A comparison of collagen and PTFE patch repair in a rabbit model of congenital diaphragmatic hernia

Design and fabrication of polycaprolactone/gelatin composite scaffolds for diaphragmatic muscle reconstruction

Diaphragmatic wall defects caused by congenital disorders or disease remain a major challenge for physicians worldwide. Polymeric patches have been extensively explored within research laboratories and the clinic for soft tissue and diaphragm reconstruction. However, patch usage may be associated with allergic reaction, infection, granulation, and recurrence of the hernia. In this study, we designed and fabricated a porous scaffold using a combination of 3D printing and freeze-drying techniques. A 3D printed polycaprolactone (PCL) mesh was used to reinforcegelatin scaffolds, representing an advantage over previously reported examples since it provides mechanical strength and flexibility. In vitro studies showed that adherent cells were anchorage-dependent and grew as a monolayer attached to the scaffolds. Microscopic observations indicated better cell attachments for the scaffolds with higher gelatin content as compared with the PCL control samples. Tensile testing demonstrated the mechanical strength of samples was significantly greater than adult diaphragm tissue. The biocompatibility of the specimens was investigated in vivo using a subcutaneous implantation method in Bagg albino adult mice for 20 days, with the results indicating superior cellular behavior and attachment on scaffolds containing gelatin in comparison to pure PCL scaffolds, suggesting that the porous PCL/gelatin scaffolds have potential as biodegradable and flexible constructs for diaphragm reconstruction.

Scaffold-Free Bio-3D Printing Using Spheroids as "Bio-Inks" for Tissue (Re-)Construction and Drug Response Tests

In recent years, scaffold-free bio-3D printing using cell aggregates (spheroids) as "bio-inks" has attracted increasing attention as a method for 3D cell construction. Bio-3D printing uses a technique called the Kenzan method, wherein spheroids are placed one-by-one in a microneedle array (the "Kenzan") using a bio-3D printer. The bio-3D printer is a machine that was developed to perform bio-3D printing automatically. Recently, it has been reported that cell constructs can be produced by a bio-3D printer using spheroids composed of many types of cells and that this can contribute to tissue (re-)construction. This progress report summarizes the production and effectiveness of various cell constructs prepared using bio-3D printers. It also considers the future issues and prospects of various cell constructs obtained by using this method for further development of scaffold-free 3D cell constructions.

Diaphragm Repair with a Novel Cross-Linked Collagen Biomaterial in a Growing Rabbit Model

Background

Neonates with congenital diaphragmatic hernia and large defects often require patch closure. Acellular collagen matrices (ACM) have been suggested as an alternative to synthetic durable patches as they are remodeled by the host or could also be used for tissue engineering purposes.

Materials and Methods

2.0x1.0 cm diaphragmatic defects were created in 6-weeks old New-Zealand white rabbits. We compared reconstruction with a purpose-designed cross-linked ACM (Matricel) to 4-layer non-cross-linked small intestinal submucosa (SIS) and a 1-layer synthetic Dual Mesh (Gore-Tex). Unoperated animals or animals undergoing primary closure (4/0 polyglecaprone) served as age-matched controls. 60 (n = 25) resp. 90 (n = 17) days later, animals underwent chest x-ray and obduction for gross examination of explants, scoring of adhesion and inflammatory response. Also, uniaxial tensiometry was done, comparing explants to contralateral native diaphragmatic tissue.

