Aging and injury affect nuclear shape heterogeneity in tendon

Area of Science:

• Biomedical Engineering
• Tissue Engineering
• Cell Biology

Background:

• Histological stains with qualitative scoring are standard for tissue analysis but lack sensitivity and fail to capture cellular heterogeneity.
• Quantitative analysis offers insights into pathological mechanisms but cannot fully represent structural variations across cell subpopulations.
• Cell and nuclear shape are increasingly recognized as critical indicators of cell function and malfunction.

Purpose of the Study:

• To develop and apply advanced image analysis techniques for quantitative assessment of cell and nuclear morphology in tendon tissue.
• To investigate the association between cell nuclear shape, aging, and injury in tendon.
• To explore the heterogeneity of cell nuclei populations within specific extracellular matrix regions.

Main Methods:

• Utilized Visually Aided Morpho-Phenotyping Image Recognition (VAMPIRE) for automated cell segmentation based on shape.
• Integrated VAMPIRE with the ability to discriminate cells in protein-rich extracellular matrix regions.
• Applied the methodology to rat and human tendon tissues undergoing aging and injury.

Main Results:

• Identified multiple nuclear shape modes in rat tendon during maturity and aging.
• Discovered distinct subgroups of cell nuclei shapes in proteoglycan-rich regions during aging.
• Observed that immunomarkers (αSMA, CD31, CD146) associated with injury in rat tendons correlated with more rounded nuclear shapes.
• Found that human tendon cell nuclei at injury sites were more rounded compared to uninjured tissues.

Conclusions:

• Tendon tissue alterations during aging and injury are associated with variations in cell nuclear morphology.
• The study identified region-specific subpopulations of cells based on nuclear shape.
• The developed methodologies enhance the understanding of cell heterogeneity in tendon aging and injury and offer potential for clinical applications.