Biomechanical Comparison of Four Soft Tissue Replacement Materials: An In Vitro Evaluation of Single and Multilaminate Porcine Small Intestinal Submucosa, Canine Fascia Lata, and Polypropylene Mesh

Viscoelastic Properties of Acellular Matrices of Porcine Esophageal Mucosa and Comparison with Acellular Matrices of Porcine Small Intestine Submucosa and Bovine Pericardium

The aim of this study was to compare the viscoelastic properties of a decellularized mesh from the porcine esophagus, prepared by our group, with two commercial acellular tissues derived from porcine small intestine submucosa and bovine pericardium for use in medical devices. The tissues' viscoelastic properties were characterized by creep tests in tension, applying the load in the direction of the fibers or the transverse direction, and also by dynamic-shear mechanical tests between parallel plates or in tension at frequencies between 0.1 and 35 Hz. All the tests were performed in triplicate at a constant temperature of 37 °C immersed in distilled water. The tissues' surface and cross-sectional microstructure were observed by scanning electron microscopy (SEM) to characterize the orientation of the fibers. The matrices of the porcine esophagus present an elastic modulus in the order of 60 MPa when loaded in the longitudinal direction while those of the porcine intestine submucosa and bovine pericardium have an elastic modulus below 5 MPa. Nevertheless, the shear modulus of bovine pericardium nearly triplicates that of the esophageal matrix. The viscoelasticity of decellularized esophageal mucosa is characterized by a fast change in the creep compliance with time. The slope of the creep curve in the double logarithmic plot is twice that of the control samples. These results are consistent with the microstructure observed under electron microscopy regarding the orientation of the fibers that make up the matrices.

Long-term outcome of autologous fascia lata grafting with conjunctival flap overlay in horses with ulcerative keratitis and keratomalacia

OBJECTIVES

To describe the technique, postoperative complications, and outcome after autologous fascia lata grafting with conjunctival flap overlay in horses with ulcerative keratitis and keratomalacia.

STUDY DESIGN

Retrospective case series.

ANIMALS

Eleven horses with ulcerative keratitis and keratomalacia.

METHODS

Horses included had undergone fascia lata grafting with conjunctival flap overlay due to impending or recent corneal perforation. Preceding therapy, lesion characteristics, postoperative complications, and short- and long-term outcomes were recorded.

RESULTS

Postoperative complications included complete (1/11) or partial (2/11) dehiscence of the conjunctival flap and fascia lata graft, postoperative pneumonia (1/11), intermittent hypercreatinemia (2/11) and mild uveitis after trimming of the conjunctival flap (9/10). The donor sites healed without complications (11/11). A satisfactory short-term outcome (at cessation of medical therapy) was achieved in all horses (11/11). Long-term follow-up (median 29 months, range 7-127 months) was available for 10/11 horses. A comfortable eye with functional vision was achieved in 9/10 horses with long-term follow-up, including 3/4 horses with prior corneal perforation and 1/11 horses in which the fascia lata graft completely dehisced 15 days after surgery. Enucleation was required in a single horse (1/10) after phthisis bulbi developed 7 months postoperatively.

CONCLUSION

Fascia lata grafting with conjunctival flap overlay appears to be a viable solution for globe preservation in horses with ulcerative keratitis and keratomalacia. Long-term ocular comfort with functional visual outcomes can be achieved in most cases with limited concerns for donor site morbidity while bypassing acquisition, storage or lesion-size limitations related to other biomaterials.

Regulatory science for hernia mesh: Current status and future perspectives

Regulatory science for medical devices aims to develop new tools, standards and approaches to assess the safety, effectiveness, quality and performance of medical devices. In the field of biomaterials, hernia mesh is a class of implants that have been successfully translated to clinical applications. With a focus on hernia mesh and its regulatory science system, this paper collected and reviewed information on hernia mesh products and biomaterials in both Chinese and American markets. The current development of regulatory science for hernia mesh, including its regulations, standards, guidance documents and classification, and the scientific evaluation of its safety and effectiveness was first reported. Then the research prospect of regulatory science for hernia mesh was discussed. New methods for the preclinical animal study and new tools for the evaluation of the safety and effectiveness of hernia mesh, such as computational modeling, big data platform and evidence-based research, were assessed. By taking the regulatory science of hernia mesh as a case study, this review provided a research basis for developing a regulatory science system of implantable medical devices, furthering the systematic evaluation of the safety and effectiveness of medical devices for better regulatory decision-making. This was the first article reviewing the regulatory science of hernia mesh and biomaterial-based implants. It also proposed and explained the concepts of evidence-based regulatory science and technical review for the first time.

