Leptin induces leiomyoma cell proliferation and extracellular matrix deposition via JAK2/STAT3 and MAPK/ERK pathways.

Objective: To investigate the molecular effects of leptin on uterine leiomyoma cells.

Design: Experimental study using in vitro culture of immortalized human leiomyoma (HuLM) cells.

Setting: Academic university center.

Patient(s): Women with uterine fibroids who underwent a hysterectomy or myomectomy.

Intervention(s): Administration of human recombinant leptin to the media of cultured HuLM cells separately or in combination with pharmacologic Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) inhibitors.

Main Outcome Measure(s): We examined HuLM tissues and cells for the expression of the leptin receptor, termed OB-R. Cellular proliferation was measured at 6, 24, and 48 hours using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. Protein expression levels of proliferating cell nuclear antigen, collagen 1, phosphorylated STAT3/total STAT3, and phosphorylated ERK1/2 and total ERK1/2 were quantified using immunoblotting. Pharmacologic inhibitors were employed to further assess the role of the JAK2/STAT3 and MAPK/ERK pathways in the proliferative response.

Result(s): The presence of OB-R was confirmed in clinical leiomyoma and myometrial tissue obtained from 3 separate human subjects using immunofluorescence staining, and the expression of OB-R in HuLM cells was identified using immunoblotting. There was no significant difference in the expression of the leptin receptor in the myometrium compared with that in the leiomyoma tissue. Leptin stimulated cell proliferation and extracellular matrix (ECM) deposition at 24 hours after treatment. Pretreatment with a JAK2/STAT3 inhibitor attenuated ECM deposition, and pretreatment with a MAPK/ERK inhibitor significantly decreased leptin's stimulatory effect on cell proliferation and ECM deposition.

Conclusion(s): Leptin induces a proliferative response and ECM deposition in HuLM cells. These findings suggest that leptin, acting through the JAK2/STAT3 and MAPK/ERK pathways, is involved in the development of uterine leiomyomas, which may partly explain their increased incidence in obese women.