Use of porcine acellular dermal matrix as a dermal substitute in rats

Red Breast Syndrome-Where Has It Gone?: A Systematic Review of Red Breast Syndrome Incidence Overtime

BACKGROUND

Red breast syndrome (RBS) has been noted in past literature as a possible complication of implant-based breast reconstruction (IBBR) with the use of acellular dermal matrices (ADMs). Since its first appearance in 2009, RBS has drawn growing medical attention with reported incidence ranging from 7%-9%. There has been a noted decrease in the emergence of RBS despite its inclusion among the analyzed complications in a number of studies. This systematic review aims to evaluate the trend in reported RBS incidence over time and appropriately determine an accurate incidence of RBS from reported literature since the emergence of the phenomena.

METHODS

A systematic literature review was performed in July 2023 that analyzed the incidence of RBS among retrospective cohort studies on complication rates of IBBR with ADM. Patient demographics, RBS incidence rates, and all-cause complications were captured. The review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines and Methodological Index for Nonrandomized Studies criteria was used to assess study quality.

RESULTS

From 2009 to 2023, a total of 48 studies (n = 6251) met inclusion criteria of which 35 studies from 2017 to 2023 were not already included in a prior systematic review (n = 5246). The mean incidence of RBS in the unreported studies was 2.88% with a weighted mean of 3.22%. Analysis of the trend in RBS over time shows an increasing reported incidence rate from 2009 with a peak in incidence between 2016 and 2017, followed by a steady decline through 2022. Twenty-six of the studies were published from 2016 to 2019.

CONCLUSIONS

The incidence of RBS among prior studies and systematic reviews has fluctuated significantly since its initial emergence in 2009. Reported incidence rates have been on the decline since 2018 with a true weighted incidence of 3.22% from analysis of recent reported studies. Potential causes for the decline in incidence include practice changes in ADM preparation, changes in the ADM brand used for IBBR, and improved categorization of RBS compared to cellulitis/infection. Despite more robust criteria for diagnosis, no consensus for management has yet been established.

Dissolvable microneedle-based wound dressing transdermally and continuously delivers anti-inflammatory and pro-angiogenic exosomes for diabetic wound treatment

Due to overactive inflammation and hindered angiogenesis, self-healing of diabetic wounds (DW) remains challenging in the clinic. Platelet-derived exosomes (PLT-Exos), a novel exosome capable of anti-inflammation and pro-angiogenesis, show great potential in DW treatment. However, previous administration of exosomes into skin wounds is topical daub or intradermal injection, which cannot intradermally deliver PLT-Exos into the dermis layer, thus impeding its long-term efficacy in anti-inflammation and pro-angiogenesis. Herein, a dissolvable microneedle-based wound dressing (PLT-Exos@ADMMA-MN) was developed for transdermal and long-term delivery of PLT-Exos. Firstly, a photo-crosslinking methacrylated acellular dermal matrix-based hydrogel (ADMMA-GEL), showing physiochemical tailorability, fast-gelling performance, excellent biocompatibility, and pro-angiogenic capacities, was synthesized as a base material of our dressing. For endowing the dressing with anti-inflammation and pro-angiogenesis, PLT-Exos were encapsulated into ADMMA-GEL with a minimum effective concentration determined by our in-vitro experiments. Then, in-vitro results show that this dressing exhibits excellent properties in anti-inflammation and pro-angiogenesis. Lastly, in-vivo experiments showed that this dressing could continuously and transdermally deliver PLT-Exos into skin wounds to switch local macrophage into M2 phenotype while stimulating neovascularization, thus proving a low-inflammatory and pro-angiogenic microenvironment for DW healing. Collectively, this study provides a novel wound dressing capable of suppressing inflammation and stimulating vascularization for DW treatment.

Acellular dermal matrix in urethral reconstruction

The management of severe urethral stricture has always posed a formidable challenge. Traditional approaches such as skin flaps, mucosal grafts, and urethroplasty may not be suitable for lengthy and intricate strictures. In the past two decades, tissue engineering solutions utilizing acellular dermal matrix have emerged as potential alternatives. Acellular dermal matrix (ADM) is a non-immunogenic biological collagen scaffold that has demonstrated its ability to induce layer-by-layer tissue regeneration. The application of ADM in urethral reconstruction through tissue engineering has become a practical endeavor. This article provides an overview of the preparation, characteristics, advantages, and disadvantages of ADM along with its utilization in urethral reconstruction via tissue engineering.

