Stem cells are the cells that play an essential role in the regeneration and development of all tissues and organs of the human body throughout our lives. Stem cells can multiply, divide and differentiate into different types of cells. The most important feature that distinguishes the stem cell from other cells is their limitless capacity for self-renewal, in other words, their ability to replicate and generate more of the same stem cells. Each system and organ in human body has a stem cell. The main cell that gives rise to the formed elements of the blood is called “Hematopoietic (blood-forming) Stem Cell’. Hematopoietic stem cells (HSCs) are produced in the bone marrow. Depending on the need within the body, they form new stem cells like themselves or they differentiate into precursor cells of blood with different functions such as red blood cells, platelets, and lymphocytes according to the body's needs.

Hematopoietic Stem Cell / Bone Marrow Transplantation in Children

Childhood is the period of the life cycle that covers the first 18 years after birth. Unlike adults, inherited (genetic) disorders represent an important group of childhood diseases. In our country, where consanguineous marriage is frequent, the incident rate of inherited diseases is high. A significant part of these life-threatening diseases that affect different systems and organs can only be cured with hemato poietic stem cell transplantation

What Are The Sources of Hematopoietic Stem Cells?

There are three resources of hematopoietic stem cells;

• Bone Marrow

Hücre kaynağı olarak kemik iliği tercih edilmiş ise, hücre toplama işi ameliyathanede genel veya epidural anestezi altında gerçekleştirilir. Çocuk vericilerde genel anestezi tercih edilir.

• Umbilical Cord Blood

It is a ready to use source of stem cells as it is collected at birth and stored under appropriate conditions. The main disadvantage of cord blood is its limited volume and the quantity of stem cells within. As the quantity of cells often aren’t enough for adults and adolescents, the umbilical cord blood is mostly used for pediatric patients.

• Peripheral Blood (Blood circulating in the veins)

Periferik kanda dolaşan kök hücrelerin miktarı kemik iliğine göre azdır. Bu nedenle kök hücre kaynağı olarak periferik kök hücre tercih edilmiş ise hücrelerin miktarını artırmak için 5 gün süre ile hastaya veya vericiye cilt altına (bir iğne ile) ilaç verilir. Beşinci gün hasta veya verici bir makinaya bağlanır. Sayıca artmış olan kök hücreler özel torbalara toplanır.

What are the Types of Hematopoietic Stem Cell / Bone 
Marrow Transplantation?

Which Diseases Can Be Treated With Hematopoietic Stem 
Cell Transplantation?

A large number of inherited or non-inherited diseases in children can be treated with hematopoietic stem cell transplantation.

Hematologic Malignencies

• Acute Lymphoblastic Leukemia 
• Acute Myeloblastic Leukemia 
• Chronic Myeloid Leukemia 
• Juvenile Myelomonocytic Leukemia 
• Myelodysplastic Syndrome
•  Non-Hodgkin Lymphoma 
• Hodgkin Lymphoma

Primary Immunodeficiency Disorders (Inherited Immune System Failure)

• Severe Combined Immunodeficiency (SCID)
•  Adenosine Deaminase Deficiency
•  Zap-70 Deficiency
• Omenn Syndrome
•  Chediak - Higashi Syndrome
•  Wiskott - Aldrich Syndrome
•  Di George Syndrome
•  IPEX Syndrome
•  Autoimmune Lymphoproliferative Syndrome (ALPS)
•  Chronic Granulomatous Disease

 Other Genetic (Inherited) Diseases

• Thalassemia Major
• Sickle Cell Anemia
• Fanconi Aplastic Anemia
•  Diamond - Blackfan Anemia
• Primary Hemophagocytic Lymphohistiocytosis
• Congenital Dyserythropoietic Anemia
• Kostmann Disease

 Bone Marrow Failure (Hematopoietic Stem Cell Defect)

•  Acquired Aplastic Anemia
• Hereditary Aplastic Anemia
   - Dyskeratosis Congenita
   - Shwachman - Diamond Syndrome
   - Amegakaryocytic thrombocytopenia
• Paroxysmal Nocturnal Hemoglobinuria

Autoimmune Diseases (Patients Who Failed Standard Therapy)

• Crohn's Disease
• Systemic Lupus Erythematosus (SLE)
• Rheumatoid Arthritis
• Evans Syndrome
• Autoimmune Hemolytic Anemia

 Metabolic Disorders 

• Wolman Disease 
• Mannosidosis Disease 
• Mucopolysaccharidosis 
• Leukodystrophies

          -Adrenoleucodystrophy (ALD) 
           -Metachromatic leukodystrophy (MLD) 
           -Globoid Cell Leukodystrophy (Krabbe)

• Osteopetrosis (Metabolic Bone Disease) 

 Solid Tumors (Autologous stem cell transplant recommended)

• Neuroblastoma 
• Ewing Sarcoma 
• Brain Tumors 
• Wilms' Tumor 
• Retinoblastoma 
• Germ Cell Tumors 
• Mesothelial and Soft Tissue Neoplasms

Donor Selection for Allogeneic HSC Transplantation

The main barrier that limits the application of stem cell transplantation is the patient lacking an HLA-identical (tissue-match) stem cell donor. The monozygotic twins and the siblings who share the same genetic inheritance are considered as HLA-identical (HLA-match). Hematopoietic stem cell transplantation is a multidisciplinary treatment used to cure life-threatening diseases that do not respond to standard therapies. Adult patients and the legal guardians (mostly parents) of pediat ric patients are informed on the cause, timing, potential outcomes, short and long-term risks of this treatment both in verbal and written terms for their approval. Following the approval, the type of transplantation, stem cell source and the donor are determined. Then the patient and the donor are prepared for the transplantation.

Because the patient’s immune system is suppressed, he/she is transferred to a strictly sterilized special unit that has the same qualifications with an intensive care unit. In order to minimize the risk of infection patient visits are forbidden. Neither the devices used in this unit are let out nor any devices from other units are accepted. HLA-identical sibling is the optimal donor for allogeneic HSC transplantation. With the support of technology, knowledge and experience, transplantation can be performed by using partially compatible related donors, if the patient lacks an HLA-identical sibling as a donor. Patients who do not have any suitable related donor, may find an matched unrelated donor in Turkey National Donor Registry and The World Bone Marrow Donor Registry (BMDW). In both institutions, the records of HLA phenotypes of volunteer stem cell donors and cord blood units are monitored and when a match donor is found, transplantation is performed.

How is Stem Cell Transplantation Performed?