Tetramethylpyrazine Stalls Lesional Progression via Inducing Senescence in Mouse with Induced Deep Endometriosis

So far, the pressing need for the development of non-hormonal therapeutics for endometriosis has been unfulfilled. In light of the evidence that platelets play important roles in the development of endometriosis and that tetramethylpyrazine has therapeutic potential, we tested the hypothesis that tetramethylpyrazine can induce cellular senescence in endometriotic lesions, hindering fibrogenesis in mice with induced deep endometriosis and that the combined use of tetramethylpyrazine and sodium tanshinone IIA sulfonate may have a synergistic effect. We induced deep endometriosis in 32 female Balb/C mice, and then randomly divided mice into equal-sized four groups: low- and high-dose tetramethylpyrazine, low-dose tetramethylpyrazine plus low-dose tanshinone IIA sulfonate and inert vehicle control. After two weeks of treatment, their lesion tissues were removed and procured. All lesions were weighed, and lesion fibrosis was quantitated by Masson trichrome staining. In addition, cellular senescence in lesions was evaluated by senescence-associated β-galactosidase, along with immunohistochemistry analyses of p53, Salvador 1, cellular communication network factor 1, hyaluronan synthase 2, surviving and granulocyte-macrophage colony stimulating factor and other markers. We found that tetramethylpyrazine treatment significantly decreased lesion weight, arrested lesional progression and ameliorated pain behaviour ostensibly via inducing senescence by p53 activation, and induction of Salvador 1 and cellular communication network factor 1 while suppressing hyaluronan synthase 2, survivin and granulocyte-macrophage colony stimulating factor, resulting in increased apoptosis and reduced lesional infiltration of alternatively activated macrophages. Tetramethylpyrazine treatment also significantly reduced the plasma concentration of P-selectin and hyaluronic acid, possibly leading to reduced lesional platelet aggregation. Thus, we conclude that tetramethylpyrazine holds the promise as therapeutics for treating endometriosis, but the tetramethylpyrazine plus tanshinone IIA sulfonate did not further enhance the therapeutic effect. These results further underscore the notion that induced senescence may play an antifibrotic role in endometriosis, and activating the senescence pathway, through treatment with tetramethylpyrazine or other similar drugs, may be a novel avenue for treating endometriosis.