Analysis of cellular and decellular allogeneic dermal grafts for the treatment of full-thickness wounds in a porcine model

The Goettingen minipig as an experimental model in wound-healing studies

Background

Deep dermal wounds in extensive burns and chronic wound-healing disorders represent a significant medical problem and require a high level of therapy to reduce the risk of infection and other long-term consequences, such as amputation. A better understanding of the wound-healing processes is essential, and animal models are indispensable to fundamental research.

Objective

This study aimed to provide a transparent protocol and prove the effectiveness of an in vivo porcine model using Goettingen minipigs for wound-healing studies.

Material and methods

Thirteen female Goettingen minipigs were kept in species-appropriate housing and were treated according to the German law for the protection of animals. The study was performed with permission from the local ethical review committee of animal welfare. The experimental procedure for studying dermal regeneration in 102 full-thickness wounds through clinical observation and histological analysis, focusing on neodermal formation, is described in detail.

Results

The Goettingen minipig model proved to be suitable in wound-healing studies. The dermal regeneration was evident and viewable without wound contamination or any rejection reaction. The histological evaluations were also reliable and clearly presented the optimized wound healing of deep dermal wounds using the different therapeutic approaches.

Conclusion

Given the great clinical need for alternative or complementary therapies, we considered the Goettingen minipig trial a reliable, ethically justifiable, effective, and reproducible in vivo model for wound-healing studies.

Use of Meshed Acellular Dermal Allograft as a Lining Material After Orbital Exenteration

PURPOSE

To evaluate the surgical outcome and safety of acellular human dermal allograft as a new lining material to the exposed orbit after exenteration.

METHODS

Retrospective case series of patients who underwent orbital exenteration followed by reconstruction with meshed-type acellular dermal allograft from 2009 to 2018 in a single tertiary institution.

RESULTS

There were 14 eyes (2 right, 12 left) of 14 patients (6 men, 8 women). Mean age at operation was 69.1 ± 16.5 years. Indication for surgery was malignancy in all patients. One patient underwent subtotal exenteration, while the rest underwent total exenteration. SureDerm Meshed was used in 12 patients, AlloDerm Meshed in 1, and CGDerm Meshed in 1. Mean follow-up period was 12.1 months. Full or nearly full epithelialization occurred in 10 of 14 patients (71.4%) at 1 month and 9 of 12 patients (75.0%) at 3 months. There was delayed epithelialization in 3 patients due to poor wound care (n = 1), adjuvant radiotherapy (n = 1), and adjuvant radiotherapy followed by cerebrospinal fluid leak (n = 1).

CONCLUSIONS

Meshed acellular human dermal allograft showed good success in reconstruction after orbital exenteration and may be considered as an alternative lining material to split-thickness skin graft after orbital exenteration.

Immune tolerance of tissue-engineered skin produced with allogeneic or xenogeneic fibroblasts and syngeneic keratinocytes grafted on mice

Organs are needed for the long-term replacement of diseased or wounded tissues. Various technologies based on cells seeded in synthetic or biomaterial scaffolds, or scaffold-free methods have been developed in order to produce substitutes that mimic native organs and tissues. For cell-based approaches, the use of living allogeneic fibroblasts could potentially lead to the production of "off-the-shelf" bioengineered organs/tissues. However, questions remain regarding the outcome of allogeneic grafts in terms of persistence of allogeneic cells, tolerance and the host immune reaction against the tissue after implantation. To evaluate graft tolerance of engineered-tissues containing non-autologous fibroblasts, tissue-engineered skin substitutes (TESs) produced with syngeneic, allogeneic or xenogeneic fibroblasts associated with syngeneic, allogeneic or xenogeneic epithelial cells were grafted in mice as primary and secondary grafts. The immune response was evaluated by histological analysis and immunodetection of M2 macrophages, CD4- and CD8-positive T cells, 15, 19, 35 and 56 days after grafting. Tissue-engineered skin composed of non-autologous epithelial cells were rejected. In contrast, TESs composed of non-autologous fibroblasts underlying syngeneic epithelial cells were still present 56 days after grafting. This work shows that TES composed of non-autologous fibroblasts and autologous epithelial cells are not rejected after grafting. STATEMENT OF SIGNIFICANCE: We found that tissue-engineered skin substitutes produced by a scaffold-free cell-based approach from allogeneic fibroblasts and autologous epithelial cells are not rejected after grafting and allow for the permanent coverage of a full-thickness skin wounds. In the field of tissue engineering, these findings open the possibility of selecting a human fibroblastic or stromal cell population based on its biological properties and adequate biosafety, banking it, in order to produce "ready-to-use" bioengineered organs/tissues that could be grafted to any patient without eliciting immune reaction after grafting. Our results can be generalized to any organs produced from fibroblasts. Thus, it is a great step with multiple applications in tissue engineering and transplantation.

Specialized Living Wound Dressing Based on the Self-Assembly Approach of Tissue Engineering

There is a high incidence of failure and recurrence for chronic skin wounds following conventional therapies. To promote healing, the use of skin substitutes containing living cells as wound dressings has been proposed. The aim of this study was to produce a scaffold-free cell-based bilayered tissue-engineered skin substitute (TES) containing living fibroblasts and keratinocytes suitable for use as wound dressing, while considering production time, handling effort during the manufacturing process, and stability of the final product. The self-assembly method, which relies on the ability of mesenchymal cells to secrete and organize connective tissue sheet sustaining keratinocyte growth, was used to produce TESs. Three fibroblast-seeding densities were tested to produce tissue sheets. At day 17, keratinocytes were added onto 1 or 3 (reference method) stacked tissue sheets. Four days later, TESs were subjected either to 4, 10, or 17 days of culture at the air–liquid interface (A/L). All resulting TESs were comparable in terms of their histological aspect, protein expression profile and contractile behavior in vitro. However, signs of extracellular matrix (ECM) digestion that progressed over culture time were noted in TESs produced with only one fibroblast-derived tissue sheet. With lower fibroblast density, the ECM of TESs was almost completely digested after 10 days A/L and lost histological integrity after grafting in athymic mice. Increasing the fibroblast seeding density 5 to 10 times solved this problem. We conclude that the proposed method allows for a 25-day production of a living TES, which retains its histological characteristics in vitro for at least two weeks.

