Benefits and Risks of Stem Cells: A Comprehensive Review

Abstract

Stem cell therapy represents a transformative approach in regenerative medicine, offering potential treatments for a wide range of degenerative and inflammatory conditions. Allogeneic and autologous stem cell therapies differ in source, immune response, and clinical applicability. Allogeneic stem cells, derived from donors, provide readily available, off-the-shelf treatments but require immunosuppression to prevent rejection. In contrast, autologous therapies, using a patient’s own cells, eliminate immune rejection risks but involve time-intensive processing and may be limited by age-related or disease-associated defects. Induced pluripotent stem cells (iPSCs) offer patient-specific therapies by reprogramming adult cells into a pluripotent state, enabling disease modeling and regenerative applications. However, iPSCs carry risks of tumorigenicity and genetic instability, complicating clinical translation. Mesenchymal stem cells (MSCs), in contrast, provide immunomodulatory and anti-inflammatory effects, making them particularly useful for conditions such as cardiovascular disease, neurodegeneration, and autoimmune disorders, though their differentiation potential is more restricted. The choice between differentiated and undifferentiated stem cells depends on safety and therapeutic goals. While differentiated cells target specific tissue repair with lower tumor risks, undifferentiated or progenitor cells offer broader regenerative potential but higher risks of improper integration or fibrosis. Additionally, the use of immunosuppression presents risks such as infection and malignancy, complicating treatment strategies. Future advancements in gene editing, encapsulation, and combination therapies aim to enhance graft survival and functional integration, improving the safety and efficacy of stem cell-based treatments across multiple diseases.

Introduction

Stem cells represent a transformative approach to regenerative medicine, offering groundbreaking potential for repairing damaged tissues. Stem cell-based therapies offer potential cures for degenerative diseases by replacing lost or damaged cells [1]. For example, dopaminergic neurons derived from neural progenitors can be transplanted in Parkinson’s disease, and cardiac progenitor cells may restore function after heart failure. Hepatic progenitors and pancreatic progenitors hold promise for treating liver and pancreatic failure, reducing dependence on organ transplants. Allogeneic stem cell therapy involves donor-derived stem cells used for treatment readily available for “off-the-shelf treatments.” On the other hand, autologous stem cell therapy uses a patient’s own stem cells; however, obtaining and expanding these cells can be time-consuming and costly, and the patient’s own cells may have age-related or disease-associated defects [2]. As described by Leavine in 1988, a benefit represents something of value that may arise, whereas a risk is the likelihood that harm (whether physical, psychological, economic, legal, or social). To date the transformative benefits of stem cell therapy continue to evolve, however, the evolution continued to be accompanied by significant challenges [3]. This review provides a contemporary review of the utility of stem cells for regenerative medicine therapies as well as the associated risks.

Allogeneic and autologous stem cell therapies differ in source, immune response, clinical application, and risks, impacting their suitability for various diseases (Table 1). Allogeneic stem cell therapy uses stem cells from a genetically different donor, which can come from cord blood, bone marrow, or stem cell banks. The primary advantage of allogeneic cells is their immediate availability, eliminating the need for patient-specific cell collection and processing. Additionally, allogeneic cells have immunomodulatory properties, allowing them to be used with minimal immune rejection. However, the major downside is the risk of immune rejection, requiring immunosuppressive therapy, and in cases like hematopoietic stem cell transplants, the possibility of graft-versus-host disease (GVHD), where the donor immune cells attack the recipient’s tissues [4]. On the other hand, autologous stem cell therapy uses the patient’s own stem cells, eliminating the risk of immune rejection and GVHD [5]. This approach is widely used in treating blood disorders, orthopedic injuries, and personalized regenerative medicine. However, autologous therapies require time-intensive processing, including cell harvesting, expansion, and sometimes genetic modification, delaying treatment availability. Additionally, in cases where the patient’s cells are already genetically defective or aged, their therapeutic potential may be limited [6]. Allogeneic therapy offers scalability and off-the-shelf solutions, making it practical for acute conditions, whereas autologous therapy is personalized and safer but may not always be feasible due to time constraints and cell quality limitations. The choice between these approaches depends on factors such as disease urgency, immune compatibility, and longterm treatment goals.

