Dr B.R.Prashanth
(Author can be contacted on ph: 9845511760 / 4288217, e mail:
orthoprash@yahoo.co.uk)
Stem Cells and Orthopaedics
Stem cells are basic human cells that have potential to give rise to many different
cell types in the body. They are simple or undifferentiated cells.
Stem cells help to create new cells in existing healthy tissues and may help to repair
tissues in those structures that are injured or damaged. They are the basis for the
specific cell types that makes up each organ in the body.
When stem cells divide they create progenitor cells. Unlike stem cells, progenitor
cells can become cells with more specialized functions, such as brain cells, red
blood cells or - of particular interest to orthopaedic surgeons—components of
specialized tissue such as bone or cartilage.
Orthopaedic surgeons have focused their attention on mesenchymal stem cells.
Unlike embryonal stem cells, mesenchymal stem cells are obtained from living adult
tissue.
Bone marrow stromal cells are mesenchymal stem cells that, in the proper
environment, can differentiate into cells that are part of the musculoskeletal system.
They can help to form trabecular bone, tendon, articular cartilage, ligaments and part
of the bone marrow.
Stem cell procedures are being used for treating bone fractures and nonunions,
regenerating articular cartilage in arthritic joints (Hip and knee arthritis), healing
ligaments or tendons, and replacing degenerative vertebral disks.
Stem Cells: Frequently Asked Questions
What are stem cells?
Stem cells help to create new cells in existing healthy tissues, and may help repair
tissues in areas that are injured or damaged. They are the basis for the specific cell
types that make up each organ in the body.
Stem cells are distinguished from other cells by a few important characteristics: they
have the ability to self-renew; they have the ability to divide for a long period of time;
and, under certain conditions, they can be induced to differentiate into specialized
cells with distinct functions (phenotypes) including, but not limited to, cardiac cells,
liver cells, fat cells, bone cells, cartilage cells, nerve cells, and connective tissue
cells. What clinicians learn about controlling stem cell differentiation can become the
basis for new treatments of many serious diseases and injuries.
What types of stem cells exist?
Doctors and Scientists primarily work with two main types of stem cells: adult stem
cells and embryonic stem cells. Adult stem cells are used in research for orthopaedic
conditions.
Adult stem cells are more tissue-specific and are therefore more useful to
orthopaedic surgeons who are attempting to repair bone, muscle, and cartilage.
Orthopaedic surgeons who use cell therapy typically work with adult stem cells.
The most common (and probably the most studied) source for adult stem cells is the
bone marrow, which contains two types: hematopoietic (blood forming cells) and
mesenchymal stem cells. Of particular interest in orthopaedics are bone marrow
stromal cells. These are mesenchymal stem cells that, in the proper environment,
can differentiate into cells that are part of the musculoskeletal system. They can help
to form trabecular bone, tendon, articular cartilage, ligaments, and part of the bone
marrow.
Researchers in the last 10 years have reported the presence of adult stem cells in
several other tissues aside from bone marrow, including the brain, hair follicles,
dental pulp, skin, liver, skeletal muscle, blood vessel walls, pancreas, and intestine.
How are adult stem cells obtained?
Adult stem cells are most commonly obtained from the outside part of the pelvis,
the iliac crest. A needle is inserted in the iliac bone and bone marrow is withdrawn
or aspirated through the needle. Several samples may be obtained from one area in
this manner.
The stem cells may then be separated from other cells in the marrow and grown or
expanded in the laboratory. This may take from 7 to 21 days.
When stem cells are placed in a specific tissue environment, such as bone, they
become activated. As they divide, they create new stem cells and second
generation, progenitor cells. It is the progenitor cells which may differentiate into
newer cells with the same phenotype as the host tissue.
What potential uses do researchers think stem cells have?
Stem cell researchers are hopeful that, in the future, a wide range of diseases and
traumatic injuries will be cured by some application of cell therapy using stem cells.
Currently, donated organs and tissues are used to replace lost or damaged tissue in
many disorders. The great regenerative potential of stem cells has created intense
research involving experiments aimed at replacing tissues to treat Parkinson's and
Alzheimer's diseases, osteoarthritis, rheumatoid arthritis, spinal cord injury, stroke,
burns, heart disease, and diabetes.
While some success has been achieved with laboratory animals, a number of
successful trials have been conducted on humans. These, however, have shown the
great potential for stem cells.
Another reason why stem cell biologists are excited about this field is that human
stem cells could also be used to test new drugs.
What are some examples of musculoskeletal treatments using stem
cells?
At this point, most musculoskeletal treatments using stem cells are performed at
centers as part of controlled clinical trials. Stem cell procedures are being developed
to treat bone fractures and nonunions, regenerate articular cartilage in arthritic joints,
and heal ligaments or tendons. These are detailed below.
Bone fractures and nonunions: In bone, progenitor cells may give rise to
osteoblasts, which become mature bone cells, or osteocytes. Osteocytes are the
living cells in mature bone tissue. Stem cells may stimulate bone growth and
promote healing of injured bone.
Traditionally, bone defects have been treated with solid bone graft material placed at
the site of the fracture or nonunion. Stem cells and progenitor cells are now placed
along with the bone graft to stimulate and speed the healing.
Articular cartilage: The lining of joints is called the articular cartilage. Damage to
the articular cartilage can frequently lead to degeneration of the joint and painful
arthritis. Current techniques to treat articular cartilage damage use grafting and
transplantation of cartilage to fill the defects. However, those stem cells will create
growth of primary hyaline cartilage to restore the normal joint surface and this
technique has been used in patients for Arthritis.
Ligaments and tendons: Mesenchymal stem cells may also develop into cells that
are specific for connective tissue. This would allow faster healing of ligament and
tendon injuries, such as quadriceps or Achilles tendon ruptures. In this instance,
stem cells would be included as part of a primary repair process.
Are there any musculoskeletal treatment success stories utilizing
stem cells?
A novel stem cells-based technique for regeneration of damaged cartilage, useful in
the treatment of arthritis, has been popularised by Orthopaedic Surgeons from
United Kingdom, in partnership with Surgeons from South Korea. This is performed
as a key hole Surgery and the specially-made gel would be used for putting the stem
cells in the damaged part during the minimally invasive procedure. This new
technique is FDA-approved and could be effective in young and middle aged
patients when the arthritis is in initial stages. This procedure has been performed on
several hundred patients with promising results and is cost effective compared to
Joint Replacement.
What are some treatments on the horizon (5 to 10 yrs from now)?
Stem cells for cell therapies are still in the experimental phases for several diseases,
conditions, and disabilities, including Type 1 diabetes (diabetes mellitus); Parkinson's
and Alzheimer's diseases; muscle disorders, including dystrophies like Duchenne
and Becker; multiple sclerosis; spinal cord injuries; ischemic brain strokes; burns;
and heart ailments. Moreover, cancer therapy and detection is likely to be
revolutionized by advances and greater understanding gained through stem cell
science.
It is expected, however, that as more knowledge of tissue engineering is obtained,
stem cell procedures will become more common in the near future.