Characterization and modeling of the in-plane collagen fiber distribution in the porcine dermis.

The structural arrangement of collagen fibers in the plane of the dermis layer plays a critical role in accurately predicting the mechanical behavior of skin tissues. This paper combines a histological analysis with statistical modeling to characterize and model the in-plane collagen fiber distribution in the porcine dermis. The histology data reveals that the fiber distribution in the plane of the porcine dermis is non-symmetric. The histology data forms the basis of our model, which employs a combination of two π-periodic von-Mises distribution density functions to create a non-symmetric distribution. We demonstrate that a non-symmetric in-plane fiber distribution is a significant improvement over a symmetric distribution.

Implantation of biologic mesh in ventral hernia repair-does it make sense?

BACKGROUND: Biological acellular porcine dermis mesh, such as Permacol™, has been used since 2009 to treat abdominal incisional hernias in a septic context. This study investigated the risk factors for incisional hernia recurrence after biological mesh augmentation. RESULTS: Over a period of 6 years from February 2009 to February 2015, 68 patients underwent surgery. The mesh was placed intraperitoneally with closure of the anterior fascia in 27 cases (39.7%). The biological mesh was placed in the retromuscular pre-fascial plane in 1 case (1.5%) and pre-aponeurotic plane in 1 case (1.5%). Closure of the anterior fascia was not achieved in 39 cases, including 20 cases in which the mesh was placed intraperitoneally (intraperitoneal bridging group, 29.4%) and 19 cases in which the mesh was placed between the edges of the fascia (inlay bridging group, 27.9%). There were 37 cases of postoperative surgical site infections (54.4%), and Clavien-Dindo morbidity staging indicated stage I-II and III-IV complications in 19.1% and 44.1% of the cases, respectively. The recurrence rate was 61.8%, and the mortality rate was 0%. The rate of recurrence was significantly lower in the «fascia approximated¼ group (37%), p = 0.001). Univariate analyses of risk factors for procedural failure indicated an increased risk of recurrence in cases of postoperative surgical site infections, complications of Clavien-Dindo grade III or higher, an absent fascial closure in front of the mesh (OR = 8.69), an operating time longer than 180 min, and a VHWG score higher than 2. After logistic regression, the risk factors for recurrence were postoperative infections (OR = 6.2), placement of bridged biological mesh (OR = 22.3), and postoperative morbidity grade III or higher (OR = 16.7). CONCLUSIONS: Patients with postoperative surgical site infections are at an increased risk for recurrence, and bridged mesh placements lack efficacy. Overall, this study challenges the purported advantage of biologics in treating incisional hernia repairs.

Porcine dermal patches as a risk factor for recurrence after congenital diaphragmatic hernia repair.

PURPOSE: Recurrence of congenital diaphragmatic hernia (CDH) is a treatment-related morbidity which can be preventable. There is no consensus about the ideal material for diaphragmatic substitution. The aim of our study is to identify if the use of porcine dermis patches increases the risk of CDH recurrence. METHODS: Retrospective review of medical records of CDH patients treated between 2013 and 2017 in our center was carried out. Demographic, clinical and surgical variables were collected. Regression analysis was performed to identify which factors increase the risk of recurrence. RESULTS: 50 patients entered the study. 94% of the patients had a left CDH, mean observed/expected lung-to-head ratio was 46%. 17 patients underwent a primary closure, the rest a patch closure: 25 Gore-Tex® and 8 porcine dermis patches were used. Seven patients presented recurrence (14%). Median follow-up time was 3.5 years (1.2-6.2). Univariate analysis revealed that the use of a porcine dermis patch (75%) increased the risk of recurrence compared with Gore-Tex® patch (4%) and primary closure (0%) p < 0.001 (HR 58.7; IC 95%: 6.9-501.2; p < 0.001). CONCLUSION: The main risk factor for CDH recurrence is the use of a porcine dermis patch. We do not recommend the use of these patches for CDH repair.

The use of acellular porcine dermis, hyaluronic acid and polynucleotides in the treatment of cutaneous ulcers: Single blind randomised clinical trial.

