Fetal tissue engineering: diaphragmatic replacement

Diaphragmatic hernia repair porcine model to compare the performance of biodegradable membranes against Gore-Tex®

BACKGROUND

Patch repair of congenital diaphragmatic hernia (CDH) using Gore-Tex® is associated with infection, adhesions, hernia recurrence, long-term musculoskeletal sequels and poor tissue regeneration. To overcome these limitations, the performance of two novel biodegradable membranes was tested to repair CDH in a growing pig model.

METHODS

Twelve male pigs were randomly assigned to 3 different groups of 4 animals each, determined by the type of patch used during thoracoscopic diaphragmatic hernia repair (Gore-Tex®, polycaprolactone electrospun membrane-PCLem, and decellularized human chorion membrane-dHCM). After 7 weeks, all animals were euthanized, followed by necropsy for diaphragmatic evaluation and histological analysis.

RESULTS

Thoracoscopic defect creation and diaphragmatic repair were performed without any technical difficulty in all groups. However, hernia recurrence rate was 0% in Gore-Tex®, 50% in PCLem and 100% in dHCM groups. At euthanasia, Gore-Tex® patches appeared virtually unchanged and covered with a fibrotic capsule, while PCLem and dHCM patches were replaced by either floppy connective tissue or vascularized and floppy regenerated membranous tissue, respectively.

CONCLUSION

Gore-Tex® was associated with a higher survival rate and lower recurrence. Nevertheless, the proposed biodegradable membranes were associated with better tissue integration when compared with Gore-Tex®.

Liver pathological alterations in fetal rabbit model of congenital diaphragmatic hernia

To date, fetal liver implication is not a well-understood phenomenon in congenital diaphragmatic hernia (CDH). We evaluated the fetal morphologic changes on liver growth after surgical procedure in CDH experimental model. A diaphragmatic defect at gestational day E25 and tracheal occlusion (TO) at E27 were surgically created in rabbit fetuses. Five experimental groups were assessed: control group, left CDH, right CDH, CDH + TO, and TO alone. Body and organ growth were measured. For histological evaluation of the CDH effect, liver sections were collected. Left-CDH group had livers with increased leukocyte infiltration in comparison with controls (p = 0.02). Increased capillary sinusoid congestion and hepatocyte vacuolation were greater in left-CDH compared with the right-CDH group (p = 0.05). Capillary sinusoid congestion and interstitial edema were more evident in the left-CDH compared with CDH + TO group (p = 0.05). Increases in sinusoid congestion, hepatocyte vacuolation, and interstitial edema were also greater in the CDH + TO compared with controls (p ≤ 0.02). Intrathoracic liver weight was higher in right-CDH compared with left-CDH group (p < 0.001). Total lung weights (TLW) were significantly lower in both left-CDH compared with controls (p < 0.001), CDH + TO (p = 0.01), and TO (p < 0.01) and in right-CDH compared with CDH + TO (p < 0.01) and TO (p < 0.01). Decreased kidney and heart weights were also recorded. Hemodynamics and structural fetal liver changes in laterality were noted in CDH model. Regulation of intrathoracic liver weights seems to be disturbed by the absence of diaphragmic contact. Pulmonary injury is supported by the effect of a first hit, while the growth of internal organs suggests a multisystemic remodeling related to the fetal adaptation.

Regeneration and tissue engineering: How pediatric surgeons contributed to building a new field to change the future of medicine

The authors highlight the speciality field of regenerative medicine and its application to health care. Academic pediatric surgeons have been the early pioneers here sharing exciting discovery and the opportunities for research enterprise. An overview of current and future therapeutics is provided for the reader.

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.

Autologous bionic tissue for inguinal hernia repair

The prosthetic mesh, which is widely used in tension-free hernioplasty, often result in avascular stiff fibrotic scar or mesh shrinkage, causing chronic pain and infection. Here, we developed an autologous bionic tissue (ABT), which was composed of autologous bone marrow-derived mesenchymal stem cells (MSCs), poly (lactic-co-glycolic acid) (PLGA) porous scaffolds, and extracellular matrix (ECM) produced by MSCs for inguinal hernioplasty. In ABT, MSCs produced a variety of ECM composites, such as structural proteins (insoluble collagen, elastin) that provided mechanical properties, macromolecules (hyaluronic acid, glycosaminoglycan) as water and cytokines reservoir, and cell-engaging proteins (fibronectin, laminin). The above ECM composites reached the highest level in 21 days. ECM degradation related cytokines (MMP-9 and its inhibitor TIMP-1) reached the highest level on the 14th day. ECM increased the mechanical properties, elasticity, and flexibility of PLGA. Compared with the PLGA, ABT greatly inhibited inflammatory factors and promoted anti-inflammatory factors (p < 0.05), and gradually reduced the M1/M2 ratio in vivo (p < 0.05). After implantation, the thickness of tissue regeneration (p < 0.05), the number of capillaries or mature vessels (p < 0.05), the mechanical properties of ABT (p < 0.05) were greater than PLGA. MSCs and ECM could reduce the inflammation caused by PLGA, and prevent PLGA from earlier degradation and facilitate host cellular infiltration, thus ABT could greatly promote tissue regeneration in hernia repairs.

Biomaterials in fetal surgery

Fetal surgery and fetal therapy involve surgical interventions on the fetus in utero to correct or ameliorate congenital abnormalities and give a developing fetus the best chance at a healthy life. Historical use of biomaterials in fetal surgery has been limited, and most biomaterials used in fetal surgeries today were originally developed for adult or pediatric patients. However, as the field of fetal surgery moves from open surgeries to minimally invasive procedures, many opportunities exist for innovative biomaterials engineers to create materials designed specifically for the unique challenges and opportunities of maternal-fetal surgery. Here, we review biomaterials currently used in clinical fetal surgery as well as promising biomaterials in development for eventual clinical translation. We also highlight unmet challenges in fetal surgery that could particularly benefit from novel biomaterials, including fetal membrane sealing and minimally invasive myelomeningocele defect repair. Finally, we conclude with a discussion of the underdeveloped fetal immune system and opportunities for exploitation with novel immunomodulating biomaterials.