Multicenter effect analysis of one-step acellular dermis combined with autologous ultra-thin split thickness skin composite transplantation in treating burn and traumatic wounds

To evaluate the efficacy of one-step acellular dermis combined with autologous split thickness skin grafting in the treatment of burn or trauma wounds by a multicenter controlled study. In patients with extensive burns, it is even difficult to repair the wounds due to the shortage of autologous skin. The traditional skin grafting method has the disadvantages of large damage to the donor site, insufficient skin source and unsatisfactory appearance, wear resistance and elasticity of the wound tissue after skin grafting. One-step acellular dermis combined with autologous ultra-thin split thickness skin graft can achieve better healing effect in the treatment of burn and trauma wounds. A total of 1208 patients who underwent single-layer skin grafting and one-step composite skin grafting in the First Affiliated Hospital of Wannan Medical College, Wuhan Third People's Hospital and Lu 'an People's Hospital from 2019 to 2022 were retrospectively analysed. The total hospitalization cost, total operation cost, hospitalization days after surgery, wound healing rate after 1 week of skin grafting and scar follow-up at 6 months after discharge were compared and studied. The total cost of hospitalization and operation in the composite skin grafting group was significantly higher than those in the single-layer autologous skin grafting group. The wound healing rate after 1 week of skin grafting and the VSS score of scar in the follow-up of 6 months after discharge were better than those in the single-layer skin grafting group. One-step acellular dermis combined with autologous ultra-thin split thickness skin graft has high wound healing rate, less scar, smooth appearance and good elasticity in repairing burn and trauma wounds, which can provide an ideal repair method for wounds.

Current insights in the preclinical study of palatal wound healing and oronasal fistula after cleft palate repair

Poor palatal wound healing after cleft palate repair could lead to unfavorable prognosis such as oronasal fistula (ONF), which might affect the patient's velopharyngeal function as well as their quality of life. Thus, restoring poor palatal wound healing for avoiding the occurrence of ONF should be considered the key to postoperative care after cleft palate repair. This review provided current insights in the preclinical study of poor palatal wound healing after cleft palate repair. This review comprehensively introduced the animal model establishment for palatal wound healing and related ONF, including the models by mice, rats, piglets, and dogs, and then demonstrated the aspects for investigating poor palatal wound healing and related treatments, including possible signaling pathways that could be involved in the formation of poor palatal wound healing, the related microbiota changes because of the deformity of palatal structure, and the studies for potential therapeutic strategies for palatal wound healing and ONF. The purpose of this review was to show the state of the art in preclinical studies about palatal wound healing after cleft palate repair and to show the promising aspects for better management of palatal wound healing.

The effect of ostrich acellular dermal matrix on keratinized gingival width

Background

Xenogeneic grafts have gained attention due to advantages in compare of autografts. This study aimed to compare Xeno (ostrich) Acellular Dermal Matrix (XADM) with the free gingival graft (FGG) to increase the width of Keratinized gingiva (KGW) in dogs.

Materials and Methods

This split mouth animal study was performed on 10 mixed breed dogs. The upper second premolar sites were randomly selected for grafting by XADM (test) or FGG (control). Measurements of KGW were recorded before surgery, 1, 3, and 6 months after surgery. Biopsies from grafted sites for histologic and histomorphometric evaluations were harvested 6 months after surgery. Data were analyzed by repeated measured, paired samples t-test, and Wilcoxon Signed rank test. P < 0.05 was considered statistically significant.

Results

KGW increased in the two study groups after surgery with no significant statistical difference between them at any time intervals (P > 0.05). The graft shrinkage was 23% and 21% for the test and control groups, respectively, without statistically significant difference (P > 0.05). Histomorphometric evaluation showed no significant difference between the two study groups. Foreign body reaction was not seen in any of the study groups.

Conclusion

Increased KWG was similar between the two study groups. With regard to FGG limitations, XADM may be assumed as a suitable alternative for FGG. It should be noted that this research was an animal study and clinical trials on human should be performed to approve the efficacy and safety of this material.

