Pathological and immunological differences of arterial thrombi and wall caused by three different periodontal bacterial injections in rat models and proposals on the pathogeneses of vascular diseases.

OBJECTIVES: Periodontal bacteria that have been studied show a strong connection to various vascular diseases. Among the many kinds of periodontal bacteria, Porphyromonas gingivalis (Pg) is well examined in the general aspects and in a rat model. However, whether other periodontal bacteria work or react differently is not studied well. MATERIAL AND METHODS: We chose Aggregatibacter actinomycetemcomitans (Aa) and Prevotella intermedia (Pi) as different types of periodontal bacteria. Low-density and high-density bacterial solutions were injected in the small artery of rats' groins using our rat model. Eighteen limbs of 9 SD male rats (500-650 g) were used. After 7 days, 14-18 days, and 28 days, the rats were sacrificed. A pathological and an immuno-histochemical study was conducted and reported on the low-density group with 12 limbs because the Pi group lacked a high-density study. Immuno-histochemical staining of live Pg was performed on three limbs of three rats at 1 h, 3 h, and 1 week after injection. RESULTS: The appearances from the acute, at 7 days, to chronic phases, at 28 days, were observed. The differences of the species were certainly observed in the internal elastic lamina (IEL), and immuno-histochemical reactions. The inflammatory reactions, such as cellular distribution or intra-thrombus materials, were similar in all. One week later, we could not see any living bacteria in the specimen or immunological observation. CONCLUSIONS: The three species were essentially the same, except for Aa's stronger disruption of IEL, and more CD3 (Pan T cell) in Pi and more CD79a (Pan B cell) in Pg. We propose a new concept of a possible mechanism of vascular diseases, in which the work of LPS (lipopolysaccharides) and a toll-like receptor (TLR) is emphasized.

Oral-bacterial-induced arterial and venous thrombus in rats: Pathological and immunological studies.

Objectives: Our study investigated the pathological outcome of experimental thrombi that incorporate oral bacteria. Material and methods: A small artery and vein in the rats' groins were injected with a solution containing periodontal bacteria Porphyromonas gingivalis and followed up for 28 days. In all, 18 limbs of nine male rats (500-650 g) were used for the arterial study, and eight limbs of four rats were used for the veins. Two densities of the bacterial solution and two arterial thicknesses sizes were used in the arterial study. Both proximal and distal arteries and veins were ligated loosely using a monofilament nylon suture before bacterial suspensions or control solutions were injected into the ligated vessels. Results: After 7, 14-18, and 28 days, the rats were sacrificed. Pathology and immunohistochemistry were performed. All specimens exhibited thrombus formation and an acute inflammation reaction with granulocytes at 7 days and then settled down to chronic fibrous change with plasma cells or macrophages at 28 days in the arterial thrombus. CD3 (Pan T-cells), CD79a (Pan B cells in the rats), and IgG were observed in the process of the healing of the arterial thrombus. Venous changes showed relatively clear recanalization that appeared at 7 days, which is slightly different from the artery. Granulocytes were present from 7 to 28 days. Conclusions: Periodontal bacteria act as an inflammatory core in the vessels, but not as an infectious agent, in our experiments, because of their low ability to invade tissues.