hyaluronan

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Hyaluronan

Hyaluronic acid ground substance in the dermis providing water retention and migration scaffolding.

Biology

Hyaluronic acid (HA) is a high-molecular-weight glycosaminoglycan that is a major component of the dermal extracellular matrix. HA has exceptional water-binding capacity, retaining up to 1000 times its weight in water, which maintains tissue hydration and turgor. In the papillary dermis, HA concentration is highest, creating a hydrated environment that facilitates cell migration and nutrient diffusion.

During wound healing, HA in the wound area is disrupted. Fibroblasts produce new HA as part of the provisional matrix, and HA facilitates keratinocyte migration by providing a hydrated scaffold. HA is degraded by hyaluronidases with moderate turnover.

This module is a groundwork module (disabled by default) that adds the hyaluronan PDE field with water retention and migration scaffold coupling.

Model

Hyaluronan PDE: slow diffusion 0.01 (high molecular weight HA is viscous), hyaluronidase decay 0.005.

Initialization: sub-layer profile. Papillary dermis has highest concentration (basal_density = 0.8, HA-rich). Reticular dermis has lower concentration (reticular_density = 0.4). Epidermis = 0.

Wound response: zeros hyaluronan in wound voxels.

Source term: fibroblast production at production_rate per step (when fibroblast module active).

Water retention coupling: local water capacity is augmented by water_retention_factor * local_HA, increasing tissue hydration where HA is present.

Migration scaffold coupling: keratinocyte migration speed is augmented by migration_scaffold_factor * local_HA, facilitating cell movement through HA-rich matrix.

Parameters

From modules/hyaluronan/config.toml:

Parameter	Default	Units	Description	Source
enabled	false	bool	Master switch (groundwork module)	Convention
diffusion	0.01	-	Slow lateral spread (high MW HA)	Calibrated
decay	0.005	per step	Hyaluronidase turnover	Stern et al. 2006 (DOI)
basal_density	0.8	normalized	Baseline in papillary dermis (HA-rich)	Toole 2004 (DOI)
reticular_density	0.4	normalized	Lower in reticular dermis	Toole 2004
production_rate	0.002	per step	Fibroblast HA synthesis	Calibrated
water_retention_factor	0.5	multiplier	HA contribution to local water capacity	Calibrated
migration_scaffold_factor	0.3	multiplier	HA contribution to migration speed	Calibrated

Coupling

Reads

Field	Source module	How used
(none)	-	HA is produced by fibroblast agents, not read from fields

Writes

Field	Consumer modules	What is written
Hyaluronan	tissue (water retention, migration scaffold)	HA concentration per voxel

Validation

No validation dataset yet. Parameter values derived from:

• Toole 2004: HA biology and distribution
• Stern et al. 2006: hyaluronidase turnover
• Aya & Bhangal 2014: HA in wound healing
• Chen & Abatangelo 1999: HA functions in wound repair

Metrics

Column	Units	Description
mean_hyaluronan_wound	a.u.	Mean hyaluronan in wound

Source files

File	Purpose
hyaluronan_pde.h	Hyaluronan PDE with sub-layer profile and fibroblast production
config.toml	Module configuration