Porcine Acellular Dermal Matrix Promotes Migration and Suppresses Inflammation of Keratinocytes by Mediating the AKT Signaling Pathway

Porcine acellular dermal matrix (pADM) is known to accelerate wound healing. However, the underlying molecular mechanism remains unclear. This study aimed to investigate the effects of pADM on wound healing and its underlying mechanisms. HaCaT cells were treated with hydrogen peroxide (H2O2) or pADM, and the appropriate treatment concentration was determined using the cell counting kit-8 and flow cytometry. Cell migration was assessed using a Transwell assay and scratch test. Inflammation was evaluated using enzyme-linked immunosorbent assay. Western blotting was performed to measure the levels of protein kinase B (AKT) pathway-related proteins. The results showed that H2O2 inhibited cell viability and induced apoptosis in a dose-dependent manner. pADM promoted cell migration and decreased the levels of interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) in H2O2-treated HaCaT cells. Moreover, pADM rescued the downregulation of phosphorylated (p)-AKT and p-mechanistic target of rapamycin (mTOR) induced by H2O2. LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, abrogated migration and anti-inflammatory response caused by pADM. In conclusion, pADM promotes cell migration and inhibits inflammation by activating the AKT pathway under oxidative stress. These findings support the use of pADM for post-traumatic therapy and reveal a novel underlying mechanism of action.

Decellularized tympanic membrane scaffold with bone marrow mesenchymal stem cells for repairing tympanic membrane perforation

BACKGROUND

Tympanic membrane perforation (TMP) is a common disease in otology, and few acellular techniques have been reported for repairing this condition. Decellularized extracellular matrix (ECM) scaffolds have been used in organ reconstruction.

OBJECTIVE

This study on tissue engineering aimed to develop a tympanic membrane (TM) scaffold prepared using detergent immersion and bone marrow mesenchymal stem cells (BMSCs) as repair materials to reconstruct the TM.

RESULTS

General structure was observed that the decellularized TM scaffold with BMSCs retained the original intact anatomical ECM structure, with no cell residue, as observed using scanning electron microscopy (SEM), and exhibited low immunogenicity. Therefore, we seeded the decellularized TM scaffold with BMSCs for recellularization. Histology and eosin staining, SEM and immunofluorescence in vivo showed that the recellularized TM patch had a natural ultrastructure and was suitable for the migration and proliferation of BMSCs. The auditory brainstem response (ABR) evaluated after recellularized TM patch repair was slightly higher than that of the normal TM, but the difference was not significant.

CONCLUSION

The synthetic ECM scaffold provides temporary physical support for the three-dimensional growth of cells during the tissue developmental stage. The scaffold stimulates cells to secrete their own ECM required for tissue regeneration. The recellularized TM patch shows potential as a natural, ultrastructure biological material for TM reconstruction.

Observation of Palatal Wound Healing Process Following Various Degrees of Mucoperiosteal and Bone Trauma in a Young Rat Model

Simple Summary

The exact correlation of palatal trauma to maxillary inhibition has not been demonstrated. This paper determines the influence of different degrees of palatal trauma on maxillofacial growth and assesses whether usage of ADM can help rescue the inhibited growth during palatal wound healing. This research would help the surgeons comprehensively understand the impact of palatal trauma on maxillary growth and the therapeutic effect of the ADM.

Abstract

The accidental injury or surgery on soft and hard palatal tissue has an adverse impact on normal maxillary morphology. To design a single-factor experiment that excludes other interfering factors on maxillary growth, a young rat model was established to simulate the various degrees of palatal trauma. Eight maxillary parameters were measured to evaluate the impact of palatal trauma on maxillary growth. Furthermore, the acellular dermal matrix (ADM) was applied to cure the palatal trauma and alleviate the adverse impact of bone denudation on the maxillary growth. Micro-CT scanning and histology analyses were used. One-way ANOVA with least significant difference (LSD) post-test was used to evaluate the statistical significance. The palatal trauma mainly disturbed the transverse development of the maxilla. ADM promotes mucosa healing, but there is still an inhibitory effect on maxillofacial growth.

