![1. Resorbable polymers are used which are hydrolysed and then
phagocytosed, the greatest advantage of such material is their easy
and cheap production in a controllable & reproducible manner at
large scale.
2. Less compatibility than natural polymers
3. Synthetic polymers used are PGA [poly(glycolic acid)],
PLA[Poly(l-lactic acid)], polycarbonate, polycaprolactone.
4. PLA, PGA and PLGA[poly(lactic-co-glycolic acid) are most widely
used, PLA is amorphous and hydrophobic degrading to release lactic
acid.](https://image.slidesharecdn.com/arushetissueengg-141222234316-conversion-gate01/85/Tissue-engg-12-320.jpg)
Tissue engg.
- 1. TISSUE ENGINEERING Arushe Tickoo B.Tech Biotech
- 2. Tissue Engineering Tissue Engineering is the in vitro development (growth) of tissues or organs to replace or support the function of defective or injured body parts. Tissue Engineering is using a persons cells to create a new artificial fully alive tissue or organ that can replace or improve/heal the old one in the body.
- 3. Principle 1. Tissue engineering implies the addition of suitable cell types to a suitable support matrix, through which an organised and functional tissue is formed (resembling the tissue engineering) 2. Epithelial and endothelial cell layers organize themselves easily in vitro, but connective tissues do not form appropriate structures spontaneously. 3. Simple concept: Building material (e.g., extracellular matrix or biodegradable polymer), seed it with living cells and bathe it with growth factors. When the cells multiply, they fill up the scaffold and grow into three-dimensional tissue, and once implanted in the body, the cells recreate their intended tissue functions.
- 6. Initially approved by FDA for treatment of venous leg ulcers, later on in 2000 for treatment of diabetic foot ulcers. Apligraf contains two types of cells – an outer layer of protective skin cells, and an inner layer of cells contained within collagen. Both types of cells contain substances similar to those found in human skin. Apligraf does not contain certain things in skin such as hair follicles, sweat glands or blood vessels. Pro-osteon is a coralline hydroxyapatite, bone like graft used to fill defects in bone. In 1960’s artificial skin was being used to treat burn victims, later on modified into synthetic fibres for artificial skin grafts. 1n 1990’s pro-osteon coral derived bone graft material was introduced and 1996 integra’s was approved for as an tissue regeneration product. In 1998 “Apligraf ” approved for treatment of ulcers,
- 7. PRO OSTEON Pro Osteon Implant 500 Apligraf (artificial skin)
- 8. Cell substrate and Support material Nature of the support material depends on the information and suitability for the adherent cell types. It is divided into 5 broad classes: Traditional Abiotic materials (metals and ceramics) Bio- prostheses Natural materials are modified to make them biologically inert Synthetic Resorbable polymers are used Semi-natural Natural polymers Natural material are conjugated with synthetic material Biomolecule s such as proteins and polysacchari des are used
- 9. BIOINERT RESORBABLE BIOACTIVE Support material Bio-Compatibility 1. No material can be totally inert when implanted but the group known as “bioinert” only provoke the formation of scar tissues (eg: stainless steel in artificial hips) 2. Resorbable materials dissolve when implanted with generation of harmless dissolution products (eg: polymers like PLLA using suturing) Poly(L-lactic) acid is a biodegradable thermoplastic a aliphatic polyester derived from renewable resources, such as corn starch (in the United States), tapioca roots, chips or starch (mostly in Asia), or sugarcane. 3. Bioactive material stimulate a biological response from the body (eg: synthetic hydroxyapatite ceramics and bioactive glasses.
- 10. Bioprostheses 1. It is formed by the extensive cross-linking of natural tissue eg: porcin heart valves and tendons 2. These are designed and fabricated primarily to function as long as possible independently and without modification by surrounding tissue eg: collagen based connective tissue stabilized by glutaraldehyde, can survive unchanged for many years. Traditional support materials are not used because they do not integrate within reasonable period.
