Spinning the web:

new implants for optimised tissue engineering of the pelvic floor

V.E. StegehuisA, drs. C.M. DiedrichB, drs. M. RioolC, dr. S.A.J. ZaatC, Prof. dr. J.P.W.R. RooversB

A A-KO Master student, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands. B Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. C Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.

Figure 4: Histology new generation implant group. (A) 4 days post-insertion; an influx of granulocytes,

monocytes and lymphocytes is seen in the tissue surrounding the implant (indicated by the arrow). (B) and

(C) 14 resp. 30 days post-insertion; a pronounced inflammatory response is seen in the surrounding of the

implant. The arrows in (C) indicate foreign-body giant cells (FBGC). A FBGC is a collection of fused

macrophages.

Materials and methods

• Subcutaneous mice model with three experimental conditions (n = 20 per condition):

PP implant, new generation implant and sham surgery (9).

• At day 4, 9, 14, 21 or 30 after insertion the FBR was determined through semi-

quantitatively histology analysis by staining the obtained tissue with haematoxylin

and eosin (H&E).

• The FBR has been quantified by the following benchmarks: inflammation, fibrosis,

collagen deposition and vascularization.

References 1. Maher et al. (2010). Surgical management of pelvic organ prolapse in women. The Cochrane Database of Systematic Reviews. 2010(4).

2. Salvatore et al. (2002) Prosthetic surgery for genital prolapse: functional outcome. Neurourol Urodyn. 21:296-7.

3. Denman et al. (2008) Reoperation 10 years after surgically managed pelvic organ prolapse and urinary incontinence. Am J Obstet Gynecol. 198(5):555

4. Olsen et al. (1997) Epidemiology of surgically managed pelvic organ prolapse and urinary incontinence. Obstet and gynecol. 89(4):501-6.

5. Lukacz et al. (2006) Parity, mode of delivery, and pelvic floor disorders. Obstet and gynecol. 107(6):1253-60.

6. Boulanger et al. (2006) Tissue integration and tolerance to meshes used in gynecologic surgery: an experimental study. Eur J Obstet Gynecol Reprod Biol. 125(1):103-8.

7. Elmer et al. (2009) Histological inflammatory response to transvaginal polypropylene mesh for pelvic reconstructive surgery. J Urol 181(3):1189-95.

8. Wang et al. (2004) A histologic and immunohistochemical analysis of defective vaginal healing after continence taping procedures: a prospective case-controlled pilot

study. AJOG; 191(6):1868-74

9. Riool et al. (2014) Staphylococcus epidermidis originating from titanium implants infects surrounding tissue and immune cells. ACTA BIOMATER.10(12):5202-5212

Correspondence to:

V.E. Stegehuis, Maastricht University

v.stegehuis@student.maastrichtuniversity.nl

Department of Obstetrics and Gynecology

Academic Medical Centre

Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands

T +3120 566 3400

F +3120 697 4128

Maastricht University

P.O. Box 616

6200 MD Maastricht, The Netherlands

Background

Pelvic organ prolapse (POP) is a common, multifactorial disease characterized by

weakening of the pelvic floor and subsequent prolapse of the pelvic organs.

Reconstructive surgeries aim to re-establish organ support and to create the

appropriate environment for functional tissue repair. However, the current use of

polypropylene (PP) implants is associated with implant erosion and pelvic pain,

suggesting suboptimal material properties (1, 2). These shortcomings are prone to

adverse events, leading to a chronic loss in quality of life due to social inconvenience

or chronic pelvic pain (3-5).

Novel, more enduring synthetic implants are used as an alternative, but the material

used in current synthetic implants do not seem to achieve a solid tissue integration with

the host tissue (3-5). In general, there is a lack of understanding of the influence of

implant properties and daily loading (e.g. coughing, laughing, heavy lifting) on the

Foreign Body Response (FBR). The aim was to evaluate the FBR in a new generation

of implants in mice compared with PP implants.

Macroscopic results

• Macroscopic analysis showed strong integration and encapsulation of the PP

implant, as opposed to new generation implant, where almost no encapsulation was

observed.

• In mice with the PP implant, more integration into the surrounding tissue and into the

implant was seen. The new generation implant was lying loosely under the skin, yet

was hard to remove as a whole (see figure 1).

Figure 3: Histology PP implant group. (A) 4 days post-insertion; early fibroblasts, fibrin fibers and a

lymphocyte and granulocyte induced inflammatory response is seen. (B) 14 days post-insertion; fibroblasts

and connective tissue is seen around the implant (C): 30 days post-insertion, the tissue surrounding the PP

implant seems recovered and the implant is well accepted by the tissue, as seen by the generated

connective tissue and reduced inflammatory response.

A

Figure 2: Histology sham group. (A) 4 days post-insertion; a post-surgery image of wound healing is seen.

(B) and (C): 14 days resp. 30 days post-insertion; normal histology without FBR or inflammation is seen.

A B C

B C

Figure 1: (A) Removal of the PP implant. (B) Removal of the new generation implant.

Microscopic results

• Histology is shown in figures 2-4. Semi-quantitative analysis showed a more

pronounced and intense FBR to the new generation implant compared with the PP

implant. Particularly 30 days post-insertion, high amounts of FBGC were seen in the

new generation implant histology analysis, whereas the FBGC were mostly

disappeared after 30 days in the PP implant.

• In the sham group, only a post-insertion wound healing response was present, and

no further FBR has been observed.

A B C

Discussion

• The PP implant provoked a lesser FBR than the new generation implant. However, it is

uncertain what the consequences will be of the prolonged presence of FBGC on the generation

of connective tissue in the new generation implant.

• A longer follow-up and other staining for connective tissue may be helpful in determining

whether the presence of FBGC is positive or negative over an extended period of time in terms

of a sustained FBR and generation of connective tissue.

• Implant insertion other than the vagina may induce a different or delayed response.

Nevertheless, a subcutaneous mice model has been extensively used to assess biomaterial

related responses and is thus a valid and illustrious animal model for the aim of this study (9).

Conclusion

• Implant characteristics have a direct influence on tissue integration and the FBR, in this study

in favor of the PP implant, where a less severe FBR was seen.

• The FBR in vaginally implanted biomaterials must be explored, since this response might differ

from the FBR in dorsally implanted biomaterials as the vaginal environment is significantly

different in terms physiological characteristics.

• Future research is warranted to determine the FBR to the new generation implant compared

with other implants, as the results in the current study were not hypothesized.

B A