An Improved Understanding of the Pathophysiology of Pelvic Organ Prolapse: A 3D In Vitro Model under Static and Mechanical Loading Conditions.

The suboptimal outcomes of pelvic organ prolapse (POP) surgery illustrate the demand for improved therapies. However, their development is hampered by the limited knowledge on the cellular pathophysiology of POP. Current investigations, that are limited to tissues and 2D in vitro models, provide highly inconclusive results on how the extracellular matrix (ECM) metabolism and fibroblasts are affected in POP. This study uses a physiologically relevant 3D in vitro model to investigate the cellular pathophysiology of POP by determining the differences between POP and non-POP fibroblasts on ECM metabolism, proliferation, and fibroblast-to-myofibroblast (FMT) transition. This model, based on the synthetic and biomimetic polyisocyanide hydrogel, enables the incorporation of mechanical loading, which simulates the forces exerted on the pelvic floor. Under static conditions, 3D cultured POP fibroblasts are less proliferative, undergo FMT, and exhibit lower collagen and elastin contents compared to non-POP fibroblasts. However, under mechanical loading, the differences between POP and non-POP fibroblasts are less pronounced. This study contributes to the development of more comprehensive models that can accurately mimic the POP pathophysiology, which will aid in an enhanced understanding and may contribute to improved therapies in the future.

Injectable polyisocyanide hydrogel as healing supplement for connective tissue regeneration in an abdominal wound model.

In pelvic organ prolapse (POP) patients, the uterus, bladder and/or rectum descends into vagina due to weakened support tissues. High recurrence rates after POP surgery suggest an urgent need for improved surgical outcomes. Our aim is to promote connective tissue healing that results in stimulated tissue support functions by surgically applying a hydrogel functionalized with biological cues. We used known vaginal wound healing promoting factors (basic fibroblast growth factor, ß-estradiol, adipose-derived stem cells) in the biomimetic and injectable polyisocyanide (PIC) hydrogel, which in itself induces regenerative vaginal fibroblast behavior. The regenerative capacity of injected PIC hydrogel, and the additional pro-regenerative effects of these bioactive factors was evaluated in abdominal wounds in rabbits. Assessment of connective tissue healing (tensile testing, histology, immunohistochemistry) revealed that injection with all PIC formulations resulted in a statistically significant stiffness and collagen increase over time, in contrast to sham. Histological evaluation indicated new tissue growth with moderate to mild immune activity at the hydrogel - tissue interface. The results suggest that PIC injection in an abdominal wound improves healing towards regaining load-bearing capacity, which encourages us to investigate application of the hydrogel in a more translational vaginal model for POP surgery in sheep.

Growth Factor Immobilization to Synthetic Hydrogels: Bioactive bFGF-Functionalized Polyisocyanide Hydrogels.

With its involvement in cell proliferation, migration and differentiation basic fibroblast growth factor (bFGF) has great potential for tissue engineering purposes. So far, however, clinical translation of soluble bFGF-based therapies is unsuccessful, because the required effective doses are often supraphysiological, which may cause adverse effects. An effective solution is growth factor immobilization, whereby bFGF retains its bioactivity at increased efficacy. Studied carriers include films, solid scaffolds, and particles, as well as natural and synthetic hydrogels. However, these synthetic hydrogels poorly resemble the characteristics of the native extracellular matrix (ECM). In this work, bFGF is covalently conjugated to the synthetic, but highly biocompatible, polyisocyanide-based hydrogel (PIC-bFGF), which closely mimics the architecture and mechanical properties of the ECM. The growth factor conjugation protocol is straightforward and readily extrapolated to other growth factors or proteins. The PIC-bFGF hydrogel shows a prolonged bioactivity up to 4 weeks although no clear effects on the ECM metabolism are observed. Beyond the future potential of the PIC-bFGF hydrogel toward various tissue engineering applications, this work underlines that simple biological conjugation procedures are a powerful strategy to induce additional bioactivity in 3D synthetic cell culture matrices.

Vaginal Fibroblast Behavior as a Function of Stiffness Changes in a Polyisocyanide Hydrogel for Prolapse Repair.

There is an urgent need for improved outcomes in the treatment of pelvic organ prolapse (POP). Success of primary surgery relies on the load bearing capacity of plicated connective tissue underneath the vaginal wall, which is compromised due to an altered vaginal fibroblast function and collagen composition. There is an important factor in connective tissue repair that relates to changes in stiffness of the vaginal fibroblast microenvironment, which influences cell activity through cellular mechanosensing. The aim of this study is to investigate the effect of stiffness changes on vaginal fibroblast functions that relate to connective tissue healing in prolapse repair. The substrate stiffness was controlled by changing the polymer concentration in the fibrous and strongly biomimetic polyisocyanide (PIC) hydrogel. We analyzed stiffness during cell culture and assessed the consequential fibroblast proliferation, morphology, collagen deposition, and contraction. Our results show that increasing stiffness coincides with vaginal fibroblast alignment, promotes collagen deposition, and inhibits PIC gel contraction. These findings suggest that the matrix stiffness directly influences vaginal fibroblast functionality. Moreover, we observed a buildup in stiffness and collagen, with an enhanced fibroblast and collagen organization on the PIC-substrate, which indicate an enhanced structural integrity of the hydrogel-cell construct. An improved tissue structure during healing is relevant in the functional repair of POP. Therefore, this study encourages future research in the use of PIC gels as a supplement in prolapse surgery, whereby the hydrogel stiffness should be considered.

