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Womens Health

Women's Health - Poster Session C

Poster L21 - Examining myofibroblast origin in excised mesh-vaginal tissue following complications with surgical mesh implantation for pelvic organ prolapse treatment

Friday, October 25, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Pelvic organ prolapse (POP), affecting ~50% of women over age 50, is a condition in which the pelvic organs descend into the vagina secondary to weakened pelvic floor connective tissue (1). Symptoms include incontinence, sexual dysfunction, and pain (2,3). In the US, 12.6% of women will undergo POP repair surgery by age 80; 1/3 of these surgeries utilize polypropylene mesh (PPM) for repair (4-6). Over 10% of women face complications such as mesh exposure and pain, requiring mesh excision surgery (7,8). A recent study indicates that increased mesh burden (amount of mesh in contact with the vagina) increases complications in a non-human primate model of POP repair (9).

Macrophages mediate the foreign body response to implanted PPM and persist in mesh-explants from women decades following implantation (10). Fibroblasts, native to the vagina, transition to myofibroblasts in response to PPM and increase in prevalence following mesh implantation. While myofibroblasts are vital for wound healing, they are rare in normal vagina; their long-term persistence is pathologic. Emerging data suggests that macrophages may transition to myofibroblasts (MMF cells) and are the primary source of this phenotype in the context of a foreign material induced fibrosis (11).

We aimed to determine if MMF cells were present in women with complications as evidenced by the presence of a macrophage marker on myofibroblasts. We define differences in the fibroblast to myofibroblast transitioned (FMF) as compared to MMF cells with increasing mesh burden. Our hypothesis was that high mesh burden is correlated to increased MMF cell presence.

Materials and

Methods:  Eleven samples removed for from women with complications mesh exposure (n=7) or wrinkling/banding (n=4) were randomly selected for analysis from an ongoing human mesh biorepository study at Magee Womens Research Institute in Pittsburgh, PA (IRB: CR19080175-010). Following mesh excision surgery, mesh-vagina explants were fresh-frozen and stored in OCT at -80C. Tissue blocks from the samples were cryosectioned at 7 µm and labeled for alpha smooth muscle actin (αSMA), vimentin (Vim), and CD68 (macrophage) using immunofluorescent labeling. Labeled slides were then imaged at 10x magnification using a Nikon 90i microscope. The adventitial layer of the tissue samples (i.e., the layer of the vagina where mesh is attached) and the mesh fibers present within the samples were then outlined using QuPath, an open-source analysis software. Cell thresholding and quantification was performed to identify and quantify, respectively, the number of cells in each sample that were labeled for αSMA and Vim (myofibroblasts, FMF transitioned), CD68 (macrophage), and αSMA, Vim (fibroblasts), and CD68 (myofibroblast, MMT transitioned). The following parameters were quantified: mesh burden - percentage of space occupied by mesh fibers, adventitial area (mm2), total mesh fiber area (mm2), and the number of fibroblasts, macrophages, myofibroblasts, and MMFs. Mesh burden was divided into quartiles and compared. Statistical analysis of resulting data utilized Chi Square tests for trend with a 90% confidence interval and Mann Whitney U-tests with a α=0.10 using GraphPad Prism (v10.2.3).

Results, Conclusions, and Discussions: The demographics of the sample patients are summarized in Table 1. Mean age was 61.75 years, median gravidity was 3.58, and median parity was 2.92. To control for hormonal status all patients were postmenopausal and used vaginal estrogen.

MMF cells were highly represented in adventitia of the vagina throughout all the samples, which is the site of mesh implantation, as seen in Table 2. There was a significant difference in the number of fibroblasts present compared to myofibroblasts (p=0.04) and compared to the amount of MMF cells present (p < 0.0001). There was also a significant difference between the amount of myofibroblasts and MMF cells (p=0.03). Interestingly, there was no difference between the number of macrophages and the number of MMF cells present (p=0.08). This leads us to believe that MMF cells are a specialized subset of macrophages and are not derived from fibroblasts.

As shown in Figure 1B, highly organized FMF derived myofibroblasts (αSMA+Vim+) were present immediately surrounding the macrophages and encased mesh fibers in samples from patients with a lower mesh burden. In higher mesh burden specimen, this organized response was not present (as seen in Figure 1D) and MMF cells increased in abundance instead. Overall, as seen in Table 3, there is a high correlation in the mesh burden, or amount of mesh area, and the amount of myofibroblasts (p < 0.0001).

We have shown for the first time that myofibroblasts derived from macrophages are present in mesh vaginal explants from women with complications, and that the presence of these cells increase with mesh burden. Further studies are needed to define the role of this cell type in mesh induced complications and the threshold at which mesh burden triggers the MMF transition. More immunofluorescence staining will be completed to characterize macrophage populations to determine if macrophage phenotype plays a role in myofibroblast proliferation. Additionally, future studies will correlate the presence of MMF with patient symptoms such as pain.

Acknowledgements (Optional):  References

1. Pelvic Organ Prolapse. Mayo Clinic, 2024.

2. Wood LN, Anger JT. Urinary incontinence in women. BMJ. 2014;349:g4531. Published 2014 Sep 15. doi:10.1136/bmj.g4531

3. Zargham M, Alizadeh F, Moayednia A, Haghdani S, Nouri-Mahdavi K. The role of pelvic organs prolapse in the etiology of urinary incontinence in women. Adv Biomed Res. 2013;2:22. Published 2013 Mar 6. doi:10.4103/2277-9175.108010

4. Barber MD, Brubaker L, Burgio KL, et al. Comparison of 2 transvaginal surgical approaches and perioperative behavioral therapy for apical vaginal prolapse: the OPTIMAL randomized trial [published correction appears in JAMA. 2015 Jun 9;313(22):2287. doi: 10.1001/jama.2015.4817]. JAMA. 2014;311(10):1023-1034. doi:10.1001/jama.2014.1719

5. Mattsson NK, Karjalainen P, Tolppanen AM, et al. Methods of surgery for pelvic organ prolapse in a nationwide cohort (FINPOP 2015). Acta Obstet Gynecol Scand. 2019;98(4):451-459. doi:10.1111/aogs.13520

6. Jonsson Funk M, Edenfield AL, Pate V, Visco AG, Weidner AC, Wu JM. Trends in use of surgical mesh for pelvic organ prolapse. Am J Obstet Gynecol. 2013;208(1):79.e1-79.e797. doi:10.1016/j.ajog.2012.11.008

7. Liang R, Abramowitch S, Knight K, et al. Vaginal degeneration following implantation of synthetic mesh with increased stiffness. BJOG. 2013;120(2):233-243. doi:10.1111/1471-0528.12085

8. Hachim D, Wang N, Lopresti ST, et al. Effects of aging upon the host response to implants. J Biomed Mater Res A. 2017;105(5):1281-1292. doi:10.1002/jbm.a.36013

9. Knight KM, King GE, Palcsey SL, Suda A, Liang R, Moalli PA. Mesh deformation: A mechanism underlying polypropylene prolapse mesh complications in vivo. Acta Biomater. 2022;148:323-335. doi:10.1016/j.actbio.2022.05.051

10. Nolfi AL, Brown BN, Liang R, et al. Host response to synthetic mesh in women with mesh complications. Am J Obstet Gynecol. 2016;215(2):206.e1-206.e2068. doi:10.1016/j.ajog.2016.04.008

11. Lis-López L, Bauset C, Seco-Cervera M, Cosín-Roger J. Is the Macrophage Phenotype Determinant for Fibrosis Development?. Biomedicines. 2021;9(12):1747. Published 2021 Nov 23. doi:10.3390/biomedicines9121747