Engineering and repair of diaphragm using biosheet (a collagenous connective tissue membrane) in rabbits

BACKGROUND

Prosthetic patches can be used to repair large congenital diaphragmatic hernia defects but may be associated with infection, recurrence, and thoracic deformity. Biosheets (collagenous connective tissue membranes) have been used in regenerative medicine. We evaluated the efficacy of Biosheets in a rabbit model.

METHODS

Biosheets were prepared by embedding silicone plates in dorsal subcutaneous pouches of rabbits for 4weeks. In group 1 (n=11), Gore-Tex® sheets (1.8×1.8cm) were implanted into a diaphragmatic defect. In group 2 (n=11), Seamdura®, a bioabsorbable artificial dural substitute, was implanted in the same manner. In group 3 (n=14), biosheets were autologously transplanted into the diaphragmatic defects. All rabbits were euthanized 3months after transplantation to evaluate their graft status.

RESULTS

Herniation of liver was observed in 5 rabbits (45%) in group 1, 8 (73%) in group 2, and 3 (21%) in group 3. A significant difference was noted between groups 2 and 3 (P=0.017). Biosheets had equivalent burst strength and modulus of elasticity as native diaphragm. Muscular tissue regeneration in transplanted biosheets in group 3 was confirmed histologically.

CONCLUSION

Biosheets may be applied to diaphragmatic repair and replacement of diaphragmatic muscular tissue.

LEVEL OF EVIDENCE

Level III.

Isolation of myogenic progenitor cell population from human placenta: A pilot study

PURPOSE

The purpose of this study was to demonstrate a method of isolating myogenic progenitor cells from human placenta chorionic villi and to confirm the myogenic characteristics of the isolated cells.

METHODS

Cells were isolated from chorionic villi of a second trimester male placenta via a combined enzymatic digestion and explant culture. A morphologically distinct subpopulation of elongated and multinucleated cells was identified. This subpopulation was manually passaged from the explant culture, expanded, and analyzed by fluorescence in situ hybridization (FISH) assay, immunocytochemistry, and flow cytometry. Myogenic characteristics including alignment and fusion were tested by growing these cells on aligned polylactic acid microfibrous scaffold in a fusion media composed of 2% horse serum in Dulbecco's modified Eagle medium/high glucose.

RESULTS

The expanded subpopulation was uniformly positive for integrin α-7. Presence of Y-chromosome by FISH analysis confirmed chorionic villus origin rather than maternal cell contamination. Isolated cells grew, aligned, and fused on the microfibrous scaffold, and they expressed myogenin, desmin, and MHC confirming their myogenic identity.

CONCLUSION

Myogenic progenitor cells can be isolated from human chorionic villi. This opens the possibility for translational and clinical applications using autologous myogenic cells for possible engraftment in treatment of chest and abdominal wall defects.

Tissue Engineering to Repair Diaphragmatic Defect in a Rat Model

Tissue engineering is an emerging strategy for repairing damaged tissues or organs. The current study explored using decellularized rat diaphragm scaffolds combined with human amniotic fluid-derived multipotent stromal cells (hAFMSC) to provide a scaffold, stem cell construct that would allow structural barrier function during tissue ingrowth/regeneration. We created an innovative cell infusion system that allowed hAFMSC to embed into scaffolds and then implanted the composite tissues into rats with surgically created left-sided diaphragmatic defects. Control rats received decellularized diaphragm scaffolds alone. We found that the composite tissues that combined hAFMSCs demonstrated improved physiological function as well as the muscular-tendon structure, compared with the native contralateral hemidiaphragm of the same rat. Our results indicate that the decellularized diaphragm scaffolds are a potential support material for diaphragmatic hernia repair and the composite grafts with hAFMSC are able to accelerate the functional recovery of diaphragmatic hernia.

Comparisons of human amniotic mesenchymal stem cell viability in FDA-approved collagen-based scaffolds: Implications for engineered diaphragmatic replacement

BACKGROUND/PURPOSE

We sought to examine amniotic fluid mesenchymal stem cell (afMSC) viability within two FDA-approved collagen-based scaffolds, as a prerequisite to clinical translation of afMSC-based engineered diaphragmatic repair.

METHODS

Human afMSCs were seeded in a human-derived collagen hydrogel and in a bovine-derived collagen sheet at 3 matching densities. Cell viability was analyzed at 1, 3, and 5days using an ATP-based 3D bioluminescence assay. Statistical comparisons were by ANOVA (P<0.05).

RESULTS

There was a highly significant 3-way interaction between scaffold type, seeding density, and time in 3D culture as determinants of cell viability, clearly favoring the human hydrogel (P<0.001). In both scaffolds, cell viability was highest at the highest seeding density of 150,000 cells/mL. Time in 3D culture impacted cell viability at the optimal seeding density in the human hydrogel, with the highest levels on days 1 (P<0.001) and 5 (P=0.05) with no significant effect in the bovine sheet (P=0.39-0.96).

CONCLUSIONS

Among clinically-approved cell delivery vehicles, mesenchymal stem cell viability is significantly enhanced in a collagen hydrogel when compared with a collagen sheet. Cell viability can be further optimized by seeding density and time in 3D culture. These data further support the regulatory viability of clinical trials of engineered diaphragmatic repair.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Regenerative medicine solutions in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) remains a major challenge and associated mortality is still significant. Patients have benefited from current therapeutic options, but most severe cases are still associated to poor outcome. Regenerative medicine is emerging as a valid option in many diseases and clinical trials are currently happening for various conditions in children and adults. We report here the advancement in the field which will help both in the understanding of further CDH development and in offering new treatment options for the difficult situations such as repair of large diaphragmatic defects and lung hypoplasia. The authors believe that advancements in regenerative medicine may lead to increase of CDH patients׳ survival.

