What are Stem Cells?

Stem cells are unique cells with the potential to develop into many different cell types in the body during early life and growth. They serve as a sort of internal repair system, dividing essentially without limit to replenish other cells. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.

Where Can They Be Collected?

Stem cells can be derived from various sources:

Embryonic Stem Cells:
These are derived from embryos. Most embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro—in an in vitro fertilization clinic—and then donated for research purposes with informed consent of the donors.

Adult Stem Cells:
Found in small numbers in most adult tissues, such as bone marrow or fat. They have a more limited ability to give rise to various cells of the body.

Induced Pluripotent Stem Cells (iPSCs):
These are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.

History of Stem Cells

The history of stem cell therapies is one of a limited number of clinical applications despite vast therapeutic potential. Major breakthroughs in stem cell research have not yet enjoyed clinical success—all stem cell therapies, except hematopoietic stem cell transplantations, remain experimental. The increased risk of organ failure and neurodegenerative disease, associated with our ability to push the boundaries of life expectancy, comes an increased pressure to pioneer novel stem cell-based therapeutic approaches¹.

Ethics and Laws Around Stem Cells

The ethical debate around stem cell research, particularly embryonic stem cell research, is intense. The primary ethical concern is the destruction of preimplantation blastocysts to create new cell lines. This debate has led to restrictions on certain stem cell therapies, often in favor of less controversial cells, which might have worse outcomes for patients¹. In 2009, the International Stem Cell Banking Initiative (ISCBI) provided guidance on the best practices for the procurement, cell banking, testing, and distribution of human embryonic stem cell lines for research purposes

Types of Stems Cells

Based on Potency

Totipotent Stem Cells:

Can differentiate into all possible cell types.
Example: Zygote (the fertilized egg).

Pluripotent Stem Cells:

Can differentiate into almost all cell types.
Examples: Embryonic stem cells (ESCs), Induced pluripotent stem cells (iPSCs).

Multipotent Stem Cells:

Can differentiate into a closely related family of cells.
Examples: Hematopoietic stem cells (can become red and white blood cells or platelets), Mesenchymal stem cells (can become bone, cartilage, fat, or muscle cells).

Oligopotent Stem Cells:

Can differentiate into a few cell types.
Example: Lymphoid or myeloid stem cells (types of hematopoietic stem cells).

Unipotent Stem Cells:

Can produce only one cell type, but have the property of self-renewal.
Example: Muscle stem cells.

Based on Source:

Embryonic Stem Cells (ESCs):
Derived from the inner cell mass of blastocysts in developing embryos.

Adult (or Somatic) Stem Cells:
Found in various tissues in the body and can produce cells of their tissue of origin.
Examples: Hematopoietic stem cells, Neural stem cells, Mesenchymal stem cells.
Induced Pluripotent Stem Cells (iPSCs):
Adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.

Cord Blood Stem Cells:
Found in the blood of the umbilical cord and placenta.

Amniotic Stem Cells:
Found in the amniotic fluid.

Neural Stem Cells:
Found in the nervous system.

Mesenchymal Stem Cells:
Found in various tissues, including bone marrow, fat, and umbilical cord blood.

Hematopoietic Stem Cells:
Found in bone marrow and cord blood.

Epithelial Stem Cells:
Found in the lining of the digestive system and skin.

Fetal Stem Cells:
Taken from the tissue of a fetus.

Example: Skin Therapy

Injecting stem cells into the skin is a therapeutic approach that capitalizes on the regenerative potential of stem cells. Here's a breakdown of how and why this process works:

How It Works:

Stem Cell Harvesting:
The first step involves harvesting stem cells. Adipose-derived stem cells (ADSCs) are commonly used for skin treatments. These cells are extracted from the patient's own fat tissue, typically from areas like the abdomen or thighs, using a process called liposuction.

Stem Cell Processing:
Once harvested, the fat tissue is processed to isolate the stem cells. This involves breaking down the tissue and separating the stem cells from other cell types.

Stem Cell Activation (Optional):
In some cases, the isolated stem cells might be exposed to certain growth factors or conditions that 'activate' them, making them more potent or directing them towards a specific differentiation pathway.

Injection:
The isolated (and possibly activated) stem cells are then injected into the target area of the skin using fine needles. This could be areas of scarring, wrinkles, or other skin damage.

Why It Works:

Cell Differentiation:
Stem cells have the ability to differentiate into various cell types. When injected into the skin, they can potentially turn into skin cells, fibroblasts (cells that produce collagen), or other relevant cell types, aiding in tissue regeneration.

Paracrine Signaling:
Stem cells release growth factors and cytokines, which are signaling molecules that can stimulate the body's own repair mechanisms. These factors can promote angiogenesis (formation of new blood vessels), increase collagen production, and reduce inflammation, all of which are crucial for skin repair and rejuvenation.

Anti-inflammatory Effects:
Stem cells, especially mesenchymal stem cells, have anti-inflammatory properties. By reducing inflammation, they can promote a more conducive environment for healing and repair.

Stimulating Resident Stem Cells:
The injected stem cells can also stimulate the activity of the skin's own resident stem cells, further amplifying the repair process.

