Rethinking Critical Limb Ischemia In The Age of Regenerative Medicine

Critical Limb Ischemia (CLI) is among the most severe forms of peripheral artery disease (PAD). The blood flow in the body’s lower extremities gets critically compromised. The problem is characterized by persistent resting pain, non-healing wounds, and damaged tissue. If left untreated, the condition potentially leads to limb amputation.  The prevalence of certain co-morbid conditions like diabetes, smoking, obesity, or aging contributes to CLI occurrence. 

Currently, Critical Limb Ischemia treatment focuses on restoration of the blood flow. The most popular approaches involve medication, endovascular procedures, or bypass surgery. While these treatment approaches are established, none contribute to the prevention of progressive tissue loss. Such therapeutic gaps prompted researchers to rethink Critical Limb Ischemia (CLI) management strategies. The emergence of regenerative medicine aims to boost the body’s natural healing mechanism by promoting tissue repair, anti-inflammation, and naive blood vessel formation. The current article elaborates clinical insights into Critical Limb Ischemia and unveils how stem cell therapy is reshaping limb preservation. 

Ask The Expert

What Causes Critical Limb Ischemia (CLI)? 

Gradual buildup of plaque in peripheral arteries leads to atherosclerosis. This narrows the arteries and restricts adequate blood flow in the leg and foot. Plaque buildup contributes to early signs of PAD like leg cramps or achiness. Severe restriction of blood flow leads to scarred or dead tissue that is unhealed. The major Critical Limb Ischemia causes include:

• Progressive arterial blockage (plaque formation in the blood vessels responsible for carrying blood from heart to the limbs)
• Metabolic disorders like diabetes, vascular complications, chronic kidney conditions
• Lifestyle factors like smoking, hypertension, and hyperlipidemia
• Aging, psychological factors like stress or depression

How To Recognise Critical Limb Ischemia (CLI)?

Early Recognition of CLI is Crucial for Opting for Treatment at an Adequate Time. Critical Limb Ischemia Symptoms Include:

• Persistent rest pain in lower limbs
• Prolonged non-healing ulcers, wounds, or gangrene 
• Skin discoloration where skin appears purple, greenish, or black due to dead tissue
• Cold extremities 

How Conventional Critical Limb Ischemia (CLI) Treatment Falls Short? 

Currently, Critical Limb Ischemia Treatment focuses on blood flow restoration. Clinicians diagnose the severity of the CLI symptoms and recommend suitable treatment procedures. This includes: 

• Leg Revascularization: Surgical procedure to support blood flow in the legs. However, patients with unhealed wounds or gangrene have irreversible damage where the procedure fails
• Venous Arterialization: Provider connects arteries to veins, enabling flow of oxygen-rich blood to the foot
• Wound Care: Removal of dead tissue (debridement) to prevent further tissue damage and support healing of surrounding tissue. The procedure often comes with antibiotic introduction to prevent infection or cure an existing one
• Amputation: Removal of the affected limb portion when all other procedures fall short. Clinicians often recommend prosthetics and physical therapy to support function. 
• Medications: Clinician recommends certain medications for complication management. For instance, anticoagulants and antiplatelet drugs to prevent further blood clots. High doses of statins to reduce bad cholesterol, hypertensive drugs to lower blood pressure, or medication to manage diabetes 

*NOTE: Conventional Critical Limb Ischemia Treatment is well established and efficiently manages symptoms. However, for the huge patient population the disease progression does not stop. Rethinking the treatment regimen with regenerative medicine has introduced new hope through facilitating regeneration and repair. 

Regenerative Medicine: Laying Hope on Limb Preservation

Researchers in regenerative medicine are targeting the underlying cause of Critical Limb Ischemia. It does not intend to replace conventional medicine but to complement its potential benefits. For instance, the surgical procedure restores the restricted blood flow, and regenerative medicine promotes naive cell regeneration and boosts repair mechanisms. Stem cell therapy for CLI is widely investigated to promote angiogenesis, anti-inflammation, support wound healing, and improve microvascular circulation. Along with vascular intervention, regenerative medicine aids in creating healthier microenvironments to support tissue recovery. Research and clinical application are at an early stage, but the complementary stage reflects a shift towards enabling vascular restoration and tissue regeneration.

How Does Stem Cell Therapy for CLI Work?

Stem cells introduce regenerative and repair signals to promote tissue regeneration and prevent tissue loss. Researchers are widely exploring mesenchymal stem cells (MSCs) ability to stimulate new blood vessel formation. The cells are isolated from distinct sources including umbilical cord blood/tissue, adipose tissue, and bone marrow. Various studies reported the superiority of MSCs isolated from umbilical cord tissue or blood. The cells are naive and have intrinsic capacity to differentiate into endothelial cells (blood vessels linings). They also release growth factors like VEGF, FGF, etc., that promote angiogenesis. 