Preparation of a nano- and micro-fibrous decellularized scaffold seeded with autologous mesenchymal stem cells for inguinal hernia repair

Prosthetic meshes used for hernioplasty are usually complicated with chronic pain due to avascular fibrotic scar or mesh shrinkage. In this study, we developed a tissue-engineered mesh (TEM) by seeding autologous bone marrow-derived mesenchymal stem cells onto nanosized fibers decellularized aorta (DA). DA was achieved by decellularizing the aorta sample sequentially with physical, mechanical, biological enzymatic digestion, and chemical detergent processes. The tertiary structure of DA was constituted with micro-, submicro-, and nanosized fibers, and the original strength of fresh aorta was retained. Inguinal hernia rabbit models were treated with TEMs or acellular meshes (AMs). After implantation, TEM-treated rabbit models showed no hernia recurrence, whereas AM-treated animals displayed bulges in inguinal area. At harvest, TEMs were thicker, have less adhesion, and have stronger mechanical strength compared to AMs (P<0.05). Moreover, TEM showed better cell infiltration, tissue regeneration, and neovascularization (P<0.05). Therefore, these cell-seeded DAs with nanosized fibers have potential for use in inguinal hernioplasty.

Human amniotic fluid: a source of stem cells for possible therapeutic use

Stem cells are undifferentiated cells with the capacity for differentiation. Amniotic fluid cells have emerged only recently as a possible source of stem cells for clinical purposes. There are no ethical or sampling constraints for the use of amniocentesis as a standard clinical procedure for obtaining an abundant supply of amniotic fluid cells. Amniotic fluid cells of human origin proliferate rapidly and are multipotent with the potential for expansion in vitro to multiple cell lines. Tissue engineering technologies that use amniotic fluid cells are being explored. Amniotic fluid cells may be of clinical benefit for fetal therapies, degenerative disease, and regenerative medicine applications. We present a comprehensive review of the evolution of human amniotic fluid cells as a possible modality for therapeutic use.

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.

Prenatal management of the fetus with isolated congenital diaphragmatic hernia in the era of the TOTAL trial

Congenital diaphragmatic hernia (CDH) may be isolated or associated with other structural anomalies, the latter with poor prognosis. The defect allows viscera to herniate through the defect into the chest, competing for space with the developing lungs. At birth, pulmonary hypoplasia leads to respiratory insufficiency and persistent pulmonary hypertension that is lethal in up to 30% of patients. When isolated, survival chances can be predicted by antenatal measurement of lung size and liver herniation. Chromosomal microarrays and exome sequencing contribute to understanding genetic factors underlying isolated CDH. Prenatal intervention aims at stimulating lung development, clinically achieved by percutaneous fetal endoscopic tracheal occlusion (FETO) under local anesthesia. The Tracheal Occlusion To Accelerate Lung growth trial (www.totaltrial.eu) is an international randomized trial investigating the role of fetal therapy for severe and moderate pulmonary hypoplasia. Despite an apparent increase in survival following FETO, the search for lesser invasive and more potent prenatal interventions must continue.

Controversies in the management of severe congenital diaphragmatic hernia

Despite years of progress in perinatal care, severe congenital diaphragmatic hernia (CDH) remains a clinical challenge. Controversies include almost every facet of clinical care: the definition of severe CDH by prenatal and postnatal criteria, fetal surgical intervention, ventilator management, pulmonary hypertension management, use of extracorporeal membrane oxygenation, surgical considerations, and long-term follow-up. Breakthroughs are likely only possible by sharing of experience, collaboration between institutions and innovative therapies within well-designed multicenter clinical trials.

Tracheal bioengineering: the next steps. Proceeds of an International Society of Cell Therapy Pulmonary Cellular Therapy Signature Series Workshop, Paris, France, April 22, 2014

There has been significant and exciting recent progress in the development of bioengineering approaches for generating tracheal tissue that can be used for congenital and acquired tracheal diseases. This includes a growing clinical experience in both pediatric and adult patients with life-threatening tracheal diseases. However, not all of these attempts have been successful, and there is ongoing discussion and debate about the optimal approaches to be used. These include considerations of optimal materials, particularly use of synthetic versus biologic scaffolds, appropriate cellularization of the scaffolds, optimal surgical approaches and optimal measure of both clinical and biologic outcomes. To address these issues, the International Society of Cell Therapy convened a first-ever meeting of the leading clinicians and tracheal biologists, along with experts in regulatory and ethical affairs, to discuss and debate the issues. A series of recommendations are presented for how to best move the field ahead.

Full thickness abdominal wall defect in growing rats as a model for congenital diaphragmatic hernia prosthetic repair

BACKGROUND

Large congenital diaphragmatic hernia may require prosthetic correction. Acellular collagen matrices were introduced to avoid complications owing to the use of synthetic patches. We tested 3 different ACM for reconstruction of an abdominal wall defect in an animal model that mimics the fast growth during infancy.

METHODS

Pelvisoft® (CR Bard, Covington, GA) and 2 investigational ACM were used for primary reconstruction of a full thickness abdominal wall defect. 3months-old rats (n=26) were allowed to survive for 90days after implantation. Anatomical, tensiometric and histological analyses were performed. Based on good outcomes, we did the same with 1month-old rats (n=54). Unoperated rats were used for obtaining reference tensiometric values of selected native tissues.

RESULTS

Major wound complications were exclusively observed in 1month-old rats. All explants in both groups thinned significantly (p<0.03) and had an elastic modulus increasing over time, far above that from native tissues at 90days of life. Both investigational ACM induced a more vigorous foreign body reaction than Pelvisoft(®).

CONCLUSIONS

The shift from 3 to 1month-old rats was associated with wound complications. Pelvisoft® showed a better biocompatibility than the 2 investigational ACM. Passive biomechanical properties of all explants were still not comparable to that of native tissues.

Tissue engineering in congenital diaphragmatic hernia

Engineered diaphragmatic repair is emblematic of perinatal regenerative medicine and of the fetal tissue engineering concept. The alternative of a cellularized graft for the repair of a congenital diaphragmatic defect in the neonatal period is both biologically justifiable by the mechanisms behind diaphragmatic hernia recurrence as well as an ideal match for fetal mesenchymal stem cell-based constructs. It has been among the most developed experimental pursuits in neonatal tissue engineering, of which clinical application should be forthcoming.