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention because of their native structures, comparatively high bioactivity, low immunogenicity and good biodegradability, which are difficult to be imitated by synthetic materials. Recently, DMs have been demonstrated to possess great potential to overcome the disadvantages of autografts and have become a kind of promising material for tissue engineering. In this systematic review, we aimed to not only provide a quick access for understanding DMs, but also bring new ideas to utilize them more appropriately in tissue engineering. Firstly, the preparation of DMs was introduced. Then, the updated applications of DMs derived from different tissues and organs in tissue engineering were comprehensively summarized. In particular, their advantages, drawbacks and current improvements were emphasized. Moreover, we analyzed and proposed future perspectives.

Biocompatibility of allogenic canine fascia lata: In vitro evaluation and small case series

OBJECTIVE

To evaluate the biocompatibility of canine fascia lata (FL) in vitro and after FL allograft implantation in dogs with clinical disease.

STUDY DESIGN

In vitro experiment and small case series.

SAMPLE POPULATION

Six dogs treated with allogenic freeze-dried FL.

METHODS

Fibroblasts were cultured on disks of FL, polypropylene mesh (PM; negative control), and porcine small intestinal submucosa (SIS; positive control). Constructs were compared at 3, 7, and 14 days for water content, DNA amounts, scanning electron microscopy, and histology. Records of dogs treated with FL allografts with follow-up examination were reviewed for signalment, indication for surgery, surgical procedure, and outcomes. All owners were invited to complete a standardized questionnaire for long-term follow-up.

RESULTS

Water content was greater in FL and SIS than in PM (P = .03). Fascia lata constructs contained more DNA compared with PM constructs at days 7 and 14 (P < .05), whereas SIS constructs did not differ from FL or PM. Fibroblasts appeared spherical and distributed throughout FL constructs, whereas they appeared stellate and remained on the surface of SIS and PM. Fascia lata allografts were implanted in six dogs with surgical conditions. No incisional complications were noted. All dogs had good to excellent long-term outcomes, except one that experienced recurrence of a perineal hernia 2 years after repair.

CONCLUSION

In vitro, canine FL allowed attachment and proliferation of fibroblasts throughout layers of the graft. Canine allogenic FL was clinically well tolerated in this small population of dogs.

CLINICAL SIGNIFICANCE

Allogenic FL is biocompatible and can be considered an alternative to SIS for soft tissue augmentation in dogs.

Use of fascia lata autograft for repair of urinary bladder defect in rabbits

The aim of this study was to investigate the compatibility of a fascia lata autograft for urinary bladder tissue defect, to evaluate the biomechanical, radiographical, macroscopical, biochemical, and histopathological test findings, and early and late complications of the surgical processes in rabbits. Thirty two adult healthy New Zealand rabbits were randomly allocated to 4 different groups of 8 animals. A 2 × 2 cm urinary bladder defect was repaired by the same size of fascia lata in experimental groups (Group 1, 2, 3). Rabbits in Group 1, 2 and 3 were euthanized at the end of the 4th, 8thand 12thweek after surgeries, respectively. No surgical procedure was carried out for the urinary bladder of the rabbits in the control group, but their urinary bladders were used for biomechanical tests and the values compared with those of Group 1, 2 and 3. Histopathological examination of the grafted area was performed. The grafted area was consistent with that of the tissue of urinary bladder. No significant difference was found between the urinary bladder and the grafted area. No differences in biomechanical tests were recorded between grafted and ungrafted urinary bladders. Histopathologically, fascia lata turned into a normal urinary bladder tissue. Therefore, a fascia lata autograft can be succesfully used in urinary bladder defects. Fascia lata grafts can be used successfully in pathological conditions of the urinary bladder that require a new tissue.

