In a recent study published in BMC Women’s Health, researchers explore the involvement and altered expression of BBOX1 antisense ribonucleic acid (RNA) 1 (BBOX1-AS1) and microRNA-19b (miR-19b) in polycystic ovary syndrome (PCOS).

Study: The long non-coding RNA BBOX1 antisense RNA 1 is upregulated in polycystic ovary syndrome (PCOS) and suppresses the role of microRNA-19b within the proliferation of ovarian granulose cells. Image Credit: Orawan Pattarawimonchai / Shutterstock.com

What’s PCOS?

BBOX1-AS1 is an extended non-coding RNA (lncRNA) that’s related to several human diseases, including ovarian cancer. In ovarian cancer, BBOX1-AS1 upregulates podocalyxin-like protein 1 (PODXL) by sponging miR-361-3p, thereby promoting cancer progression.

PCOS is a clinical disorder that affects 4-12% of girls of reproductive age. Since PCOS affects ovaries, the researchers of the present study hypothesized that BBOX1-AS1 also interacts with miR-19b to take part in PCOS.

Theca cells autonomously produce androgen and progesterone, whereas granulosa cells convert theca cells-produced androgens into estrogens. Taken together, these cells are key determinants of ovarian steroidogenesis. 

In PCOS, elevated levels of gonadotropin-releasing hormone (GnRH) stimulate the proliferation of steroids and luteinizing hormone (LH)-producing granulosa cells. This results in increased proliferation and reduced apoptosis of granulosa cells, in addition to reduced follicle-stimulating hormone (FSH) levels, which likely facilitate PCOS progression.

These hormonal imbalances manifest as quite a few cysts within the ovary, which, without proper treatment, reduce egg quality, prevent ovulation, and result in infertility. So far, the reason behind PCOS is unknown. 

Genetic targets of PCOS

Understanding ncRNA functions in diseased states like PCOS and cancer could facilitate the event of novel treatments.

Furthermore, ncRNAs, similar to lncRNAs and microRNAs (miRNAs), don’t contain coding information; nevertheless, they interact with DNAs, other RNAs, and proteins to take part in multiple biological processes, similar to protein/gene expression regulation and chromatin stability. Due to this fact, lncRNAs may very well be the next-generation molecular targets for PCOS treatment.

Previous studies have reported the downregulation of MiR-19b in PCOS and the way it enhances granulosa cell proliferation; nevertheless, its upstream regulator is unknown. Nevertheless, miR-19b could also be a possible molecular goal of PCOS treatment. 

In regards to the study

In the current study, researchers investigate the potential involvement of miR-19b-BBOX1-AS1 interaction in PCOS.

A complete of 80 PCOS patients were recruited to take part in the study. The common age of the study cohort was about 30 years.

All study participants received the primary round of in-vitro fertilization (IVF) treatment at Hainan Women and Children Medical Center in China to donate follicular fluid samples for this study. The control group comprised 80 females who received IVF treatment due to male aspects, somewhat than a PCOS diagnosis. 

KGN cells, that are human granulosa-like tumor cells, were used to organize nuclear and cytoplasmic fractions to isolate RNA. Quantitative reverse transcription-polymerase chain response (RT-qPCR) was subsequently used to evaluate BBOX1-AS1 and miR-19b accumulation in follicular fluid. A correlation evaluation was performed between miR-19b and BBOX1-AS1 across PCOS and control samples.

The RNA-RNA pulldown assay was used to find out the binding of miR-19b to the wild type (wt) and mutant (mut) BBOX1-AS1 in KGN cells. The BrdU assay allowed the researchers to analyze the regulatory role of BBOX1-AS1 and miR-19b in regulating KGN cell proliferation.

Study findings

In striking contrast to miR-19b, BBOX1-AS1 was highly upregulated in PCOS. These findings show the role of BBOX1-AS1 in PCOS, much like its involvement with several different ovarian disorders.

The RNA-RNA pulldown assay confirmed that miR-19b binds to BBOX1-AS1; nevertheless, these ncRNAs weren’t correlated across PCOS and control samples. Correlation evaluation suggested that the ncRNAs didn’t regulate the expression of each other.

In truth, only BBOX1-AS1-wt, somewhat than the mutant BBOX1-AS1, directly interacted with miR-19b, suppressed its activity and inhibited granulosa cell proliferation.

Conclusions

The present study characterised the role of the BBOX1-AS1/miR-19b axis in PCOS. Although BBOX1-AS1 expression was high, miR-19b was down-regulated in PCOS.

Future studies are needed to verify that BBOX1-AS1 endogenously competes with miR-19b for its suppression to steer to PCOS ultimately. Moreover, additional research is required to elucidate the involvement of the BBOX1-AS1/miR-19b axis in oxidative stress-induced damage to ovaries underlying most ovarian disorders. 

Journal reference:

• Zhou, Z., Zhang, Y., Tan, C. et al. (2023). The long non-coding RNA BBOX1 antisense RNA 1 is upregulated in polycystic ovary syndrome (PCOS) and suppresses the role of microRNA-19b within the proliferation of ovarian granulose cells. BMC Women’s Health 23(508). doi:10.1186/s12905-023-02632-5