The Key Mechanism of Action in Critical Limb Ischemia Patients Includes:

• Angiogenesis: Stem cells promote new blood vessel formation. It supports adequate blood flow in the ischemic area. 
• Wound Healing: Stem cells boost the body’s repair mechanism. For patients with co-morbid conditions like diabetes, it promotes faster wound healing.
• Undertakes Collateral Pathway: Stem cells support small blood vessel network growth surrounding blocked arteries 
• Paracrine Signalling: Stem cells secrete various bioactive molecules such as growth factors, cytokines, and signalling molecules. For instance, releases of anti-inflammatory cytokines neutralizes the effect of pro-inflammatory cytokine and modulate immune response
• Regeneration: A portion of the MSCs differentiate into endothelial cells, thus supporting blood vessel inner linings

What Does Current Research Say About Stem Cell Therapy for CLI?

Although Stem Cell Therapy for CLI Research is at an Early Stage of Development, the Outcome Looks Quite Promising. The Key Findings Include:

• The majority of the studies highlighted safety and tolerance parameters
• Improvement in blood perfusion, tissue oxygenation, and microvascular circulation
• Enhanced angiogenesis helped with improved blood supply to the ischemic tissues
• Some clinical studies reported improvement in rest pain that comforted the patient
• Improved wound healing among patients with chronic non-healing ulcers
• Preserved surrounding tissue by improving oxygen and nutritional supply
• Improved quality of life of the patient and reduced risk of limb salvage [1]

*Although the current research outcome looks promising in CLI treatment, it is at an early stage of research and clinical application. 

What Is The Current Scope of Improvement?

• Current studies are based on small patient groups, which makes drawing definitive conclusions difficult. There is a need for large-scale studies for a longer time period
• Optimisation of stem cell type, source, isolation procedure, dosage, timings, and delivery techniques for maintaining treatment outcome quality
• Determination of long-term efficacy and safety of the stem cell treatment
• Development of effective combination approach involving stem cell therapy with other regenerative approaches like exosomes, biomaterial scaffold, gene-enhanced stem cell technology
• The outcome of the stem cell therapy varies among individuals. It depends on the individual’s factors, disease severity, co-morbid condition, etc.

*Advancells, India is a leading supplier of clinical-grade stem cells for chronic diseases including CLI. The cells undergo a stringent quality control process and are dispatched with a Certificate of Authentication (CoA)

Why Is Patient Selection an Important Criterion?

Stem Cells Might Not Benefit Everyone in a Similar Manner. The Key Patient Selection Criteria Include:

• Patients not responding to conventional treatment are a major focus of the current clinical research
• Patients with active infection are not a good choice
• Development of personalised strategies based on an individual’s needs plays a crucial role in its success

*NOTE: Currently, clinicians are collaborating with stem cell researchers to develop combination treatment for CLI patients. The intention is prevention of further tissue decline and halting the risk of limb amputation. 

Conclusion 

Chronic limb ischemia is a serious condition that increases the risk of limb amputation. It is the most severe form of PAD that potentially creates life-threatening conditions. The current conventional CLI treatment focuses on symptom management. However, the approaches might not be suitable for every patient. The emerging regenerative medicine aims to support new blood vessel formation, boost tissue regeneration, and repair mechanisms. Implication of stem cells with conventional treatment aids in better treatment outcomes and improvement in patients’ quality of life.

References

1. Lozano Navarro LV, Chen X, Giratá Viviescas LT, Ardila-Roa AK, Luna-Gonzalez ML, Sossa CL, Arango-Rodríguez ML. Mesenchymal stem cells for critical limb ischemia: their function, mechanism, and therapeutic potential. Stem cell research & therapy. 2022 Jul 26;13(1):345. 

FAQ’s

Q- Can Stem Cell Therapy Cure CLI?

No, currently stem cell therapy is investigated as a regenerative approach. They release various bioactive molecules that promote new blood vessel formation, reduce inflammation, and modulate immune response. Current clinical outcomes mark stem cells’ ability to complement or support conventional treatment and improve patients’ quality of life.

Q- What are the Early Symptoms of CLI?

Early Critical Limb Ischemia symptoms include persistent rest pain in the feet or legs, slowed wound healing, skin discoloration, temperature drop, or gangrene.  

Q- What is the Best CLI Treatment?

The key treatment options includes includes medication, angioplasty, bypass surgery, and stenting. In extreme cases, limb amputation are recommended. Clinicians recommend adequate treatment depending on disease severity and co-existing health conditions.