Unveiling the Therapeutic Promise of Mesenchymal Stem Cells: From Clinical Applications to Mechanistic Insights

Mesenchymal stem cells (MSCs) are adult stem cells. With their unique biological characteristics and remarkable therapeutic potential, MSCs have become a rising star in the field of disease research. As of May 2024, there were more than 1,200 ongoing clinical trials involving MSCs worldwide, and over 27 MSC-related products had been approved, providing preliminary evidence of their clinical value.

To help readers quickly and systematically grasp the essential knowledge of MSCs, we have planned a series of posts covering the following topics in sequence: an overview of MSCs, in vitro culture and expansion, trilineage differentiation, and applications in cell therapy.

In this issue of Cell Culture Academy, we examine MSC trilineage differentiation to elucidate its underlying mechanisms and potential applications.

This issue of Cell Culture Academy highlights the clinical and mechanistic perspectives of MSCs, offering a comprehensive synthesis of their therapeutic applications and recent research progress.

I. Therapeutic Advantages

Stem cell–based therapy represents one of the most promising frontiers in regenerative medicine. The fundamental concept lies in utilizing the self-renewal and differentiation capacities of stem cells to repair or replace damaged tissues and cells, thereby enabling effective treatment of various diseases.

Among the different stem cell types, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs) are the three most extensively investigated and clinically relevant categories. Compared with ESCs and iPSCs, MSCs possess several distinct advantages:

1. High Safety Profile

ESCs and iPSCs have the potential to differentiate into all cell lineages, which carries a risk of teratoma formation following transplantation. In contrast, MSCs are adult multipotent stem cells with more restricted differentiation capacity, primarily differentiating into osteogenic, chondrogenic, and adipogenic lineages,resulting in a substantially lower tumorigenic risk.

2. Low Immunogenicity

MSCs express low levels of major histocompatibility complex (MHC) molecules, which play a central role in immune recognition of “self” versus “non-self”. This property contributes to their immune evasive nature and reduces the likelihood of rejection reactions during allogeneic transplantation.

3. Minimal Ethical Concerns

Unlike ESCs, MSCs can be derived from adult or perinatal tissues, including umbilical cord, adipose tissue, and bone marrow, thereby circumventing the ethical controversies associated with the use of embryonic sources.

4. Accessible Sourcing and Robust Expansion

MSCs can be obtained through safe and minimally invasive procedures, such as umbilical cord or adipose tissue collection. Moreover, they can be stably expanded in vitro, facilitating the development of large-scale cell banks that meet clinical-grade standards.

Owing to these attributes, MSCs exhibit broad therapeutic potential in genetic engineering, tissue regeneration, and disease treatment, and have become a central focus of clinical research and biopharmaceutical development (Table 1).

Table 1. Clinically Approved Mesenchymal Stem Cell Products (Partial)

Ⅱ. Regulation of Mesenchymal 

1.Immunomodulatory Mechanisms

MSCs modulate both innate and adaptive immune responsesvia paracrine signaling, direct cell–cell interactions, and metabolic regulation.

Paracrine Effects: MSCs secrete a broad spectrum of immunomodulatory factors, including cytokines, growth factors, chemokines, and enzymes. These factors act synergistically or antagonistically to reshape the local microenvironment and directly regulate immune cell activity (e.g., T cells, macrophages), thereby suppressing inflammationand promoting tissue repair.

Cell–Cell Interactions: MSCs engage with immune cells—such as T cells, B cells, dendritic cells (DCs), natural killer (NK) cells, neutrophils, and macrophages—through surface molecules including PD-L1, FasL, and ICAM-1. These interactions can inhibit immune cell proliferationor induce apoptosis, contributing to immunosuppression.

Metabolic Regulation: MSCs modulate immune cell function through the production of metabolites such as indoleamine 2,3-dioxygenase (IDO)and prostaglandin E2 (PGE2), which are generated via specific metabolic pathways.

2.Extracellular Vesicles and Exosomes

MSCs communicate with surrounding cells and tissues by secreting extracellular vesicles (MSC-EVs) that carry bioactive molecules, including proteins, mRNAs, and miRNAs. MSC-EVs generally contain exosomes (30-120 nm), microvesicles (MVs, 100-1,000 nm), and apoptotic bodies. Exosomes play a central role:

Immunomodulation:Exosomes regulate immune responses by suppressing the release of proinflammatory factors and modulating immune cell activity, including T cells, macrophages, and NK cells, via miRNA transfer, protein-mediated signaling, or receptor-mediated endocytosis.

Regulation of Signaling Pathways:Exosomes can activate or inhibit key immune-related signaling pathways, such as NF-κB, STAT3, and PI3K/AKT, thereby influencing immunomodulatory and tissue repair processes.