Results

Overall weight nearly doubled from 1,554±242 g at surgery to 2,837±265 g at obduction (+84%). X-rays did show rare elevation of the left diaphragm (SIS = 1, Gore-Tex = 1, unoperated control = 1), but no herniation of abdominal organs. 56% of SIS and 10% of Matricel patches degraded with visceral bulging in four (SIS = 3, Matricel = 1). Adhesion scores were limited: 0.5 (Matricel) to 1 (SIS, Gore-Tex) to the left lung (p = 0.008) and 2.5 (Gore-Tex), 3 (SIS) and 4 (Matricel) to the liver (p<0.0001). Tensiometry revealed a reduced bursting strength but normal compliance for SIS. Compliance was reduced in Matricel and Gore-Tex (p<0.01). Inflammatory response was characterized by a more polymorphonuclear cell (SIS) resp. macrophage (Matricel) type of infiltrate (p<0.05). Fibrosis was similar for all groups, except there was less mature collagen deposited to Gore-Tex implants (p<0.05).

Conclusions

Matricel induced a macrophage-dominated inflammatory response, more adhesions, had appropriate strength but a lesser compliance compared to native tissue. The herein investigated ACM is not a viable option for CDH repair.

Newly designed bioabsorbable substitute for the treatment of diaphragmatic defects

PURPOSE

Earlier studies have investigated the suitability of various materials and autologous grafts for the repair of diaphragmatic defects. Our group investigated the feasibility of using an artificial diaphragm (AD) to repair wide diaphragmatic defects.

METHODS

Twelve pigs were laparotomized and, in each pig, a defect was fashioned by resecting a round 8-cm diameter hole in the left diaphragm. Next, the defect was repaired by implanting an AD. The animals were relaparotomized 8 or 24 weeks after implantation for gross, histological and radiological observation of the implanted sites.

RESULTS

All recipient animals survived until killing for evaluation. Chest X-ray examinations showed no differences between the preoperative diaphragms and the grafted diaphragms at 8 and 24 weeks after implantation. At 8 weeks after implantation, the implanted sites exhibited fibrous adhesions to the liver and lungs without deformities or penetrations. Parts of the surface tissue at the graft sites had a varnished appearance similar to those of the native diaphragm. Histology performed at 8 weeks detected no trace of the ADs in the graft sites; however, numerous inflammatory cells and profuse fibrous connective tissue were observed. At 24 weeks after implantation, no differences were found in the thorax between the areas with the grafts and the unaffected areas. Histology of the graft sites in the thorax confirmed growth of mesothelial cells similar to that observed in the native diaphragm.

CONCLUSIONS

Artificial diaphragms can be a novel substitute for diaphragmatic repair.

Absorbable versus nonabsorbable mesh repair of congenital diaphragmatic hernias in a growing animal model

INTRODUCTION

The repair of large congenital diaphragmatic hernia frequently results in patch disruption and recurrence as patients grow in size. Absorbable meshes allow for ingrowth of endogenous tissue as they are degraded, providing a more natural and durable repair. The aim of this study was to compare the characteristics of the new diaphragmatic tissue between an absorbable biologic mesh and a nonabsorbable mesh for repairing diaphragmatic hernia in a growing animal model.

METHODS

The left hemi-diaphragm of twenty 2-month-old Yucatan pigs was nearly completely resected. Small intestinal submucosa (SIS; Cook Biotech, Lafayette, IN) and expanded polytetrafluoroethylene (ePTFE; W.L. Gore & Associates, Flagstaff, AZ) were randomly assigned to cover the defect in 10 animals each, and were survived for 6 months. During necropsy, newly formed diaphragmatic tissue was evaluated and compared between the two groups.

RESULTS

At necropsy, the animals had tripled their weight. Patch disruption and herniation occurred in 3 animals in the ePTFE group and none in the SIS group. The SIS mesh had better integration to the chest wall (2.8 ± 0.2 versus 1.3 ± 0.3), more muscle growth within the newly formed diaphragmatic tissue (1.9 ± 0.2 versus 0.4 ± 0.2), and less fibrotic tissue (2.1 ± 0.5 versus 3.4 ± 0.4) than ePTFE. There was no difference between SIS and ePTFE in terms of adhesion scores to the lung (2 ± 0.4 versus 2.4 ± 0.4) and liver (1.8 ± 0.3 versus 2.2 ± 0.5).