Use of Mechanical Stretching to Treat Skin Graft Contracture

After transplantation, skin grafts contract to different degrees, thus affecting the appearance and function of the skin graft sites. The exact mechanism of contracture after skin grafting remains unclear, and reliable treatment measures are lacking; therefore, new treatment methods must be identified. Many types of centripetal contraction forces affect skin graft operation, thus leading to centripetal contracture. Therefore, antagonizing the centripetal contraction of skin grafts may be a feasible method to intervene in skin contracture. Here, the authors propose the first reported mechanical stretching method to address contracture after skin grafting. A full-thickness skin graft model was established on the backs of SD rats. The skin in the experimental group was stretched unilaterally or bidirectionally with a self-made elastic stretching device, whereas the skin was non-stretched in the control group. The rats were sacrificed 2 weeks after stretching. The area, length, and width of the skin were measured. The grafts were cut and fixed with formalin. Routine paraffin sections were stained with hematoxylin-eosin, picric acid-Sirius red, Victoria blue, and anti-alpha-smooth muscle actin (SMA). Mechanical stretching made the graft lengthen in the direction of the stress and had an important influence on collagen deposition and alpha-SMA expression in the graft. This method warrants further in-depth study to provide a basis for clinical application.

Reduced Graphene Oxide Incorporated Acellular Dermal Composite Scaffold Enables Efficient Local Delivery of Mesenchymal Stem Cells for Accelerating Diabetic Wound Healing

Chronic skin wounds caused by diabetes mellitus (DM) have been acknowledged as one of the most intractable complications. Local transplantation of mesenchymal stem cells (MSCs) is a promising method, but strategies for stabilizing and efficiently delivering active MSCs according to the wound circumstance with high proteolysis remain the main barrier. Hereon, the study demonstrates the feasibility of incorporating reduced graphene oxide (RGO) nanoparticles with an acellular dermal matrix (ADM) to improve physicochemical characteristics of natural scaffold material and fabricate a highly efficient local transplantation system for MSCs in diabetic wound healing. Under the influence of RGO nanoparticles, the ADM-RGO composite scaffolds achieved high stability and strong mechanical behaviors. In vitro, conductive ADM-RGO scaffolds demonstrated an admirable milieu for stem cells adhesion and proliferation. After having been cocultured with MSCs, the ADM-RGO-MSC composite scaffolds were transplanted into the full-thickness wound of a diabetic model that was induced by streptozotocin (STZ) to evaluate its effects. As a result, the ADM-RGO composite scaffold delivered with MSCs supported robust vascularization and collagen deposition as well as rapid re-epithelialization during diabetic wound healing. Overall, the versatile nature of the ADM-RGO composite scaffold makes it an efficient transplanting mediator for pluripotent stem cells in tissue engineering applications. The composite scaffold delivered with MSCs presents a promising approach for nonhealing diabetic wounds.

A novel antibacterial acellular porcine dermal matrix cross-linked with oxidized chitosan oligosaccharide and modified by in situ synthesis of silver nanoparticles for wound healing applications

Not only are the physicochemical properties and biocompatibility of biomaterials important considerations, but also their antibacterial properties. In this study, a novel chemically-cross-linked antibacterial porcine acellular dermal matrix (pADM) scaffold was fabricated according to a two-step method. A naturally-derived oxidized chitosan oligosaccharide (OCOS) was used to cross-linked pADM (termed OCOS-pADM) to improve its physicochemical properties. Residual aldehyde groups within the OCOS-pADM were used in a redox reaction with Ag ions to produce Ag nanoparticles (AgNPs) in situ. As the AgNPs were tightly adhered onto the scaffold fibrils (termed OCOS-AgNPs-pADM), this effectively functionalized scaffold with antibacterial properties. The generated AgNPs were characterized by UV-Vis diffuse reflectance spectroscopy, XPS and SEM. The results of DSC, TG and enzymatic degradation demonstrated that OCOS-AgNPs-pADM possessed improved thermal stability and resistance to enzymatic degradation compared with pADM scaffolds. The kinetic experiment of the release of silver showed that silver was released in a controllable way. After introducing AgNPs into scaffolds, the OCOS-AgNPs-pADM possessed wide-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, MTT assay and CLSM showed that the scaffolds had good biocompatibility. Pieces of OCOS-AgNPs-pADM were implanted into Sprague-Dawley rats to characterize their ability to repair full-thickness skin wounds. And results showed that the OCOS-AgNPs-pADM could accelerate the wound healing process. Overall, this work contributes new insight into the chemical cross-linking and functionalization of pADM scaffolds. In addition, as novel antibacterial scaffolds, OCOS-AgNPs-pADMs have the potential for development as wound dressing materials.