Table 1:Comparison of Allogenic and Autologus Stem Cell Approaches.

Induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs) are two widely studied stem cell types in regenerative medicine.

1) iPSCs are reprogrammed adult cells (e.g., skin or blood cells) that regain pluripotency, allowing them to differentiate into any cell type in the body. iPSCs are widely used for disease modeling, drug testing, and regenerative therapies due to their ability to generate patient-specific cells, reducing immune rejection risks [7]. Because they are derived from a patient’s own cells, iPSCs enable personalized treatment without immune rejection. iPSCs also facilitate disease modeling for conditions like neurodegenerative disorders, cardiovascular disease, and diabetes, facilitating the development of targeted therapies [8]. However, they pose risks of tumor formation and genetic instability. While iPSCs offer greater versatility, their safety and regulatory challenges make clinical translation more complex, whereas MSCs are more readily available for therapeutic applications, particularly in inflammation-related diseases. Genetic mutations introduced during reprogramming could alter immune responses unpredictably. Risks of immune rejection must be addressed before widespread clinical application [9]. In addition, pluripotent stem cells (iPSCs and ESCs) pose a risk of tumor formation (teratomas) due to their unlimited proliferative capacity.

2) MSCs are multipotent stem cells that reside in bone marrow, adipose tissue, and umbilical cord blood [10]. MSCs primarily differentiate into osteocytes, chondrocytes, or adipocytes and possess immunomodulatory properties, making them ideal for treating autoimmune diseases, inflammatory disorders, and musculoskeletal injuries [11]. The anti-inflammatory and immunomodulatory properties [12] make MSCs attractive for treating conditions like autoimmune diseases, cardiovascular disorders, and neurodegeneration [13]. Unlike iPSCs, MSCs are considered safer for direct transplantation, as they have a lower risk of tumor formation and are often used in allogeneic treatments with minimal immune rejection [14]. However, their differentiation potential is more limited, and they may not be suitable for conditions requiring the regeneration of highly specialized cells, such as neurons or pancreatic β-cells.

There are reports of transplanted stem cells failing to integrate properly into host tissues due to poor vascularization, inflammatory environments, lack of necessary growth factors or other factors, thereby reducing their long-term survival and effectiveness. The choice between iPSCs and MSCs depends on the specific disease, the need for differentiation, and the associated risks of each stem cell type.

Differentiated and non-differentiated (or partially differentiated) stem cells differ significantly in their therapeutic applications, risks, and clinical readiness [15] (Table 2). Differentiated stem cells are fully specialized into specific cell types, such as neurons, cardiomyocytes, or insulin-producing β-cells, making them ideal for direct transplantation in regenerative medicine. The utility may be limited as differentiated cells can only perform the function of their specialized type [16]. Since they are committed to a specific lineage, they have a lower risk of uncontrolled proliferation and tumor formation, improving safety in clinical use. However, they may still face challenges. Immune rejection is still a possibility depending on origin. Limited self-renewal capacity also presents a challenge [17]. In contrast, non-differentiated or partially differentiated stem cells retain high plasticity, allowing them to generate multiple cell types for broader therapeutic applications. The advantage resides in the potential for personalized medicine, disease modeling, and drug discovery. However, the ability to proliferate indefinitely increases risk of teratoma formation and immune rejection if used as allogeneic transplant. Improper differentiation may lead to abnormal tissue formation or fibrosis, limiting functional recovery. For example, cardiac progenitors used in heart repair may differentiate into fibrotic tissue instead of functional cardiomyocytes, reducing therapeutic efficacy. Partially differentiated cells, such as progenitor cells, strike a balance between differentiation potential and safety, offering enhanced regenerative capacity while reducing tumorigenic risks. The choice between these stem cell types depends on factors such as disease requirements, safety considerations, and ethical and regulatory constraints [18].

Table 2:Comparison of differentiated versus non-differentiated stem cell therapeutic approaches.

Immune suppression poses significant risks, including increased susceptibility to infections, potential organ toxicity from long-term drug use, and a higher likelihood of developing malignancies due to reduced immune surveillance [19]. Additionally, immunosuppressive therapies can lead to complications such as GVHD in allogeneic stem cell transplants, where donor immune cells attack the recipient’s tissues [20]. In contrast, autologous stem cell therapy eliminates the need for immune suppression, reducing these risks. However, autologous approaches have their own challenges, such as the need for extensive cell processing, potential genetic mutations in the patient’s cells, and limitations in generating sufficient functional cells for transplantation. While both strategies have therapeutic value, the choice depends on factors like disease type, treatment goals, and patient-specific risks [21].

