A Role for HAPLN1 During Phenotypic Modulation of Human Lung Fibroblasts In Vitro

Area of Science:

• Extracellular Matrix Biology
• Cellular Differentiation
• Fibrosis Research

Background:

• Hyaluronan and proteoglycan link protein 1 (HAPLN1) is crucial for stabilizing interactions between versican and hyaluronan in the extracellular matrix (ECM).
• These ECM interactions are known to facilitate fibroblast proliferation and their differentiation into myofibroblasts.
• The specific role of HAPLN1 in fibroblast proliferation and myofibroblast conversion remained uninvestigated.

Purpose of the Study:

• To investigate the cellular and extracellular matrix localization of HAPLN1 during human lung fibroblast proliferation and myofibroblast conversion.
• To explore the functional role of HAPLN1 in modulating fibroblast differentiation and extracellular matrix organization.

Main Methods:

• Immunocytochemistry was employed to assess the localization of HAPLN1 in cultured human lung fibroblasts.
• Confocal microscopy was utilized to visualize the spatial distribution of HAPLN1 relative to versican and hyaluronan.
• Functional assays involved the addition of exogenous HAPLN1 and versican to assess their impact on myofibroblast formation (α-SMA expression).

Main Results:

• HAPLN1 was found in pericellular matrices, associated with versican and hyaluronan on the cell surface and within the ECM.
• Nuclear and total HAPLN1 levels increased post-myofibroblast induction, with distinct ECM localization patterns observed for HAPLN1 and versican.
• Exogenous HAPLN1, but not full-length versican, promoted myofibroblast formation and altered hyaluronan-rich ECM compaction.

Conclusions:

• HAPLN1 exhibits dynamic intracellular and extracellular localization changes during fibroblast proliferation and myofibroblast differentiation.
• HAPLN1 plays a functional role in promoting myofibroblast conversion, potentially by modulating hyaluronan network structure.
• These findings suggest HAPLN1 may be a key mediator in fibrotic remodeling processes.