Treatment of third-degree burn wounds in animal specimens: acellular dermis or partial-thickness skin graft

Several dermal products have been introduced to substitute dermal tissues. In this study we review the effects of these products on repairing third-degree burn wounds and managing complications in animal specimens. Using an interventional approach, rats were randomly assigned to four groups (G1 to G4). Two wounds were created on the back of each rat. An open wound was left on the back of rats in G1; in G2, wounds were covered with a thick rat derived-ADM product and overlying thin skin graft; on G3 rats, similar third degree ulcers were made with one ulcer covered with harvested thin skin graft. In G4, ulcers were covered with a thin rat derived-ADM product and thin graft. Factors such as take rate, histopathological score, wound contracture and graft contracture were compared on the 7th, 15th, 21st and 30th day. Mean graft take rate on the 30th day in the thick ADM, thin ADM and graft group showed a significant difference (p=0.015). Histopathological score on the 30th day in the thin ADM, thick ADM and graft group showed no considerable difference. Mean graft take rate was significantly better in the thin ADM and graft group than in the thick ADM group. Wound contracture was significantly more severe in the thick ADM and control group than in the thin ADM and graft group.

The Combined Effects of Bone Marrow-Derived Mesenchymal Stem Cells and Microporous Porcine Acellular Dermal Matrices on the Regeneration of Skin Accessory Cells In Vivo

We investigated the effects of microporous porcine acellular dermal matrices (MPADM)-containing bone marrow-derived mesenchymal stem cells (BMMSCs) on accessory skin cell regeneration in vivo. Two kinds of the porcine acellular dermal matrices were prepared: one with microsized pores (the MPADM) and another without pores (the PADM). BMMSC populations from a Sprague-Dawley (SD) rat were seeded on both PADMs and MPADMs and cultured in vitro for 5 days. These rats were randomly divided into four groups: BMMSCs on an MPADM and covered with a PADM layer (group A), MPADM without cells and covered with a split-thickness skin graft (SSG) (group B), BMMSCs on an MPADM and covered with an SSG (group C), and BMMSCs on a PADM and covered with an SSG (group D). On post-surgery day (PSD) 5, all groups survived, except for group D. On PSD 7, there was no significant difference in the functional vascularization between groups A, B, and C. On PSD 14, large quantities of new capillaries, a larger rough endoplasmic reticulum in fibroblasts, and de novo unmyelinated nerve endings could be observed at the junction between the skin graft and the dermal matrix in group C; however, these structures were absent in groups A and B. The experimental results showed that MPADM could induce exogenous differentiation of BMMSCs in vivo and promote reconstruction of skin accessory cells.

Effects of porcine acellular dermal matrix treatment on wound healing and scar formation: Role of Jag1 expression in epidermal stem cells

Skin wound healing involves Notch/Jagged1 signaling. However, little is known how Jag1 expression level in epidermal stem cells (ESCs) contributes to wound healing and scar formation. We applied multiple cellular and molecular techniques to examine how Jag1 expression in ESCs modulates ESCs differentiation to myofibroblasts (MFB) in vitro, interpret how Jag1 expression in ESCs is involved in wound healing and scar formation in mice, and evaluate the effects of porcine acellular dermal matrix (ADM) treatment on wound healing and scar formation. We found that Jag1, Notch1 and Hes1 expression was up-regulated in the wound tissue during the period of wound healing. Furthermore, Jag1 expression level in the ESCs was positively associated with the level of differentiation to MFB. ESC-specific knockout of Jag1 delayed wound healing and promoted scar formation in vivo. In addition, we reported that porcine ADM treatment after skin incision could accelerate wound closure and reduce scar formation in vivo. This effect was associated with decreased expression of MFB markers, including α-SMA Col-1 and Col-III in wound tissues. Finally, we confirmed that porcine ADM treatment could increase Jag1, Notch1 and Hesl expression in wound tissues. Taken together, our results suggested that ESC-specific Jag1 expression levels are critical for wound healing and scar formation, and porcine ADM treatment would be beneficial in promoting wound healing and preventing scar formation by enhancing Notch/Jagged1 signaling pathway in ESCs.