Diaphragmatic muscle reconstruction with an aligned electrospun poly(ε-caprolactone)/collagen hybrid scaffold

Large diaphragmatic muscle defects in congenital diaphragmatic hernia (CDH) are reconstructed by prosthetic materials or autologous grafts, which are associated with high complications and reherniation. In this study we examined the feasibility of using aligned electrospun poly(ε-caprolactone) (PCL)/collagen hybrid scaffolds for diaphragmatic muscle reconstruction. The hybrid scaffolds were implanted into a central left hemi-diaphragmatic defect (approximately 70% of the diaphragmatic tissue on the left side) in rats. Radiographic and magnetic resonance imaging (MRI) analyses showed no evidence of herniation or retraction up to 6 months after implantation. Histological and immunohistochemical evaluations revealed ingrowth of muscle tissue into the scaffolds. The mechanical properties of the retrieved diaphragmatic scaffolds were similar to those of normal diaphragm at the designated time points. Our results show that the aligned electrospun hybrid scaffolds allowed muscle cell migration and tissue formation. The aligned scaffolds may provide implantable functional muscle tissues for patients with diaphragmatic muscle defects.

Heparinized collagen scaffolds with and without growth factors for the repair of diaphragmatic hernia: construction and in vivo evaluation

A regenerative medicine approach to restore the morphology and function of the diaphragm in congenital diaphragmatic hernia is especially challenging because of the position and flat nature of this organ, allowing cell ingrowth primarily from the perimeter. Use of porous collagen scaffolds for the closure of surgically created diaphragmatic defects in rats has been shown feasible, but better ingrowth of cells, specifically blood vessels and muscle cells, is warranted. To stimulate this process, heparin, a glycosaminoglycan involved in growth factor binding, was covalently bound to porous collagenous scaffolds (14%), with or without vascular endothelial growth factor (VEGF; 0.4 µg/mg scaffold), hepatocyte growth factor (HGF; 0.5 µg/mg scaffold) or a combination of VEGF + HGF (0.2 + 0.5 µg/mg scaffold). All components were located primarily at the outside of scaffolds. Scaffolds were implanted in the diaphragm of rats and evaluated after 2 and 12 weeks. No herniations or eventrations were observed, and in several cases, growth factor-substituted scaffolds showed macroscopically visible blood vessels at the lung site. The addition of heparin led to an accelerated ingrowth of blood vessels at 2 weeks. In all scaffold types, giant cells and immune cells were present primarily at the liver side of the scaffold, and immune cells and individual macrophages at the lung side; these cell types decreased in number from week 2 to week 12. The addition of growth factors did not influence cellular response to the scaffolds, indicating that further optimization with respect to dosage and release profile is needed.

Human amniotic fluid derived cells can competently substitute dermal fibroblasts in a tissue-engineered dermo-epidermal skin analog

PURPOSE

Human amniotic fluid comprises cells with high differentiation capacity, thus representing a potential cell source for skin tissue engineering. In this experimental study, we investigated the ability of human amniotic fluid derived cells to substitute dermal fibroblasts and support epidermis formation and stratification in a humanized animal model.

METHODS

Dermo-epidermal skin grafts with either amniocytes or with fibroblasts in the dermis were compared in a rat model. Full-thickness skin wounds on the back of immuno-incompetent rats were covered with skin grafts with (1) amniocytes in the dermis, (2) fibroblasts in the dermis, or, (3) acellular dermis. Grafts were excised 7 and 21 days post transplantation. Histology and immunofluorescence were performed to investigate epidermis formation, stratification, and expression of established skin markers.

RESULTS

The epidermis of skin grafts engineered with amniocytes showed near-normal anatomy, a continuous basal lamina, and a stratum corneum. Expression patterns for keratin 15, keratin 16, and Ki67 were similar to grafts with fibroblasts; keratin 1 expression was not yet fully established in all suprabasal cell layers, expression of keratin 19 was increased and not only restricted to the basal cell layer as seen in grafts with fibroblasts. In grafts with acellular dermis, keratinocytes did not survive.

CONCLUSION

Dermo-epidermal skin grafts with amniocytes show near-normal physiological behavior suggesting that amniocytes substitute fibroblast function to support the essential cross-talk between mesenchyme and epithelia needed for epidermal stratification. This novel finding has considerable implications regarding tissue engineering.

Regenerative medicine for the respiratory system: distant future or tomorrow's treatment?

Regenerative medicine (RM) is a new field of biomedical science that focuses on the regeneration of tissues and organs and the restoration of organ function. Although regeneration of organ systems such as bone, cartilage, and heart has attracted intense scientific research over recent decades, RM research regarding the respiratory system, including the trachea, the lung proper, and the diaphragm, has lagged behind. However, the last 5 years have witnessed novel approaches and initial clinical applications of tissue-engineered constructs to restore organ structure and function. In this regard, this article briefly addresses the basics of RM and introduces the key elements necessary for tissue regeneration, including (stem) cells, biomaterials, and extracellular matrices. In addition, the current status of the (clinical) application of RM to the respiratory system is discussed, and bottlenecks and recent approaches are identified. For the trachea, several initial clinical studies have been reported and have used various combinations of cells and scaffolds. Although promising, the methods used in these studies require optimization and standardization. For the lung proper, only (stem) cell-based approaches have been probed clinically, but it is becoming apparent that combinations of cells and scaffolds are required to successfully restore the lung's architecture and function. In the case of the diaphragm, clinical applications have focused on the use of decellularized scaffolds, but novel scaffolds, with or without cells, are clearly needed for true regeneration of diaphragmatic tissue. We conclude that respiratory treatment with RM will not be realized tomorrow, but its future looks promising.

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.

Patch repair for congenital diaphragmatic hernia: is it really a problem?

BACKGROUND

Large congenital diaphragmatic hernia (CDH) defects often require the use of synthetic patches for tension-free repair. Although high rates of recurrence and other morbidities have been previously reported, our favorable perception of patch repair prompted this review.

METHODS

A single-center retrospective chart review of CDH cases repaired between January 1, 1999, and October 1, 2010. Patch repairs were performed by multiple surgeons with an effort to construct a tension-free dome-shaped patch.

RESULTS

One hundred eighty-four children underwent CDH repair of whom 99 (53.8%) required a patch. Seventy-four (74.7%) of the 99 patients who underwent patch repair survived to discharge and were compared with 75 primary repair survivors. Of those undergoing patch repair, 88% were prenatally diagnosed, 55% had liver herniation, and 22 (29.9%) were repaired on extracorporeal membrane oxygenation. Two patients experienced a recurrence after a patch repair and 3 after a primary repair for a rate of 5.4% and 4.0%, respectively (P = 1.0).

