Stem cell transplant is a medical procedure in which the injured or destroyed cells in the body are replaced with healthy stem cells.¹ It is a complicated non-surgical procedure divided into different steps.

Now, the question arises what is stem cell?

Stem cells are a unique type of cells, found in tissues of the body that have the characteristic of regeneration and self-renewal in the same or different kinds of cells.² There are various types of stem cells, based on their origin, that are used in the maintenance and repair of tissues.

Sources of stem cells

As mentioned, stem cells are present throughout the body, and based on their origin they are divided into the following types:

• Embryonic stem cells - these stem cells are found in the cell mass of an embryo and can be differentiated into all types of tissues
• Adult stem cells - they are found throughout the body parts and can produce at least one kind of healthy tissue³
• Hematopoietic stem cells - are collected from bone marrow, peripheral stem cells, and the umbilical cord. Most commonly used transplant cells treating major conditions⁴
• Perinatal stem cells
• Mesenchymal stem cells

The stem cell transplant is a five-step process 

• Tests & examination - it includes general tests like ECG, X-ray, and Blood tests to ensure that the patient is healthy to undergo transplantation
• Harvesting - it is a process of collecting stem cells that will be used in transplant, various sources of stem cell harvesting are mentioned in the article
• Conditioning treatment - the patient undergoes chemotherapy or radiotherapy to destroy existing cancer cells or damaged cells
• Transplant - after the conditioning treatment is finished, the stem cells are transplanted into the body through a tube called a central line
• Recovery - the patient needs weeks to recover after undergoing transplantation⁵

Conditions treated by stem cell therapy

Stem cell transplant has been used as a treatment strategy for decades, it has shown significance in treating: 

• Liver disease - it includes, hepatitis B, C, liver cirrhosis, and alcoholic liver disease
• Heart dysfunction- cardiac function in humans
• Cancers
• Neural regeneration - treatment of degenerative brain cells like Alzheimer's, Parkinson's disease, etc
• Inflammatory bowel disease
• Osteoarticular disease - can improve bone health by increasing bone regenerationAutoimmune disease
• Lung disease - cystic fibrosis, pneumonia
• Renal disease³

Types of stem cell transplant

Following are different stem cell transplants:

• Autologous stem cell transplant- the stem cells are collected from the patient and transplanted later
  • This transplant decreases the chance of complications and immune rejection
• Allogenic stem cell transplant- cells are collected from donors who may be related to the patient
  • In this, the donor's immune system helps eliminate disease 
  • Transplantation with a related donor has shown a positive effect in conditions where bone marrow transplant failed, leukaemia conditions, selected myeloma, and lymphoma patients
  • Unrelated donors are mainly used in immunodeficiency condition⁶
• Syngeneic stem cell transplant- this transplant is done by using stem cells derived from the patient's identical twins⁷

Stem cell sources

• Bone marrow - Bone marrow stem cells were the first stem cells to be collected and the most widely used therapy in treating cancer some benign conditions, and hereditary conditions⁴
• Peripheral blood stem cell - the stem cells are derived from the blood of the patient or an unrelated donor and given to the patient to replace or destroy damaged stem cells⁸
• Umbilical cord - Developed during pregnancy, stem cells can be harvested from different umbilical cord parts
  • Wharton's jelly - most used part for stem cell collection 
  • Cord lining - cells are used in treating corneal epithelial defects, burns,s and ulcer healing⁴

Preparation of stem cell transplant

Before starting the stem cell process, the patient undergoes pre-transplant evaluation, and various tests and exams are conducted to check the general health of the patient. The person needs to be in good health for the successful transplantation. Tests conducted are ECG, X-ray, blood tests, biopsy, and a test for the patient’s psychosocial condition.

Conditioning regimen

A person undergoes chemotherapy or radiation to destroy cancer cells and reduce the risk of transplant rejection. In the conditioning regimen, a range of medications is given through a tube attached to a vein near the heart. This procedure lasts two weeks and the patient may feel some temporary side effects like sickness, hair loss, and tiredness.

