Note: Hujjat al-Islam Dr. Mohammad Mehdi Karimi-Nia is an Assistant Professor at the University of Quranic Sciences and Knowledge and a member of the Scientific Council of the “Health and Medical Jurisprudence” Group at the Research Institute for Contemporary Jurisprudential Studies. He holds a Level Four (Ph.D.) degree in Islamic Jurisprudence and Principles from the Qom Seminary and a Ph.D. in “Quran and Sciences” with a specialization in “Quran and Law” from Al-Mustafa International University. He has authored numerous works and conducted extensive research in medical jurisprudence. His most significant publications in this field are the books Sex Reassignment from the Perspective of Jurisprudence and Law and Sex Reassignment with an Emphasis on Imam Khomeini’s Perspective. He has published around three hundred articles and twenty books. One of his key areas of interest in medical jurisprudence is the jurisprudential examination of stem cells. We discussed the applications of stem cells with him, and he elaborated on these applications in detail. The full text of Contemporary Jurisprudence’s exclusive interview with the member of the Scientific Council of the Health and Medical Jurisprudence Group at the Research Institute for Contemporary Jurisprudential Studies follows:

Contemporary Jurisprudence: What are stem cells, and which cells do they include?

Karimi-Nia: Stem cells are a specific type of cell with the ability to differentiate into various cell types in the body. These cells possess a key characteristic: they can divide indefinitely and differentiate into specialized cells, such as neural, muscular, blood, and other tissue cells (Cheti).

These cells can be considered as mother or progenitor cells with high potential for repairing and regenerating damaged tissues.

Stem cells are primarily divided into two main types:

Embryonic Stem Cells: These cells are derived from early-stage embryos and are capable of differentiating into any cell type in the human body (pluripotent). They have an unlimited capacity to differentiate into various cell types.

Adult Stem Cells: These cells are found in adult tissues and have the ability to differentiate into certain cell types, though not as extensively as embryonic stem cells. They are primarily located in tissues such as bone marrow, skin, and intestines, where they contribute to tissue repair and regeneration.

Additionally, there is another type of stem cell known as Induced Pluripotent Stem Cells (iPSCs), which are created from adult cells that are genetically reprogrammed to exhibit properties similar to embryonic stem cells.

Stem cells have significant potential for treating various diseases, regenerating damaged tissues, and advancing scientific research.

Characteristics of Stem Cells

• Self-Renewal: Stem cells can continuously divide and increase their numbers.
• Differentiation: These cells can transform into various specialized cell types, such as neural, cardiac, or skin cells.
• Regenerative Potential: Stem cells can be used to repair damaged tissues and treat various diseases.

Applications of Stem Cells

• Regenerative Medicine: Repairing damaged tissues caused by diseases such as heart disease, diabetes, neurological disorders, etc.
• Treatment of Blood Disorders: Using cord blood stem cell transplants to treat conditions like thalassemia and sickle cell anemia.
• Disease Modeling: Studying diseases in laboratory settings using stem cells.
• Tissue Engineering: Creating artificial tissues for transplantation into patients’ bodies.

Future of Stem Cells Research in the field of stem cells is advancing rapidly, and it is expected that broader applications of these cells in treating diseases will emerge in the near future. However, numerous challenges still need to be addressed.

Contemporary Jurisprudence: Are stem cells limited to umbilical cord cells, or do they also include other cells, such as adult bone marrow cells?

Karimi-Nia: No, stem cells are not limited to umbilical cord cells. In fact, stem cells come in various types and are found in different tissues of the human body. Therefore, stem cells extend beyond umbilical cord cells.

Stem cells are categorized as follows:

Embryonic Stem Cells: These cells are obtained from the inner cell mass of early-stage embryos. They are the most pluripotent type of stem cells, capable of differentiating into any cell type in the body.

Adult Stem Cells: These are found in various tissues of adults. For example, bone marrow contains hematopoietic stem cells that continuously produce new blood cells. Other tissues, such as the brain, liver, and skin, also contain stem cells used for tissue repair and regeneration.

Umbilical Cord Blood Stem Cells: These cells are extracted from the umbilical cord blood of newborns. They are similar to hematopoietic stem cells in bone marrow and are primarily used to treat blood disorders.

Thus, adult bone marrow cells are also a type of stem cell. These cells play a critical role in producing new blood cells and are used in bone marrow transplants to treat blood disorders such as leukemia.