CONCLUSIONS

These results demonstrate that synthetic patch repair for CDH can be performed with a very low rate of recurrence challenging the need for alternative approaches to diaphragmatic replacement. High rates of recurrence reported for patch repair may be technical rather than intrinsic to the patch.

Amniotic fluid-derived stem cells in regenerative medicine research

The stem cells isolated from amniotic fluid present an exciting possible contribution to the field of regenerative medicine and amniotic fluid-derived stem (AFS) cells have significant potential for research and therapeutic applications. AFS cells are multipotent, showing the ability to differentiate into cell types from all three embryonic germ layers. They express both embryonic and adult stem cell markers, expand extensively without feeder cells, double in 36 h, and are not tumorigenic. The AFS cells can be maintained for over 250 population doublings and preserve their telomere length and a normal karyotype. They differentiate easily into specific cell lineages and do not require human embryo tissue for their isolation, thus avoiding the current controversies associated with the use of human embryonic stem (ES) cells. The discovery of the AFS cells has been recent, and a great deal of work remains to be performed on the characterization and use of these cells. This review describes the various differentiated lineages that AFS cells can form and the future of these promising new stem cells in regenerative medicine research.

TGF-β1 enhances contractility in engineered skeletal muscle

Scaffoldless engineered 3D skeletal muscle tissue created from satellite cells offers the potential to replace muscle tissue that is lost due to severe trauma or disease. Transforming growth factor-beta 1 (TGF-β1) plays a vital role in mediating migration and differentiation of satellite cells during the early stages of muscle development. Additionally, TGF-β1 promotes collagen type I synthesis in the extracellular matrix (ECM) of skeletal muscle, which provides a passive elastic substrate to support myofibres and facilitate the transmission of force. To determine the role of TGF-β1 in skeletal muscle construct formation and contractile function in vitro, we created tissue-engineered 3D skeletal muscle constructs with varying levels of recombinant TGF-β1 added to the cell culture medium. Prior to the addition of TGF-β1, the primary cell population was composed of 75% Pax7-positive cells. The peak force for twitch, tetanus and spontaneous force were significantly increased in the presence of 2.0 ng/ml TGF-β1 when compared to 0, 0.5 and 1.0 ng/ml TGF-β1. Visualization of the cellular structure with H&E and with immunofluorescence staining for sarcomeric myosin heavy chains and collagen type I showed denser regions of better organized myofibres in the presence of 2.0 ng/ml TGF-β1 versus 0, 0.5 and 1.0 ng/ml. The addition of 2.0 ng/ml TGF-β1 to the culture medium of engineered 3D skeletal muscle constructs enhanced contractility and extracellular matrix organization.

Antenatal management of isolated congenital diaphragmatic hernia today and tomorrow: ongoing collaborative research and development. Journal of Pediatric Surgery Lecture

The diagnosis of congenital diaphragmatic hernia should be made prenatally in virtually all cases where routine maternal ultrasonography is available. At that time, the prognosis can be predicted based on whether it is isolated and assessment of lung size and/or the position of the liver. Prenatal intervention may be offered in those selected fetuses that have a predicted poor outcome. The aim of this procedure is to reverse the key determinant of survival-pulmonary hypoplasia. Percutaneous fetal endoscopic tracheal occlusion by a balloon is a minimally invasive procedure that has been shown safe and yields a 50% survival rate in severe cases. The outcome can be predicted by the gestational age at birth, the lung size before and after balloon placement, and whether the balloon has been removed prenatally. Currently, the added value of prenatal intervention is being investigated in the Tracheal Occlusion To Accelerate Lung Growth trial ((TOTAL); a European and North American collaboration). Future developments may include better prediction of outcome by more complex algorithms reflecting combinations of prenatal predictors, gene expression profiling to reflect lung development and response to tracheal occlusion, and alternative prenatal strategies for salvaging the worst cases. Fetuses with severe hypoplasia usually require postnatal operative repair using prosthetic patches, and tissue engineering offers the potential for ex utero culture.

What can regenerative medicine offer for infants with laryngotracheal agenesis?

BACKGROUND

Laryngotracheal agenesis is a rare congenital disorder but has devastating consequences. Recent achievements in regenerative medicine have opened up new vistas in therapeutic strategies for these infants.

OBJECTIVE

To provide a state-of-the-art review concerning recent achievements in tissue engineering as applied to fetal airway reconstruction and to discuss the use of autologous human amniotic stem cells to prepare organs in advance for babies with laryngotracheal agenesis.

DATA SOURCES AND REVIEW METHODS

A structured search of the current literature (up to and including June 2011). The authors searched PubMed, EMBASE, CINAHL, Web of Science, BIOSIS Previews, Cambridge Scientific Abstracts, ICTRP, and additional sources for published and unpublished trials.

RESULTS

Over the past 15 years, progress has been made in advancing the boundaries of regenerative medicine from the laboratory to the clinical setting through translational research. Most experience has been gained with adult stem cells and synthetic materials or decellularized scaffolds. The optimal cell source for fetal tissue engineering remains to be determined, but a combination of decellularized scaffolds and amniotic fluid stem cells holds great promise for fetal tissue engineering.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Current treatment strategies for laryngotracheal agenesis are suboptimal, and fetal tissue engineering offers an alternative to conventional treatments. Use of human amniotic fluid stem cells for preparing autologous tissue-engineered organ constructs prenatally is an attractive concept. Although this approach is still in its experimental stages, further preclinical and clinical studies are encouraged to define its exact role in the pediatric laryngological setting.