Cierre de un gran defecto de la pared torácica y abdominal usando omento y malla de polipropileno en un canino

Este reporte de caso describe la resección quirúrgica exitosa de un condroma de gran tamaño localizado en las dos últimas costillas y pared abdominal craneal izquierda de un canino, usando una malla de polipropileno, omento y avance del diafragma. Se discute la técnica quirúrgica y los materiales utilizados en el procedimiento, así como la evolución posquirúrgica del paciente.

Pericardial flap to repair a pulmonary laceration in a cat with pyothorax

Case summary

A 2-year-old female neutered domestic shorthair cat was presented for investigation of acute onset tachypnoea and dyspnoea. Pyothorax was diagnosed based on thoracic radiographs and fluid analysis. Medical treatment consisted of bilateral thoracostomy tube placement, antibiotic therapy and thoracic lavage. After 12 days of medical management infection was still present, warranting exploratory thoracotomy. At surgery, encapsulated abscesses were found in the left lung, right cranial and right middle lobes. The right caudal lobe was the only macroscopically non-abscessated lobe, and appeared to have a parenchymal laceration 8 mm long over the dorsolateral surface. Following partial pericardiectomy, mediastinectomy and debridement of abscesses, a pericardial flap was reflected caudolaterally and apposed over the laceration to seal the affected lung lobe. This flap was sutured to a rim of fibrinous adhesion that was partially covering this lobe. After 8 days the cat was discharged with antibiotic therapy for 3 more weeks. Follow-up assessment at 19 and 38 weeks postoperatively confirmed the cat to have good exercise tolerance. Thoracic radiographs at 19 weeks revealed good bilateral aeration of the pulmonary parenchyma without pleural effusion.

Relevance and novel information

Lung lobe laceration can be treated by lung lobectomy or direct suturing of the lung parenchyma. This is the first report using a pericardial flap to repair a lung laceration. Pericardial flap was successfully used to treat this lung laceration where lobectomy was contraindicated. Encouraging results were present at 8 months postoperatively.

Viable cryopreserved umbilical tissue (vCUT) reduces post-operative adhesions in a rabbit abdominal adhesion model

Post-operative adhesions, a common complication of surgery, cause pain, impair organ functionality, and often require additional surgical interventions. Control of inflammation, protection of injured tissue, and rapid tissue repair are critical for adhesion prevention. Adhesion barriers are biomaterials used to prevent adhesions by physical separation of opposing injured tissues. Current adhesion barriers have poor anti-inflammatory and tissue regenerative properties. Umbilical cord tissue (UT), a part of the placenta, is inherently soft, conforming, biocompatible, and biodegradable, with antimicrobial, anti-inflammatory, and antifibrotic properties, making it an attractive alternative to currently available adhesion barriers. While use of fresh tissue is preferable, availability and short storage time limit its clinical use. A viable cryopreserved UT (vCUT) "point of care" allograft has recently become available. vCUT retains the extracellular matrix, growth factors, and native viable cells with the added advantage of a long shelf life at -80 °C. In this study, vCUT's anti-adhesion property was evaluated in a rabbit abdominal adhesion model. The cecum was abraded on two opposing sides, and vCUT was sutured to the abdominal wall on the treatment side; whereas the contralateral side of the abdomen served as an internal untreated control. Gross and histological evaluation was performed at 7, 28, and 67 days post-surgery. No adhesions were detectable on the vCUT treated side at all time points. Histological scores for adhesion, inflammation, and fibrosis were lower on the vCUT treated side as compared to the control side. In conclusion, the data supports the use of vCUT as an adhesion barrier in surgical procedures.

In vivo biomechanical properties of heavy versus light weight monofilament polypropylene meshes. Does the knitting pattern matter?

AIMS

This work evaluated the post-implant biomechanical properties of light-weight (LW) and heavy-weight (HW) monofilament polypropylene (PP) meshes with different knitting patterns in an animal model in vivo.

METHODS

Forty-five adult female Wistar rats were divided into three groups and randomly implanted with 32 × 32 mm HW-PP (62 gm^-2 ) orLW-PP (16 gm^-2 ) in the lower abdomen. LW-PPwas tested orthogonally (called LWL and LWT) to reproduce the longitudinal and transverse planes of the vaginal wall, respectively. Abdominal walls were removed at 7, 30, and 60 days, and then tested for tensile load (maximum load until avulsion from the tissue), deflection, and stiffness to maximum load. Explants were compared over time and between groups.