CONCLUSION

SIS allows for tissue ingrowth from surrounding tissue as it degrades, providing a more durable repair with 30% less incidence of herniation in a porcine model. As the diaphragm grows, SIS resulted in a more natural repair of the defect with more tissue growth, better tissue integration, and a comparable adhesion formation to ePTFE.

Adhesive performance of biomimetic adhesive-coated biologic scaffolds

Surgical repair of a discontinuity in traumatized or degenerated soft tissues is traditionally accomplished using sutures. A current trend is to reinforce this primary repair with surgical grafts, meshes, or patches secured with perforating mechanical devices (i.e., sutures, staples, or tacks). These fixation methods frequently lead to chronic pain and mesh detachment. We developed a series of biodegradable adhesive polymers that are synthetic mimics of mussel adhesive proteins (MAPs), composed of 3,4-dihydroxyphenylalanine (DOPA)-derivatives, polyethylene glycol (PEG), and polycaprolactone (PCL). These polymers can be cast into films, and their mechanical properties, extent of swelling, and degradation rate can be tailored through the composition of the polymers as well as blending with additives. When coated onto a biologic mesh used for hernia repair, these adhesive constructs demonstrated adhesive strengths significantly higher than fibrin glue. With further development, a precoated bioadhesive mesh may represent a new surgical option for soft tissue repair.

Is biocompatibility affected by constant shear stress?--comparison of three commercially available meshes in a rabbit model

Mesh implants as standard treatment for tissue defects can be adapted to patient's needs by specific bioactive coatings. The biophysical interaction with the surrounding tissue must be understood to describe the influence of coatings qualitatively and quantitatively. This study investigates the use of meshes to repair diaphragmatic defects. The physical stress in this tissue is high in comparison to other applications. Therefore, knowledge gained from this experimental model can be applied to other locations. Meshes were implanted on surgically created diaphragmatic defects in growing rabbits. A standardized load model was used to investigate 33 rabbits. The commercial products Ultrapro®, Surgisis®, and Proceed® were implanted. The adhesive properties of the meshes as well as the defect size were determined macroscopically at explantation after 4 months. Sections of the explanted meshes and diaphragms were examined histologically and immunohistochemically. The median defect size for all mesh groups decreased from the initial size of 10 mm down to 4.5 mm at explantation. No statistically significant differences were seen between the three mesh groups. Surgisis® was found to be completely disintegrated after 4 months. Ultrapro® and Proceed® showed no macroscopic differences compared to their original appearance. Both sealed the original diaphragmatic defect as tightly as at time of implantation. Histological and immunohistochemical analyses showed significant differences between the three mesh groups. Proceed® caused stronger inflammatory reaction in the surrounding tissue and inferior connective tissue formation. Regarding the composition of the newly generated tissue within the defect area, Ultrapro® and Surgisis® were found superior. This can sufficiently be explained by the different gradient of inflammatory reaction in the surrounding tissue. Because Surgisis® offers no sufficiently lasting support for the diaphragmatic defect, our future main focus for mesh modification is laid on Ultrapro®.

Permacol: a potential biologic patch alternative in congenital diaphragmatic hernia repair

PURPOSE

Recurrence is a well-known complication after patch repair of congenital diaphragmatic hernia (CDH). We propose that a newer, "bioprosthetic" material may lower recurrence rates. The purpose of this study is to compare outcomes of CDH repair with synthetic Gore-Tex (W. L. Gore and Associates, Neward, Del) to the bioprosthetic Permacol (Tissue Science Laboratories Inc, Andover, Mass).

METHODS

We performed a retrospective review of 100 consecutive patients with CDH with survival more than 30 days at Children's Medical Center of Dallas (Dallas, Tex) from 1999 to 2007. The incidence and timing of recurrence, as well as comorbidities were assessed.

