HEMATOPOIETIC STEM CELL TRANSPLANTATION :-
This process now known as stem cell transplantation.
Stem cells are responsible for production of white blood cells, RBCs and Platelets.
Stem cells also circulate in blood in small amount PBSCT (Peripheral stem cell transplantation).
SOURCES OF STEM CELLS
1. Bone marrow :-
- stem cells can be collected from bone marrow of a donor.
- This process require general anaesthesia so cells can be harvested / collected by multiple needle puncture.
Sites for bone marrow aspiration
- Posterior iliac crest (adult)
- Tibia (children)
2.Peripheral blood :- Stem cells can be found in blood in very small ammount.
- Following chemotherapy bone marrow is stimulated and stem cells leave the bone marrow and enter into the peripheral blood.
- These cells can be collected by a special harvesting technique known as Apheresis.
- Growth factor is also given to increase stem cells.
3.Placenta or umbilical cord blood :-
- Umbilical cord blood is a rich source of stem cells.
- The cells can be extracted from the cord after delivery and preserve for permanent and can be a source of stem cells.
- This process don't represent a risk to baby or mother.
TYPES BASED ON SOURCE OF DONOR CELLS :
1. Allogenic HSCT :- From a donor other than the patient.
2. Autologus :- From the patient
3. Syngenic :- From an identical twins
1.AlloHSCTs are used primarily for diseases of the bone marrow and are dependent on the availability of a human leukocyte antigen-matched donor.
AlloHSCT may involve either myeloablative (high dose) or nonmyeloablative( mini transplant).
Ablative AlloHSCT :-
- The recipient receives high doses of chemotherapy and possibly total-body irradiation to completely eradicate (ablate) the bone marrow and any malignant cells and help prevent rejection of the donor stem cells.
- The collected HSCS that are infused IV into the recipients travel to sites in the body where they produce bone marrow and establish themselves through the process of engraftment.
- Once engraftment is complete (2 to 4 weeks, sometimes longer), the new bone marrow becomes functional and begins producing RBCs, WBCs and platelets.
Nonablative AlloHSCT
The chemotherapy doses are lower and are aimed at destroying malignant cells (without completely eradicating the bone marrow), thus suppressing the recipient's immune system to allow engraftment of donor stem cells.
2. Autologus HSCT :-
3.Syngenic transplant :- Syngeneic transplants result in less incidence of GVHD and graft rejection.
There is also less graft-versus-tumor effect to fight the malignancy.
Syngeneic transplant is associated with transmission of genetic defects.
For this reason, even when an identical twin is available for marrow donation, another matched sibling or even an unrelated donor may be the most suitable donor to combat an aggressive malignancy.
PROCESS OF BONE MARROW TRANSPLANTATION :-
Stem cells are administered same as Blood transfusion through a central catheter.
Stem cell can be given IV infusion.
Engraftment When stem cells move from blood to patients bone is known as engraftments.
It will takes several weeks ( 2-6 weeks)
Engraftment sign :-
- Increase number of blood cells ( WBCs, RBCs, Platelets).
COMPLICATIONS :-
1. Graft Failure
2.Graft vs host disease (GVHD) :-
Occurs with allogenic transplant
In this stem cell transfused form a new immune system and see patients Body as foreign body and attack on patients body.
3.Veno occlusive disease ( Hepatic sinosoidal obstruction syndrome) occurs related to chemotherapy induced inflammmation of sinusoidal epithelium.
Inflammation causes embolization of RBCs, resulting in destruction, fibrosis and occlusion of sinusoids.
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