Frequent Application of the New Gelatin-Collagen Nonwoven Accelerates Wound Healing

OBJECTIVE

Mortality after chronic wounds is high. Thus, proper and effective therapy is of critical importance. Adult mammalian skin cannot regenerate spontaneously. It heals under scar formation in a process of repair. In general, wound closure is achieved through a combination of contraction, scar formation, and regeneration. To enhance wound healing, research groups are continuously inventing and evaluating novel skin replacement products. A single application of a new gelatin-collagen nonwoven accelerates wound closure of full-thickness skin defects. Therefore, the authors' objective was to evaluate the effect of a higher application frequency of the nonwoven on wound closure in a minipig model.

MATERIALS AND METHODS

Four full-thickness skin defects were created surgically on the dorsum of 12 Göttingen minipigs. Next, 3 wounds were treated randomly with a novel gelatin-collagen nonwoven in different thicknesses, while the fourth wound was left untreated and served as the control wound. Moreover, 6 minipigs achieved multiple applications of the wound dressing. During the experimental period of 21 days, a close-up photographic documentation was performed. Finally, the areas of the initial wounds were excised and examined histologically.

RESULTS

More frequent application of the nonwoven achieved accelerated wound healing and better epidermis quality compared with a single application. Mean time until wound closure of all wounds treated with a multiple application of the nonwoven was 11.0 (± 1.2) days, compared with a single application of the nonwoven with 12.4 (± 1.26) days and control wounds with 13.5 (± 1.19) days. Furthermore, the epidermal thickness of all wounds treated with multiple applications of the nonwoven was increased by 10.67 μm (31.89 ± 8.86 μm, P = .0007) compared with a single application of the nonwoven and by 6.53 μm (27.75 ± 7.24 μm, P = .0435) compared with the control group.

CONCLUSIONS

Multiple applications of the gelatin-collagen nonwoven may be an appropriate treatment for chronic wounds leading to a fast wound closure through a combination of contraction and re-epithelialization.

Root coverage using a coronally advanced flap with or without acellular dermal matrix: a meta-analysis

Purpose

Gingival recession is a major esthetic concern and may lead to root sensitivity during periodontal treatment. Coronally advanced flaps (CAFs) with and without acellular dermal matrix (ADM) are widely used in root coverage procedures. The aim of this study was to analyze the efficacy of CAF in combination with ADM in the treatment of gingival recession.

Methods

PubMed, The Cochrane Library, and Embase were used to identify relevant articles. The articles were screened, data were extracted, and the quality of the studies was assessed by three reviewers with expertise in clinical practice, trials, statistics, and biomedical editing. The clinical endpoints of interest included changes in recession, probing depth (PD), clinical attachment level (CAL), and keratinized tissue (KT).

Results

Ten randomized controlled trials were identified, including six studies that compared CAFs with ADM and CAFs using connective tissue grafting (CTG) and four studies that compared CAFs with or without ADM. No statistically significant differences were found between the use of ADM and CTG, whereas statistically significant differences were found between groups in which ADM and CAF were combined and groups that underwent CAF alone with regard to recession coverage, CAL, and KT. The combination of CAF with an ADM allograft achieved more favorable recession coverage and recovery of CAL and KT than CAF alone.

Conclusions

The results from the ADM and CTG groups suggest that both procedures may be equally effective in clinical practice. Given the limitations of this study, further investigation is needed to clarify the effectiveness of ADM and CAF in clinical practice.

ECM and ECM-like materials - Biomaterials for applications in regenerative medicine and cancer therapy

Regenerative strategies such as stem cell-based therapies and tissue engineering applications are being developed with the aim to replace, remodel, regenerate or support damaged tissues and organs. In addition to careful cell type selection, the design of appropriate three-dimensional (3D) scaffolds is essential for the generation of bio-inspired replacement tissues. Such scaffolds are usually made of degradable or non-degradable biomaterials and can serve as cell or drug carriers. The development of more effective and efficient drug carrier systems is also highly relevant for novel cancer treatment strategies. In this review, we provide a summary of current approaches that employ ECM and ECM-like materials, or ECM-synthetic polymer hybrids, as biomaterials in the field of regenerative medicine. We further discuss the utilization of such materials for cell and drug delivery, and highlight strategies for their use as vehicles for cancer therapy.

Alteration of biomechanical properties of skin in acute cold contact injury

BACKGROUND

The prevalence of acute cold injury has increased recently. Despite new research findings, these injuries and their resulting tissue damage are still not entirely understood. Especially, little is known about alteration of skin biomechanical properties.

METHODS

A total of 36 acute cold contact wounds with different depths were generated on the abdomen of six Göttingen minipigs. Alteration of biomechanical properties of skin was evaluated objectively after 15 and 360 min using a Cutometer device. Biopsies for histological evaluation were taken, and the depth of injury was correlated with biomechanical properties.

RESULTS

Calculated elasticity (Ue), firmness of skin (R0) and overall elasticity (R8) demonstrated a continuous decrease, whereas other parameters demonstrated an initial increase with increasing depth of injury 15 min after wound generation. All parameters showed an increase compared to healthy skin, 360 min after wound generation. Furthermore, an alteration of values over time was detected.

CONCLUSION

Alteration of biomechanical properties of skin is a function of damaged tissue structures. The presented results demonstrate a decrease of main elastic parameters with increasing depth of injury and indicate progressive tissue damage over time. Skin elasticity measurements are a valuable tool in acute cold contact injury depth assessment and may act as an influencing factor in management decisions.

