger that wakes the endothelium up. It’s what drives nitric oxide production, what pushes eNOS expression, and what allows structural change to begin.

In ischemic limbs, where perfusion is static or severely reduced, that trigger is missing. And without it, no matter how many growth factors or progenitor cells you deliver, the environment stays hostile – acidic, inflamed, low in oxygen – and fundamentally unreceptive to repair. The tissue environment itself becomes chemically and structurally unwelcoming: acidic, inflamed, oxygen-poor, and resistant to repair. Without restoring this dynamic stimulus, no amount of cellular or pharmacologic input can fully reactivate the regenerative machinery.

Thus, combining pneumatic stimulation with oxygenated perfusion creates a biosynthetically conducive setting for NV to occur.

This is addressed through programmed pneumatic compression therapy (PCP) using devices like the ArtAssist system, which:

• Increases shear stress by cyclically compressing the calf and foot.
• Enhances EC activity and NO production.
• Improves tissue perfusion, waste clearance, and local biosynthesis of angiogenic factors.

In combination with G-CSF, this creates a favorable environment for NV.

Endothelial Function and Nitric Oxide (NO) at Chronic Limb Ischemia

Endothelial NO synthase (eNOS) plays a pivotal role:

• NO induces vasodilation, enhances oxygen delivery, and maintains vessel tone.
• It stimulates production of VEGF and FGF, driving angiogenesis.
• NO also promotes fibrinolysis by enhancing tPA release and inhibiting platelet aggregation.

Mechanical stimulation via PCP enhances eNOS activity and reduces oxidative stress, preserving NO signaling.

Chronic Thrombus and Endogenous Fibrinolysis in Chronic Limb Ischemia

In CLTI, thrombosis exacerbates ischemia. Traditional fibrinolytic therapy poses hemorrhagic risks. However, gradual, physiologic fibrinolysis observed in G-CSF-treated patients showed:

• Segmental arterial recanalization.
• Marked increases in plasmin and fibrin degradation products.
• No hemorrhagic events, despite neutrophilia.

Mechanisms include:

• NO-induced endothelial tPA production.
• Neutrophil-derived enzymes and cytokines enhancing EC function.
• Shear stress and inflammation further inducing fibrinolytic factor release.

This safe, slow thrombus dissolution over weeks offers a transformative strategy.

Role of Neutrophils and Endothelial Crosstalk at Chronic Limb Ischemia

Contrary to prior belief, neutrophils under G-CSF influence become pro-angiogenic and support fibrinolysis via:

• Secretion of proteases like elastase and cathepsin G.
• Induction of EC signaling via PAR-1 and PAR-2, leading to tPA release.
• Promotion of NETs, which interact with ECs to modulate fibrinolytic gene expression.

In this setting, neutrophils serve as key initiators of vascular remodeling and clot breakdown.

Inflammatory Modulation and Pharmacologic Synergies

The review highlights the influence of:

• Inflammatory cytokines (TNF-α, IL-1β) that upregulate tPA in ECs.
• Reactive oxygen species (ROS) that activate redox-sensitive pathways enhancing fibrinolysis.
• Bradykinin and histamine, vasoactive agents that stimulate tPA release.
• Statins and PPAR-alpha agonists, which pharmacologically increase EC fibrinolytic capacity.

By integrating biological stimuli, physical stress, and selective drug use, the microenvironment becomes optimized for endogenous repair.

Anti-Fibrinolytic Counterbalances at Chronic Limb Ischemia

The body maintains clot integrity via:

• PAI-1, a potent tPA/uPA inhibitor, produced by ECs, VSMCs, platelets, and hepatocytes.
• TAFI, which blocks plasmin formation.
• Annexin A2, which coordinates tPA and plasminogen assembly on ECs but is itself modulated by inflammation.

G-CSF therapy modulates these mechanisms indirectly, tipping the balance in favor of safe, controlled fibrinolysis.

Clinical Evidence and Implications in conneciton with Chronic Limb Ischemia

Although earlier trials using G-CSF or GM-CSF in cardiovascular ischemia produced mixed results, they lacked:

• Modern proteomic/cytometric profiling.
• An understanding of mechanism-based dosimetry.
• Supportive strategies like compression therapy.

By correcting these, the current approach offers a reproducible, low-risk, and non-invasive method of treating chronic ischemia, with potential applicability across other organs (e.g., brain, heart, kidney).

A major limitation in earlier G-CSF or GM-CSF trials was the inadequate appreciation of the tissue microenvironment. Mobilizing cells alone proved insufficient without ensuring the ischemic niche could support them. Acidosis, oxidative stress, and waste metabolite accumulation impaired enzyme function and blunted regenerative signaling.

By contrast, this novel regimen actively reconditions the microenvironment – through improved oxygenation, mechanical stimulation, and endogenous pathway activation – so that mobilized cells can thrive and function effectively. This paradigm shift, recognizing both cellular mobilization and environmental optimization, is essential for consistent clinical translation.

Call for Paradigm Shift

Here is a passionate call to move beyond:

• Expensive and often temporary mechanical revascularization.
• Surgical models that do not restore natural biology.

I urge the vascular surgery community to embrace

• Tissue-level revascularization.
• Strategies aligned with Nature’s own regenerative principles.
• Optimization of the biosynthetic and biomechanical microenvironment, correcting acidosis, enhancing oxygenation, and enabling enzyme activity.
• Clinical translation of 21st-century cellular and molecular science.

Conclusion

This review positions G-CSF-driven cellular mobilization, combined with pneumatic stimulation and environmental reconditioning, as a leading-edge solution to CLTI. It bridges advanced biology with accessible clinical practice, arguing that regeneration should supplement – if not replace – mechanical revascularization in many chronic ischemia patients.

The integration of immune modulation, progenitor biology, and shear-based hemodynamics reflects a new paradigm in vascular care—one that leverages Nature’s intrinsic mechanisms to overcome the obstacles of modern chronic ischemic disease.

Dr. Darwin Eton

MD, FACS, DFSVS, retired Professor of Vascular Surgery

Honored for Advancing Research in the Management of Vascular Disease

About Dr. Darwin Eton

Dr. Darwin Eton, MD, FACS, DFSVS is a Retired Professor of Vascular Surgery and former director of advanced clinical programs in peripheral vascular disease. Over the course of his career, Dr. Eton has been instrumental in reshaping how vascular surgeons and scientists understand ischemic pathophysiology, particularly in the context of regenerative and cellular therapeutics.

To learn more about Dr. Eton’s academic and clinical contributions, refer to the news feature and search for:
“Darwin Eton MD, FACS Honored for Advancing Research in the Management of Vascular Disease”

If you wnt to go deeper in, please refer to:

A recent JVS article (https://doi.org/10.1016/j.jvsvi.2025.100190)
provides a 2025 summary of the mechanisms and cellular participants of neovascularization and fibrinolysis.

The severity of chronic ischemia arising from progression of multi-level arterial occlusive is attenuated by Neovascularization (NV). No matter how clever and refined our surgical/interventional procedures have become, the emphasis needs to change if we are truly committed to achieving durable, low-risk, cost effective solutions for our chronic ischemia patients.
Keep on reading … https://doi.org/10.1002/term.3284