Degradable Supramolecular Fibrous Hydrogel as a Medical Device for the Treatment of Pelvic Organ Prolapse

Introduction:: Pelvic organ prolapse (POP) affects approximately 50% of parous women resulting in the descent of pelvic organs (vagina, bladder, uterus, small bowel, and rectum) due to weakened anatomical support structures. Uterosacral ligament suspension (USLS) is a common surgical treatment for POP. However, the relatively high failure rate of up to 40%^[1] underscores a strong clinical need for complementary treatment strategies, such as biomaterial augmentation. To address the need for alternative materials and a suitable animal model to investigate prolapse repair, our lab developed a hyaluronic acid (HA) based fibrous hydrogel^[2] as well as a rodent USLS model^[3] to investigate the augmentation of native tissue repair procedures. In this work, we present what we believe is the first study to use a rodent prolapse model to investigate a hydrogel biomaterial for the treatment of POP. Supramolecularly-assembled hyaluronic acid (HA) hydrogel nanofibers encapsulated in a matrix metalloproteinase (MMP)-degradable HA hydrogel create an injectable scaffold showing excellent biocompatibility and hemocompatibility. The hydrogel can be successfully delivered and localized to the suture sites of the USLS procedure, where it gradually degrades over 6 weeks. Our hypothesis was that the hydrogel augmentation of USLS would improve tissue integration at the USL-vaginal vault junction, therefore improving stability of the repair compared to sutures alone. A mechanical pull-off test and histological analysis at 24 weeks post-operative provide context for tissue structure and force required for failure with results showing a significant increase in force required for failure compared to the USLS repair alone.


Materials and Methods:: The supramolecularly-assembled HA hydrogel fibers were produced via electrospinning using guest (adamantane, Ad) and host (β-cyclodextrin, CD) modified methacrylated HA (MeHA) (Fig 1A). The resulting Ad-MeHA and CD-MeHA hydrogel fibers were mixed with a degradable peptide (MeP) modified HA (MePHA) to create an injectable hydrogel composite scaffold capable to suture site application (Fig 1B). A total of 30 multiparous (2-litter, 4-6 months old) female breeders were obtained from Charles River. Following hysterectomy, USLS was performed by affixing the vaginal vault to the USLs via absorbable suture (polydiaxanone, PDS II). The newly formed USL-vaginal vault junction stabilizes the cervical/uterine stump (Fig 1C). To evaluate in vivo hydrogel degradation, hydrogel nanofibers were labeled with a cyanine 7.5 conjugated peptide (Fig 2A) prior to suture site delivery (Fig 2B) and then serial images were taken during a 6-week period postoperative using a LagoX live imaging (Fig 2C). Tensile “pull-off” test on native uterosacral ligaments (USL, n = 8), as well as on animals who had undergone suture only USLS repair (USLS, n = 8) and hydrogel-augmented USLS repair (USLS+H, n = 8) (Fig 3A) was performed in situ at 24-weeks following surgery (Fig 3B). Histological studies were conducted on n = 2 specimen per group. Slides from each specimen were stained with Masson’s trichrome (MT) and then collagen content (blue stain) and muscle fiber content (red stain) was quantified using ImageJ (Fig 4A).


Results, Conclusions, and Discussions:: With this study we describe the first hydrogel augmentation of USLS in rodents, demonstrating the usefulness of the USLS rat model in the investigation of therapeutics for prolapse treatment. This is significant since there is an urgent clinical need for materials intended for the treatment of prolapse to be tested in pelvic floor models. To the authors’ knowledge, this is the first study to investigate the use of a hydrogel for augmentation of a USLS procedure. We were able to assess the in vivo efficacy of our supramolecular fibrous hydrogel composite to augment USLS repair in our newly developed animal model. With a carrier hydrogel to encapsulate the guest-host fibers, the material was used to augment the USL-vaginal vault interface created during the USLS procedure. At 24 weeks postoperative, the histological analysis demonstrated a reduction in collagen content in both the USLS (56.1 ± 3.0%) and the USLS+H (63.5 ± 4.7%) groups compared to the native control (USL, 80.3 ± 7.3%) showing the impact of the suture repair on the vaginal vault tissue structure. However, the differences in the muscle fiber content (USL: 11.8 ± 0.9%, USLS: 53.3 ± 2.3%, USLS+H: 20.3 ± 1.3%) provides additional context for the mechanical pull-off test and the improved pull-out load of the USLS+H group compared to the USLS suture only group. Applying an in situ tensile pull-off method, the repair with hydrogel augmentation significantly increased the pull-out load (~ 1.4 N) compared to the USLS procedure with sutures alone (~ 0.9 N). This demonstrated that the hydrogel assisted in recovery of mechanical properties to be closer to the intact USL tissue (pull-out force ~ 1.7 N). In vivo hydrogel degradation tracking demonstrated exponential decay of fluorescent signal resulting in near dissolution of the hydrogel at 6 weeks post-surgery (~ 94% degraded), further supporting the premise that superior tissue healing and integration accounts for the recovery of tensile resistance. Together, these results support the potential of this hydrogel platform to augment USLS procedures.


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References (Optional): : [1] J. E. Jelovsek, M. D. Barber, P. Norton, L. Brubaker, M. Gantz, H. E. Richter, A. Weidner, S. Menefee, J. Schaffer, N. Pugh, et al., JAMA - J. Am. Med. Assoc. 2018, 319, 1554.

[2] B. Miller, A. Hansrisuk, C. B. Highley, S. R. Caliari, ACS Biomater. Sci. Eng. 2021, DOI 10.1021/acsbiomaterials.1c00275.

[3] B. J. Miller, B. K. Jones, J. S. Turner, S. R. Caliari, M. H. Vaughan, J. Vis. Exp. 2022, 186, DOI 10.3791/64311.