RESULTS

Primary repair was performed in 63 patients and patch repair in 37, divided between Gore-Tex (29) and Permacol (8). Overall recurrences were as follows: 1 (2%), 8 (28%), and 0 in the primary, Gore-Tex, and Permacol groups, respectively. Median follow-up was 57 months for Gore-Tex and 20 months for Permacol. Median time to recurrence in the Gore-Tex group was 12 months, with no Permacol recurrences. Both the Gore-Tex and Permacol groups had similar comorbidities, including prematurity, congenital heart disease (76% and 63%, respectively), and the need for extracorporeal membrane oxygenation support (38% and 25%).

CONCLUSION

Our results suggest that Permacol may have lower recurrence rates compared to Gore-Tex and is a promising alternative biologic graft for CDH repair.

Vitamin A deficiency (VAD), teratogenic, and surgical models of congenital diaphragmatic hernia (CDH)

Congenital diaphragmatic hernia (CDH) is a congenital malformation that occurs with a frequency of 0.08 to 0.45 per 1,000 births. Children with CDH are born with the abdominal contents herniated through the diaphragm and exhibit an associated pulmonary hypoplasia which is frequently accompanied by severe morbidity and mortality. Although the etiology of CDH is largely unknown, considerable progress has been made in understanding its molecular mechanisms through the usage of genetic, teratogenic, and surgical models. The following review focuses on the teratogenic and surgical models of CDH and the possible molecular mechanisms of nitrofen (a diphenyl ether, formerly used as an herbicide) in both induction of CDH and pulmonary hypoplasia. In addition, the mechanisms of other compounds including several anti-inflammatory agents that have been linked to CDH will be discussed. Furthermore, this review will also explore the importance of vitamin A in lung and diaphragm development and the possible mechanisms of teratogen interference in vitamin A homeostasis. Continued exploration of these models will bring forth a clearer understanding of CDH and its molecular underpinnings, which will ultimately facilitate development of therapeutic strategies.

Incorporation of Integra in tissue defects: a pilot study in the rat model

Integra has been shown to be very useful in accelerating the growth of neodermis. It has found extensive use in case of burns as a primary dressing immediately after a burn, after release of contractures and following scar revision. It has been used to achieve cover after the debridement of extensive infective processes involving the skin. Encouraged by these results we have assessed the application of Integra to augment and/or patch defects of the urinary bladder, diaphragm and the abdominal wall in the rat model. This was a pilot study and involved the incorporation of Integra in the diaphragm, the urinary bladder (extramucosal) and the muscle layer of the abdominal wall. Eight adult Wistar rats were given general anaesthesia and Integra was implanted with absorbable sutures at the sites mentioned. The omentum was hitched to the collagen matrix surface to revascularise the graft. The silicone was left in situ. The operative period was covered with antibiotics. The anaesthesia was then reversed. Postoperatively the rats were given analgesia and feeds started immediately. The rats were sacrificed after 3 weeks. The abdominal cavity was examined for adhesions. The Integra implant along with adjacent tissue was harvested and examined histologically. There were no visible intra-abdominal adhesions. The histology revealed good degree of neovascularisation and fibrosis in and adjacent to the implant. This was comparable to the changes seen in the skin. This pilot study has shown that implanting Integra invokes a similar response in deeper tissues and it can develop neovascularisation from the omentum. Hence, this could find some application in treating congenital conditions such as diaphragmatic hernias, abdominal wall defects and for bladders requiring augmentation. Our initial results are quite encouraging and we feel that this field should be further explored.

The whole truth: comparative analysis of diaphragmatic hernia repair using 4-ply vs 8-ply small intestinal submucosa in a growing animal model

BACKGROUND

Diaphragmatic reconstruction remains a challenging problem. There is limited information concerning the use of small intestinal submucosa (SIS) in congenital diaphragmatic hernia repair. A canine model was used to evaluate the use of a SIS patch in diaphragmatic reconstruction.

