Regenerative Medicine Applications in Pelvic Reconstructive Surgery



Regenerative Medicine Applications in Pelvic Reconstructive Surgery


Jeffrey L. Cornella



Introduction

The number of clinical consultations for urinary incontinence and pelvic organ prolapse are increasing in the United States. Demographic data has predicted a 35% increase in pelvic floor disorders over a 20-year period ending in 2030.1 A percentage of these patients will be managed with pelvic reconstructive surgery for symptomatic incontinence and prolapse. A subgroup of those operative patients will require additional surgery for symptomatic recurrence. Wu et al.2 estimated a cumulative incidence of a subsequent surgery for women aged older than 65 years at 9.9%. The medical cost outlay for procedures related to pelvic floor dysfunction is estimated to be 714,000,000 dollars annually in 2001 dollars.3 It is predicted that the number of women undergoing stress incontinence surgery will increase 47.2% from 2010 to 2050.4 It is highly desirable that operations for pelvic floor dysfunction have limited morbidity, restore quality of life, and have a low risk of anatomic recurrence. This chapter discusses how regenerative medicine offers promise in the clinical and surgical response to female pelvic floor dysfunction.


THE LIMITATIONS OF MESH IMPLANTED TRANSVAGINALLY

Recurrent issues of prolapse and incontinence are associated with decreased innervation, weakened tissues, and the effects of aging. An attempt has been made to mitigate these factors and decrease the rate of prolapse recurrence with the use of synthetic mesh. The clinical results have been only partially successful because synthetic materials are not consistent with an optimal homeostasis for biochemistry and biomechanics of pelvic floor tissues. Systematic reviews have shown insufficient evidence for the use of synthetic materials in the apical and posterior compartments.5 A prospective study comparing native tissue repair with augmented synthetic mesh in the anterior and posterior compartments, showed no benefit in terms of outcomes and demonstrated a cumulative 12% risk of synthetic mesh complications.6

Synthetic materials can have deleterious effects on vaginal histomorphologic, biochemical, and mechanical end points when implanted into the vaginal wall. This can include negative effects on collagen, elastin, and smooth muscle.7,8

The debacle of complications and associated litigation related to a variety of synthetic materials and their application demonstrates that they are not adequate to fully meet the future medical demands of pelvic floor dysfunction and its sequelae.


VAGINAL HOMEOSTASIS AND THE RISKS OF PELVIC FLOOR DYSFUNCTION

It is important to understand the biochemical and biomechanical pathophysiologic factors predisposing to pelvic floor dysfunction. This understanding is intrinsic to a scientific foundation for regenerative medicine response to adverse tissue factors.

The integrity of the pelvic support tissues is dependent on connective tissue (structural proteins), fibroblasts, matrix, smooth muscle, adhesion molecules, muscle integrity, and innervation. Individuals may have genetic connective tissue deficiencies leading to prolapse.9 A systematic review reported an association between joint hypermobility and pelvic organ prolapse in women.10 There been multiple studies assessing tissue proteins and cross-linking enzymes, including lysyl oxidases and fibulins, in patients with prolapse.11,12 Collagen changes in pelvic organ prolapse show abnormal biochemical composition with fibrils becoming bulkier, more uneven in width, and exhibiting changing ratios of type I to type III collagen.13 Studies are beginning to assess genes at the transcriptional level and their effects on structural proteins and matrix. Expressions of extracellular matrix remodeling proteins were shown to be altered in the vaginal tissue of premenopausal women with severe pelvic organ prolapse as compared asymptomatic controls.14
The authors postulated that dysregulation of matrix metalloproteinases (MMP)/tissue inhibitor of metalloproteinases complexes and protein abnormalities may cause connective tissue defects in pelvic organ prolapse patients. Damaser et al. found that bone morphogenetic protein 1 (BMP1) gene expression was more than twofold higher in women with pelvic organ prolapse compared with controls, regardless of menopausal status (lysyl oxidases require activation by BMP1).15

Vaginal delivery, aging, and occupational stresses can increase nerve, muscle, and connective tissue damage. A Swedish nationwide matched cohort study shows an estimated probability of symptomatic prolapse 12 times higher following vaginal delivery as compared to caesarean delivery in patients reaching age 64 years.16 The interaction between vaginal delivery and aging was the most important factor for the occurrence of symptomatic prolapse.


SECONDARY EFFECTS OF PROLAPSE ON TISSUE BIOCHEMISTRY

In addition to the genetic effects on tissue biochemistry and resultant prolapse, vaginal relaxation itself can result in secondary changes of structural proteins and matrix. This further compounds the difficulty of assessing pelvic tissue pathophysiology.

Kerkhof et al.17 used premenopausal patients as their own controls comparing biopsies from an isolated cystocele and a well-supported vaginal apex. Results showed a higher amount of collagen III, elastin, and a significant increase of smooth muscle cells at the pelvic organ prolapse site compared to the apex. Apex biopsies were also compared to a control group without prolapse, which showed no histologic or biochemical differences. A similar study in premenopausal patients showed delayed fibroblast-mediated collagen contraction and lower production of MMP-2 at the site the cystocele compared to the supported apex.18 This implied an acquired rather than an intrinsic tissue defect. There is evidence that mechanical strain induces oxidative stress, promotes apoptosis, and senescence of pelvic support fibroblasts.19

There may be a benefit to regenerative medicine intervention in mild to moderate prolapse prior to secondary biochemical changes which further weaken the tissues.


REGENERATIVE MEDICINE OPPORTUNITIES IN FEMALE PELVIC RECONSTRUCTION

Regenerative interventions in pelvic floor dysfunction include tissue-engineered implants, urethral injection, and the use of growth factors, exosomes, nanovesicles, micro ribonucleic acids (miRNAs), and other inducers for injection into tissues to induce desirable substrate changes.

Tissue-engineered three-layered vaginas had been created and implanted in animal models and humans. Atala et al. reported an 8-year follow-up in female patients with vaginal agenesis.20 The patient cells were taken from vulvar biopsies and seeded onto Surgisis which acted as the scaffolding sized to the patient’s estimated pelvic dimensions measured on magnetic resonance imaging. Immunohistochemical analysis confirmed the presence of normal smooth muscle and epithelium in this trilayered structure. This has a benefit over common neovagina constructs which create a structure lacking smooth muscle.

Surgisis is extracellular matrix from porcine subintestinal submucosa. Extracellular matrix-like materials can also be created by nano-spinning or automated three-dimensional printing.21 Matrix can be seeded with adipose-derived mesenchymal stem cells (AMCs) and nanovesicles, small interfering ribonucleic acids (siRNAs), or miRNAs to create a good manufacturing practice (GMP) hybrid tissue construct that could be implanted into humans.22

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May 1, 2023 | Posted by in GYNECOLOGY | Comments Off on Regenerative Medicine Applications in Pelvic Reconstructive Surgery

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