Complex dependence of substrate stiffness and serum concentration on cell-force generation

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Mechanobiology

Background:

• Collagen is a key biomaterial in tissue engineering applications.
• Mechanical stimulation influences cell behavior, orientation, and signaling within engineered tissues.
• Understanding force transmission in cell-seeded collagen is vital for effective tissue regeneration.

Purpose of the Study:

• To investigate the transfer of applied mechanical load to resident cells within 3D collagen constructs.
• To quantify micromovement within collagen gels under uniaxial strain.
• To assess the impact of collagen's viscoelastic properties on mechanical force transmission.

Main Methods:

• Embedding stainless steel markers in collagen constructs to report micromovement.
• Applying uniaxial strain (0-15%) to cell-seeded and unseeded collagen constructs.
• Recording material responses and marker bar movement relative to gel deformation.

Main Results:

• Viscoelastic properties of collagen led to minimal marker bar movement compared to gel deformation.
• Cell seeding density (1 million/mL) did not significantly alter collagen's viscoelastic properties within the tested strain range.
• Increased collagen stiffness at higher strain rates correlated with decreased marker movement, indicating reduced force transfer.

Conclusions:

• Collagen's viscoelasticity significantly limits the transfer of applied mechanical loads to resident cells.
• As collagen constructs mature and stiffen (e.g., via ECM deposition), mechanical stimulation protocols need adjustment.
• Tailoring mechanical stimulation over time is essential for achieving predictable and consistent cellular responses in maturing engineered tissues.