Why Are Bone Marrow Stem Cells Important?

• Continuous Blood Cell Production: Bone marrow acts as the body’s factory for producing blood cells. Bone marrow stem cells continuously divide to generate new blood cells.
• Bone Marrow Transplantation: In bone marrow transplants, healthy stem cells from a donor are transplanted into a patient. These cells settle in the patient’s bone marrow and begin producing healthy blood cells.
• Treatment of Blood Disorders: Bone marrow transplantation is a primary method for treating blood disorders such as leukemia, aplastic anemia, and immune deficiencies.

In conclusion, stem cells are not limited to umbilical cord cells and are present in various body tissues. Each type of stem cell has its own specific characteristics and applications.

Contemporary Jurisprudence: What are the current uses of stem cells?

Karimi-Nia: Stem cells are currently used in various medical fields and are recognized as one of the most important tools in modern therapeutic approaches. The use of stem cells is continuously expanding, and extensive research is being conducted to improve treatment methods using these cells. Below are some of the current applications of stem cells:

Bone Marrow Transplantation and Treatment of Blood Cancers: One of the most well-known applications of stem cells is bone marrow transplantation. In this method, hematopoietic stem cells from the bone marrow of a healthy individual are transplanted into a patient to treat conditions such as leukemia, aplastic anemia, and immune disorders.

Hematopoietic stem cell transplantation is one of the most common uses of stem cells today, particularly for treating leukemia, lymphoma, and other blood disorders such as severe anemia and thalassemia. These cells are sourced from bone marrow or umbilical cord blood and are used to regenerate blood cells in patients who have undergone chemotherapy or radiotherapy.

Treatment of Immune System Disorders: Autoimmune diseases such as multiple sclerosis (MS), lupus, and rheumatoid arthritis are treated using mesenchymal stem cells (MSCs). Stem cells can regenerate the immune system and reduce abnormal immune responses.

Treatment of Neurological Disorders and Spinal Cord Injuries: Neurological conditions such as Parkinson’s disease, Alzheimer’s disease, and spinal cord injuries are among the areas where stem cells can be effective. Due to their ability to differentiate into neural cells, stem cells enable the regeneration and repair of damaged neural tissues. They help improve neurological function by replacing damaged neural cells and producing neuroprotective substances.

Treatment of Heart Diseases: Stem cells can be used to repair damaged heart tissue following a heart attack or congenital heart diseases. By generating new blood vessels and heart cells, they improve heart function.

After a heart attack, heart tissue may become damaged, reducing heart function. Stem cells can help produce new heart cells and repair damaged heart tissue, reducing complications and improving cardiac performance.

Repair of Skin Tissue and Burns: Stem cells are used to treat severe burns and chronic wounds, such as diabetic ulcers. They accelerate the regeneration and repair of skin tissues, speeding up the healing process.

Stem cells can also be used to treat skin conditions such as psoriasis (a severe form of eczema).

Treatment of Eye Diseases: Stem cells are used to treat certain eye conditions, such as macular degeneration and retinopathy. They help regenerate retinal cells and prevent vision loss.

Research Related to Diabetes Treatment: Stem cells are being researched to produce beta cells in the pancreas that generate insulin. This application is under investigation for treating type 1 diabetes, where the immune system destroys beta cells, potentially reducing patients’ reliance on external insulin.

Dental Applications: Stem cells extracted from baby teeth or dental pulp are used to regenerate dental tissues and repair jawbones. This application aids in treating oral and dental issues and replacing teeth.

Treatment of Liver and Kidney Diseases: Stem cells are considered a potential solution for treating liver failure and kidney failure. Research is ongoing to use stem cells to generate new liver and kidney cells to replace damaged ones.

Stem cells can be used to repair damaged liver tissue caused by chronic liver diseases such as cirrhosis.

Treatment of Infertility: Emerging research is exploring the use of stem cells to treat infertility. These cells can help produce new eggs and sperm in individuals with reproductive issues.

Iran also uses stem cells to treat infertility. Research on using stem cells to produce new eggs and sperm, particularly for individuals unable to reproduce due to various diseases, is progressing.

Tissue Engineering and Artificial Organ Production: One of the forward-looking applications of stem cells is in tissue engineering and the creation of artificial organs. Stem cells can be used to produce organs such as the heart, kidney, or liver, reducing the need for organ transplantation.

Stem cells can also be used to produce other artificial tissues, such as cartilage, bone, and skin, for repairing tissue damage and replacing damaged tissues.