Transplant procedure

The transplant process is a non-surgical procedure that requires a day or more to be completed after the success of conditioning.it is a painless process in which the stem cells collected are slowly passed into the body through an IV tube. After stem cell transfusion is completed, the body needs weeks to make new blood cells, and for that, the patient is advised to stay in the hospital.⁵

Recovery and long-term care

Short term recovery

A month of hospital stay is important so that the stem cells start producing new healthy cells and observe any major side effects or infections.

Below are some conditions that the patient undergoes. Some side effects that are normal and temporary include:

• Tiredness
• Loss of appetite
• Vomiting

To prevent malnutrition, constant IV fluids are given. A person undergoes regular platelet and blood transfusions. If the person has a chance of infection, the hospital stay can be increased by a month or two.

Long term follow-up

The patient is obliged to visit the clinic for regular checkups for a year, to prevent any future complications and risks. The patient needs to be careful to not develop any infection. If the person develops an infection, they need to be hospitalized immediately and the hospital stay can last up to a year.

Risks and complications 

Short term complications

After completion of the transplant process, a patient faces depression, fatigue, limited physical activity, and undergoes heavy medications that last for 6 months to a year. There is a chance of infection that can affect the person's health.

Long term risks

One of the long-term risks after transplants through the allogenic method is GVHD (Graft-versus-host-disease). It is a condition that occurs when the donor immune system (graft) when transplanted into the recipient (host) body considers the host as foreign and attacks the host. GVHD is a major cause of mortality after transplantation, according to a study 30-70% of patients can face acute GVHD while 20-50% face chronic GVHD that affects different parts of the body.⁹ Constant follow-up and screening are important to prevent GVHD and other complications that can occur after a transplant. 

Future direction

Stem cell transplants are currently used for treating disorders related to bone marrow, blood diseases, multiple sclerosis, cancer, and many more. Stem cells have more potential that needs to be studied further and experimented. 

Stem cells in gene editing

Gene-edited stem cells can be used to treat hereditary disorders and genetic diseases. More studies and trials are required to understand gene editing in stem cell therapy.

Stem cells for autoimmune disease treatment

Stem cells have the potential to treat autoimmune diseases including AIDS, type 1 diabetes, rheumatoid arthritis, and multiple sclerosis, but it needs concentrated studies and clinical trials to test this.

Regenerative medicines

Stem cells can be used in replacing damaged tissues or organs with healthy cells which can be a treatment for heart diseases, Parkinson's' disease, spinal cord injury, and more.

Personalised medicine

Harvesting stem cells from patients can lead to unlimited personalised cells for treatment, it can be custom-made treatments that will reduce the risk of stem cell rejection. 

Tissue engineering

Tissue engineering can lead to more precise and effective treatment.

Artificial organs and body parts

In the future, there might be a possibility of creating artificial body parts using stem cells, but a lot more studies and experiments are needed to test this.¹⁰

Summary

Stem cells are unique cells that have the power to regenerate and renew in any tissue and body organs based on the tissue they originated in, they are divided into different types. The most common types of stem cells used in transplants are mesenchymal stem cells and hematopoietic stem cells. 

Stem cell transplants are expensive and painless non-surgical procedures that are conducted in different steps starting from normal tests and completing after transplant. The transplant is a 2-day process that needs 2-3 weeks of hospital stay for the stem cells to regenerate into new blood cells. The person needs a year-long recovery time. A few complications can be observed in the person which might be temporary or long-term conditions like GVHD, that needs proper observation and medications. 

To reduce the chance of any post-transplant risks it is important to undergo regular checkups, screening, and immediate hospitalisation after a confirmed infection. Stem cell transplant in the modern medical field has paramount importance in treating several chronic conditions like cancer, lymphoma, myeloma, sclerosis, Crohn's disease, lung disease and many more.

Many more potentials of stem cells need to be studied and clinical trials must be conducted to find more therapeutic effects of stem cells. Understanding stem cells might open new doors in treating incurable diseases and disorders, it can help maintain the quality of life of patients.