- 12. 1. Resorbable polymers are used which are hydrolysed and then phagocytosed, the greatest advantage of such material is their easy and cheap production in a controllable & reproducible manner at large scale. 2. Less compatibility than natural polymers 3. Synthetic polymers used are PGA [poly(glycolic acid)], PLA[Poly(l-lactic acid)], polycarbonate, polycaprolactone. 4. PLA, PGA and PLGA[poly(lactic-co-glycolic acid) are most widely used, PLA is amorphous and hydrophobic degrading to release lactic acid.
- 13. Semi natural & natural substrate Natural macromolecules are cross-linked polysaccharides, chemically cross-linked polysaccharide is mammalian hyaluronan, stabilized by benzyl esterification of increasing number of side chains.
- 14. Collagen sponges are also used, prepared from various insoluble and aggregated collagen eg: collagen scaffold in tubular shape, with smooth muscles and endothelial cells Tissue engineered heart valve Tissue engineered vascular graft
- 15. Types of cells 1. Autologous cells are obtained from the same individual to which they will be re-implanted. Autologous cells have the fewest problems with rejection and pathogen transmission, however in some cases might not be available 2. Allogeneic cells come from the body of a donor of the same species. 3. Xenogenic cells are these isolated from individuals of another species. In particular animal cells have been used quite extensively in experiments aimed at the construction of cardiovascular implants. 4. Syngenic or isogenic cells are isolated from genetically identical organisms, such as twins, clones, or highly inbred research animal models
- 16. Stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. According to their source stem cells are divided into "adult" and "embryonic" stem cells, the first class being multipotent and the latter mostly pluripotent; some cells are totipotent, in the earliest stages of the embryo. Scaffolds Cells are often implanted or 'seeded' into an artificial structure capable of supporting three-dimensional tissue formation. Scaffolds usually serve at least one of the following purposes: 1. Allow cell attachment and migration 2. Deliver and retain cells and biochemical factors 3. Enable diffusion of vital cell nutrients and expressed products
- 17. Allow the manipulation of cells to form as correctly shaped Structures that are able to support 3-D cell structures Scaffold
- 18. Stem cells Undifferentiated cells with ability to divide in culture & give rise to different forms of specialized cells. Characteristic Features: 1. They are capable of dividing & renewing themselves for long periods 2. They are unspecialized 3. They can give rise to specialized cell types. Pluripotent cells Totipotent cells Multipotent cells
- 19. Stem cells could be: 1. Embryonic stem cells 2. Adult stem cells
- 20. Embryonic stem cell lines are cultures of cells derived from epiblast tissue of inner cell mass of a blastocyst or earlier morula stage embryos — approximately 4 to 5 days old in humans & consisting of 50–150 cells. ES cells are pluripotent & give rise during development to all derivatives of 3 primary germ layers: 1. ectoderm, 2. endoderm & 3. mesoderm. Embryonic stem cells
- 22. Totipotent stem cells can differentiate into embryonic & extra embryonic cell types. Such cells can construct a complete, viable organism. These cells are produced from fusion of an egg & sperm cell. Eg: Fertilized egg Multipotent stem cells give rise to a limited range of cells within a tissue type. Eg: Hematopoietic stem cells Pluripotent stem cells are descendants of totipotent cells & can differentiate into nearly all cells, but cannot give rise to an entire organism. i.e. cells derived from any of three germ layers
- 24. Unipotent cells can produce only one cell type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells. E.g. muscle stem cells.
- 26. Mesenchymal Mesenchymal stem cells, or MSCs, are multipotent stromal cells that can differentiate into a variety of cell types, including: osteoblasts (bone cells), chondrocytes (cartilage cells), and adipocytes (fat cells).