Treatment of Blood Disorders: In addition to bone marrow transplantation, stem cells can be used to treat other blood disorders such as thalassemia and sickle cell anemia.

In conclusion, the use of stem cells is rapidly advancing and plays a significant role in treating many acute and chronic diseases, including cancers, heart diseases, neurological disorders, and immune system disorders. This field continues to expand with new scientific and technological advancements, and it is expected that more applications for these versatile cells will emerge in the future.

It should be noted that the use of stem cells in treatment is still in its early stages, and many applications are in the research phase. Consulting with a specialist physician and experts is essential before deciding on any stem cell-based treatment.

Cosmetic and Restorative Applications: Some of these applications include:

• Hair Transplantation: Using mesenchymal stem cells for hair regrowth.
• Skin Rejuvenation: Injecting stem cells into the skin to repair damaged tissues and rejuvenate the skin.
• Wound Healing: Using stem cells to accelerate wound healing.

Research Applications: Some research applications of stem cells include:

• Disease Studies: Using stem cells to better understand the cellular and molecular processes leading to various diseases.
• Drug Testing: Using stem cells to evaluate the safety and efficacy of new drugs before clinical trials.
• Genetic Research: Investigating the causes of genetic defects in cells and finding ways to treat or prevent them.

Forward-Looking Applications: Some of these applications include:

• Tooth Regeneration: Ongoing research to use stem cells for growing new teeth.
• Gene Therapy: Combining stem cells with gene therapy to treat various diseases.
• Organ Regeneration: Efforts to grow new cells or tissues to replace damaged organs such as the liver or heart.

Other Applications of Stem Cells:

• Growing new cells or tissues in the laboratory to replace damaged organs or tissues.
• Investigating the causes of genetic defects in cells and their treatment methods.
• Researching the development of various diseases, particularly cancers.
• Testing the safety and efficacy of new drugs.
• Increasing height in adults using somatic stem cells.
• Gene therapy combined with stem cells to treat diseases.
• Use in various scientific research.

Mechanisms of Stem Cell Function in Disease Treatment:

• Proliferation and Replacement of Damaged Cells: After being injected into a damaged area, stem cells begin to proliferate and replace damaged cells.
• Tissue Repair: Stem cells can accelerate tissue repair by secreting growth factors and other substances.
• Immune System Modulation: Stem cells can modulate immune responses and prevent inflammatory reactions.

Contemporary Jurisprudence: Do you confirm the claim that “so far, no medical use of stem cells or umbilical cord blood banks has been made in Iran”? Is the use of stem cells in Iran different from other countries?

Karimi-Nia: The claim that “so far, no medical use of stem cells or umbilical cord blood banks has been made in Iran” is incorrect. In Iran, stem cells and umbilical cord blood banks are widely used in treating various diseases. Since the 1990s, Iranian researchers and scientists have been active in this field and have achieved significant results.

Based on available information, Iran has made remarkable progress in the field of stem cells, their medical applications, and research, and is recognized as one of the leading countries in the region in this area. There are significant research and treatment centers in Iran that use stem cells to treat various diseases.

Main Areas of Stem Cell Applications in Iran:

• Bone Marrow Transplantation: One of the most common applications of stem cells in Iran, used to treat blood disorders such as leukemia, aplastic anemia, and immune disorders.
• Heart Diseases: Stem cells are used to repair damaged heart tissue following heart attacks or congenital heart diseases.
• Neurological Disorders: Iranian researchers are exploring the use of stem cells to treat conditions such as Parkinson’s, Alzheimer’s, and spinal cord injuries.
• Skin Diseases: Stem cells are used to repair burns, chronic wounds, and skin conditions such as psoriasis.
• Tissue Engineering: Stem cells are used to produce artificial tissues such as cartilage, bone, and skin.
• Liver Diseases: Stem cells are used to repair damaged liver tissue caused by chronic liver diseases such as cirrhosis.
• Rheumatological Diseases: Stem cells are being studied for the treatment of inflammatory joint diseases such as rheumatoid arthritis.

Active Research and Treatment Centers in Iran:

Royan Research Institute: Established in 1991, Royan Research Institute is one of Iran’s most prestigious research and treatment centers in the field of stem cells. It operates in biotechnology, genetics, and the treatment of diseases using stem cells. Royan has become a leading center in this field with extensive research on embryonic and adult stem cells. It is active in the production and storage of umbilical cord blood and bone marrow stem cells and has achieved significant success in treating genetic diseases, cancers, and neurological disorders.