RESULTS

LW-PP meshes implanted in the LWT fashion (vaginal transverse plane) showed comparable maximum load and stiffness to HW-PP meshes, and LW-PP meshes implanted in the LWL fashion (vaginal longitudinal plane) presented lower maximum load and stiffness than the HW-PP meshes. There were no significant differences in the values of deflection at maximum load between the studied meshes as a function of time.

CONCLUSIONS

The final mechanical behavior of PP mesh can be changed by its weight and knitting pattern. These properties may be useful in making more biocompatible prostheses for pelvic organ prolapse (POP) with less foreign material to maintain longitudinal vaginal elasticity and minimize sexual symptoms while maintaining transverse resistance (i.e., between vaginal fornixes) to prevent POP recurrence. Neurourol. Urodynam. 36:73-79, 2017. © 2015 Wiley Periodicals, Inc.

Biomechanical comparison of canine fascia lata and thoracolumbar fascia: an in vitro evaluation of replacement tissues for body wall reconstruction

OBJECTIVES

To compare the suitability of thoracolumbar fascia (TLF) and fascia lata (FL) for body wall defect repair in dogs, by examining their biomechanical properties and useable surface area.

STUDY DESIGN

Experimental.

ANIMALS

Dogs (n = 8).

METHODS

Fresh TLF and FL grafts were obtained, surface area was calculated before testing to failure in 2 different modes: tensile testing and resistance to suture pullout, in 2 perpendicular orientations.

RESULTS

Useable TLF surface area was significantly greater than for FL. Maximum load, energy to break, and elastic modulus of FL was significantly greater than that of TLF in tensile testing, but no apparent difference in the ultimate stress or strain was identified. There was no overall difference in suture pullout load between TLF and FL. During tensile testing, tissue orientation had a significant influence on ultimate load, stress, and elastic modulus for both tissue types, with strain and energy to break only having significant effects for TLF and FL, respectively.

CONCLUSIONS

The greater tensile strength and stiffness of FL compared to TLF was not reflected in its material properties, implying any difference was a consequence of greater thickness. Suture pullout was not significantly different between the 2 tissues, perhaps limiting the clinical significance of the tissue mechanics. Tissues were anisotropic with respect to mechanical properties, thus orientation may be an important factor.

Nanostructured polyurethane-poly-lactic-co-glycolic acid scaffolds increase bladder tissue regeneration: an in vivo study

Although showing much promise for numerous tissue engineering applications, polyurethane and poly-lactic-co-glycolic acid (PLGA) have suffered from a lack of cytocompatibility, sometimes leading to poor tissue integration. Nanotechnology (or the use of materials with surface features or constituent dimensions less than 100 nm in at least one direction) has started to transform currently implanted materials (such as polyurethane and PLGA) to promote tissue regeneration. This is because nanostructured surface features can be used to change medical device surface energy to alter initial protein adsorption events important for promoting tissue-forming cell functions. Thus, due to their altered surface energetics, the objective of the present in vivo study was to create nanoscale surface features on a new polyurethane and PLGA composite scaffold (by soaking the polyurethane side and PLGA side in HNO₃ and NaOH, respectively) and determine bladder tissue regeneration using a minipig model. The novel nanostructured scaffolds were further functionalized with IKVAV and YIGSR peptides to improve cellular responses. Results provided the first evidence of increased in vivo bladder tissue regeneration when using a composite of nanostructured polyurethane and PLGA compared with control ileal segments. Due to additional surgery, extended potentially problematic healing times, metabolic complications, donor site morbidity, and sometimes limited availability, ileal segment repair of a bladder defect is not optimal and, thus, a synthetic analog is highly desirable. In summary, this study indicates significant promise for the use of nanostructured polyurethane and PLGA composites to increase bladder tissue repair for a wide range of regenerative medicine applications, such as regenerating bladder tissue after removal of cancerous tissue, disease, or other trauma.