Comparison of different cooling rates for fibroblast and keratinocyte cryopreservation

Easy, cost-effective and reliable cryopreservation protocols are crucial for the successful and effective application of tissue engineering. Several different protocols are in use, but no comprehensive comparisons across different machine-based and manual methods have been made. Here, we compare the effects of different cooling rates on the post-thaw survival and proliferative capacity of two basic cell lines for skin tissue engineering fibroblasts and keratinocytes, cultured and frozen in suspension or as a monolayer. We demonstrate that effectiveness of cryopreservation cannot be reliably determined immediately after thawing: the results at this stage were not indicative of cell growth in culture 3 days post-thaw. Cryopreservation of fibroblasts in an adherent state greatly diminishes their subsequent growth potential. This was not observed when freezing in suspension. In keratinocytes, however, adherent freezing is as effective as freezing in suspension, which could lead to significant cost and labour savings in a tissue-engineering environment. The 'optimal' cryopreservation protocol depends on cell type and intended use. Where time, ease and cost are dominant factors, the direct freezing into a nitrogen tank (straight freeze) approach remains a viable method. The most effective solution across the board, as measured by viability 3 days post-thaw, was the commonly used, freezing container method. Where machine-controlled cryopreservation is deemed important for tissue-engineering Good Manufacturing Practice, we present results using a portfolio of different cooling rates, identifying the 'optimal' protocol depending on cell type and culture method. Copyright © 2013 John Wiley & Sons, Ltd.

Whole-organ re-engineering: a regenerative medicine approach to digestive organ replacement

Recovery from end-stage organ failure presents a challenge for the medical community, considering the limitations of extracorporeal assist devices and the shortage of donors when organ replacement is needed. There is a need for new methods to promote recovery from organ failure and regenerative medicine is an option that should be considered. Recent progress in the field of tissue engineering has opened avenues for potential clinical applications, including the use of microfluidic devices for diagnostic purposes, and bioreactors or cell/tissue-based therapies for transplantation. Early attempts to engineer tissues produced thin, planar constructs; however, recent approaches using synthetic scaffolds and decellularized tissue have achieved a more complex level of tissue organization in organs such as the urinary bladder and trachea, with some success in clinical trials. In this context, the concept of decellularization technology has been applied to produce whole organ-derived scaffolds by removing cellular content while retaining all the necessary vascular and structural cues of the native organ. In this review, we focus on organ decellularization as a new regenerative medicine approach for whole organs, which may be applied in the field of digestive surgery.

Implantation of a porcine acellular dermal graft in a primate model of rotator cuff repair

BACKGROUND

Non-cross-linked xenogeneic extracellular matrix graft materials have typically elicited a hypersensitivity reaction when implanted into humans or other primates. The purpose of this study was to examine the histologic and immune response to a non-cross-linked porcine-derived dermal extracellular matrix graft processed to remove the α-gal epitope.

MATERIALS AND METHODS

Eight African green monkeys were implanted with porcine acellular dermal matrix (Conexa Reconstructive Tissue Matrix; Tornier Inc, Edina, MN, USA) to repair and augment a partial excision defect of the supraspinatus tendon of the rotator cuff. Four animals each were sacrificed at 3 months and 6 months, and histologic samples were compared with tissues harvested from unoperated shoulders.

RESULTS

Gross examination of grafted Conexa showed the appearance of integration proximally with tendon and distally with bone in each operated rotator cuff complex. Histologically, Conexa appeared to have remodeled to tendon-like architecture, with homogeneous distribution of fibroblast cells and parallel alignment of collagen fibers, with the direction of force evident by 3 months after implantation. Abundant vasculature observed at 3 months, which diminished to native tendon levels by 6 months, also indicated this to be a period of significant remodeling with an absence of significant inflammation, as evidenced by immunochemical methods and serum analysis.

CONCLUSION

Conexa porcine acellular dermal matrix allows for incorporation of host tendon tissue without a hypersensitivity reaction in a primate model and should be a safe material for augmentation of human rotator cuff repair.

Mathematical modeling and frequency gradient analysis of cellular and vascular invasion into integra and strattice: toward optimal design of tissue regeneration scaffolds

BACKGROUND

Rapid, effective host cell invasion and vascularization is essential for durable incorporation of avascular tissue-replacement scaffolds. In this study, the authors sought to qualitatively and quantitatively determine which of two commercially available products (i.e., Strattice and Integra) facilitates more rapid cellular and vascular invasion in a murine model of graft incorporation.

METHODS

Integra and Strattice were implanted subcutaneously into the dorsa of C57BL/6 mice; harvested after 3, 7, or 14 days; and stained with hematoxylin and eosin, 4',6-diamidino-2-phenylindole, and immunohistochemical stains for CD31 and α-smooth muscle actin. Exponential decay equations describing cellular invasion through each layer were fit to each material/time point. Mean cell density and cell frequency maps were created denoting extent of invasion by location within the scaffold.

RESULTS

Qualitative analysis demonstrated extensive cellular infiltration into Integra by 3 days and increasing over the remaining 14 days. Invasion of Strattice was sparse, even after 14 days. α-Smooth muscle actin immunohistochemistry revealed blood vessel formation within Integra by 14 days but no analogous neovascularization in Strattice. Mean decay equations for Integra and Strattice were y = 76.3(0.59) and y = 75.5(0.33), respectively. Both cell density measurements and frequency mapping demonstrated that, at all time points, Integra manifested a greater density/depth of cellular invasion when compared with Strattice.

CONCLUSIONS

These data confirm empiric clinical observations that Integra is more rapidly invaded than Strattice when placed in a suitable host bed. A remnant microvasculature template is not sufficient for effective cellular ingrowth into an artificial tissue construct. These findings provide insight into means for improving future dermal replacement products.