Reconstruction of chronic ulcers is often hampered by lack of local tissues and poor general conditions. Conservative approaches with debridement and advanced medications, such as polyurethane foam, stand as mainstays. However, the healing process is often slow, thus increasing the risk for infection or other complications. In such cases, porcine dermis (PD) and polynucleotides-added hyaluronic acid (PAHA) were previously reported to accelerate healing. The aim of the study was to compare the efficacy of PD, PAHA and polyurethane foam in chronic ulcers. Thirty patients were randomly divided into 3 groups: group 1 was treated with advanced medications, group 2 with PD, group 3 with PAHA. Standardised photographs and biopsies were taken before treatment and at 30-day follow-up. Photographs were processed to calculate the wound area. Specimens were stained with Haematoxylin/Eosin, Masson trichrome, and immunohistochemically for CD34, alpha-Smooth Muscle Actin (α-SMA), Collagen types I and III, Ki67. The re-epithelialized area was larger in patients treated with PD and PAHA compared with those treated with polyurethane foam (P < .05 and P < .01, respectively). Specimens from patients treated with PD and PAHA showed a higher number of myofibroblasts (α-SMA+, P < .01), neo-angiogenesis (CD34+, P < .01), proliferating dermal cells (Ki67+, P < .01), proliferating keratinocytes (Ki67+, P < .01) and collagen type 1 deposition (P < .05). No difference was found between PD and PAHA. PD and PAHA proved to be more effective than polyurethane foam in the treatment of chronic ulcers. These approaches are a versatile and reliable option to address such cases.

The Effect of Strain Rate on the Stress Relaxation of the Pig Dermis: A Hyper-Viscoelastic Approach.

The understanding of strain rate-dependent mechanical properties of the skin is important for accurate prediction of its biomechanics under different loading conditions. This study investigated the effect of strain rate, i.e., 0.025/s (low), 0.5/s (medium), and 1.25/s (high), ranging in the physiological loading rate of connective tissue, on the stress-relaxation response of the porcine dermis. Results show that in the initial phase of the relaxation, the value of stress relaxation (extent of relaxation) was found higher for high strain rate. However, the equilibrium stress was found strain rate independent. A Mooney-Rivlin-based five-term quasi-linear viscoelastic (QLV) model was proposed to determine the effect of strain rate on the stress-relaxation behavior of the porcine dermis. The value of relaxation modulus G1 and G2 were found higher for the high strain rate, whereas the reverse trend was observed for G3, G4, and G5. Moreover, the value of time constants τ1,τ2,τ3τ4, and τ5 were found higher for low strain rate. Statistical analysis shows no significant difference in the values of G5, τ4, and τ5 among the three strain rates. The proposed model was found capable to fit the stress-relaxation response of skin with great accuracy, e.g., root-mean-squared-error (RMSE) value equal to 0.015 ± 0.00012 MPa. Moreover, this hyper-viscoelastic model can be utilized: to quantify the effects of age and diseases on the skin; to simulate the stresses on sutures during large wound closure and impact loading.

[Abdominal traumatic evisceration: reconstruction abdominal wall with biologic mesh and negative pressure therapy]. / Evisceración abdominal traumática: reconstrucción de pared abdominal con malla biológica y terapia de presión negativa.

INTRODUCTION: Abdominal traumatic evisceration as a result of high energy trauma is uncommon. Once repaired the possible internal damage, an abdominal wall defect of high complexity may exist, whose reconstruction represents a surgical challenge. CASE REPORT: Politraumatized male with important abdominal muculocutaneous avulsion and evisceration. After initial repair, the patient developed a big eventration in which we use a porcine dermis-derived mesh (PermacolTM), a safe and effective alternative in abdominal wall repair, thanks to its seamless integration with other tissues, even when exposed. Negative pressure therapy has been used for the management of wound complications after surgical implantation of PermacolTM mesh. We describe our experience with the use of PermacolTM mesh and negative pressure therapy to aid the wound closure after skin necrosis and exposed mesh.