Small intestinal submucosa segments as matrix for tissue engineering: review

Tissue engineering (TE) is an emerging interdisciplinary field aiming at the restoration or improvement of impaired tissue function. A combination of cells, scaffold materials, engineering methods, and biochemical and physiological factors is employed to generate the desired tissue substitute. Scaffolds often play a pivotal role in the engineering process supporting a three-dimensional tissue formation. The ideal scaffold should mimic the native extracellular environment providing mechanical and biological properties to allow cell attachment, migration, and differentiation, as well as remodeling by the host organism. The scaffold should be nonimmunogenic and should ideally be resorbed by the host over time, leaving behind only the regenerated tissue. More than 40 years ago, a preparation of the small intestine was introduced for the replacement of vascular structures. Since then the small intestinal submucosa (SIS) has gained a lot of interest in TE and subsequent clinical applications, as this material exhibits key features of a highly supportive scaffold. This review will focus on the general properties of the SIS and its applications in therapeutical approaches as well as in generating tissue substitutes in vitro. Furthermore, the main problem of TE, which is the insufficient nourishment of cells within three-dimensional, artificial tissues exceeding certain dimensions is addressed. To solve this issue the implementation of another small intestine-derived preparation, the biological vascularized matrix (BioVaM), could be a feasible option. The BioVaM comprises in addition to SIS the arterial and venous mesenteric pedicles and exhibits thereby a perfusable vessel bed that is preserved after decellularization.

Confocal laser scanning microscopy evaluation of an acellular dermis tissue transplant (Epiflex®)

The structure of a biological scaffold is a major determinant of its biological characteristics and its interaction with cells. An acellular dermis tissue transplant must undergo a series of processing steps, to remove cells and genetic material and provide the sterility required for surgical use. During manufacturing and sterilization the structure and composition of tissue transplants may change.

The composition of the human cell-free dermis transplant Epiflex® was investigated with specific attention paid to its structure, matrix composition, cellular content and biomechanics.

We demonstrated that after processing, the structure of Epiflex remains almost unchanged with an intact collagen network and extracellular matrix (ECM) protein composition providing natural cell interactions. Although the ready to use transplant does contain some cellular and DNA debris, the processing procedure results in a total destruction of cells and active DNA which is a requirement for an immunologically inert and biologically safe substrate. Its biomechanical parameters do not change significantly during the processing.

Porcine urinary bladder matrix-polypropylene mesh: a novel scaffold material reduces immunorejection in rat pelvic surgery

INTRODUCTION AND HYPOTHESIS

The present study set out to modify polypropylene vaginal surgical material using porcine urinary bladder matrix (UBM) in order to improve biocompatibility. The aim was to develop a compound scaffold that induced less vaginal erosion and to evaluate host immunoreactivity to this material in vivo.

METHODS

Forty-eight Sprague-Dawley rats were randomly divided into four equal groups. One group underwent a sham operation, and the other groups underwent vaginal implantation with different materials: UBM (U); UBM + polypropylene (UP); or polypropylene (P). The host tissue response was determined by macro-observation, and by histological and immunohistochemical methods at 7, 14, 21, or 28 days after surgery.

RESULTS

The inflammation reaction was strongest throughout the entire observation time in Group P, but was weaker and had a tendency to decrease with time in Groups U and UP. The presence of the UBM material in the compound scaffold allowed the polypropylene to fuse with newly proliferating surrounding tissue and resulted in less rejection of the material by the host, as indicated by the reduced appearance of CD4-, and CD8-positive cells.

CONCLUSIONS

Porcine UBM allowed mechanical isolation of polypropylene, and also reduced the immune reaction to polypropylene. This study suggests that the UBM + polypropylene compound scaffold may be a promising material for clinical use in pelvic reconstruction surgery.

Treatment of corneal ulcers: when is surgery indicated?

PRACTICAL RELEVANCE

While corneal ulcers in cats frequently arise secondarily to feline herpesvirus (FHV-1) infection, and thus medical therapy is often indicated, other causes include trauma, eyelid abnormalities (agenesis, entropion, dermoids and neoplasia), tear film abnormalities and neurological deficiencies (trigeminal nerve paralysis or facial nerve paralysis). In some such cases, surgery is required. Treatment always needs to be tailored carefully according to the depth and progression of the ulcer, any concurrent ophthalmic disease, the patient's general health and demeanour, and owner compliance and financial circumstances.

PATIENT GROUP

All age groups and breeds can suffer with ulcerative keratitis although some breeds are over-represented for some types of corneal ulceration.

EVIDENCE BASE

The scientific literature on feline ulcerative keratitis is extensive. This article reviews the surgical indications for corneal ulceration in cats with reference to the current evidence base.