1. Decellularized scaffolds for skin tissue engineering
School of Advanced
Technologies in medicine,
Tehran University of Medical Sciences
Decellularized scaffolds for skin tissue engineering
Prof. Jafar Ai
Dr. Somayeh Ebrahimi
Dr. Somayeh Ebrahimi

2. The skin is the largest organ in the human body.
It consists of about 10% of our body mass.
Dr. Somayeh Ebrahimi

3. The Anatomy of Human Skin
Epidermis (5 layers)
Keratinocytes provide protective properties.
Melanocytes provide pigmentation.
Langerhans’ cells help immune system.
Merkel cells provide sensory receptors.
Dermis (2 layers)
Collagen, glycoaminoglycans, elastine, ect.
Fibroblasts are principal cellular constituent.
Vascular structures, nerves, skin appendages.
Hypodermis (fatty layer)
Adipose tissue plus connective tissue.
Anchors skin to underlying tissues.
Shook absorber and insulator.
Dr. Somayeh Ebrahimi

4. Keratinocytes and Fibroblasts

5. Skin defects caused by burns, venous and diabetic ulcers, or acute injury occasionally induce life-threatening situations.
Many burned people die, their body couldn’t produce new skin
Dr. Somayeh Ebrahimi

6. Burn Classification Dr. Somayeh Ebrahimi
Skin defects can be divided based on their depth of injury as:
I) epidermal
II) superficial partial-thickness
III) deep partial-thickness and full-thickness skin wounds
Dr. Somayeh Ebrahimi

7. Skin Grafting Dr. Somayeh Ebrahimi
In the past, a burn victims only option for repair was a method known as a skin graph.
This requires doctors to surgically cut a piece of unburned skin from your body and place it on the burned area.
This can cause bleeding, infection, nerve damage, and in some cases, a repeat graph is required.
Dr. Somayeh Ebrahimi

8. Tissue engineering scaffolds Growth factors cells
Organ transplantation is an approach for the repair and replacement of unhealthy tissues or organs, but is often hindered by death of donor tissues/organs and immunological problems associated with infectious diseases.
scaffolds
Growth factors
cells

10. Decellularized scaffolds
The process of decellularization of a scaffold involves the discharge of cellular contents from the tissues or organs, retaining only the components of the native ECM.
The decellularized scaffolds can later be recellularized with suitable cells for the purpose of creating tissue-engineered grafts suitable for tissue/organ transplantation.

11. In addition, it can be tailor-made with all the characteristic features of an ideal scaffold, such as:
Biocompatibility
Biodegradability
Non-immunogenicity
and the ability to provide structural, mechanical, biochemical and biological cues for cell adhesion, proliferation, migration, differentiation and continued function, with a hope of potential clinical translation.
Therefore, the decellularized scaffold can be considered to be an attractive system for tissue engineering.

12. Current state of decellularization methodologies
Physicals
Chemicals
Enzymatic

13. Physical methods

14. Chemical methods Acids and bases Non-ionic detergents (Triton X-100)
Ionic detergents (SDS)
Zwitterionic detergents (CHAPS and SB-10/SB-16)
Tri(n-butyl)phosphate (TnBP)
Hypotonic and hypertonic treatments
Chelating agents
Alcohols and acetone

15. Enzymatic methods
Protease
Trypsin: cleaves peptide bonds on the C-side of Arg and Lys
Dispase: selectively cleaves specific peptides, mainly fibronectin and collagen IV
Nuclease
DNase
RNase
Lipase

16. Protease inhibitors
Protease inhibitors such as phenylmethylsulfonylfluoride (PMSF), Aprotonin, and Leupeptin
A buffered solution of pH 7–8 further inhibits many proteases
Control of temperature and time of exposure to the lysis solutions can also limit the activity of the proteases.

17. The advantages of decellularization
Minimizes immunological response upon implantation
Allows for the use of xenogeneic materials
Ability to conserve the mechanical integrity of native tissue
Ability to retain the biochemical composition of native tissue
Ability to retain the three-dimensional microarchitecture of native tissue
Retains the bio inductive properties (cryptic peptides) to facilitate tissue remodeling
Widely applicable and economical
Long-term storage capability
Potential for an off-the-shelf product

18. Small Intestine Sub-mucosal layer (SIS)
Reagents
SDS, TritonX-100, SDC, per-acetic acid
Decellularization method
Immersion, agitation, perfusion

20. Before processing
After processing

22. Recellularization
Tissue-engineered skin exists as cells grown in vitro and subsequently seeded onto a scaffold or some porous material which is then placed in vivo at the site of injury.

23. Process of Skin Engineering
Patient has a skin biopsy
The skin is then peeled and separated into the epidermis and dermis.
Keratinocytes and Fibroblasts are then isolated from one another.
Transferred into a culture on top
of a scaffold.
The final skin is finished after
about 3 to 4 weeks.

28. Towards the Future Dr. Somayeh Ebrahimi
Skin engineering still has much room to evolve.
More dermo-epidermal substitutes will be created that will speed the process and the wait time for the patient.
An increase of “off the shelf” dermal and epidermal substitutes will allow patients quick and easy access to repairing their burns or wounds.
A skin that includes sweat glands and hair follicles to help mimic real skin is also being created.
In the future, engineered skin will replace skin graphs as the predominant method for treating skin defects.
Dr. Somayeh Ebrahimi

29. Thanks for your attention
Dr. Somayeh Ebrahimi