The application of iPSCs and MSCs in specific diseases varies based on their unique properties and therapeutic potential. iPSCs, with their pluripotent nature, can differentiate into nearly any cell type, making them ideal for regenerative treatments in conditions requiring the replacement of specialized cells. In diabetes, iPSCs are used to generate insulin-producing β-cells, offering a potential cure for Type 1 diabetes [22,23]. In neurodegenerative diseases such as Parkinson’s and Alzheimer’s, iPSC-derived neurons hold promise for restoring lost function, while also enabling disease modeling for drug discovery [24]. iPSCs are also valuable in cardiovascular disease, where they can generate patient-specific cardiomyocytes for heart regeneration [25]. However, iPSC therapy faces challenges like tumorigenic risk and immune rejection if not autologous. In contrast, MSCs are multipotent and primarily contribute to tissue repair, anti-inflammatory effects, and immunomodulation rather than direct cell replacement. MSCs are widely used in treating aging-related disorders due to their ability to reduce inflammation, promote tissue regeneration, and improve mitochondrial function [26]. In cardiovascular disease, MSCs enhance heart repair by secreting growth factors that promote angiogenesis and reduce fibrosis. For neurodegeneration, MSCs provide neuroprotection by modulating immune responses and reducing oxidative stress rather than directly replacing neurons. While iPSCs are more suited for cell replacement therapies, MSCs are advantageous for immune modulation and promoting endogenous repair. The choice between iPSCs and MSCs depends on whether the goal is to replace lost cells or to support and enhance the body’s natural healing processes.

Additional risks of stem cell interventions

Despite the ease of isolating peripheral stem cells for use as autologous treatment, especially in the case of MSC, there have been reported harm caused by either improper processing, purification, and/or quality control by the cell processing lab. An alarming estimate of 700 clinics are using unapproved therapies. In 2019, Pew research identified 69 reports of harm, including lifelong disabilities and death, dating as early as 2004. In their updated research [27], the team identified an additional 265 cases of harm related to these stem cell products, bringing the total number of adverse events (AE) to 334 and the total number of subsequent deaths to 20. More alarmingly, the risk of infection or other serious complications is significantly enhanced when therapeutic administration is performed by an untrained individual.

Summary

Current trends in stem cell therapy span multiple conditions, emphasizing transplantation strategies, immune compatibility, and differentiation efficiency. A key distinction exists between autologous and allogeneic therapies: autologous stem cells, derived from a patient’s own body, reduce immune rejection but are costly and time-intensive, while allogeneic approaches, using donor cells, enable scalability but often require immunosuppression, which carries risks such as infection and malignancy. Another major consideration is differentiated versus undifferentiated stem cells. Whereas differentiated cells offer targeted tissue replacement (e.g., insulin-producing beta cells for diabetes or dopamine neurons for Parkinson’s), survival and functional integration remain challenges. In contrast, undifferentiated stem cells, particularly MSCs, exert immunomodulatory and regenerative effects, reducing inflammation and supporting endogenous tissue repair without direct cell replacement, making them widely applicable across autoimmune, neurodegenerative, and inflammatory diseases. iPSCs hold immense potential for personalized regenerative medicine, allowing patient-specific cell generation without ethical concerns associated with embryonic stem cells. However, risks such as tumorigenicity, differentiation variability, and high production costs remain obstacles to widespread clinical use. MSCs, while not replacing damaged cells, are being explored for conditions like arthritis, cardiovascular disease, and neurodegeneration, where immune regulation and tissue repair are critical. Innovations in gene editing, encapsulation technologies, and combination therapies are being developed to enhance graft survival, reduce immune rejection, and improve therapeutic efficacy. While iPSCs promise precise, patient-specific treatments, MSCs provide immediate, scalable options for reducing inflammation and promoting healing, making both approaches complementary in regenerative medicine. Notwithstanding, addressing risks is essential to move the field forward.

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