The making of fetal surgery

Fetal diagnosis prompts the question for fetal therapy in highly selected cases. Some conditions are suitable for in utero surgical intervention. This paper reviews historically important steps in the development of fetal surgery. The first invasive fetal intervention in 1963 was an intra-uterine blood transfusion. It took another 20 years to understand the pathophysiology of other candidate fetal conditions and to develop safe anaesthetic and surgical techniques before the team at the University of California at San Francisco performed its first urinary diversion through hysterotomy. This procedure would be abandoned as renal and pulmonary function could be just as effectively salvaged by ultrasound-guided insertion of a bladder shunt. Fetoscopy is another method for direct access to the feto-placental unit. It was historically used for fetal visualisation to guide biopsies or for vascular access but was also abandoned following the introduction of high-resolution ultrasound. Miniaturisation revived fetoscopy in the 1990 s, since when it has been successfully used to operate on the placenta and umbilical cord. Today, it is also used in fetuses with congenital diaphragmatic hernia (CDH), in whom lung growth is triggered by percutaneous tracheal occlusion. It can also be used to diagnose and treat urinary obstruction. Many fetal interventions remain investigational but for a number of conditions randomised trials have established the role of in utero surgery, making fetal surgery a clinical reality in a number of fetal therapy programmes. The safety of fetal surgery is such that even non-lethal conditions, such as myelomeningocoele repair, are at this moment considered a potential indication. This, as well as fetal intervention for CDH, is currently being investigated in randomised trials.

Tissue engineering approach to repair abdominal wall defects using cell-seeded bovine tunica vaginalis in a rabbit model

The aim of this study was to engineer skeletal muscle tissue for repair abdominal wall defects. Myoblast were seeded onto the scaffolds and cultivated in vitro for 5 days. Full thickness abdominal wall defects (3 x 4 cm) were created in 18 male New Zealand white rabbits and randomly divided into two equal groups. The defects of the first group were repaired with myoblast-seeded-bovine tunica vaginalis whereas the second group repaired with non-seeded-bovine tunica vaginalis and function as a control. Three animals were sacrificed at 7th, 14th, and 30th days of post-implantation from each group and the explanted specimens were subjected to macroscopic and microscopic analysis. In every case, seeded scaffolds have better deposition of newly formed collagen with neo-vascularisation than control group. Interestingly, multinucleated myotubes and myofibers were only detected in cell-seeded group. This study demonstrated that myoblast-seeded-bovine tunica vaginalis can be used as an effective scaffold to repair severe and large abdominal wall defects with regeneration of skeletal muscle tissue.

Fetal tissue engineering

Attempts at harnessing the prospective benefits of the therapeutic use of fetal cells or tissues date many decades before the modern era of transplantation. The first reported transplantation of human fetal tissue took place in 1922. Fetal cells or tissues also have been used as helpful investigational tools since the 1930s. Still, it was only in the last three decades that fetal tissue transplantation in people has started to lead to favorable outcomes, yet by and large anecdotally. This article offers an outlook on a relatively new dimension in fetal cell-based therapies, namely the engineering of tissues in the laboratory, along with its prospective applications.

Focused in vivo genetic analysis of implanted engineered myofascial constructs

Successfully engineering functional muscle tissue either in vitro or in vivo to treat muscle defects rather than using the host muscle transfer would be revolutionary. Tissue engineering is on the cutting edge of biomedical research, bridging a gap between the clinic and the bench top. A new focus on skeletal muscle tissue engineering has led investigators to explore the application of satellite cells (autologous muscle precursor cells) as a vehicle for engineering tissues either in vitro or in vivo. However, few skeletal muscle tissue-engineering studies have reported on successful generation of living tissue substitutes for functional skeletal muscle replacement. Our model system combines a novel aligned collagen tube and autologous skeletal muscle satellite cells to create an engineered tissue repair for a surgically created ventral hernia as previously reported [SA Fann, L Terracio, W Yan, et al., A model of tissue-engineered ventral hernia repair, J Invest Surg. 2006;19(3):193-205]. Several key features we specifically observe are the significant persistence of transplanted skeletal muscle cell mass within the engineered repair, the integration of new tissue with adjacent native muscle, and the presence of significant neovascularization. In this study, we report on our experience investigating the genetic signals important to the integration of neoskeletal muscle tissue. The knowledge gained from our model system applies to the repair of severely injured extremities, maxillofacial reconstructions, and restorative procedures following tumor excision in other areas of the body.

In vitro and in vivo evaluation of acellular diaphragmatic matrices seeded with muscle precursors cells and coated with VEGF silica gels to repair muscle defect of the diaphragm

In this work, a bioartificial system consisting of VEGF-loaded porous silica gel and myoblasts cultured on acellular diaphragmatic matrix (ADM) has been implanted to repair a surgically created diaphragmatic defect in Lewis rats. ADMs exerted a strong angiogenic response on chorio-allantoic membrane. Cytotoxicity, VEGF release and matrix erodibility in vitro tests demonstrated that the silica support was nontoxic and that the VEGF bioactivity was maintained after matrix entrapment and it was released within a timeframe that can be modulated by synthesis parameters. Different grafts composed by ADMs with and without autologous male myoblasts or/and VEGF-loaded porous silica gel have been implanted to repair previously created diaphragmatic defects in female Lewis rats. Patches composed of ADMs and myoblasts appeared well preserved until 8 weeks, and contained multinucleated cells and cholinergic fibers. At 8 weeks, the implanted cells were still present inside the patches. The disappointing results obtained when VEGF was delivered by porous silica gel were probably due to an abnormal angiogenic response following an excess of local growth factor concentration. Taken together, these results confirmed that our matrices contained biologically active angiogenic factors which were per se sufficient to induce neo-vessels formation, thus allowing the survival of implanted myoblasts.

Evaluation of diaphragmatic hernia repair using PLGA mesh-collagen sponge hybrid scaffold: an experimental study in a rat model

Patch closure is necessary to achieve tension-free repair in large congenital diaphragmatic hernia. However, the use of prosthetic material may lead to granulation, allergic reaction, infection, recurrence of hernia, and thoracic deformity. Tissue engineering may become an alternative treatment strategy for diaphragmatic hernia repair, since the regenerated autologous tissue is expected to grow potentially without rejection or infection. We evaluated the efficacy of diaphragmatic hernia repair in a rat model using a poly-lactic-co-glycolic acid (PLGA) mesh-collagen sponge hybrid scaffold, designed for in situ tissue engineering. Twenty-four F344 female rats were used. Oval-shaped defects were surgically created in the left diaphragm and repaired with three different grafts, including PLGA mesh in group 1 (n = 7), PLGA mesh-collagen sponge hybrid scaffold in group 2 (n = 7), and PLGA mesh-collagen sponge hybrid scaffold seeded with bone marrow-derived mesenchymal stem cells (MSCs) in group 3 (n = 10). The animals were killed at 1, 2, and 3 months after operation. The specimens were examined macroscopically and microscopically. No recurrence or eventration was observed. In all animals, autologous fibrous tissue with vascularization was generated at the graft site. Although no muscular tissue was detected, scattered desmin-positive cells were observed in groups 2 and 3. The 'neodiaphragm' in groups 2 and 3 was significantly thicker compared with that in group 1. There was no significant difference in the 'neodiaphragm' between groups 2 and 3. The PLGA mesh-collagen sponge hybrid scaffold provided better promotion of autologous in situ tissue regeneration in the diaphragm, suggesting its potential application to diaphragmatic repair in place of other prosthetic patches.