METHODS

Eleven beagle puppies (1.6-4.2 kg, 8 weeks old) underwent left subcostal laparotomy, central left hemidiaphragm excision (2 x 7 cm, 50% loss), and reconstruction with a 4-ply group I (n = 5) or 8-ply group II (n = 6) SIS patch. Chest radiographs were taken at time of operation and 3 and 6 months postoperatively. Animals were killed at 6 months. Adhesion formation (both pleural and abdominal), gross visual evaluation of the patch, and histology were compared.

RESULTS

In group I (4-ply), 1 animal died at 3 months from patch deterioration accompanied by stomach herniation that resulted in respiratory failure. In the 4 remaining animals, chest radiographs showed no evidence of herniation or eventration. On physical examination, there was no evidence of chest wall deformity. During gross surgical examination, the 4-ply patches showed thinning, multiple defects, and liver herniation in 3 animals. In 1 pup, the patch was thickened, intact, well incorporated at the repair site, and adherent to the liver and spleen. In group II (8-ply), 1 animal died of cardiopulmonary failure in the early postoperative period. In the other 5 animals, chest radiographs showed evidence of eventration in 1. On gross examination the patch adhered to the liver in all 5 surviving animals. In 4, the patches were thickened, viable, but had some shrinkage. One patch pulled away from the native diaphragm laterally; however, no visceral herniation was present. In the 1 animal with eventration, there was no evidence of a patch. Adhesion scores (AS) were graded and determined by the sum of extent (0-4), type (0-4), and tenacity (0-3). Average abdominal AS in group I was 5.6 +/- 0.8 vs 10.2 +/- 0.2 (P = .079) for group II. Average lung AS was 0.6 +/- 0.6 in group I vs 3.8 +/- 1.1 (P = .0476) for group II. Histological examination showed group II patches had greater collagen deposition with central calcification and mild inflammation within the residual graft, whereas group I patches were much thinner and were composed of granulation tissue without evidence of residual graft.

CONCLUSIONS

These data indicate that 8-ply SIS repair of diaphragmatic defects was superior (80%; 4/5 to 4-ply, 20%; 1/5, success). Organ adherence appears to be necessary for neovascularization of the SIS composite. Eight-ply grafts appear to be more durable and persist for a longer period, which may improve neovascularization. Long-term follow-up to evaluate remodeling characteristics of the patch material is required.

Abdominal wall repair using a biodegradable scaffold seeded with cells

BACKGROUND/PURPOSE

The repair of large abdominal wall defects is still a challenge for pediatric surgeons. Synthetic materials, however, may lead to high complication rates. This study was aimed at applying tissue-engineering methods to abdominal wall repair.

METHODS

3T3 mouse fibroblasts were expanded in vitro. In the next step, a biodegradable material--polyglycolic acid (PGA)--was actively seeded with 10(7) cells/scm of PGA scaffold. Culture medium (Dulbecco's Modified Eagle's Medium with 10% fetal bovine serum) was changed every 6 hours after seeding cells on PGA fibers. Under general anaesthesia, C57BL/6J black mice underwent creation of a 2 x 3-cm abdominal wall defect (60%-70% of abdominal surface). The defect was repaired in the experimental group with the fibroblast-seeded PGA scaffold. In the first control group, the defect was covered with acellular PGA, and in the second control group, by skin closure. Animals were killed after 30 days to assess the histologic and gross findings.

RESULTS

No abdominal hernia was found in animals repaired with cell-seeded and acellular scaffolds. All animals with skin closure died within 7 days. In every case, tissue-engineered construct was thicker then in controls. Histologic and gross examination revealed a good neovascularisation in tissue-engineered abdominal walls comparing to the acellular matrix. There was no intensive scar formation between abdominal wall and skin.

CONCLUSIONS

Engineered soft tissue constructs can provide structural replacement of severe and large abdominal wall defects. Tissue engineering in the near future will possibly enter clinical practice.