Stem Cell Cytoskeletal Responses to Pulsatile Flow in Heart Valve Tissue Engineering Studies

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Cellular Mechanobiology

Background:

• Pediatric heart valve replacement is limited due to growth constraints.
• Heart valve tissue engineering using human bone marrow stem cells (HBMSCs) offers a promising alternative.
• Mechanical forces, like shear stress, significantly influence stem cell behavior in vitro.

Purpose of the Study:

• To investigate the effects of fluid-induced shear stresses on HBMSCs.
• To analyze changes in HBMSC actin cytoskeleton and nuclear shape under different flow conditions.
• To evaluate the impact of shear stress on key gene expression relevant to valvulogenesis.

Main Methods:

• HBMSCs were cultured in microfluidic channels under pulsatile shear stress (PSS), steady shear stress (SS), and no flow conditions.
• Actin filament structure was visualized and quantified.
• Gene expression analysis was performed, focusing on valvulogenesis-related genes.

Main Results:

• PSS significantly increased actin filament number, density, and angle while decreasing filament length compared to SS and no flow.
• No significant differences in nuclear shape were observed across the experimental groups.
• The gene klf2a, critical for valve development, was significantly upregulated exclusively in the PSS group.

Conclusions:

• HBMSCs exhibit unique actin cytoskeleton alterations in response to PSS, distinct from SS and static conditions.
• These PSS-induced cytoskeletal changes, along with altered gene expression, suggest a mechanism for initiating valvulogenesis.
• Findings provide a cellular basis for optimizing in vitro protocols in heart valve tissue engineering by controlling mechanical environments.