Salvage of calvarial bone graft using acellular dermal matrix in nasal reconstruction and secondary rhinoplasty for frontonasal dysplasia

Frontonasal dysplasia is a severe malformation composed of cranial, ophthalmic, nasal, upper lip, and palatal deformities. Reconstruction in these patients requires complex craniofacial efforts. A 19-year-old woman with frontonasal dysplasia was treated at our institution where she had undergone multiple prior reconstructive surgeries including facial bipartition and cantilevered calvarial bone graft for nasal reconstruction. She later presented with a palpable bone graft prominence, associated contour deformity, and an area of overlying paper-thin skin at the nasal tip. Although there was no ulceration, the threat of graft extrusion required immediate attention. The prominent bone graft tip was debrided, and the overlying soft tissue envelope was augmented using acellular dermal matrix. No surgical complication was encountered. The patient had successful salvage of the bone graft and a pleasing aesthetic outcome at 9 months of follow-up. The use of acellular dermal matrix has proven to be beneficial in the correction of nasal contour deformities given its soft, natural appearance, availability, affordability, and safety. Its use also avoids further donor site morbidity. We suggest acellular dermal matrix as a graft material in revision rhinoplasties for cases of acquired nasal contour deformity and threatened bone graft extrusion. This is the first report known to the authors using acellular dermal matrix during staged nasal reconstruction in a patient experiencing frontonasal dysplasia.

Dorsal Augmentation with AlloDerm

The augmentation-reduction principle is becoming pervasive in nasal surgery. Rhinoplasty surgeons have discovered that nasal skin does not consistently contract. Therefore, nasal augmentation is an increasingly accepted technique, and grafts are required. Autogenous cartilage is the grafting material of choice. There are drawbacks to autogenous material, especially in secondary rhinoplasty patients who are often graft-depleted. Cartilage grafts may cause unsightly irregularities over time. Therefore, an interest in alternative soft tissue substitutes has developed. AlloDerm is freeze-dried acellular cadaver dermis. AlloDerm acts as a filler to expand portions of the nasal skin envelope to balance the overresected nose and adhere to the augmentation-reduction principle. AlloDerm facilitates touch-ups, especially in the author's own personal patients. It is soft, thin, and pliable and can be placed under very thin skin. AlloDerm obviates the necessity for graft harvest. It is safe in that it can eliminate the risk of donor-site problems for dorsal onlays such as cranial bone or rib grafts. It is natural and acts as an excellent camouflage graft when used as padding over a cartilage graft. It is incorporated into the surrounding tissue and does not develop unsightly irregularities over time. Extrusion is rare. It does not shift over time. It is especially useful in donor-site-depleted patients. Overcorrection is absolutely necessary because a portion of the implanted AlloDerm is always absorbed. Resorption is most common over the bony dorsum with about 20 to 30% of the graft absorbing. Resorption is disappointing for the patient and frustrating for the surgeon. Absorption does not seem to relate to the number of layers used. No graft absorption has been noted after 1 year. Therefore, it is safe to assume that the patient has a stable result from the AlloDerm graft after 1 year, and no further change should be anticipated. It is easy to use. The advantages and caveats should be kept in mind when evaluating a patient for a dorsal graft.

The use of decellularized dermal grafting (AlloDerm) in persistent oro-nasal fistulas after tertiary cleft palate repair

To assess the efficacy of decellularized dermal grafting as an adjunct to the closure of recurrent oro-nasal fistulas. Five consecutive patients with recurrent oro-nasal fistulas were repaired with decellularized dermal grafting sandwiched between oral and nasal flaps of a von Langenbeck palatal repair. All patients had previously undergone a minimum of three prior palatal repairs with the recurrence of their oro-nasal fistula in the post-alveolar area. Decellularized dermal graft was placed between the nasal mucosa and the levator veli palatine muscle. Patients were followed postoperatively and assessed for infection, dehiscence, signs of rejection, and fistula recurrence. All patients were followed for an average of three months. Clinical examination revealed no recurrence of their oro-nasal fistula nor associated symptoms of nasal reflux. Decellularized dermal grafts were not rejected nor extruded from the site of surgical repair. Decellularized dermal graft should be considered for use in the treatment of recurrent oro-nasal fistula after cleft palate repair. We would also like to encourage further clinical study.

Repair of oronasal fistulae with acellular dermal matrices

BACKGROUND

The authors examined the efficacy of a novel technique for oronasal fistula repair using acellular dermal matrix grafts. In part I, an animal model was used to demonstrate proof-of-concept; in part II, the method was applied to oronasal fistula repair in the clinical setting.

METHODS

In part I, oronasal fistulas were created in Yorkshire piglets (n = 6) and allowed to mature for 2 weeks. In three animals, acellular dermal grafts were interposed between the oral and nasal mucosa traversing the palatal fistulas. Mucosal edges were not closed. Three weeks postoperatively, the palates were examined histologically. The fistulas of control piglets (n = 3) remained unrepaired and were examined 5 weeks after their creation. In part II, acellular dermal grafts were interposed between the oral and nasal mucosa in nine consecutive patients undergoing oronasal fistula repair. Complete closure of the oral and nasal mucosa was achieved in two patients. In the remainder, nasal closure was affected by interposition of the dermal matrices beneath a complete oral mucosal closure.

RESULTS

All animals that underwent fistula repair demonstrated successful healing with revascularization, complete reepithelialization, and cellular infiltration into the grafts. All control fistulas remained patent. Successful fistula closure was observed in all patients. In two patients, early oral mucosal dehiscence and exposure of the dermal graft was followed by complete healing.

CONCLUSIONS

This study demonstrates successful closure of palatal fistulas in an animal model and in cleft palate patients using interposition grafts of acellular dermis. This novel method offers promise as a simple and effective technique for tension-free closure of oronasal fistulas.

The Role of Bioprosthetics in Abdominal Wall Reconstruction

In several common situations, bioprosthetic materials may have distinct advantages over synthetic mesh and autologous flap or graft techniques for abdominal wall reconstruction. These off-the-shelf materials entail no donor site morbidity and are used successfully in contaminated wounds owing to their ability to resist infection, become revascularized and incorporated into host tissue, and reduce visceral adhesions. Fibrovascular incorporation into surrounding tissues and implant remodeling reduce the risks associated with a persistent foreign body, such as chronic infection, enterocutaneous fistulae, and cutaneous exposure. Disadvantages of bioprosthetic materials include higher implant cost relative to synthetic mesh, limited size of individual sheets in some cases, and risk of seroma formation. Bioprosthetic mesh has been used for abdominal wall reconstruction for approximately 5 years, so long-term studies are not available. Current laboratory and clinical evidence suggests that these materials provide a strong, durable musculofascial repair when used for abdominal wall repair. Further studies and ongoing clinical experience will be important in determining the indications for which bioprosthetic mesh will have the greatest impact. Currently available commercial products have distinct differences that result in varied clinical biologic and physiologic activity. New products and modifications to existing products may further enhance the benefits of bioprosthetic mesh, particularly in challenging cases. The use of bioprosthetic mesh has attracted interest in a relatively short period of time, with rapidly increasing indications and volume of cases successfully performed. Bioprosthetic mesh likely will play a progressively greater role in trunk reconstruction in the future.