Growth Factor-Reinforced ECM Fabricated from Chemically Hypoxic MSC Sheet with Improved In Vivo Wound Repair Activity

MSC treatment can promote cutaneous wound repair through multiple mechanisms, and paracrine mediators secreted by MSC are responsible for most of its therapeutic benefits. Recently, MSC sheet composed of live MSCs and their secreted ECMs was reported to promote wound healing; however, whether its ECM alone could accelerate wound closure remained unknown. In this study, Nc-ECM and Cc-ECM were prepared from nonconditioned and CoCl₂-conditioned MSC sheets, respectively, and their wound healing properties were evaluated in a mouse model of full-thickness skin defect. Our results showed that Nc-ECM can significantly promote wound repair through early adipocyte recruitment, rapid reepithelialization, enhanced granulation tissue growth, and augmented angiogenesis. Moreover, conditioning of MSC sheet with CoCl₂ dramatically enriched its ECM with collagen I, collagen III, TGF-β1, VEGF, and bFGF via activation of HIF-1α and hence remarkably improved its ECM's in vivo wound healing potency. All the Cc-ECM-treated wounds completely healed on day 7, while Nc-ECM-treated wounds healed about 85.0% ± 8.6%, and no-treatment wounds only healed 69.8% ± 9.6% (p < 0.05). Therefore, we believe that such growth factor-reinforced ECM fabricated from chemically hypoxic MSC sheet has the potential for clinical translation and will lead to a MSC-derived, cost-effective, bankable biomaterial for wound management.

Oil mixes omega 9, 6 and 3, enriched with seaweed, promoted reduction of thermal burned modulating NF-kB and Ki-67

PURPOSE

To examine the effects of the oil mixes (ω-9, ω-6 and ω-3) in rats subjected to thermal burn. It was also aimed to assess whether the sources of ω3 would interfere with the effect of such mixes on the thermal injury.

METHODS

Thirty-six rats distributed into five groups: burned + water, burned + isolipid mix, burned + oil mix 1 (ALA), burned + oil mix 2 (ALA + EPA + DHA of fish) and burned + oil mix 3 (ALA + DHA from seaweed). The thermal injury was involving total thickness of skin. After the burns animals received the oil mixes for seven days. The lesions were evaluated by immunohistochemistry.

RESULTS

Animals receiving mix 3 showed a smaller extension of the thermal injury as compared to those that were supplemented with other oils mixes. Expression of Ki-67 in the receiving Mix 3 increased as compared to all the other groups. Animals supplemented with mix 3 were able to inhibit NF-κB in injured tissue.

CONCLUSION

Rats received oil mix in which the source of ω3 (ALA+DHA of seaweed) showed inhibition of NF-κB, increase in cell proliferation, and reduction the extension of thermal lesion.

The effect of porcine ADM to improve the burn wound healing

To study the effect of porcine acellular dermal matrix (ADM) on the burn wound healing. Seventy healthy Wistar rats were inflicted with 2 cm second degree burn and divided into 2 groups; one group was treated with porcine ADM and the other with Povidone Iodine Cream. Biopsies were taken on day 1, 3, 5, 7, 10, 14, 21 for histopathological and biochemical analysis to test PCNA, K19, Integrin-β1, PDGF, EGF and FGF. The results revealed relatively better and faster regeneration after treatment of porcine ADM, along with greatly increased synthesis in collagen in the experimental group. PCNA, K19, Integrin-β1 had an increase and then tapered down, and were stronger in the experimental group than in the contrast group during 21 days after burns. PDGF, EGF and FGF levels increased on day 3, peaked on day 5 and then started to decrease, while significantly enhanced expression of relevant growth factors were observed in the experimental group. Porcine ADM stimulate collagen synthesis, stem cells proliferation and differentiation, and the expression of relevant growth factors and ultimately improve the burn wound healing.