INTRODUCCION: La evisceración abdominal traumática como consecuencia de un traumatismo de alta energía es poco frecuente. Una vez reparado el posible daño interno, puede existir un gran defecto en la pared abdominal, de alta complejidad, cuya reconstrucción representa un desafío para el cirujano. CASO CLINICO: Varón politraumatizado que presenta una importante avulsión músculocutánea abdominal con evisceración. Tras la reconstrucción inicial, desarrolló una gran eventración para cuya corrección utilizamos una malla biológica de dermis porcina (PermacolTM), una alternativa segura y efectiva en la reparación, gracias a su perfecta integración con el resto de tejidos, incluso cuando queda expuesta. La terapia de presión negativa ha sido utilizada para el manejo de complicaciones después de la colocación de la malla. Presentamos nuestra experiencia en el uso de la malla de PermacolTM y la terapia de presión negativa para conseguir el cierre de la herida tras la necrosis cutánea que ocasionó la exposición de la malla.

Biocompatible porcine dermis graft to treat severe cystocele: impact on quality of life and sexuality.

PURPOSE: To study the quality of life (QoL) and sexual function changes of women affected by severe cystocele treated using biocompatible porcine dermis graft. METHODS: 20 women (ranging in age from 47 to 71 years, mean age 58.7) with third- and fourth-degree cystocele (according to Baden and Walker classification) were enrolled. The Short Form-36 questionnaire to assess QoL was administrated at baseline and 12 months after surgical treatment. The Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ-12) to measure the changes of sexual behavior was used at baseline and 12 months after surgical treatment. Each woman underwent translabial color Doppler ultrasonography to measure the clitoral blood flow before and 12 months after surgical treatment. RESULTS: Women reported QoL improvement (P < 0.001). By PISQ-12, improvement of the behavioral emotive factor score, the physical factor score, the partner-related factor score and of the total score during the 12-month follow-up with respect to baseline experience was observed (P < 0.001). Color Doppler measurement showed that the mean pulsatility index, peak systolic velocity, resistance index and end-diastolic velocity of clitoral arteries did not significantly change (P = NS). CONCLUSIONS: Biocompatible porcine dermis graft to treat severe cystocele considerably improves QoL and sexual function, and does not influence clitoral blood flow. Our data could add new information about sexual behavior after prolapse treatment using this kind of graft, particularly about the impact on clitoral blood flow changes.

Process-induced extracellular matrix alterations affect the mechanisms of soft tissue repair and regeneration.

Extracellular matrices derived from animal tissues for human tissue repairs are processed by various methods of physical, chemical, or enzymatic decellularization, viral inactivation, and terminal sterilization. The mechanisms of action in tissue repair vary among bioscaffolds and are suggested to be associated with process-induced extracellular matrix modifications. We compared three non-cross-linked, commercially available extracellular matrix scaffolds (Strattice, Veritas, and XenMatrix), and correlated extracellular matrix alterations to in vivo biological responses upon implantation in non-human primates. Structural evaluation showed significant differences in retaining native tissue extracellular matrix histology and ultrastructural features among bioscaffolds. Tissue processing may cause both the condensation of collagen fibers and fragmentation or separation of collagen bundles. Calorimetric analysis showed significant differences in the stability of bioscaffolds. The intrinsic denaturation temperature was measured to be 51°C, 38°C, and 44°C for Strattice, Veritas, and XenMatrix, respectively, demonstrating more extracellular matrix modifications in the Veritas and XenMatrix scaffolds. Consequently, the susceptibility to collagenase degradation was increased in Veritas and XenMatrix when compared to their respective source tissues. Using a non-human primate model, three bioscaffolds were found to elicit different biological responses, have distinct mechanisms of action, and yield various outcomes of tissue repair. Strattice permitted cell repopulation and was remodeled over 6 months. Veritas was unstable at body temperature, resulting in rapid absorption with moderate inflammation. XenMatrix caused severe inflammation and sustained immune reactions. This study demonstrates that extracellular matrix alterations significantly affect biological responses in soft tissue repair and regeneration. The data offer useful insights into the rational design of extracellular matrix products and bioscaffolds of tissue engineering.