Electrospining: Suspension electrospinning of decellularized extracellular matrix: a new approach to preserve biological activity

Background

Tissue engineering scaffolds composed of decellularized extracellular matrix (dECM) have shown great ability to support regeneration in many applications. dECM provides structural and biological cues to guide tissue remodeling through its complex composition of fibrin, proteoglycans, growth factors, cytokines, and mRNA. Cells interact with and absorb dECM, resulting in the release of bioactive products such as chemically attractive low molecular weight proteins, angiogenic growth factors, and mRNA. Tissue-specific dECM successfully promotes angiogenesis, myogenesis, neurogenesis, and immunomodulatory behaviors by supporting cell recruitment, proliferation, and tissue-specific differentiation. Small intestinal submucosa (SIS) is one of the most prominent dECM scaffolds on the market as it contains high levels of growth factors and nutrients to support continuous regeneration of the intestinal lining. In clinical trials, SIS scaffolds have successfully regenerated airway, abdominal wall, diaphragm, intestine, bladder, rotator cuff, skin, and urethra tissues.

The main point of this paper

dECM Scaffold Fabrication Challenges:

Fabrication of dECM into specialized structures for targeted applications is challenging because the bioactivity of proteins and growth factors is easily inactivated by enzymatic digestion, heat exposure, or harsh solvents

Current clinical practice is limited to the use of native dECM sheets, whose macro- and micro-morphology are limited by the structure of the harvested tissue

Rheological Evaluation:

To facilitate electrospinning or infusion “spinnability”, rigorous rheological evaluation of dECM suspensions is required, including homogenization level, concentration, and particle size

Homogenization enhances particle interactions and imparts the necessary elastic behavior to withstand electrostatic pull without rupture

Versatility of dECM Scaffolds:

The versatility of the dECM suspension electrospinning method is demonstrated by electrospinning different ECM compositions, including the use of Using different decellularization techniques or tissue sources

Bioactivity retention:

The bioactivity retention of dECM after electrospinning was confirmed in the study using cell proliferation, angiogenesis and macrophage assays

Compared with the traditional digested and dissolved dECM spinning solution, the new suspended electrospinning method uses incompletely digested dECM, which may maintain a higher level of protein structure, translating into ECM scaffolds with higher bioactivity retention and slower absorption rate

Tissue engineering applications:

Decellularized extracellular matrix (dECM) has a strong regenerative potential as a tissue engineering scaffold, providing a specific microenvironment suitable for promoting cell proliferation, migration, attachment and regulating differentiation

dECM-based scaffolds address key challenges, including poor mechanical strength and insufficient stability, to promote the reconstruction of damaged tissues or organs

Suspended electrospinning of pure dECM fiber meshes: a new approach to retain biological activity

Limitations of clinical application of dECM:

Currently, clinical application of dECM scaffolds is limited to freeze-drying them into sheets in their native form.

Advantages of electrospinning technology:

Electrospinning technology is able to control the macro- and microstructure of the scaffold and is a versatile scaffold manufacturing technology.

Challenges of dECM electrospinning:

In traditional methods, dECM is mixed with synthetic materials or completely dissolved by enzymatic digestion. These strategies will reduce the innate bioactivity of dECM and limit its regenerative potential.

Novel suspended electrospinning method:

A new suspended electrospinning method was developed to fabricate pure dECM fiber meshes and retain their inherent bioactivity.

Systematic study of key rheological properties:

Suspension parameters, including homogeneity, concentration and particle size, were studied to determine the key rheological properties required for "spinnability".

Homogenization enhances the interaction between particles and imparts the elastic behavior required to withstand electrostatic stretching.

Summarize

In this study, we rigorously evaluated the properties of dECM suspensions required to support fiber formation during electrospinning. Homogenization was identified as a mechanism to enhance particle interactions and elastic behavior of dECM suspensions. Cross-strain amplitudes of loss and storage modulus curves greater than 100% were identified as functional rheological predictors of spinnable dECM suspensions. The sensitivity of fiber morphology to suspension concentration followed a similar trend as the concentration of the polymer solution varied during electrospinning. Interestingly, fiber morphology and spinning were relatively independent of dried particle size as the suspension particles resolved to a consistent state. The versatility of this dECM suspension electrospinning approach was demonstrated by utilizing three different decellularization and preparation techniques and three dECM tissue sources of different composition, suggesting the potential to fabricate ECM scaffolds from tissue sources that have heretofore been resolved into powders and mimic the native ECM composition of target organ systems. These groups displayed similar rheological predictors of spinnability; namely, cross-strain amplitudes above 100%. These studies illustrate the impact of each dECM preparation step on fiber collection, so that this protocol can be easily adapted to specific tissue sources and applications. Our primary goal in developing this novel suspended electrospinning method was to increase the retention of bioactivity in the mesh after processing, which is a major limitation of current dECM spinning methods using synthetic polymer blends or enzymatic digestion. The regenerative capacity of these electrospun SIS meshes was similar to that of decellularized SIS sheet controls in terms of cell proliferation, angiogenesis, and immunomodulation. Overall, this study clarifies the key parameters guiding the suspended electrospinning of dECM, providing researchers with a framework to use this new method to fabricate dECM scaffolds that retain their natural regenerative capacity.