Cross-linked xenogenic collagen implantation in the sheep model for vaginal surgery

Abstract

The properties of meshes used in reconstructive surgery affect the host response and biomechanical characteristics of the grafted tissue. Whereas durable synthetics induce a chronic inflammation, biological grafts are usually considered as more biocompatible. The location of implantation is another determinant of the host response: the vagina is a different environment with specific function and anatomy. Herein, we evaluated a cross-linked acellular collagen matrix (ACM), pretreated by the anti-calcification procedure ADAPT® in a sheep model for vaginal surgery. Ten sheep were implanted with a cross-linked ACM, and six controls were implanted with a polypropylene (PP; 56 g/m2) control. One implant was inserted in the lower rectovaginal septum, and one was used for abdominal wall defect reconstruction. Grafts were removed after 180 days; all graft-related complications were recorded, and explants underwent bi-axial tensiometry and contractility testing. Half of ACM-implanted animals had palpable induration in the vaginal implantation area, two of these also on the abdominal implant. One animal had a vaginal exposure. Vaginal ACMs were 63 % less stiff compared to abdominal ACM explants (p = 0.01) but comparable to vaginal PP explants. Seven anterior vaginal ACM explants showed areas of graft degradation on histology. There was no overall difference in vaginal contractility. Considering histologic degradation in the anterior vaginal implant as representative for the host, posterior ACM explants of animals with degradation had a 60 % reduced contractility as compared to PP (p = 0.048). Three abdominal implants showed histologic degradation; those were more compliant than non-degraded implants. Vaginal implantation with ACM was associated with graft-related complications (GRCs) and biomechanical properties comparable to PP. Partially degraded ACM had a decreased vaginal contractility.

Comparative Anatomy of the Ovine and Female Pelvis

“…Lastly, the ovine levator ani muscle retracts the anus yet not truly supporting pelvic organs, Gynecol Obstet Invest 2017;82:582-591 DOI: 10.1159/000454771 590 which rest rather on the bony pelvic floor. Our dissections confirmed the presence of extravaginal spaces of relevance to surgical experimentation [10][11][12]. Given the different urethral insertion point, dissection of the ventral vaginal wall is more difficult in its lower part, yet feasible above the urethra.…”

“…Those ewes display collagen metabolism changes, yet the role of estrogens remains unclear [9]. Translational researchers increasingly use this model; however, there is a need for a detailed comparative anatomical study [10][11][12]. Although anatomical descriptions of relevant pelvic structures can be found in veterinarian text books, we found they had insufficient detail for the translational and clinical researchers.…”

“…Sheep are cheap, easily accessible, and there are less ethical constraints than with non-human primates. Consequently, we and others have started to use this model for vaginal surgery and biomechanics [10,11,24,25].…”

Morphological and Functional Changes in the Vagina following Critical Lifespan Events in the Ewe

“…These studies reported discordant results [17,46]. Another study in which contractility was tested, did so for the purpose of documenting the impact of foreignmaterial implantation in pelvic floor reconstruction [47]. In our sheep, we saw an increase in contractility when the ewes became reproductive and a drop at menopause.…”

In vivo response to polypropylene following implantation in animal models: a review of biocompatibility

“…Biologically derived materials are classed as acellular collagen matrices and are often derived from the dermis, pericardium, small intestinal submucosa or urinary bladder matrix of bovine or porcine origin [1, 22, 59]. These materials can undergo crosslinking, the formation of excessive intra- and inter-molecular bonds, to improve the longevity of the material [59].…”