Liver position is a prenatal predictive factor of prosthetic repair in congenital diaphragmatic hernia

OBJECTIVE

To determine whether any common maternal-fetal variable has prenatal predictive value of prosthetic repair in congenital diaphragmatic hernia.

METHODS

This was a 5-year single-center retrospective review of fetal congenital diaphragmatic hernia referrals. Multiple prenatal variables were correlated with the need for a prosthetic repair. Statistical analyses were by Fisher's exact and Mann-Whitney U-tests, as appropriate (p < 0.05).

RESULTS

Fetal liver position was a predictor of prosthetic repair. The presence or absence of liver herniation was correlated with prosthetic repair rates of 83.3 and 23.1%, respectively (p < 0.001). All patients with moderate/severe liver herniation required a prosthetic patch.

CONCLUSION

Liver herniation has prenatal predictive value for the need for prosthetic repair in congenital diaphragmatic hernia. This finding should be valuable during prenatal counseling for clinical trials of engineered diaphragmatic repair.

Hydrogels for tissue engineering and delivery of tissue-inducing substances

This manuscript presents hydrogels (HGs) from a tissue engineering perspective being especially written for those who are approaching this field by offering a concise but inclusive review of hydrogel synthesis, properties, characterization methods, and applications.

Tissue-Engineered Axially Vascularized Contractile Skeletal Muscle

BACKGROUND

As tissue-engineered muscle constructs increase in scale, their size is limited by the need for a vascular supply. In this work, the authors demonstrate a method of producing three-dimensional contractile skeletal muscles in vivo by incorporating an axial vascular pedicle.

METHODS

Primary myoblast cultures were generated from adult F344 rat soleus muscle. The cells were suspended in a fibrinogen hydrogel contained within cylindrical silicone chambers, and situated around the femoral vessels in isogeneic adult recipient rats. The constructs were allowed to incubate in vivo for 3 weeks, at which point they were explanted and subjected to isometric force measurements and histologic evaluation.

RESULTS

The resulting three-dimensional engineered skeletal muscle constructs produced longitudinal contractile force when electrically stimulated. Length-tension, force-voltage, and force-frequency relationships were similar to those found in developing skeletal muscle. Desmin staining demonstrated that individual myoblasts had undergone fusion to form multinucleated myotubes. Von Willebrand staining showed that the local environment within the chamber was richly angiogenic, and capillaries had grown into and throughout the constructs from the femoral artery and vein.

CONCLUSIONS

Three-dimensional, vascularized skeletal muscle can be engineered in vivo. The resulting tissues have histologic and functional properties consistent with native skeletal muscle.

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.

Use of a biodegradable patch for reconstruction of large thoracic cage defects in growing children

BACKGROUND/PURPOSE

At our institution, procedures were developed to enlarge and stabilize the thoracic cavity of children born with severe-enough abnormalities of the thoracic cage as to result in lack of normal lung growth and function. In addition to the device known as the vertical expandable prosthetic titanium rib (VEPTR), some type of patch material was needed to cover large congenital defects of the chest cage owing to rib absence or to cover defects created because of the expansion process. Initially, synthetic material, polytetrafluorethylene (Gore-Tex, WL Gore and Associates, Flagstaff, Ariz) was used, but this proved itself to be restrictive over time and required removal. Thus, a nonsynthetic biodegradable patch material was adopted for coverage of the defects (Surgisis, Cook, Bloomington, Ind).

METHODS

From October 2001 through October 2004, 26 growing children undergoing thoracic cage reconstruction received the biodegradable extracellular matrix patch derived from porcine SIS (Cook). A patch was deemed necessary if any one of the following conditions was obtained: (a) herniation of the lung was likely; (b) chest wall musculature was significantly diminished; (c) injury to the lung was likely at reoperation; (d) the defect was greater than 2 x 2 cm.

RESULTS

During the follow-up period, 41 months thus far, each of the 26 children has undergone routine, scheduled expansions or change-out procedures every 6 months. The SIS has not required removal for any reason and has not restricted growth of the thoracic cage.

CONCLUSIONS

Compared with synthetic soft tissue patch material, the nonsynthetic, biodegradable soft tissue patch (SIS) has proven to be a superior alternative, thus far, to others for use in our population of patients for reconstruction of the thoracic cage in the growing child.

Prosthetic patches for congenital diaphragmatic hernia repair: Surgisis vs Gore-Tex

PURPOSE

The sequelae of congenital diaphragmatic hernia (CDH) continue well beyond the perinatal period. Up to 50% of these patients have subsequent recurrent herniation or small bowel obstruction (SBO). A recent trend has been toward the use of bioactive prosthetic materials. We reviewed different patch closure techniques used for CDH repair at our institution and their association with these sequelae.

METHODS

A retrospective review was performed of 152 records for patients with CDH. Newborns that underwent patch repair for CDH and survived for at least 30 days were included in the analysis. Primary outcomes evaluated were recurrent herniation and SBO. Two types of prostheses were examined, Gore-Tex, an artificial material, and Surgisis, a bioactive material.

RESULTS

Twelve (44%) of 27 patients who had Surgisis repair had recurrent herniation. Seventeen (38%) of 45 patients who had a Gore-Tex repair had recurrent herniation. Two additional patients in each group presented with SBO. No significant difference in recurrent herniation rates was observed (P > .5). The time to recurrence was similar in both groups (log-rank, P = .75), with most recurrences (92% Surgisis, 76% Gore-Tex) occurring in the first year.

