Influence of Hyaluranon (HA) Preparations on Ionizing-Radiation-Treated Collagen-based Tissues
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It has been previously observed that moderate-molecular-weight hyaluronic acid (HA), also known as hyaluronan, provides reversible physical protection to collagen-rich tissues as monitored by a unique tissue-on-tissue friction test. Considering the possible benefits of such a formulation to irradiated head-and-neck cancer patients who have lost all natural salivary lubrication, human oral mucosa (OM) was collected from fresh anatomical donations and tested against a chemically cross-linked standard pericardium reference material for its ability to take up HA reversibly and preserve desirable tissue properties after simple drying and re-wetting, as well as after exposure to clinically-used doses of gamma irradiation (usually productive of dry mouth symptoms). The research methods included, before-and-after 70 Gray Cs-137 irradiation, tensile testing and tissue-on-tissue friction testing, with HA preparations applied prophylactically or subsequently. Collateral data on each preparation was obtained by Contact Angle goniometry for Critical Surface Tension determination and Multiple Attenuated Internal Reflection Infrared (MAIR-IR) spectrometry for surface compositions. It was discovered that the added HA significantly relieved the tensile strain of both normal and irradiated samples, and also provided some modulation of the radiation-induced crosslinking and "embrittling" of oral mucosal tissues. Re-wetted oral mucosal physical damage during tissue-on-tissue friction was significantly reduced by HA-solution application, but not by water alone. Weight measurements illustrated that HA was actually taken up into the native and irradiated tissues, and was completely reversible by plain water exposure, so the effect was more than superficial lubrication which lasts only short times. However, the weighing disparities between HA and DW (distilled water) were not statistically significant. Radiation-induced chain scission might have also occurred, although studies of the release of hydroxyproline showed a minimum of such effects. Therefore, the predominant mechanisms of protection of HA formulations are friction reduction and strain relief, which now remain to be correlated with subjective pain relief and improved oral function.