Extracellular Matrix - Derived Biomaterials

extracelullar matrix

living environment od cells, substantial part of tissues is extracellular space

non cellular component of tissues and organs: biological material composed of polymeric networks

parts of extracellular matrix

several types of macromolecules (proteins and polysaccharides)

locally secreted and assembled into organized meshwork

close association with surface of cell that produced them

smaller molecules are bound

Function of ECM

functions as adhesive substrate

provides structure

presents growth factors to receptors

requestors and stores growth factor

senses and transducer mechanical signals

ECM Function: Adhesive Substrate

tracks to direct migratory cells

concentration gradients for haptotactic migration EC

ECM Function: Providing Structure

define tissue boundaries

provides integrity and elasticity to developing organs

degraded by invasive cell during development and disease

ECM Function: presents growth factors to receptors

controls spatial distribution of ECM bound surface molecules

facilities crosstalk between growth factor receptors and ECM receptors

ECM Function: sequesters and stores growth factors

allows for patio-temporal regulation of factor release

organizes morphogen gradients

mediates release of factors in presence of appropriate cell-mediated forces or proteolytic degradation

ECM Function: senses and transducer mechanical signals

defines mechanical proeprties permissive/instructive to cell differentiation

activate intracellular signaling through interaction with cell-surface receptors

engages cytoskeletal machinery and synergies with growth factor signaling

Cells continue to interact with ECM

chemical, mechanical, and topographic cues provide cells with cell shape, migration, growth, orientation, adhesion, differentiation, division, and fate

molecular singlalinf by celular adhesion receptors (integrals)

ECM is modified by cells as they proliferate, differentiate, and migrate

How do cells communicate with ECM?

uses interns, largest family of ECM molecule receptors

transmembrane heterdimers, linkers between the ECM and actin cytoskeleton

cells both bind to and respond to ECM

understanding cell matrix interactions is essential to understand and direct tissue response to biomaterials

Extracellulat domain: binds to ECM-moleculues

Intracellular domain: binds to cytoskeleton and also to specific molecules of signal transduction pathways

Components of ECM

Water (65% of tissue weight)

secreted by variety of cells: fibroblasts, bone, and cartilage cells

polymer forming proteins

• structural proteins

• elongated molecules usually insoluble

• special mechanical properties, resulting from unique structure

Collagens (strength) and elastic fibers (elasticity)

Collagen

must abundant protein in mammals 25-30% of total protein amss

secreted bt connective tissue cells

predominant structural component of ECM in bones, cartilage, tendons, and skin

collagen superfamily compromises 28 members

Tensile Strength of Collagen Fibers

long and highly stable molecule with rigid structure that provides structure framework and strength of tissues

Triple Helix Secondary Structure

three polypeptides alpha chains twisted around one another in a rope like triple helix (braid)

intra and intermolecular cross linked collagen fibrils into strong fibers

self assembly of collagen fibrils into collagen fibers due to hydrophobic, electrostatic, and cross linking interactions

Collagen Fiibers for Structure-Function Relations

orientation pattern marches mechanical function

What is collagen-based biomaterials used for in biomedical applications?

used as tissue filler, for nerve guides, wound healing, drug delivery, scaffold in tissue engineering and bioinks

Elastic Fiber

responsible for tissue elasticity

used in tissues requiring reversible extensibility or deformability

inelastic collagen fibrils are interwoven with elastic fibers to limit extent of stretching and prevent tissue from tearing

Elastin: mechanical behavior

main component of elastic fibers is elastin

elastin resists tension and endow resilience to ECM by passive, entropy driven mechanism allowing stretching and recoil

ability to stretch resting molecular length and recoil without damage to protein

allows many tissues in body to resume shape after stretching or contracting

Why does elastin work the way it does?

during elastin synthesis: cross linking of elastin precursor molecule

elation is rich in hydrophobic amino acids that cluster to avoid waterE

Elastin-based biomaterials (Tropoelastin-coated scaffolds)

used as coating

enhance integration of scaffolds into hosts

provides biological cues for cell adhesion

used as scaffold and as hydrogel matrices

Adhesive Glycoproteins (Fibronectin, Tenascin, Laminin)

binds to both cells and ECM (laminin and fibronectin)

red for coatings and surface modifications of scaffolds to improve host-biomaterial interaction

Laminin

large ECM family of proteins, cross-like structure

separate binding domains to cells and ECM molecules

localized at basement membrane: sheets of highly organized and specialized ECM beneath many types of cell sheets

function: organization of ECM, regulate cell-matrixa adhesion, cell migration and cell shape

Fibronectin

different domains: binds cell surfaces and different ECM molecules

RGD amino acid sequence as the integral-binding region

Functions: cell migration and proliferation, wound healing, maintenance of cell cytoskeleton