Collagen Production:
As the skin ages, collagen production decreases, leading to wrinkles and reduced skin elasticity. Stem cells can stimulate fibroblasts, the cells responsible for collagen production, leading to improved skin texture and elasticity.

Injecting stem cells into the skin leverages the cells' natural regenerative and signaling capabilities to repair damage, reduce signs of aging, and improve skin health. It's a minimally invasive procedure that taps into the body's own repair mechanisms. 

Studies

1. Skin Tissue Regeneration for Burn Injury

• Abstract: The skin, being the largest organ, is vulnerable to various damages, especially burn injuries. Tissue regeneration technology enhances skin repair through re-epidermalization, epidermal-stromal cell interactions, angiogenesis, and inhabitation of hypertrophic scars and keloids. The use of various skin substitutes has significantly increased the success rates of skin healing for burn injuries. The study reviews skin replacement with cells, growth factors, scaffolds, or cell-seeded scaffolds for skin tissue reconstruction.
• Reference: Skin tissue regeneration for burn injury by A. Shpichka et al.

2. Silk Fibroin Scaffolds Seeded with Wharton’s Jelly Mesenchymal Stem Cells for Cutaneous Wound Healing

• Abstract: The study investigated the wound healing effects of electrospun silk fibroin scaffolds cellularized with human Wharton’s jelly mesenchymal stem cells. The results indicated enhanced re-epithelialization of the wound and reduced formation of fibrotic scar tissue, highlighting the potential therapeutic effects of stem cell-based tissue engineering approaches to non-healing wound treatment.
• Reference: Silk fibroin scaffolds seeded with Wharton’s jelly mesenchymal stem cells by J. E. Millán-Rivero et al.

3. Hair Regeneration Therapy Using Proteins Secreted by Adipose-Derived Stem Cells

• Abstract: Adipose-derived stem cells (ADSCs) secrete cytokines essential for hair growth. The study introduced a new therapy with ADSC conditioned medium (ADSC-CM) for hair growth treatment. The therapy does not require specialized facilities and can be a valuable treatment for hair regeneration.
• Reference: The Latest Advance in Hair Regeneration Therapy Using Proteins Secreted by Adipose-Derived Stem Cells by H. Fukuoka et al.

4. Adipose-Derived Stem Cells for Skin Regeneration

• Abstract: Intractable skin ulcers resulting from various conditions represent significant challenges. Cell-based therapy using adipose-derived stem cells (ASCs) may provide solutions for such disorders. The study suggests that ASCs may have a positive effect on wound healing and can be a useful tool for future cell-based therapy.
• Reference: Adipose-derived stem cells for skin regeneration by H. Mizuno and Masaki Nambu.

References

Stem Cells and Skin:

1. J. Poulos. The limited application of stem cells in medicine: a review. Link

2. International Stem Cell Banking Initiative (ISCBI). Points to consider in the development of seed stocks of pluripotent stem cells for clinical applications. Link

3. G. Fischbach and R. Fischbach. Amendment history: Corrigendum (December 2004) Stem cells: science, policy, and ethics.

Application of Stem Cells in Skin Therapy:

4. A. Shpichka et al. Skin tissue regeneration for burn injury. Link

5. J. E. Millán-Rivero et al. Silk fibroin scaffolds seeded with Wharton’s jelly mesenchymal stem cells. Link

6. H. Fukuoka et al. The Latest Advance in Hair Regeneration Therapy Using Proteins Secreted by Adipose-Derived Stem Cells.

7. H. Mizuno and Masaki Nambu. Adipose-derived stem cells for skin regeneration.

8. Q. Shi et al. Exosomes from oral tissue stem cells: biological effects and applications. Link

9. Xiaoyan Wang et al. Bone marrow mesenchymal stem cells increase skin regeneration efficiency in skin and soft tissue expansion.

10. Lixing Zhang et al. Novel pneumatically assisted atomization device for living cell delivery: application of sprayed mesenchymal stem cells for skin regeneration. Link

11. Leyla Norouzi-Barough et al. Therapeutic potential of mesenchymal stem cell-derived exosomes. Link

12. S. Choudhury et al. Recent advances in the induced pluripotent stem cell-based skin regeneration. Link

13. Yizhou Huang et al. Urine-Derived Stem Cells for Regenerative Medicine: Basic Biology, Applications, and Challenges. Link

14. Chunyi Li. Antler Stem Cells Sustain Regenerative Wound Healing in Deer and in Rats. Link

15. Araiz Ali and J. Gupta. Applications of Stem Cell Therapy and Adipose-Derived Stem Cells for Skin Repair. Link

Injecting Stem Cells into Skin:

16. Jae-Hong Kim et al. Adipose-derived stem cells as a new therapeutic modality for ageing skin. Link

17. Y. Kuo et al. Adipose-Derived Stem Cells Accelerate Diabetic Wound Healing. Link

18. E. Raposio et al. Adipose-Derived Stem Cells Added to Platelet-rich Plasma for Chronic Skin Ulcer Therapy. Link

19. G. Gauglitz and M. Jeschke. Combined gene and stem cell therapy for cutaneous wound healing. Link