In vivo molecular engineering of the urethra for treatment of stress incontinence using novel biomimetic proteoglycans

Abstract

Stress urinary incontinence (SUI), a serious condition which affects ~56% of postmenopausal women, is the involuntary leakage of urine through urethra during physical activity that causes an increase in abdominal pressure. SUI is associated with a decrease in compliance and volume of urethral tissue, likely due to a reduced proteoglycan: collagen ratio in the extracellular matrix and collagen disorganization. Here, we investigated the use of biomimetic proteoglycans (BPGs) to molecularly engineer urethral tissue of New Zealand White rabbits to examine biocompatibility in vivo. BPG concentrations of 50 mg/mL (n = 6, 1 week) and 200 mg/mL (n = 6, 1 week and n = 6, 6 weeks) dissolved in 1× phosphate‐buffered saline (PBS) were injected transurethrally using a 9 French cystoscope, and were compared to PBS‐injected controls (n = 3, 1 week) and non‐injected controls (n = 2, 1 week). Urethral compression pressure measurements confirm BPG injections did not modify normal urethral pressure, as intended. Histological assessment demonstrated biological tolerance of BPGs in urethra and no inflammatory response was detected after 1 and 6 weeks compared to non‐injected controls. Confocal imaging of fluorescently‐labeled BPG injected urethral specimens demonstrated the integration of BPGs into the interstitial connective tissue and confirmed they were still present after 6 weeks. A general decrease of collagen density was exhibited near injection sites which may be due to increased hydration induced by BPGs. Injection of BPGs is a novel approach that demonstrates potential as molecular treatment for SUI and may be able to reverse some of the degenerative tissue changes of individuals affected by this condition. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: 00B: 000–000, 2019. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2409–2418, 2019.

Modulating physical properties of porcine urethra with injection of novel biomimetic proteoglycans ex vivo

“…AT a molecular level, integration of BPG250 into the matrix and the subsequent swelling of the matrix is hypothesized to decrease the collagen density because the BPGs and water molecules space out the collagen fibrils. An in royalsocietypublishing.org/journal/rsfs Interface Focus 9: 20190013 vivo study where BPG250 was injected into rabbit urethra (0.5 ml injection of 200 mg ml 21 BPG250 solution) showed noticeable bulking spots at the injection site [38]. The study also revealed there was no adverse histological response induced by injection of BPG250 into the urethra, and no morphological differences between the control and BPG250injected groups [38].…”

“…Per cent water uptake was highest for the 100 mg ml 21 samples with a significant difference compared with the PBS sample group ( p , 0.05). Like the natural hydrating proteoglycan of urethral tissue versican, BPG250 composed of a royalsocietypublishing.org/journal/rsfs Interface Focus 9: 20190013 vivo study where BPG250 was injected into rabbit urethra (0.5 ml injection of 200 mg ml 21 BPG250 solution) showed noticeable bulking spots at the injection site [38]. The study also revealed there was no adverse histological response induced by injection of BPG250 into the urethra, and no morphological differences between the control and BPG250injected groups [38].…”

“…An in royalsocietypublishing.org/journal/rsfs Interface Focus 9: 20190013 vivo study where BPG250 was injected into rabbit urethra (0.5 ml injection of 200 mg ml 21 BPG250 solution) showed noticeable bulking spots at the injection site [38]. The study also revealed there was no adverse histological response induced by injection of BPG250 into the urethra, and no morphological differences between the control and BPG250injected groups [38]. Biopsy punches with a 10 mm diameter were used to prepare the porcine samples for this experiment.…”

Biomimetic proteoglycans as a tool to engineer the structure and mechanics of porcine bioprosthetic heart valves

“…BPG10 diffused throughout the porcine aortic valve leaflet and colocalized with ECM components in all three regions of the tissue. Previously we have found that BPG10 has a particularly strong propensity to colocalize with collagen VI, 24,70 a beaded network‐forming collagen found in the pericellular matrix of chondrocytes in articular cartilage and other tissues, 71 and undergoes adhesive interactions with aggrecan, the major proteoglycan of articular cartilage ECM 28 . Similarly, chondroitin sulfate‐containing proteoglycans and hyaluronic acid are also known to associate with fibrillin‐containing microfibrils responsible for elastin fiber formation 72–75 .…”

“…46 Glutaraldehyde-based fixation is generally believed to increase the modulus of tissue through the introduction of covalent crosslinks, however, this assumption is contentious 67,80,85 15,20 Indeed, PGs and GAGs are known to play this role in musculoskeletal tissues 86,87 and our lab has previously shown that BPGs may modulate the mechanical properties of tissue via these mechanisms. 22,32,70 The distribution of modulus values in the valve leaflet spongiosa is likely associated with heterogeneity in extracellular matrix structure and composition at similar scales (on the order of 10s of μm). For example,…”