Pregnancy and parity impair the connective tissue that is supporting the urethra, resulting in stress urinary incontinence (SUI). Mid-urethral slings (MUS) are used to support the urethra in an estimated 750,000 patients/year. Polypropylene slings (PS) are effective; however, patients with atrophied vagina, those requiring revision of failed PS or those who are affected by the negative publicity around transvaginal meshes opt for autografts. Donor site morbidity, pain, prolonged hospital stay and hernia risk at harvest site, render autografts less than ideal. Currently, there are limited clinically reliable alternatives to MUS autografts when PS slings are contraindicated. We developed the only known functionally load-bearing woven collagen mesh (CollaMesh) via a biofabrication process called electrocompaction. The open connected-pore network of CollaMesh enables cell seeding and facilitates rapid tissue integration in vivo. Only when crosslinked with genipin, CollaMesh promotes de novo collagen deposition in vivo in amounts comparable to that attained by PS. The stiffness of healing genipin mesh matches that of vaginal tissue. Favorable outcome from genipin crosslinked collagen mesh is accompanied by elevation of pro-regenerative M2-macrophages; however, only after 5 months. The hypothesis of the proposed project is delivery of autologous-blood derived M2 macrophages via genipin crosslinked collagen meshes will result in faster regeneration, e.g. earlier deposition of collagen, earlier inception of neovascularization and earlier attainment of mechanical robustness than the collagen meshes which are implanted without M2 macrophages. Furthermore, the indicated performance metrics will match those of PS as the clinical control group. To the best of our knowledge, this is the first time an immunoregenerative approach is used to address SUI via readily obtainable blood-derived autologous macrophages.
Aim 1 will enhance the immunoregenerative capacity of M2 macrophages by modulating genipin crosslinking dose and via IL-4 delivery in vitro (Sub Aim 1.1); and, determine an effective cell seeding density that will enhance connective tissue formation and neovascularization in vivo (Sub Aim 1.2).
Aim 2 will evaluate the effects of M2 macrophage delivery on in vivo functional outcome on stress urinary incontinence treatment. Rats rendered chronically incontinent will be treated with M2 macrophage seeded CollaMesh and appropriate controls (PS, incontinent). Leak point pressure, urethral contractility, tissue stiffness, quantitative immuno/histological assessment of de novo tissue formation and cells types will be investigated in sling and urethral domains. An exploratory aim will establish a proof of concept study in ewes to demonstrate the feasibility of macrophage delivery in human sized knitted CollaMesh sling to bridge this R21 to R01 studies. The clinical need for improved slings in repairing urinary incontinence is real; thus, the potential of the proposed approach for future impact is high. CollaMesh may emerge as a translational candidate in treating patients who are contraindicated to PS. The concept may find place in other applications such as hernia repair and wound healing.
The soft tissue around the tube that discharges the urine from the bladder is damaged during childbirth, resulting in urinary leakage. In some patients, strips of tissue is harvested from their abdomens and implanted under the urinary tube to provide support. This project will develop a mesh made from natural collagen fibers supplemented with blood-derived cells to make a permanent support structure as an alternative to abdomen harvested tissue.