Laminin/Fibronectin Based Biomaterials

used as coating and for surface medication of biomaterials

Proteoglycans

core protein + glucosaminoglycans

large complexe that are highly diverse

GAGs are highly negatively charged: traps a lot of water

resists compression by retaining water and by occupying large volume

forms porous hydrated gels that fill most of extracellular space

Hyaluronic Acid

provides compression strength, lubrication and hydration within ECM and regulates cell functions

great biocompatibility, biodegradability, and bioactivity

versatile molecule in both drug delivery and tissue engineering applications, including formulations of coatings, nanoparticles and hydrogels

Fibrinogen and Fibrin

promotes cell adhesion and migration

used as hemostatic agent, sealant, scaffold and bioink

Fibrin

provisional metric during wound healing and also primary protein component of blood clots, rich in growth factor

Fibrinogen

precursor of fibrin

Tissue Engineering

extracellular matrix-derived biomaterials

scaffold mimicking target tissue’s ECM

ingredients of tissue engineering: cells, cell signaling, scaffold (biomaterial) E

ECM-based Biomaterials

main use as scaffold for tissue engineering

• biocompatible, biodegradable and bioactive

• temporary ECM to accommodate cells and support 3D tissue regeneration

  • degraded in body and replaced by natural ECM produced by host cells

Applications of Scaffolds in ECM-Based Biomaterials

tissue regeneration, wound healing, drug / growth factor delivery, cellular models

ECM Varies in Composition from One Tissue to Another

varying commotion of collagen, GAGs and elastic fibers generate different properties DIFFERENT ECM RATIO

Best Scaffold for TE

ECM of target tissue is in active state

architectural, biological and mechanical features of ECM should be mimicked by ECM-dervied scaffolds

should be Porous, Biodegradable, Biocompatible, Bioactive, and recapitulate the architecture of the target tissue (chemical, physical, and mechanical parameters)

ECM-derived Biomaterials (Sources)

sources for isolating ECM protein

Species Sources fro ECM

from humans (autologous or allogenic) or other species (xenogenic)

Obtention in ECM-derived biomaterials

traditional purification methods

recombinant technology

Decellularization

Obtention (Traditional Purification Methods)

tissue isolation and processing through mechanical disruption, enzymatic digestion and precipitation

Obtention (Recombinant Technology)

• production of ECM proteins in vitro in bioreactors as recombinant proteins expressed in either bacteria, insect, or mammalian cells

• possibility to tune, modify, and manipulate the expressed protein

Obtention (decellularization)

best scaffold for engineered tissue in ECM of target tissue in native state

removing cellular compartment of living tissues, creating acellular ECM scaffolds

used in many clinical applications

preservation of ECM structure and composition of tissue, vascular networks, and specific functional and structural molecules Bi

Biofabrication Techniques

Purified ECM Component, Decellularised Tissues, In Vitro-Generated Biomaterials

Biofab Technique: hydrogen, electrospinning, and 3d dECM bioink

Bioprinting

printing of structures consisting of living cells, biomaterials and active biomolecules

applications in biomaterial inks, bionink formulations

Biofabricated Scaffolds by Electrospinning

nano and micro-sized non-woven fibers through electrostatic forced driven by high voltage electric fields

oriented multifilament nano fibers structurally similar to nano fibrous framework of native ECM

natural and synthetic polymers can be combined to improve low mechanical properties of natural polymers and low biocompatibility of synthetic ones

Scaffolds in ECM-Derived Biomaterials

further modifications of scaffolds:

• crosslinking

  • improve mechanical

  • retard biodegration

different treatments prior to implantation to minimize immune response in human body

combine with synthetic biomaterials to improve mechanical properties

Scaffold after in-vivo implantation

acellular scaffolds

• ex: human fibroblasts which express a complete dermal stroll matrix

• serves as vehicles for delivery of signals that augment the recruitment of endogenous cells

Cellular Scaffolds

bearing embedded cells to guide tissue formation

in vivo: bearing embedded cells to guide tissue formation, serve as cells carriers

• cells with regenerative capacities

When will you use acellular or cellular scaffolds?

patient with genetic disease, acute wounds, patient with extensive tissue loss, aged patients

acellular scaffold

huge number of commercially available decellularized scaffolds

limited immune reaction

low cost

without regulatory and scientific challenges of cell based therapies

no donor required

red to facilitate the repair activity of native cell populations Ce

Cellular Scaffolds

addition of a cellular component with regenerative capacity: increased biological activity over material alone

useful in patients with systemic pathologies that compromise native tissue repair responses (like diabetes and other diseases limiting wound repair)

Coatings for ECM-derived Biomaterials

coatings to improve host device transition, using laminin and fibronectin

host cell binds to ECM molecules through integral receptors

motifs present in ECM protein domains with biological activity

cell adhesion photo controlled spatio-temporally

applications is for coatings

Current Issues in ECM

excellent biomaterial suitable for many therapeutic applications

challenge:

undersstanding 3D architecture, mimic biochemical and biophysical composition, improve manufacturing processes, understand and modulate the changes that occur after in vivo placement and host remodeling