The use of Alloderm in the closure of a giant omphalocele

Giant omphaloceles are associated with a considerable loss of abdominal domain. Early primary repair of the fascia is either not possible or poorly tolerated by the infant. Current surgical options result in a ventral hernia requiring future surgery or involve the chronic use of prosthetic patches with or without tissue expanders. This case presentation describes an alternative surgical approach that results in early fascial closure using an interposition graft of Alloderm.

Pelvic, abdominal, and chest wall reconstruction with AlloDerm in patients at increased risk for mesh-related complications

BACKGROUND

The use of polypropylene mesh in the reconstruction of trunk defects increases complication rates when the mesh is placed directly over viscera or the operative site has been irradiated or contaminated with bacteria. An alternative is AlloDerm (decellularized human cadaveric dermis), which becomes vascularized and remodeled into autologous tissue after implantation. When used for fascial reconstruction, AlloDerm forms a strong repair, causes minimal abdominal adhesions, and resists infection.

METHODS

We did a retrospective study of cancer patients at increased risk for mesh-related complications who underwent trunk reconstruction with AlloDerm over a 1-year period. Risk factors included unavoidable placement of mesh directly over the bowel or lung, perioperative irradiation, and/or bacterial contamination of the defect. The indications, defect characteristics, reconstructive techniques, complications, and surgical outcomes were evaluated.

RESULTS

Thirteen patients were included in the study. Indications for reconstruction were oncologic resection, resection of enterocutaneous fistula, and/or ventral hernia repair. Seven patients had bacterial contamination at the operative site and seven patients received perioperative radiation. The mean musculofascial defect size was 435 cm. AlloDerm was placed directly over the bowel or lung in all patients. Nine patients required flap reconstruction, including 14 pedicled and two free flaps. The mean follow-up was 6.4 months. Complications occurred in six patients, however, there were no clinically evident mesh infections, hernias, or bulges.

CONCLUSIONS

AlloDerm successfully can be used in reconstructions for large, complex pelvic, chest, and abdominal wall defects even when placed directly over viscera and when the operative field is irradiated and/or contaminated with bacteria.

Waste Not, Want Not: The Use of AlloDerm in Secondary Rhinoplasty

BACKGROUND

This article describes the author's successful experience with AlloDerm onlay grafts for the correction of nasal contour deformities in secondary rhinoplasty. AlloDerm is a cadaver dermal filler graft, an off-the-shelf product that is readily available, pliable, and affordable. It is particularly suited for secondary rhinoplasty patients who are graft-depleted. The maximum dorsal augmentation is less than or equal to 3 mm; it is not a support graft. The major indication in this study was dorsal augmentation in the overresected secondary rhinoplasty patient to create a soft, smooth bridge and pleasing dorsal aesthetic lines.

METHODS

Twenty-five secondary rhinoplasty patients underwent multiple nasal corrections and were followed for 2 to 8 years.

RESULTS

Analysis demonstrated no contour changes between year 1 and year 2, showing the dermal grafts to be stable after 1 year. Long-term follow-up for 2 years or longer showed good results, although partial graft resorption (defined to be < or = 50 percent) occurred in 45 percent of patients. Resorption was most common over the bony dorsum, with approximately 20 to 30 percent of the graft absorbing; over the tip, approximately 10 to 15 percent of the graft absorbed.

CONCLUSION

Absorption did not seem to relate to the number of layers used. AlloDerm does not shift. Overall, the experience for nasal augmentation in secondary rhinoplasty was encouraging. Partial absorption, especially over the bony dorsum in a thin-skinned patient, is a definite disadvantage. Complete absorption was not seen in this study. The author has discovered that it is imperative to overcorrect the defect intraoperatively. Regrafting is possible and sometimes necessary.

Management of Gingival Recession by the Use of an Acellular Dermal Graft Material: A 12-Case Series

BACKGROUND

Different soft tissue defects can be treated by a variety of surgical procedures. Most of these techniques require the palatal area as a donor site. Recently, an acellular dermal graft has become available that can substitute for palatal donor tissue.

METHODS

This study describes the surgical technique for gingival augmentation and root coverage and the results of 12 clinical cases. A comparison between the three most popular mucogingival procedures for root coverage is also presented.

RESULTS

The results of the 12 patients and the 26 denuded surfaces have shown that we can obtain a mean root coverage of 74% with the acellular dermal graft. Thirteen out of the 26 denuded surfaces had complete root coverage. The average increase in keratinized tissue was 1.19 mm. It seems that the long-term results of the cases are stable.

CONCLUSION

The proposed technique of root coverage with an acellular dermal graft can be a good alternative to soft tissue grafts for root coverage, and it should be part of our periodontal plastic surgery armamentarium.

Viability and Function of Autologous and Allogeneic Fibroblasts Seeded in Dermal Substitutes after Implantation

BACKGROUND

Fibroblast-seeded collagen sponges have been used for the treatment of skin defects and skin ulcers. However, the viability of the fibroblasts after implantation is still unknown. The objective of this study was to investigate the viability and distribution of autologous and allogeneic fibroblasts after implantation and to clarify which type is more effective for wound healing.