The Effect of Growth Factors on Vaginal Wound Healing: A Systematic Review and Meta-analysis.

Surgical outcomes of pelvic organ prolapse (POP) surgery are poor, resulting in a 20% recurrence risk. Following the hypothesis that impaired wound healing is the main determinant of recurrent POP, growth factors have the potential to promote wound healing and may improve surgical outcomes. In this study, we systematically reviewed the effect of growth factors on vaginal wound healing in both in vitro and animal studies. For each independent comparison, the standardized mean difference and 95% CI were calculated using the Hedges' g correction. Of the 3858 retrieved studies, seven studies were included, of which six were included in meta-analysis (three in vitro studies and four in vivo studies). In vitro, basic fibroblast growth factor (bFGF) promotes proliferation, differentiation, and collagen types I and III production. Epidermal growth factor stimulates proliferation and connective tissue growth factor promotes Tenascin-C expression. These effects, however, are less pronounced in vivo; only bFGF slightly promotes collagen production. The review shows that growth factors, particularly bFGF, are able to promote vaginal wound healing in vitro. The uncertain in vivo findings suggest that preclinical models should be improved. The ultimate goal is to develop effective growth factor-supplemented therapies that improve surgical outcomes for POP.

Polyisocyanides as a substrate to trigger vaginal fibroblast functioning in an in vitro model for prolapse repair.

Pelvic organ prolapse (POP) is the descent of the bladder, uterus, and/or rectum into the vagina. POP is associated with altered vaginal fibroblast functionality and connective tissue composition in the vaginal wall. The results of surgical intervention are poor, which may be related to the lack of true restoration of the connective tissue. An innovative treatment addresses tissue repair after surgery by the introduction of a bioactive supplement that enhances the healing process through collagen and elastin deposition. As a novel strategy, we first studied the effects in an in vitro model. Here, we investigate how the presence of cell binding GRGDS (RGD) peptides on the highly biomimetic polyisocyanide (PIC) gel facilitates and promotes the function of primary vaginal fibroblasts isolated from a POP patient. Fibroblast function was analyzed in terms of morphology, proliferation, and extracellular matrix (ECM) deposition and remodeling. RGD modification of the gel facilitated cell spread and proliferation. Quantitative outcomes of the ECM content indicated increased production of collagen and elastin by fibroblasts on gels with the highest RGD density. The in vitro results suggest that PIC-RGD hydrogel application may translate into improved connective tissue healing in the pelvic floor, which is essential for its use as a regeneration promoting additive in surgery.

Animal experimental research assessing urogynecologic surgical mesh implants: Outcome measures describing the host response, a systematic review and meta-analysis.

AIM: Before the introduction of new biomaterials for prolapse surgery, animal studies on the host response are required. Unfortunately, large variation in study design hampers obtaining an overview of the safety and efficacy, and translation to clinical practice. Our aim is to systematically review the literature on all outcome measures describing the host response in animal studies assessing the biocompatibility of urogynecologic surgical mesh implants for prolapse surgery. Furthermore, by meta-analysis, we aim to assess the effect of implantation and compare this to control animals receiving sham surgery or native tissue repair. METHODS: We performed a systematic search from inception to August 2020. Since this is an explorative study we included original, controlled, and noncontrolled animal studies describing any host response to the implant. Quantitative outcome measures reported ≥10 times in ≥2 articles were eligible for meta-analysis. RESULTS: Fifty articles were included in the qualitative synthesis and 36 articles were eligible for meta-analysis. In total, 154 outcome measures were defined and classified into (1) histomorphology, (2) biomechanics and, (3) macroscopic morphology. Animals with vaginal implants demonstrated significantly increased M1 and M2 macrophages, MMP-2, neovascularization, TNF-α, and stiffness, and lower vaginal contractility compared to control animals. CONCLUSION: The host response significantly differs in animals after vaginal mesh implantation compared to control animals, both pro- and anti-inflammatory. However, we observed a paucity in the uniformity of reported outcomes. For future animal studies, we propose the development of a core outcome set, which ideally predicts the host response in women.

Scaling analysis of the viscoelastic response of linear polymers.