CONCLUSION

The rates of recurrent herniation and SBO after neonatal prosthetic patch repair of CDH were similar regardless of the prosthetic material used (Surgisis or Gore-Tex).

Diaphragmatic repair through fetal tissue engineering: a comparison between mesenchymal amniocyte- and myoblast-based constructs

PURPOSE

We have previously shown that fetal tissue engineering is a preferred alternative to diaphragmatic repair in a large animal model. This study was aimed at comparing diaphragmatic constructs seeded with mesenchymal amniocytes and fetal myoblasts in this model.

METHODS

Neonatal lambs (n = 14) underwent repair of an experimental diaphragmatic defect with identical scaffolds, either seeded with labeled autologous cells (mesenchymal amniocytes in group 1 and fetal myoblasts in group 2) or as an acellular graft (group 3). At 1 to 12 months postoperatively, implants were harvested for multiple analyses.

RESULTS

Repair failure (reherniation or eventration) was significantly higher in group 3 than in groups 1 and 2, with no difference between groups 1 and 2. Seeded fetal myoblasts quickly lost their myogenic phenotype in vivo. All grafts contained cells with a fibroblastic-myofibroblastic profile. Elastin concentrations and both modular and ultimate tensile strengths were significantly higher in group 1 than in groups 2 and 3. There were no differences in glycosaminoglycans and type I collagen levels among the groups.

CONCLUSIONS

Diaphragmatic repair with a mesenchymal amniocyte-based engineered tendon leads to improved structural outcomes when compared with equivalent fetal myoblast-based and acellular grafts. The amniotic fluid is a preferred cell source for tissue-engineered diaphragmatic reconstruction.

An injectable tissue-engineered embolus prevents luminal recanalization after vascular sclerotherapy

BACKGROUND/PURPOSE

Sclerotherapy for vascular malformations is often limited by luminal recanalization. This study examined whether an injectable tissue-engineered construct could prevent this complication in a rabbit model of venous sclerotherapy.

METHODS

Ethanol sclerotherapy of a temporarily occluded jugular vein segment was performed in 46 rabbits, which were then divided into 3 groups. Group I (n = 16) had no further manipulations. In groups II (n = 15) and III (n = 15), 0.5 mL collagen hydrogel was injected intraluminally, respectively, devoid of and seeded with autologous fibroblasts. At 1, 4, and 20 to 24 weeks postoperatively, vein segments were examined for patency and resected for histological evaluation. Statistical analysis was by Fisher's Exact test.

RESULTS

All vein segments were occluded at 1 and 4 weeks in all groups, despite histological evidence of progressive endothelial ingrowth. However, at 20 to 24 weeks, angiography demonstrated restoration of vessel patency in groups I (3/6) and II (3/5), but not in group III (0/6; P = .043), in which histology confirmed an obliterated lumen for all vessels.

CONCLUSION

An injectable, fibroblast-based, engineered construct prevents midterm to long-term recanalization in a leporine model of vascular sclerotherapy. This novel therapeutic approach may prevent recurrence of vascular malformations after sclerotherapy, thus reducing the need for repeated procedures and morbid operative resections.

Amniotic fluid and placental stem cells

The amniotic fluid and the placenta are unique sources of different populations of stem cells--mesenchymal, hematopoietic, trophoblastic--and, possibly, of more primitive stem cells. Although much of the amniotic cavity/fluid and the placenta share a common embryonic origin, the specific origins of the stem cells found in these two compartments remain to be determined. Accordingly, it is not yet known whether all or part of these two stem-cell subsets are actually the same. The multilineage potential of the different stem cell populations from these two sources has begun to be described but still much remains to be learned. Thus, it is not surprising that clinical applications related to the use of these cells have yet to be reported. Nevertheless, fertile experimental work from many different groups has introduced a number of promising novel therapeutic concepts utilizing these cells, such as in tissue engineering, cell transplantation, and gene therapy.

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.

Enhancement of intravascular sclerotherapy by tissue engineering: short-term results

BACKGROUND/PURPOSE

Treatment of vascular malformations with sclerotherapy is often complicated by reexpansion secondary to endothelial recanalization. This study examined the use of an autologous fibroblast construct to enhance intraluminal scar formation after sclerotherapy.

METHODS

New Zealand rabbits (n = 15) underwent ethanol sclerotherapy of a segment of the facial vein. After intraluminal saline flush, animals were equally divided into 3 groups. In group I, no further manipulations were performed. In groups II and III, collagen hydrogel was injected into the sclerosed vein, respectively, without and seeded with autologous green fluorescent protein-labeled fibroblasts. One week postoperatively, the vein segments were examined for patency and resected for histology.

RESULTS

The sclerosed vein segments remained occluded in all animals. Histological examination of luminal thrombi demonstrated numerous viable fibroblasts in group III, whereas there were none in the control specimens from groups I and II. The presence of the injected autologous green fluorescent protein-labeled fibroblasts within thrombi of group III was confirmed by immunohistochemistry.

CONCLUSIONS

An injectable tissue-engineered construct enhances sclerotherapy of the jugular vein in a leporine model by reliably delivering fibroblasts that populate the resultant thrombus. Further analysis of this novel therapeutic concept as a means to augment permanent scar formation and reduce luminal recanalization is warranted.

Skeletal muscle tissue engineering

The reconstruction of skeletal muscle tissue either lost by traumatic injury or tumor ablation or functional damage due to myopathies is hampered by the lack of availability of functional substitution of this native tissue. Until now, only few alternatives exist to provide functional restoration of damaged muscle tissues. Loss of muscle mass and their function can surgically managed in part using a variety of muscle transplantation or transposition techniques. These techniques represent a limited degree of success in attempts to restore the normal functioning, however they are not perfect solutions. A new alternative approach to addressing difficult tissue reconstruction is to engineer new tissues. Although those tissue engineering techniques attempting regeneration of human tissues and organs have recently entered into clinical practice, the engineering of skeletal muscle tissue ist still a scientific challenge. This article reviews some of the recent findings resulting from tissue engineering science related to the attempt of creation and regeneration of functional skeletal muscle tissue.