MATERIALS AND METHODS

Skin samples of Hartley guinea pigs were retrieved and autologous fibroblasts were isolated and cultured. Fibroblasts isolated from the skin of a Strain2 guinea pig were used as allogeneic fibroblasts. Three full-thickness wounds were created on the backs of guinea pigs and an acellular collagen sponge, a collagen sponge seeded with autologous fibroblasts, and a collagen sponge seeded with allogeneic fibroblasts were transplanted. Before implantation, fibroblasts were labeled with PKH26. The guinea pigs were sacrificed 1, 2, and 3 weeks after implantation. The epithelization and contraction of the wounds were assessed, and the viability and distribution of the seeded fibroblasts were observed in cross sections.

RESULTS

Three weeks after implantation, the PKH26-labeled autologous and allogeneic fibroblasts remained viable. In the wounds covered with the autologous fibroblast-seeded collagen sponge, the epithelization was fastest, and the percent wound contraction was smallest. In contrast, in the wounds covered with allogeneic fibroblasts, the epithelization was slowest and the percent contraction was largest.

CONCLUSION

The allogeneic fibroblasts seeded in the collagen sponge survived and remained viable on the grafted area, but did not accelerate wound healing.

Coronally positioned flap with or without acellular dermal matrix graft in the treatment of Class I gingival recessions: a randomized controlled clinical study

BACKGROUND

The aim of this study was to clinically evaluate the treatment of Class I gingival recessions by coronally positioned flap with or without acellular dermal matrix allograft (ADM).

METHODS

Thirteen patients with comparable bilateral Miller Class I gingival recessions (> or = 3.0 mm) were selected. The defects were randomly assigned to one of the treatments: coronally positioned flap and acellular dermal matrix (ADM group) or coronally positioned flap alone (CPF group). The clinical parameters included: probing depth (PD), clinical attachment level (CAL), recession height (RH), recession width (RW), height of keratinized tissue (HKT), thickness of keratinized tissue (TKT), plaque index (PI), and gingival index (GI). The measurements were taken before the surgeries and after 6 months.

RESULTS

The mean baseline recession was 3.4 mm and 3.5 mm for ADM group and CPF group, respectively. After 6 months, both treatments resulted in significant root coverage (P < 0.01), reaching an average of 2.6 mm (76%) in the ADM group and 2.5 mm (71%) in the CPF group. The difference in recession reduction between treatments was not statistically significant. There were no statistically significant differences between the treatments in PD, CAL, RH, RW, and HKT. However, the mean TKT gain was 0.7 mm for the ADM group and 0.2 mm for the CPF group (P < 0.01).

CONCLUSION

It can be concluded that both techniques could provide significant root coverage in Class I gingival recessions; however, a greater keratinized tissue thickness can be expected with ADM.

Myocardial tissue engineering and regeneration as a therapeutic alternative to transplantation

Ischemic cardiomyopathy leading to congestive heart failure remains the leading source of morbidity and mortality in Western society and medical management of this condition offers only palliative treatment. While allogeneic heart transplantation can both extend and improve the quality of life for patients with end-stage heart failure, this therapeutic option is limited by donor organ shortage. Even after successful transplantation, chronic cardiac rejection in the form of cardiac allograft vasculopathy can severely limit the lifespan of the transplanted organ. Current experimental efforts focus on cellular cardiomyoplasty, myocardial tissue engineering, and myocardial regeneration as alternative approaches to whole organ transplantation. Such strategies may offer novel forms of therapy to patients with end-stage heart failure within the near future.

Decellularized dermal grafting in cleft palate repair

OBJECTIVE

To assess the efficacy of decellularized dermal grafting used as an adjunct to the performance of primary repair of wide cleft palates.

DESIGN

Retrospective review.

SETTING

Tertiary referral center for large managed care organization.

METHODS

Seven consecutive patients with clefts of the hard and soft palates wider than 15 mm as measured at the posterior edge of the hard palate. Palates were repaired in the standard 2-flap approach with intravelar veloplasty. The decellularized dermal graft (AlloDerm) was applied immediately deep to the oral mucosal closure. Patients were followed up with serial postoperative examination. Palates were assessed for dehiscence, fistula, infection, rejection, scarring, and contracture.

RESULTS

There were no fistulas. In 2 patients, the oral mucosa dehisced, exposing the dermal graft. In 2 other cases, nasal mucosal tears were inadvertently created during closure of the nasal layer. In all cases, the decellularized dermal graft mucosalized and, by clinical examination, became incorporated into the wound. There were no cases of local inflammation or infection. The degree of scarring and contracture was indistinguishable from the adjacent scar.

CONCLUSIONS

Decellularized dermal graft is safe and effective for use in primary closure of wide clefts involving the hard and soft palates. Its application to wide clefts otherwise at risk of fistula is justified. Its use in repair of an existing fistula is also promising.

Root coverage of advanced gingival recession: a comparative study between acellular dermal matrix allograft and subepithelial connective tissue grafts

BACKGROUND

Acellular dermal matrix allograft (ADMA) has successfully been applied as a substitute for free connective tissue grafts (CTG) in various periodontal procedures, including root coverage. The purpose of this study was to clinically compare the efficiency of ADMA and CTG in the treatment of gingival recessions > or = 4 mm.

METHODS

Seven patients with bilateral recession lesions participated. Fourteen teeth presenting gingival recessions > or = 4 mm were randomly treated with ADMA or CTG covered by coronally advanced flaps. Recession, probing depth, and width of keratinized tissue were measured preoperatively and 12 months postoperatively. Changes in these clinical parameters were calculated within and compared between groups and analyzed statistically.

RESULTS

Baseline recession, probing depth, and keratinized tissue width were similar for both groups. At 12 months, root coverage gain was 4.57 mm (89.1%) versus 4.29 mm (88.7%) (P = NS), and keratinized tissue gain was 0.86 mm (36%) versus 2.14 mm (107%) (P < 0.05) for ADMA and CTG, respectively. Probing depth remained unchanged (0.22 mm/0 mm), with no difference between the groups.

CONCLUSIONS

Recession defects may be covered using ADMA or CTG, with no practical difference. However, CTG results in significantly greater gain of keratinized gingiva.

