INTRODUCTION
Regenerative medicine has potential to solve the problem associated with the transplant medicine.

BASIS OF REGENERATIVE MEDICINE
Stem cells are unprogrammed cells in the human body that can continue dividing forever and can change into other types of cells .

Where It Starts
In 1993, Joseph Vacanti and Robert Langer proposed the concept of the creation of artificial organs or tissues. It help in repair, replace, restore and regenerate damaged or diseased cells, tissues and organs.

SOURCES OF STEM CELLS
6-7 days old embryo, Bone marrow, Skeleton muscles, Retina, Epithelial tissues.
Brain, Blood and heart.

USE OF
BONE MARROW STEM CELLS
In vitro generation of functional dopamine producing cells from adult bone marrow stem cells needed for therapy of Parkinson's.Adult stem cells could be used to treat deaf patients in the future.Using a potion of growth factors and other nutrients, scientists have shown in the laboratory they are able to convert adult human bone marrow stem cells into adult brain.Scientists have created a system in rodent models that duplicates neurogenesis i.e. the process of generating new brain cells in a dish.

EPIDERMAL STEM CELLS
The epidermis is made up of stratified squamous epithelium, which consists mostly of cells called keratinocytes.The development and growth of keratinocytes starts at the basal cell layer.The top layer is made up flat, dead "squamous" cells that are constantly being sloughed off.Used for treatment of burns, ulcers and regeneration of epidermis.

HAIR FOLLICLE STEM CELLS
Stem cells taken from hair follicles may be used to restore nerve damage.Protein marker called Nestin, which is present in neural stem cells, is also present in hair follicle stem cells.Stem cells taken from hair follicle can differentiate into blood vessels and neural tissue after being transplanted to a layer of skin in the mice.When implanted into a region of a severed sciatic or tibial nerve in the mice's leg, greatly enhanced the rate of nerve regeneration and the restoration of nerve function.


CLINICAL APPLICATIONS OF EPIDERMAL STEM CELLS
Cultured human skin has been used as a source of new skin .
In tissue bioengineering and for the treatment of damaged corneal surfaces.
Used in stimulation of wound healing in chronic leg ulcers, cosmetic epidermal regeneration, and autologous epidermal grafts in the treatment of vitiligo.
Has proven beneficial in producing the therapeutic gene that could cure genetic skin defects.

NEURAL STEM CELLS
The spinal cord can be injured in four general ways: cord maceration, cord laceration, contusion injury and solid cord injury.
The adult nervous system is unable to repair itself following spinal injury.
Stem cells are present within the spinal cord but migrate away from the lesion.
Researchers identified netrin-1 as the key molecule responsible for this migratory pattern of stem cells following injury.
Netrin-1 acts as a repulsive or attractive signal, guiding nerve cells to their proper targets.
Adult stem cells remain at the injury site if we block netrin-1.


RENAL STEM CELLS
The kidney has a dramatic capacity to regenerate after acute injury.
Surviving renal epithelial cells after injury become dedifferentiated and take on mesenchymal characteristics.A minority of surviving intratubular cells possess stem cell properties and selectively proliferate after damage to neighboring cells.
Recent evidence suggests that interstitial cells may represent another extratubular stem cell niche.


CARDIAC STEM CELLS

When human heart muscle cells derived from embryonic stem cells are implanted into a rat after a heart attack, they can help rebuild the animal's heart muscle and improve function of the organ.
Cartilage and bone regeneration by transgene - activated adult stem cells.
Cartilage lesions and large bone defects due to trauma, tumor resections, osteonecrosis or diseases such as osteoarthritis or rheumatoid arthritis have remained great clinical hurdles.
Developed a novel therapeutic strategy: the transplantation of mesenchymal stem cells stimulated by differentiation factor gene transfer.
Demonstrated that chondrogenesis and new bone formation can be induced by application of bone morphogenetic proteins.

HEMATOPOIETIC STEM CELLS
The premier adult stem cells. Ability to self-renew continuously in the marrow.
Differentiate into the full complement of cell types found in blood .HSCs are among the few stem cells to be isolated in adult humans.HSCs are plastic .

PROBLEMS WITH HSCs
Relative rarity of about one in every 10,000 bone marrow cells.
Difficulty of separating them from other components of the blood.
Histocompatibility.
It has not been possible to culture HSCs in vitro (outside the body).

UMBILICAL OR CORD BLOOD CELLS
Stem cells from umbilical cord blood are "younger" stem cells than those obtained from adult bone marrow.They have higher potential for changing into different types of cells. Less immunological and therefore might be suited to use in foreigners.
Used for stem cell transplantation to reconstitute blood cell formation (the hematopoietic system) in patients.Transplants derived from umbilical cord blood are less likely to provoke graft versus host disease.

PROBLEMS WITH ESCs
• One of the difficulties specific to embryonic stem cells is their propensity to form tumors.
• Questions of how to generate functional differentiated cells.
• How to solve immune rejection issues.
• Development of practical applications lags behind adult stem cells.

ESCs OR MSCs?
• Embryonic stem cells are capable of becoming all of the cell types of the body, adult stem cells may be more limited.
• Adult stem cells can also be difficult to isolate and grow.
• Adult stem cells however do have some important scientific advantages as potential therapies.
• Adult stem cells can be taken from the patient's own tissue, and would not be rejected by that patient's own immune system.Embryonic stem cell research is still in its infancy.

CONCLUSION
Regenerative medicine is a broad definition for innovative medical therapies that will enable the body to repair, replace, restore and regenerate damaged or diseased cells, tissues and organs.A stem cell is a cell (either adult or embryonic) that is capable of indefinite renewal through cell division and retention of its generic or unspecialized state while at the same time maintaining its potential to give rise to daughter cells of a more specialized type.Pluripotent stem cells are highly versatile cells and can give rise to any specialized cell type in the body except those needed to develop a fetus.Multipotent stem cells can give rise to several specialized daughter cells but are limited to the particular tissue, organ or physiological system of origin.Its potential to treat various human ailments has been recognized and currently clinical trials are being conducted to test its suitability for transplantation into human beings.

About Author / Additional Info:
I am MTech biotech . with interest in biotech market analysis and stem cell study. Rm