Topic 3: Cell and Tissue Engineering for Tissue Regeneration
Topic 3: Cell and Tissue Engineering for Tissue Regeneration
Aim
Introduce the concept of Cell/Tissue Engineering for Tissue Repair and its three components:
Stem Cells for Tissue Engineering
Understand top-down and bottom-up tissue engineering approaches
Applications of Tissue Engineering
Tissue Regeneration
Definition: Tissue injury refers to a part of an organism's tissue that undergoes trauma from external forces and is partially lost. The remaining tissue has the capacity to regenerate and restore the same structure and function as the lost tissue.
The repair process is termed tissue regeneration, exemplified by the regeneration abilities observed in zebrafish hearts.
Use of Stem Cells in Regenerative Therapy
Stem Cells: Specialized human cells capable of developing into several different cell types with remarkable self-renewal abilities.
Functions of Stem Cells:
Plasticity: The ability to change into other cell types.
Homing: The ability to travel to sites of tissue damage.
Engraftment: The ability to unite with existing tissues.
Types of Stem Cells
Adult Stem Cells (Multipotent Stem Cells)
Found among specialized or differentiated cells in tissues or organs post-birth.
Limited ability to differentiate into various cell types and self-renew.
Embryonic Stem Cells (Pluripotent Stem Cells)
Derived from the inner cell mass (ICM) of five to six-day-old embryos.
Capable of self-renewal and differentiation into any cell type in the body.
Induced Pluripotent Stem Cells (iPSCs)
Adult cells (e.g., skin cells) reprogrammed to an embryonic stem cell-like state through the expression of genes or factors maintaining embryonic stem cells.
Key Characteristics of Stem Cells
All Stem Cells Must Have:
Self-Renewal: The capability to undergo symmetric cell division.
Differentiation: The process of asymmetric cell division leading to specific lineage cells (e.g., skin, liver, bone, cartilage).
The New Era of Regenerative Medicine
Numerous biotech firms and university laboratories are pioneering methods to replace or regenerate damaged body parts. Below are notable developments:
Bone
Use of bone-growth factors or stem cells applied to porous materials to shape new jaws or limbs. Clinical trials for a product designed to create shinbones are ongoing.
Key Companies: Creative Biomolecules, Orquest, Sulzer Orthopedics Biologics.
Skin
Organogenesis' Apligraf, a human skin equivalent, became the first engineered body part to gain FDA approval for treating leg ulcers. Further engineered skin prototypes are being developed for foot ulcers and burns.
Key Companies: Organogenesis, Advanced Tissue Sciences.
Pancreas
Technique involves harvesting insulin-producing cells from pigs, encapsulating them, and injecting into the abdomen, with plans for future human trials.
Key Companies: BioHybrid Technologies.
Heart Valves, Arteries, and Veins
A 10-year initiative commenced for building a heart, utilizing genetically engineered proteins for blood vessel regeneration.
Key Companies: Organogenesis, Genentech.
Saliva Glands
Engineering of saliva glands using aquaporins to recreate damaged glands, with successful trials in mice.
Urinary Tract and Bladder
Cartilage cells from patients injected into weakened ureters to prevent urinary issues; bladders grown from skin cells in sheep with plans to trial in humans.
Cartilage and Other Tissues
Existing products for knee cartilage regeneration, lab-grown chests, and development in cosmetic applications for breasts.
Liver and Spinal Cord Nerves
Construction of spongy membranes seeded with liver cells. Investigations into nerve growth factors for spinal cord nerve regeneration have shown that rats can regain mobility.
Need for Tissue Engineering
There is a shortage of donor tissues and organs, necessitating engineering solutions that minimize immune responses and potentially utilize the patient's cells for repair.
Ultimate Aim of Tissue Engineering: Repair, regenerate, replace, and restore damaged tissues and organs.
Fundamental Definition of Tissue Engineering
Tissue engineering aims to create functional constructs that can restore, maintain, or improve damaged tissues or entire organs.
Components involved in tissue engineering include:
Reparative cells to form a functional matrix.
Appropriate scaffolds for transplantation and structural support.
Bioactive molecules (e.g., cytokines, growth factors) that support tissue formation processes.
Scaffolds and their Properties
Scaffolds need to mimic the extracellular matrix (ECM) for cell attachment and growth.
Must be biodegradable to allow natural tissue to take over.
Desired properties include mechanical strength and biocompatibility.