Allogeneic fibroblasts in dermal substitutes induce inflammation and scar formation

In the present study, we compared the use of autologous versus allogeneic fibroblasts in dermal skin substitutes in a porcine wound model. The allogeneic fibroblast populations were isolated from female and a male pig (allo-1, - 2 and - 3) and the controls, autologous fibroblasts, from female graft-recipient pigs (control). The histocompatibility of the three donor pigs with the recipient pigs was determined with a mixed lymphocyte reaction. In two pigs, full-thickness wounds were treated with the fibroblast-seeded dermal substitutes (n = 5 per animal) and immediately overgrafted with meshed split-skin autografts. After 6 weeks, wound contraction was measured by planimetry and scar formation was scored. At 2, 4, and 6 weeks biopsies were taken and evaluated for the presence of inflammatory reactions, myofibroblasts, and scar formation. The mixed lymphocyte reaction of both recipient pigs showed the highest responses on peripheral blood mononuclear cells of the allo-3 donor pig, and was low or negative for allo-1 and allo-2. In all "allogeneic" wounds, more inflammatory cells were observed over time along with inflammatory foci consisting of a mix of lymphocytes and granulomatous cells. After 4 weeks, myofibroblasts were absent in the control wounds, whereas in "allogeneic" wounds, myofibroblasts colocalized with inflammation foci. The final scar tissue of the "allogeneic" wounds showed granulating areas with thin, immature collagen bundles. In contrast, the control wounds showed a dermal tissue with mature collagen bundles organized randomly like in normal skin. The wounds treated with allo-3 fibroblasts showed in both pigs a significant increase in scar formation and wound contraction when compared with control wounds. In conclusion, for optimal restoration of dermal skin function with minimal scar formation, skin substitutes containing autologous fibroblasts are preferred over skin substitutes with allogeneic fibroblasts.

Integra as a dermal replacement in a meshed composite skin graft in a rat model: a one-step operative procedure

BACKGROUND

Current use of Integra, the collagen-based dermal analogue, requires a two-step grafting procedure to achieve wound closure with an "ultrathin" autograft.

METHODS

A one-step operative procedure of meshed composite skin graft (MCSG) using Integra as a dermal template for a meshed split thickness autograft was developed in rats. The silicon layer of Integra was removed, the resulting dermal analogue was meshed (1:1.5), expanded, and placed on excised full thickness wound and covered with a meshed (1:1.5 or 1:6) split thickness autograft. Grafted wounds were dressed with BioBrane, Vaseline gauze, silver-impregnated nylon, or silver-nylon and direct current (SNDC). At scheduled intervals up to 3 months postgrafting, wounds were examined for epithelialization, collagen deposition and fibrosis, hair growth, and contraction. The results of wound closure and healing following the one-step procedure were compared with the outcome of the two-step grafting procedure where application of meshed Integra (step one) was followed in 14 days by removal of the silicon layer and application of the meshed autograft (step two).

RESULTS

The one-step procedure applied to meshed autograft/Integra (1:1.5/1:1.5) composite graft accelerated wound closure by 6-19 days when compared with the two-step procedure. At 3 months postgrafting, the contraction of the healed wound dressed with SNDC, BioBrane, or Vaseline gauze was reduced by 13-16% following the one-step procedure compared with the two-step procedure (p < 0.05). The one-step procedure allowed the expansion of the autograft layer to 1:6 while achieving wound healing results similar to grafting with 1:1.5 meshed autograft layer using the two-step grafting procedure.

CONCLUSION

Single-step application of meshed, thin, split thickness autograft over meshed Integra-derived dermal substitute allows more rapid wound closure with less contraction and more efficient use of graft donor skin than can be obtained with the commonly used two-step grafting procedure.

In vitro characterization of an artificial dermal scaffold

The treatment of extensive burn injuries has been enhanced by the development of artificial skin substitutes. Integra Artificial Skin, an acellular collagen-glycosaminoglycan (C-GAG) dermal equivalent requires a two-stage grafting procedure. However, preseeding the C-GAG dermal equivalent with cultured fibroblasts and keratinocytes, with the aim of performing a single-stage grafting procedure, may be beneficial in terms of replacing the requirement for traditional split-skin grafts. In this comparative in vitro study, the interactions of cultured human dermal fibroblasts and epidermal keratinocytes in Integra Artificial Skin in comparison to cadaver deepidermalized dermis (DED) was investigated. An increase in cell proliferation and migration in the C-GAG dermal equivalent was observed over time. Cocultures of fibroblasts and keratinocytes on both dermal equivalents showed positive expression of proliferation, differentiation, and extracellular matrix (ECM) protein markers. Organization of keratinocytes in the epidermal layers of DED composites were better compared to the C-GAG composites. Deposition of ECM proteins was enhanced in the presence of keratinocytes in both dermal equivalents. Results demonstrate that in vitro the C-GAG dermal equivalent is biocompatible for cell attachment, migration, proliferation, and differentiation. Preseeding Integra Artificial Skin with cultured autologous fibroblasts and keratinocytes for in vivo application, as a single-stage grafting procedure, warrants testing. A better clinical outcome may be achieved as shown by our in vitro results of the coculture composites.

An animal model of lower eyelid spacer grafting with acellular dermis

PURPOSE

Lower eyelid retraction is common in patients with dysthyroid orbitopathy and is seen less commonly in other conditions. Treatment typically requires vertical augmentation of the posterior eyelid lamella with an interpositional graft. Several autologous, homologous, and alloplastic materials have been used. We investigated the gross and microscopic in vivo histology of acellular homologous dermis used as a structural interpositional graft in the lower eyelids of Yucatan minipigs.

METHODS

This prospective, experimental study was designed as follows: Surgery was performed on the left lower eyelid of 4 Yucatan minipigs in accordance with the Massachusetts General Hospital Subcommittee on Research Animal Care guidelines. A 4 x 20-mm strip of acellular porcine dermis was prepared and sutured into place between the tarsus and conjunctiva/lower lid retractors. Tissues were harvested at 6 and 12 weeks and were evaluated histologically.