Universities of Medical Sciences: Many universities of medical sciences in Iran have active research centers in the field of stem cells. One of the most significant applications of stem cells in Iran is bone marrow transplantation, used to treat patients with blood cancers such as leukemia and genetic disorders such as thalassemia. Major hospitals in Iran, such as Shariati Hospital in Tehran, provide bone marrow transplantation services.

In addition to Shariati Hospital, other hospitals in Tehran and other cities in Iran also offer bone marrow transplantation services, using stem cells to treat blood disorders and various cancers.

Private Research Centers: Some private companies are also active in stem cell research and development, including:

• Knowledge-Based Companies: Many knowledge-based companies in Iran are engaged in stem cell research and development, offering various products and services in this field.
• Hospitals Affiliated with Universities of Medical Sciences: Many hospitals affiliated with universities of medical sciences have departments for bone marrow transplantation and other stem cell-based treatments.

Umbilical Cord Blood Banks: Umbilical cord blood banks are active in Iran. Several banks, including the Royan Umbilical Cord Blood Bank, are among the most prominent. These banks enable the storage of newborn umbilical cord blood for potential future use in treating blood disorders, genetic diseases, and certain cancers. Umbilical cord blood banks in Iran are accessible to the public, allowing parents to store their children’s umbilical cord blood for future use.

Iran University of Medical Sciences Stem Cell and Regenerative Medicine Research Center: Established in 2019, this center has initiated research and studies in the fields of stem cells and tissue regeneration.

Iran Blood Transfusion Organization Stem Cell Donor Registry: Active since 2009, this center collects hematopoietic stem cells for treating blood disorders with the help of volunteers.

Taleghani Hospital Stem Cell Transplantation Complex: This complex, which includes bone marrow transplantation and cell therapy units, a transplantation laboratory, a hematopoietic stem cell research center, and a cell culture laboratory, has been operational since 2017.

Shiraz University of Medical Sciences Stem Cell Research Institute: This institute includes five research centers:

• Organ Transplantation and Repair Research Center
• Stem Cell Technology Research Center
• Neuroscience Research Center
• Autoimmune Diseases Research Center
• Hematology Research Center

Other Research and Treatment Centers: In addition to Royan, other centers such as the Jahad Daneshgahi Biotechnology Research Institute and the Avicenna Cellular and Molecular Research Institute are active in this field. These centers conduct research and treatment in areas such as cancer, blood disorders, heart diseases, and neurological disorders using stem cells.

Iran Cell and Gene Therapy Center: This center is a pioneer in cell and gene therapy and works on advanced projects using stem cells to treat genetic diseases and cancers, particularly blood cancers and neurological disorders.

Jahad Daneshgahi Institute of Advanced Biological Sciences: This institute is active in research and treatments related to stem cells and biotechnology, focusing on infertility, cardiovascular diseases, and neurological disorders.

National Institute of Genetic Engineering and Biotechnology: This institute, active in biotechnology, conducts extensive research on stem cell production and applications, particularly for treating genetic diseases and tissue regeneration.

Shahid Beheshti University of Medical Sciences Stem Cell Research Center: This center focuses on stem cell research and its therapeutic applications for heart diseases, neurological disorders, and cancers, particularly in regenerating damaged tissues and treating chronic diseases.

Shiraz University of Medical Sciences Neuroscience Research Center: This center focuses on neural stem cell research, aiming to use stem cells to treat neurological disorders such as Parkinson’s, Alzheimer’s, and spinal cord injuries.

Iran Diabetes Association: This association has been active in using stem cells to treat diabetes, with ongoing research on regenerating pancreatic tissues to treat type 1 diabetes.

Vice Presidency for Science and Technology: Additionally, the Vice Presidency for Science and Technology is planning to establish three new stem cell centers in three major regions of the country to expand research and services in this field.

In conclusion, various research and treatment centers in Iran have made significant strides in the field of stem cells, playing a crucial role in advancing modern treatments and utilizing this technology to treat various diseases. Iran is recognized as a leading country in the region in the field of stem cells and has achieved positive results through advanced research and infrastructure development. Approximately sixty research centers across the country are engaged in stem cell research.

Challenges and Future of Stem Cells in Iran: High Costs: Stem cell treatments remain expensive, with limited insurance coverage.