- 27. There are three basic steps in tissue engineering. 1. The first step is actually getting the base cells to work with. 2. The second step is putting the altered cells into a scaffold in order to incubate the cells. 3. The final step is to put the newly created cells or organ into use. STEPS INVOLVED:
- 30. 95% of the cells in the epidermis are keratinocytes. These cells are found in the basal layer of the stratified epithelium that comprises the epidermis, and are sometimes referred to as basal cells, or basal keratinocytes. Tissue Engineered Skin Tissue engineering of skin became feasible in 1975 with the demonstration that sheets of human keratinocytes could be grown in the laboratory in a suitable form for grafting. This was a simple, cohesive sheet of cells cultured from the donor on a feeder layer of fibroblasts . The epithelial component is able to regenerate in culture, since the cells grow as a continuous sheet over a suitable surface, producing a continuous layer which progresses to form cornified layers.
- 31. Keratinocytes cells in skin
- 33. Though both scar tissue and normal skin are made with collagen proteins, they look different because of the way the collagen is arranged. In regular skin, the collagen proteins overlap in many random directions, but in scar tissue, they generally align in one direction. This makes the scar have a different texture than the surrounding skin. Scar tissue is also not as flexible as normal skin, and does not have a normal blood supply, sweat glands, or hair Various forms of implantable skin substitutes 1. Integra consists of insoluble bovine collagen type I and the glycosaminoglycan chondroitin sulfate. This can be covered in a keratinocyte sheet at the time of implantation. 2. Dermagraft consists of PGA polymer mesh of suitable pore size, seeded with human dermal fibroblasts from neonatal foreskins. 3. Apligraf consists of human dermal fibroblasts seeded into a type I collagen gel and allowed to contract under tension.
- 35. Artificial skin
- 36. Human urothelial cells and bladder smooth muscle cells can be cultured. The criteria are that the final structures need to form elastic tubes or bladders, and the implant should not allow crystal formation from urine or harbour local infections. Support materials tested have included resorbable polymers [polyglycolic acid) and poly(lactic-co-glycolic acid) co-polymer: PGA and PLGA and cross-linked collagen sponges. Urothelial and bladder muscle cells seeded onto PGA scaffolds formed urothelium-like, vascularized bilayered tissues when implanted Tissue Engineered Urothelium
- 37. Tissue engineered vascular graft Engineered bladder tissue
- 38. ARTIFICIAL BONE GRAFTS: PRO OSTEON Safe, strong, and cost effective bone grafts are now performed using synthetic material known as Pro Osteon Implant 500. It is sterile, biocompatible (meaning the body’s immune system does not reject it), and it is easily sculpted to fill a defect in fractured bones. Pro Osteon mimics the internal structure of human bone. This synthetic material is made by subjecting a common, non-decorative form to coral to a patented chemical process which converts the coral to hydroxyapatite, the same mineral content of human bone. The porous, interconnected structure of the coral remains intact, providing an ideal matrix through which new bone tissue can grow.
- 39. Using Pro Osteon on a long bone, the surgeon determines the amount of bone graft he needs and shapes the Pro Osteon block to fit into the damaged area. The graft area is stabilized with a metal plate, screws, or some other form of internal fixation. pro-osteon complex
- 40. Bioengineered Tissue Implants Regenerate Damaged Knee Cartilage ScienceDaily(July 5, 2006) Cartilage was removed from 23 patients with an average age of 36 years. After growing the cells in culture for 14 days, the researchers seeded them onto scaffolds made of esterified hyaluronic acid, grew them for another 14 days on the scaffolds, and then implanted them into the injured knees of the study patients. Cartilage regeneration was seen in ten of 23 patients, including in some patients with pre-existing early osteoarthritis of the knee secondary to traumatic injury. Maturation of the implanted, tissue-engineered cartilage was evident as early as 11 months after implantation
- 41. Tissue engineered organs (A) (B) (C) (A): tissue engineered heart valve (B): tissue engineered vascular graft (C): tissue engineered human ear
- 43. Ear growing on the mouse