Delivery of Bioactive Substances:Exosomes transport miRNAs and other functional molecules to recipient cells, mediating immunomodulatory effects. 

Additionally, microvesicles and apoptotic bodies contribute to intercellular communication, collectively modulating the local microenvironment.

3. Homing and Targeting Mechanisms

Beyond molecular-level regulation, MSCs possess intrinsic migratory and tissue-targeting capabilities. MSCs sense chemotactic signals released by injured or inflamed tissues, travel systemically via the bloodstream, traverse the vascular endothelium, and ultimately localize to sites of tissue damage.

The homing process can be delineated into five sequential steps: rolling, activation, firm adhesion, crawling, and transendothelial migration (Figure 1). Despite extensive research, enhancing the efficiency and specificity of MSC homing remains a major challenge for their clinical application.

Figure 1. Schematic representation of MSC homing mechanisms (Adapted from Reference 1)

Ⅲ. Application Directions

MSCs and their derivatives exhibit excellent biocompatibility, targeted migratory capabilities, and immunomodulatory properties, making them versatile platforms for the development of efficient and safe drug delivery systems. The principal application strategies are outlined below:

1. Engineered MSCs

Engineered MSCs, generated via genetic modification or loading with exogenous therapeutic agents, enable targeted delivery of therapeutic molecules. They have demonstrated significant targeting efficiency and therapeutic efficacy in preclinical models of pancreatic ductal adenocarcinoma, leukemia, neuroblastoma,and liver fibrosis.

2. MSC-Derived Extracellular Vesicles (EVs)

MSC-secreted exosomes and microvesicle sserve as cell-free drug delivery vehicles. When loaded with therapeutic agents such as miRNAs, mRNAs, or small-molecule drugs, these vesicles exhibit substantial therapeutic potential in the treatment of cancer, osteoarthritis, cerebral ischemia-reperfusion injury, and inflammatory diseases.

3. MSC-Biomaterial Composite Systems

The integration of MSCs with functional biomaterials(e.g., hydrogels, scaffolds, biodegradable polymers) enhances cell survival, local retention, and overall therapeutic efficacy. This strategy supports tissue engineering applications, including bone defect repair, limb regeneration, and periodontal tissue regeneration.

4. MSC Membrane-Coated Nanoparticle Systems

Nanoparticles coated with MSC membranes combine the targeted homing and immune evasion capabilities of MSCs with the controllable release kineticsand high loading capacityof nanomaterials. Such systems have demonstrated promising therapeutic potential in preclinical studies of in situ glioma, immune disorders, and myocardial injury repair.

IV. Challenges and Future Perspectives

MSCs have demonstrated considerable therapeutic potential across a variety of diseases; however, several critical challenges remain. The primary issues include:

1. Discrepancies Between In Vitro and In Vivo Outcomes

The behavior and efficacy of MSCs often differ between controlled laboratory settings and clinical environments. Translating findings from in vitro to in vivo contexts may result in changes in immunogenicity, homing efficiency, and cell survival, which can compromise therapeutic consistency and reproducibility.

2. Uncertainties in Efficacy and Safety

Although clinical studies generally confirm the favorable safety profile of MSC-based therapies, therapeutic efficacy is influenced by patient-specific factors, disease etiology, and variability in cell sources. Comprehensive, large-scale validation studies are necessary to establish long-term effectiveness and optimize treatment protocols.

3. Immune Rejection and Potential Tumorigenic Risks

Despite their intrinsically low immunogenicity, MSCs may elicit immune responses under certain microenvironmental conditions or inadvertently promote tumor cell proliferation. Consequently, rigorous longitudinal safety evaluations are essential to ensure clinical reliability.

As multipotent progenitor cells endowed with differentiation and immunomodulatory capabilities, MSCs are progressively transitioning from experimental research toward clinical implementation. Advances in standardized manufacturing processes, engineered modification strategies,and cell-free therapeutic approaches are positioning MSCs for broader, more precise applications in regenerative medicine, immunotherapy,and tissue repair.

Reference

[1]Mei R, Wan Z, Yang C, et al. Advances and clinical challenges of mesenchymal stem cell therapy. Frontiers in Immunology. 2024; 15:1421854. 

[2]Yang, G., Fan, X., Liu, Y. et al. Immunomodulatory Mechanisms and Therapeutic Potential of Mesenchymal Stem Cells. Stem Cell Reviews and Reports. 19, 1214-1231 (2023).

[3]Lu W, Allickson J. Mesenchymal stromal cell therapy: Progress to date and future outlook. Molecular Therapy. 2025 Jun 4; 33 (6): 2679-2688.

[4] X., Liao, R., Li, X. et al. Mesenchymal stem cells in treating human diseases: molecular mechanisms and clinical studies. Signal Transduction and Targeted Therapy. 10, 262 (2025).