Regulations and Standards: There is a need to develop precise standards for stem cell research and treatment. Any stem cell-based treatment must be approved by the Ministry of Health and other relevant authorities.

Shortage of Specialized Personnel: Training specialized personnel in the field of stem cells is of great importance.

Ongoing Research: Many applications of stem cells are still in the research phase and require further studies.

Before deciding on any stem cell-based treatment, consultation with a specialist physician is essential.

Despite these challenges, the future of stem cells in Iran is highly promising. With recent advancements and the high potential of stem cells in treating various diseases, the future of this field in Iran is optimistic. With increased investment in research and development and support for research, even greater progress can be achieved.

Stem Cell Research in Iran Compared to Other Countries: The use of stem cells in Iran differs from other countries. In developed countries, stem cell research and clinical applications are more extensive due to access to greater financial resources and advanced technologies. However, Iran has made significant progress in this field and, in some cases, is keeping pace with developed countries.

Based on the above:

1. Iran is considered one of the leading countries in stem cell-based treatments.
2. Extensive research has been conducted in numerous research and academic centers in Iran in the field of cell therapy.
3. Stem cell-based treatments in Iran are offered as high-quality services at a lower cost compared to other countries.

Regarding the extent of stem cell use in Iran compared to other countries, it can be said that differences exist:

• Iran is recognized as an “attractive hub for stem cell-based treatments.”
• The cost of stem cell-based treatments in Iran is significantly lower than in other countries.
• The quality of cell therapy services in Iran is comparable to global standards but is offered at a lower cost.

Therefore, not only has medical use of stem cells been made in Iran, but the country has also made significant progress in this field and is even recognized as an attractive destination for stem cell-based treatments.

Although there are differences in technology and infrastructure compared to some developed countries, Iran holds a notable position in this field, with numerous applications of stem cells in treating diseases.

Factors Affecting Stem Cell Activities in Iran:

• Investment: Government and private sector investment in stem cell research and development has played a significant role in advancing this field.
• Specialized Personnel: Training specialized personnel in stem cells is a key challenge.
• Regulations and Standards: Developing precise standards for stem cell research and treatment is of great importance.

Contemporary Jurisprudence: Is it possible to achieve human simulation, rejuvenation, or immortality through advancements in stem cell technology?

Karimi-Nia: Based on current knowledge and technology, it is not possible to achieve complete human simulation in a way that includes consciousness, awareness, and individual experiences identical to the original person. Similarly, achieving absolute immortality through stem cell technology or any other technology remains in the realm of science fiction.

Human simulation, rejuvenation, or immortality through advancements in stem cell technology is a significant and complex topic in medical science and biotechnology, encompassing various scientific, ethical, and philosophical dimensions.

Scientific, Ethical, and Philosophical Dimensions of Simulation and Immortality: Human Simulation: Simulation refers to creating a genetically identical copy of an individual. Cloning living organisms, particularly mammals, has been somewhat successful. For example, cloning animals like Dolly the sheep has been achieved, but this does not mean that aging can be completely halted or humans can be made immortal.

Human cloning, due to ethical and legal challenges as well as biological complexities, is still in the research phase and is restricted or prohibited in many countries. Human cloning raises ethical concerns such as individual rights, identity, and social consequences.

To elaborate, the cloning process includes two main types:

1. Reproductive Cloning: Creating a complete human who is genetically identical to another individual. This type of cloning is prohibited in many countries due to ethical and legal concerns.
2. Therapeutic Cloning: Using stem cells to produce human tissues and organs for treating diseases. This type of cloning is under research and development and holds promise for treating various diseases in the future.

Rejuvenation and Immortality: Using stem cells for rejuvenation and extending lifespan is an active research area. Stem cell technology enables the rejuvenation of certain body tissues and the repair of damage caused by disease or aging. Through stem cells, scientists have been able to regenerate some tissues and organs in the body, indicating the potential to improve health and extend lifespan. However, achieving complete and permanent human rejuvenation is not yet definitively possible. Therefore, there is still a long way to go to achieve technologies capable of enabling full rejuvenation or immortality.

Immortality (Non-Death): Stem cell technology and other biological sciences can theoretically contribute to extending lifespan and preventing some diseases, but complete immortality is a complex concept that depends not only on technology but also on philosophical, spiritual, and ethical considerations. From a scientific perspective, there are numerous challenges in addressing natural processes of death, such as cell degradation and genetic factors, for which comprehensive solutions have not yet been developed.

