Medicine/8.Morphology

Ph.D Shnayder S.A.

Odessa State Medical University, Odessa, Ukraine

The influence of chronic stress on connective tissue of the gingival mucosa

The complex influence rate of the environmental factors outweighs the adaptation abilities of human organism and requires the additional exertion of adaptivity mechanisms. The exhaustion of systems which provide the non-specific resistance abilities of organism leads to increase of morbidity rate of the so-called civilization pathology, including parodontic pathology. In present, only 2-10 % of the population have the unchanged periodontum. Half of the chidren population and up to 95% of adult persons are affected by the parodontic pathology, including the inflammative and destructive pathology.

However, the changes of gingival mucosa and periodontium tissue influenced by stress factors are still unclear. The unefficacy of the conservative treatment and prophylaxis aimed to eliminate the bacterial component of the periodontum disease pathogenesis requires further investigation. The specific age-related variability of the periodontum and mouth cavity mucosa response to stress factors may be of great importance.

Objective: study of the age related characteristics of the gingival mucosa reaction to the influence of the chronical emotional and pain stress.

The experimental studies of the chronic emotional and pain stress reconstruction had been carried out in rats (age 6, 12 and 18 months). The animals were discontinued at the anxiety, resistance and exhaustion stages of the chronic stress. The chronic emotional and pain stress has been reconstructed daily by the exposure to the electric current which lasted 3 hours. In these conditions the anxiety stage occurred during the first four days, the resistance stage – from the fifth to the fourteenth day of the cycle, and the exhaustion stage had started from the fifteenth day of the daily stress-generating exposure to the electrical current.

After the completion of the experiment, the areas of gingival mucosa have been taken from the animals. The tissue was homogenized. The levels of free, peptide – and protein-binded oxyproline have been determined in the supernatant homogenized mass. The protein-binded oxyproline to free oxyproline ratio had been calculated (PBO/FO). The evaluation of the basic material of the connective tissue tissue bio-polymers metabolism was based on the amount of glycose-aminoglycanes (expressed as hexuronic acids).

Results: certain age-related specific characteristics of the bio-polymeric metabolism in the connective tissue of the intact rats have been found. Animals aged 6 and 12 months had no changes of the free and protein-binded oxyproline content in the gingival connective tissue. Animals aged 18 months had the 13,2% rise of free oxyproline content in gingival mucosa; this event was accompanied by the tendency to protein-binded oxyroline content decrease and therefore resulted in total decrease of PBO/FO ratio by 16,8% and 14,3% (compared to animals aged 6 and 12 months, respectively). These changes reflect the domination of catabolic processes over the anabolic ones in the connective tissue of the rats aged 18 months; these shifts are related to the aging processes.

Further examinations revealed the age-related specific reactions of the gingival mucosa connective tissue to the influence of the chronical emotional and pain stress. At the anxiety and resistance stages of the chronic stress reaction no statistically significant changes of the bio-polymeric metabolism parameters were found in rats aged 6 months (compared to intact animals). Increase of collagen fibers destruction rate and significant decrease of their synthesis rate occurred at the exhaustion stage; these changes were supported by the decrease of the PBO/FO ratio by 18,5% (compared to intact animals).

However, the stress-induced shifts of the connective tissue bio-polymers metabolism parameters in animals aged 12 months were the same as in animals aged 6 months. Moreover, in the 18-months rats the decrease of the PBO/FO ratio by 10,5% and 24% (compared to intact animals and with rats aged 6 months, respectively) was found at the anxiety stage of the chronic stress. At the resistance stage the PBO/FO ratio had risen almost up to the level found in intact animals. However, it was stil statistically smaller than the ratio found at the resistance stage in 6- and 12 months aged animals. Note that the ratio’s restoration occurred due to collagen destruction rate decrease. It was not accompanied by any significant changes of the protein-binded oxyproline content. This fact may indicate that the rats aged 18 months have less effective rate of the connective tissue collagen fibers reparation under the exposure to stress factors.

At the chronic stress reaction exhaustion stage the rats aged 18 months had peak changes of the connective tissue bio-polymers metabolism parameters. The amount of free oxyproline exceeded the level found in intact animals and in rats aged 6 months at the same stage of stress reaction by 14% and 16,8%, respectively. Maximum inhibition of collagen biosynthesis rate occurred – it was reflected by the decrease of the protein-binded oxyproline content by 11,1% compared to the parameters of the intact animals. The maximum rate of damage of the basic component of the connective tissue was also found in animals aged 18 months. This fact is supported by the maximum stress-induced increase of the hexuronic acids content in the gingival connective tissue.

Conclusions: the chronical emotional and pain stress leads to the gingival mucosa conective tissue bio-polymers metabolism disorders; the maximum changes occur at the exhaustion stage of stress reaction. The rate of stress-induced disorders of the connective tissue increases during the aging process and reaches it’s maximum level in rats aged 18 months.