Viscoelastic response in terms of the complex shear modulus G*(ω) of the linear polymers poly(ethylene-alt-propylene), poly(isoprene), and poly(butadiene) is studied for molar masses (M) from 3k up to 1000k and over a wide temperature range starting from the glass transition temperature Tg (174 K-373 K). Master curves G'(ωτα) and G″(ωτα) are constructed for the polymer-specific relaxation. Segmental relaxation occurring close to Tg is independently addressed by single spectra. Altogether, viscoelastic response is effectively studied over 14 decades in frequency. The structural relaxation time τα used for scaling is taken from dielectric spectra. We suggest a derivative method for identifying the different power-law regimes and their exponents along G″(ωτα) ∝ ωε″. The exponent ε″ = ε″(ωτα) ≡ d ln G″(ωτα)/d ln(ωτα) reveals more details compared to conventional analyses and displays high similarity among the polymers. Within a simple scaling model, the original tube-reptation model is extended to include contour length fluctuations (CLFs). The model reproduces all signatures of the quantitative theory by Likhtman and McLeish. The characteristic times and power-law exponents are rediscovered in ε″(ωτα). The high-frequency flank of the terminal relaxation closely follows the prediction for CLF (ε″ = -0.25), i.e., G″(ω) ∝ ω-0.21±0.02. At lower frequencies, a second regime with lower exponent ε″ is observed signaling the crossover to coherent reptation. Application of the full Likhtman-McLeish calculation provides a quantitative interpolation of ε″(ωτα) at frequencies below those of the Rouse regime. The derivative method also allows identifying the entanglement time τe. However, as the exponent in the Rouse regime (ωτe > 1) varies along εeRouse = 0.66 ± 0.04 (off the Rouse prediction εRouse = 0.5) and that at ωτe < 1 is similar, only a weak manifestation of the crossover at τe is found at highest M. Yet, calculating τe/τα= (M/Mo)2, we find good agreement among the polymers when discussing ε″(ωτe). The terminal relaxation time τt is directly read off from ε″(ωτα). Plotting τt/τe as a function of Z = M/Me, we find universal behavior as predicted by the TR model. The M dependence crosses over from an exponent significantly larger than 3.0 at intermediate M to an exponent approaching 3.0 at highest M in agreement with previous reports. The frequency of the minimum in G″(ωτα) scales as τmin ∝ M1.0±0.1. An M-independent frequency marks the crossover to glassy relaxation at the highest frequencies. Independent of the amplitude of G″(ω), which may be related to sample-to-sample differences, the derivative method is a versatile tool to provide a detailed phenomenological analysis of the viscoelastic response of complex liquids.

COPD patients with severe diffusion defect in carbon monoxide diffusing capacity predict a better outcome for pulmonary rehabilitation.

PURPOSE: The aim of this study was to compare the effects of pulmonary rehabilitation (PR) on six-minute walk test (6mWT) between chronic obstructive pulmonary disease (COPD) patients with moderate or severe carbon monoxide diffusion defects. We also evaluated dyspnea sensation, pulmonary functions, blood gases analysis, quality of life parameters and psychological symptoms in both groups before and after pulmonary rehabilitation. METHODS: Patients with COPD underwent a comprehensive 8-week out-patient PR program participated in this study. Patients grouped according to diffusion capacity as moderate or severe. Outcome measures were exercise capacity (6mWT), dyspnea sensation, pulmonary function tests, blood gases analysis, quality of life (QoL) and psychological symptoms. RESULTS: A total of 68 patients enrolled in the study. Thirty-two (47%) of them had moderate diffusion defect [TlCO; 52 (47-61)mmol/kPa] and 36 (53%) of them had severe diffusion defect [TlCO; 29 (22-34)mmol/kPa]. At the end of the program, PaO2 (p=0.001), Modified Medical Research Council dyspnea scale (p=0.001), 6mWT (p<0.001) and quality of life parameters improved significantly in both groups (p<0.05). Also the improvement in DlCO (p=0.04) value and FEV1% (p=0.01) reached a statistically significant level in patients with severe diffusion defect. When comparing changes between groups, dyspnea reduced significantly in patients with severe diffusion defect (p=0.04). CONCLUSION: Pulmonary rehabilitation improves oxygenation, severity of dyspnea, exercise capacity and quality of life independent of level of carbon monoxide diffusion capacity in patents with COPD. Furthermore pulmonary rehabilitation may improve DlCO values in COPD patients with severe diffusion defect.

Ripple formation in weakly turbulent flow.

The formation of granular ripples under liquid shear flow in an annular channel is studied experimentally. The erodible granular bed is subject to weakly turbulent flows without a defined sharp boundary layer close to the granular bed. The flow field and the degree of turbulence is characterized quantitatively by using a particle image velocimeter and a laser-Doppler velocimeter, respectively. A new range of particle Reynolds numbers at the lower limit of the Shields diagram were explored. Quantitative measurements of the granular flow on the surface reveal that the threshold for particle motion coincides within the order of one percent with the threshold for ripple formation. In fully developed ripples it was found that on the leeward side of the ripples regions of low-velocity gradients exist where granular motion is scarce, indicating that the coupling between the ripples is mainly caused by the flow field of the liquid.