Methods of Tissue Engineering
Methods can be classified into Top-down and Bottom-up approaches:
Top-Down Approach: Involves seeding cells onto biomaterial scaffolds, allowing cells to proliferate and create new tissue. Challenges include the lack of basic nerves/blood vessels and nutrient supply within constructs.
Bottom-Up Approach: Involves creating modular units (e.g., cell aggregates) and assembling them into larger tissues or organs. It provides design flexibility but challenges with the bioengineered vascular network and mechanical properties.
Applications of Tissue Engineered Products
Tissue engineered products can significantly impact preclinical research:
Tissue Substitutes: Implantable in living organisms.
In Vitro Tissue Models: For drug and toxicity screening, enhancing therapeutic development cycles.
Innovations in Tissue Engineering
Research and collaborations towards engineered kidneys as implants and the emerging use of tissue chips for drug screening are being explored.
Summary of Learning Outcomes
Understanding the concept of Cell/Tissue Engineering for tissue repair and its components.
Knowledge about stem cells and their applications in tissue engineering.
Familiarity with top-down and bottom-up tissue engineering approaches along with their applications.
Topic 3: Cell and Tissue Engineering for Tissue Regeneration
The aim of Cell and Tissue Engineering for Tissue Repair involves understanding the three key components: stem cells, various tissue engineering approaches, and their applications. Tissue injury refers to trauma affecting a part of an organism’s tissue, resulting in partial loss. However, the remaining tissue has a remarkable capacity for regeneration, restoring both the structure and function of the lost tissue, as seen in zebrafish hearts.
Stem cells play a critical role in regenerative therapy as they are specialized human cells capable of developing into various cell types with impressive self-renewal abilities. Their main functions include plasticity, the ability to change into other cell types; homing, the ability to travel to tissue damage sites; and engraftment, where they unite with existing tissues. There are three main types of stem cells relevant to this field: Adult Stem Cells, which are multipotent and found among specialized cells post-birth; Embryonic Stem Cells, which are pluripotent and derived from the inner cell mass of embryos; and Induced Pluripotent Stem Cells (iPSCs), which are adult cells reprogrammed to an embryonic stem cell-like state.
All stem cells exhibit two key characteristics: self-renewal, which enables them to undergo symmetric cell division, and differentiation, the process leading to specific lineage cells such as those in the skin, liver, and cartilage. The new era of regenerative medicine is characterized by pioneering methods developed by biotech firms and university laboratories, aimed at replacing or regenerating damaged body parts. For instance, in bone regeneration, bone-growth factors or stem cells are applied to porous materials to create new jaws or limbs, with ongoing clinical trials for shinbone development. For skin, Organogenesis’ Apligraf has become the first engineered body part to gain FDA approval for treating leg ulcers.
Other significant advancements involve techniques for regenerating pancreas cells using harvested insulin-producing cells from pigs, encapsulated and injected into the abdomen, and the development of heart valves and blood vessels utilizing genetically engineered proteins. Furthermore, saliva glands are engineered using aquaporins, while innovative approaches are employed to address urinary tract and bladder issues. The ongoing construction of spongy membranes seeded with liver cells shows promise for liver regeneration, alongside research into nerve growth factors for spinal cord nerve regeneration.
Tissue engineering addresses the critical shortage of donor tissues and organs, necessitating solutions that minimize immune responses and may utilize the patient’s cells for repairs. The ultimate aim of tissue engineering is to repair, regenerate, replace, and restore damaged tissues and organs. Its fundamental definition embraces the creation of functional constructs that can restore, maintain, or improve damaged tissues or entire organs, involving reparative cells, appropriate scaffolds, and bioactive molecules like cytokines and growth factors that support tissue formation processes.
Scaffolds for tissue engineering must mimic the extracellular matrix (ECM) for effective cell attachment and growth, must be biodegradable to allow natural tissue takeover, and must possess mechanical strength and biocompatibility. Tissue engineering methods fall into two categories: top-down approaches, which seed cells onto biomaterial scaffolds to create new tissue; and bottom-up approaches, which assemble modular units like cell aggregates into larger tissues or organs. This technology significantly impacts preclinical research by providing tissue substitutes for implantable use and in vitro tissue models for drug and toxicity screening.
Innovations in tissue engineering include research collaborations targeting engineered kidneys as implants and the emerging use of tissue chips for drug development. In summary, knowledge of cell and tissue engineering for tissue repair involves comprehension of the various components, types of stem cells, and tissue engineering methods, along with their vast applications in regenerative medicine.