Therefore, at present, “complete human simulation” and “immortality” through stem cell technology are not fully possible, but this technology is on a path of progress and could play a significant role in treating diseases and improving human health in the near future.

Challenges and Limitations of Simulation and Immortality Technology: Scientific and Technical Complexities: Many scientific aspects of these technologies remain unknown and require further research.

1. Difficulty in Cell Differentiation: Although stem cells have the potential to differentiate into various cell types in the body, precisely controlling the differentiation process to produce specific cell types (e.g., neural or cardiac cells) is challenging and may lead to unexpected outcomes.
2. Cell Culture and Maintenance: Growing and maintaining stem cells in laboratory settings requires highly precise and controlled conditions. Any flaws in this process can lead to issues such as cell contamination or failure in differentiation.

Ethical Challenges: Ethical issues related to human cloning and the use of stem cells remain a subject of extensive debate. There are concerns about the potential misuse of this technology.

1. Human Embryos: Obtaining stem cells from embryos (embryonic stem cells) has sparked ethical debates, as it requires the destruction of human embryos. Many individuals and groups believe this conflicts with the human rights of embryos.
2. Therapeutic Cloning: Some techniques used in stem cell research are related to cloning technologies, raising ethical concerns about the potential for human cloning and the misuse of this technology.

Legal and Regulatory Challenges: In general, stem cell research focuses on repairing damaged tissues and organs, not complete human simulation. Research is primarily centered on extending healthy lifespans and improving quality of life. Although significant advancements have been made in these areas, there remains a considerable distance to achieving technologies capable of fully enabling human simulation, rejuvenation, or immortality, and such claims are considered unscientific.

Various laws and regulations in different countries restrict the use of these technologies.

1. Restrictive Laws: In some countries, the use of embryonic stem cells is restricted or prohibited. Laws and regulations related to stem cell use vary due to ethical and cultural concerns, which can limit research progress.
2. Patents and Intellectual Property Rights: Intellectual property rights for stem cells, related techniques, and access to this technology for individuals and organizations also pose legal and commercial challenges.

Complexity of the Brain: The human brain is the most complex organ in the body, containing billions of interconnected neurons in a complex network. Creating a simulated brain with consciousness, memory, and personality is extremely challenging.

Environmental and Genetic Factors: Aging is influenced by multiple factors, including genetics, lifestyle, environment, and random factors. Therefore, even if the aging process of cells can be slowed, other factors will still affect lifespan.

Therapeutic Challenges:

1. Cancer Risk: Embryonic stem cells have the ability to differentiate into various cell types, but this characteristic can lead to uncontrolled cell growth, resulting in tumor formation and cancers. In some cases, stem cells may proliferate uncontrollably and form tumors.
2. Immune Rejection: In stem cell transplants, particularly embryonic or mesenchymal stem cells, the recipient’s immune system may identify these cells as foreign and reject them. This increases the need for immunosuppressive drugs, which have various side effects.

Research and Treatment Costs: Processes related to stem cell research and development are highly costly, and treatments based on these cells are expensive for patients. This makes access to such treatments challenging for all segments of society.

Long-Term Side Effects: Many stem cell-based treatments are still in early research stages, and the long-term effects of these treatments on the body and health are not yet fully understood. There are concerns about potential unforeseen issues in the long term.

Complexity of Regulating Production and Use: Standardization: One of the significant technical and legal challenges is standardizing the production and use of stem cells. Without clear and standardized protocols, stem cell-based treatments may yield varying results and quality across different treatment centers.

In general, although stem cell technology holds immense potential for treating various diseases and improving quality of life, scientific, ethical, legal, and financial challenges still prevent its widespread and complete application on a global scale.

Technical Challenges:

1. Precisely controlling the differentiation of stem cells into desired cell types is difficult.
2. There is a risk of tumor formation if undifferentiated stem cells are injected.
3. There is a possibility of the immune system rejecting transplanted stem cells.

[1]. For more information, you can refer to the following sources:

1. Websites of Universities of Medical Sciences: Many universities of medical sciences in Iran have websites that provide comprehensive information about stem cell research and treatments.
2. Umbilical Cord Blood Bank Websites: These websites provide information on the storage and applications of umbilical cord blood stem cells.
3. Scientific Articles: Articles published in reputable journals offer comprehensive information on the latest advancements in stem cell research.