What are the latest updates on mesenchymal stem cell (MSC) therapy, including approved indications and experimental applications?

Latest Updates on Mesenchymal Stem Cell Therapy

FDA-Approved Indication

The FDA approved Ryoncil (remestemcel-L-rknd) in December 2024 for pediatric acute steroid-refractory graft-versus-host disease (GVHD), marking the first MSC therapy approved in the United States. 1, 2

• This approval ended a significant drought in MSC product approvals in the US, despite over 1,500 clinical trials worldwide 3
• Perinatal tissue-derived MSCs formulated with human serum albumin (HSA) and low-dose heparin achieved 76% one-year survival in steroid-resistant GVHD patients, with 100% response rate (21/21 patients) 4, 5
• This represents superior efficacy compared to MSCs prepared with AB plasma (47% one-year survival, 59% response rate) 4

Emerging Clinical Applications

While only one indication has FDA approval, MSC therapy shows promise in several conditions based on international guidelines and clinical evidence:

Graft-Versus-Host Disease (Primary Indication)

• The International Society for Stem Cell Research recommends MSC therapy for GVHD as the most evidence-supported indication 5
• Optimal dosing: 1-2 × 10⁶ cells/kg body weight 4

Multiple Sclerosis

• The Multiple Sclerosis International Federation suggests MSC therapy for patients who have failed disease-modifying therapies 5

COVID-19-Related Pneumonia

• COVID-19 Treatment Guidelines recommend MSC therapy for severe pneumonia to reduce cytokine storms and improve oxygenation 5

Rheumatic Diseases

• Clinical trials demonstrate potential benefits in systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, Sjögren's syndrome, and systemic sclerosis 6
• Evidence shows symptom relief and disease progression delay, though standardized protocols are still needed 6

Critical Safety Updates: Blood Compatibility Issues

The most significant recent update is the recognition that MSC products from different tissue sources have dramatically different safety profiles for intravascular delivery, with potentially lethal consequences if not properly managed. 4, 5

Tissue Factor Expression and Thrombotic Risk

• Adipose tissue-derived MSCs (AT-MSCs) express the highest levels of procoagulant tissue factor (TF/CD142) and can cause fatal thrombotic complications 4, 7
• Bone marrow-derived MSCs (BM-MSCs) display favorable hemocompatibility with weaker instant blood-mediated inflammatory reaction (IBMIR) 4, 5
• Perinatal tissue-derived MSCs (PT-MSCs) show intermediate procoagulant activity 7

Documented Adverse Events

• Reports include forearm vein thrombosis, peripheral microthrombi, pulmonary embolism, and suspected deaths from AT-MSC infusion 5
• The International Society for Stem Cell Research now mandates standardized hemocompatibility testing for all MSC products intended for intravascular use 4

Mandatory Safety Protocols

All MSC products for intravascular delivery must now undergo blood compatibility screening before clinical use. 4, 5

Required Testing

• Tissue factor (TF/CD142) expression profiling 4, 7
• Complement compatibility testing (C3a/C5a detection) 4
• Coagulation activation assessment 4

Anticoagulation Requirements

The International Society for Stem Cell Research strongly recommends routine use of low-dose anticoagulants (heparin) when administering MSCs intravascularly, particularly at high doses or with AT-MSCs. 7

• Heparin prevents coagulation activation and improves cell efficacy 7
• MSCs formulated with HSA plus low-dose heparin show superior outcomes compared to AB plasma formulations 4, 5
• AT-MSCs at doses ≥4 × 10⁶ cells/kg require mandatory anticoagulation 7

Absolute Contraindications

Patients with active malignant tumors should not receive MSC therapy due to potential tumor growth promotion. 5

Additional contraindications include:

• Severe blood system diseases (increased thrombosis risk) 5, 7
• Severe heart and lung function impairment (risk of microembolism) 5, 7
• Irreversible right ventricular failure 5
• Predicted survival <2 years from major comorbidities 5

Product Standardization Requirements

The field has shifted toward recognizing that MSC products are not equivalent and require individual characterization:

Cell Source Selection

• BM-MSCs remain the safest option for intravascular delivery 4
• PT-MSCs at early passage show enhanced efficacy when properly formulated 4
• AT-MSCs require extensive safety modifications before intravascular use 4

Formulation Standards

• Replace AB plasma with ABO-neutral HSA 4, 5
• Add low-dose anticoagulants (heparin or EDTA) 4, 7
• Optimize cell washing procedures to remove cryoprotectants 4
• Standardize reconstitution buffers 4

Quality Control

• The FDA now emphasizes holistic potency assays beyond basic ISCT minimal criteria 3
• Universal reference standards are needed to improve reproducibility 3
• Single-cell analyses reveal significant heterogeneity requiring tissue-specific characterization 3

Alternative Delivery Routes

For products with high TF expression or high-risk patients, consider non-intravascular routes:

• Intramuscular injection 4
• Local site delivery with biomaterial scaffolds 4
• Intrathecal or intraperitoneal administration 4
• Extracorporeal dialysis cartridge systems 4

Global Regulatory Landscape

• As of 2023, only 12 MSC therapies have regulatory approval worldwide 8
• Nine of twelve approved products are in Asia, with South Korea leading 8
• Europe, Japan, India, and South Korea have marketed products; the US approval is recent 1

Common Pitfalls to Avoid

1. Never assume equivalence between MSC products from different tissue sources 4
2. Do not use AT-MSCs intravascularly without mandatory anticoagulation and hemocompatibility testing 4, 7
3. Avoid AB plasma formulations; use HSA-based preparations instead 4, 5
4. Do not skip tissue factor expression screening before intravascular delivery 4, 7
5. Recognize that cryopreserved cells may have different properties than fresh cells initially, though they equilibrate after 2 hours 9