RESULTS

Gross examination revealed vertical elongation of the palpebral conjunctival surface. Histologic evaluation was performed with hematoxylin and eosin and Verhoeff elastin stains. Serial sections demonstrated incorporation of grafted dermal matrix into native tissues without evidence of inflammation. Definitive differentiation between grafted dermis and native dermis was not possible with light microscopy. Portions of the graft appeared to be epithelialized, whereas other histologic regions showed poorly adhesive epithelium. Inflammatory infiltrates including lymphocytes and polymorphonuclear leukocytes were not seen. No epithelioid or giant cells were identified in the sections examined.

CONCLUSIONS

Acellular homologous dermis produced no measurable untoward effects when implanted as an interpositional graft in the lower eyelid of Yucatan minipigs. On the basis of its material characteristics, it appears to be suitable for this purpose: It is readily available, easily stored, easy to manipulate, and produces minimal inflammation. Long-term persistence, early postoperative histology, and clinical eyelid elevation in humans remain to be evaluated.

Experimental assessment of the revascularization of acellular human dermis for soft-tissue augmentation

The purpose of this experimental study was to determine whether acellular human dermis was capable of complete revascularization in a subcutaneous implantation site with various placement geometries. In young adult rabbit ears, four different sheet and rolled configurations were placed and harvested after 3, 7, 14, and 28 days with silicone rubber microangiographic injections followed by histologic analysis. Revascularization of single-layer acellular human dermis occurred rapidly and was essentially complete by 14 days after surgery. No differences were observed in the ingrowth of vessels regardless of how the basement membrane was oriented. In rolled configurations, vascular ingrowth throughout the implant was slower and had not completely penetrated the grafts by 28 days after surgery at study completion. Vessel ingrowth occurred through the implant surfaces contacting the surrounding soft tissue and along the open seam of the roll. No differences were seen whether the basement membrane was oriented on either the inside or the outside of the roll. Acellular human dermis is capable of significant revascularization of its compact collagen composition in the early postoperative period. In thicker geometries, the rate and completeness of vessel ingrowth are predictably slower. Whether complete revascularization of multilayered or rolled grafts is achieved cannot be determined from this study.

The use of alloderm for the correction of nasal contour deformities

What rhinoplasty surgeon has not been frustrated by unmet expectations from unreliable graft materials? The quest for an ideal graft continues. Septal cartilage is not always adequate in amount or substance. Ear cartilage may cause unsightly irregularities over time. Cranial bone or rib harvest sites add to the complexity of the procedure and can be intimidating for many operators. This article describes the authors' successful experience with AlloDerm onlay grafts for the correction of nasal contour deformities in 58 primary and secondary rhinoplasty cases by means of the open and endonasal approaches. Forty-two patients received an open-approach procedure; the remaining 16 received grafting through an endonasal or closed approach. Thirty-seven of the patients were secondary rhinoplasty patients, and some underwent multiple nasal corrections. The indications, intraoperative surgical technique of graft placement, and representative results will be discussed. Long-term follow-up showed good results, though partial graft resorption occurred in some patients. Overall, this experience with AlloDerm for nasal augmentation was encouraging.

Ophthalmic plastic applications of acellular dermal allografts

PURPOSE

Clinical problems of contracted conjunctival fornices, superior sulcus defects, and soft tissue contour defects in the periorbital region have not shown good, sustained results with a range of autologous and alloplastic implants. AlloDerm (Lifecell Corp., Woodlands, TX) is an acellular dermal graft processed from human donor tissue. The authors sought to assess the efficacy of AlloDerm as a soft tissue replacement in a variety of oculoplastic applications.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Twenty-three patients.

METHODS

Applications were broadly classified as barrier/scaffolding (i.e., primary and secondary implant coverage, lid spacer graft) and volume augmentation (i.e., superior sulcus and other periorbital soft tissue contour defects). Barrier grafts were applied as single sheets. Stacked sheets or rolled grafts were used for augmentation. Collectively, this material was used in 29 cases with 3 to 16 months' follow-up.

MAIN OUTCOME MEASURES

Clinical evaluation of outcome and complications.

RESULTS

As a soft tissue scaffolding and barrier implant, AlloDerm persisted sufficiently to permit repopulation with native tissue. Rolled/stacked implants demonstrated unpredictable resorption. Upper eyelid grafts seemed to have higher resorption rates than lower eyelid grafts. One case of anophthalmic superior sulcus augmentation required two revision surgeries to provide sufficient volume augmentation. The grafts were well tolerated, with no cases of infection or explanation.

CONCLUSION

Acellular human dermis is an excellent barrier and reconstructive grafting material that provides an alternative to autologous grafts and other alloplastic material, avoids harvesting autologous tissue, possesses excellent handling properties, and is associated with minimal inflammation. Long-term follow-up is required to evaluate persistence.

Subgingival acellular dermal matrix allograft for the treatment of gingival recession: a case report

Root coverage procedures using subgingival soft tissue grafts or guided tissue regeneration have attracted much interest within the past 2 decades. Recently, acellular dermal matrix allograft (ADMA) has been introduced as a substitute for palatal donor tissue in gingival augmentation procedures. This study was undertaken to examine the potential of ADMA to be used as a substitute for autogenous connective tissue graft material in a root coverage procedure in a case with moderate gingival recession combined with reduced keratinized attached gingiva. After thorough root planing and conditioning of the root surface with a saturated solution of tetracycline-HCl, a trapezoidal mucoperiosteal flap was raised and the papillae were de-epithelialized. The exposed bone surrounding the exposed root surface was perforated with a No. 2 round drill, and the exposed root and surrounding bone were covered by ADMA. The allograft was stabilized by 5-0 vicryl sutures. The flap was coronally positioned to completely cover the ADMA. Healing was uneventful. Eight-month observations and measurements showed root coverage of more than 3.5 mm (>80%), a gingival margin that was harmonious with the neighboring teeth, and an increase of the zone of keratinized attached gingiva, from 1 to 3 mm. Within the limitations of these clinical observations, it is suggested that ADMA may be a possible substitute to free autogenous connective tissue grafts and/or bioabsorbable barrier membranes. Further clinical and histological studies are necessary to understand the healing process of this surgical wound.