In vitro investigation on the biodegradability and biocompatibility of genipin cross-linked porcine acellular dermal matrix with intrinsic fluorescence

As a biocompatible and bioactive natural tissue engineering scaffold, porcine acellular dermal matrix (PADM) has limitations for the application in tissue regeneration due to its low strength and rapid biodegradation. Here, purified PADM was modified by a nontoxic cross-linker (genipin) to enhance its mechanical properties and improve its resistance to enzymatic degradation. In vitro testing results demonstrated that the stiffness of the genipin cross-linked PADM was improved and biodegradation rate was decreased. Results of cell proliferation assays showed that the cross-linking reaction by genipin did not undermine the cytocompatibility of PADM. Furthermore, genipin cross-linking imparted an observable fluorescence allowing visualization of the scaffold's three-dimensional (3D) porous structure and cell distribution by confocal laser scanning microscopy (CLSM). Immunostaining of the cell nuclei and cytoskeleton indicated that MC3T3-E1 preosteoblasts were tightly adhered to and uniformly distributed onto the cross-linked PADM scaffold. Results of this study suggest that the 3D porous genipin cross-linked PADM with intrinsic fluorescence may have broader applications for tissue engineering scaffolds where higher mechanical stiffness is needed.

Phase-contrast microtomography with synchrotron radiation technology: a new noninvasive technique to analyze the three-dimensional structure of dermal tissues

BACKGROUND

Since the three-dimensional (3-D) structure of dermal tissue has an important role in regulating cell behavior and directing the wound healing process, the characteristic of the 3-D structure of dermal tissue needs to be clarified.

OBJECTIVE

To explore the different 3-D structures between normal and scar dermal tissues.

MATERIAL AND METHODS

Phase-contrast microtomography with synchrotron radiation technology was applied to detect the 3-D structure of dermal tissues.

RESULTS

The normal dermal tissue consists of elliptical structures formed by fiber bundles interwoven in a helical manner. A regular louver-like structure was observed on the fibers. In scar tissue, the fiber bundles were arrayed in parallel, the louver-like structures were disordered.

CONCLUSION

The study demonstrates the mesoscopic difference between normal dermal tissue and scar tissue, suggests that the high level of interweaving capability of collagen is compromised/lost when dermal tissue is injured, and provides a basis for future studies.

Evaluation of functions and tissue compatibility of poly (D,L-lactic-co-glycolic acid) seeded with human dermal fibroblasts

In tissue engineering and wound-healing applications, dermal substitutes are used to provide fibroblasts with the mechanical support for their growth and then to facilitate the skin formation. In this study, three-dimensional porous poly(lactic-co-glycolic acid) (PLGA) 65/35 scaffolds were prepared and then the composites of the scaffolds and human fetal dermal fibroblasts were fabricated as a tissue-engineered dermal substitute. The function and tissue compatibility of the artificial dermal substitute were evaluated at the levels of gene expression (by RT-PCR) and protein expression (total collagen quantities), as well as by histological and immunohistochemical analysis. The PCR products indicated that the mRNA of type-I collagen, mainly secreted by the fibroblasts onto the PLGA scaffolds, was clearly expressed after 4 weeks. The amount of total collagen synthesized from the cells was shown to increase gradually during the initial culture period and slightly decreased afterwards. After 8 weeks of culture, the fibroblasts were well attached and migrated entirely throughout the pores of the PLGA scaffold with normal function. Furthermore, the positively stained type-I collagen was intensively detected throughout the pores. These results suggest that the function and tissue compatibility may be important criteria in evaluating an artificial tissue-engineered skin.

Abdominal ventral hernia repair with current biological prostheses: an experimental large animal model

Biologic prostheses have emerged to address the limitations of synthetic materials for ventral hernia repairs; however, they lack experimental comparative data. Fifteen swine were randomly assigned to 1 of 3 bioprosthetic groups (DermaMatrix, AlloDerm, and Permacol) after creation of a full thickness ventral fascial defect. At 15 weeks, host incorporation, hernia recurrence, adhesion formation, neovascularization, inflammation, and biomechanical properties were assessed. No animals had hernia recurrence or eventration. DermaMatrix and Alloderm implants demonstrated more adhesions, greater inflammatory infiltration, and more longitudinal laxity, but near identical neovascularization and tensile strength to Permacol. We found that porcine acellular dermal products (Permacol) contain following essential properties of an ideal ventral hernia repair material: low inflammation, less elastin and stretch, lower adhesion rates and cost, and more contracture. The addition of lower cost xenogeneic acellular dermal products to the repertoire of available acellular dermal products demonstrates promise, but requires long-term clinical studies to verify advantages and efficacy.

Transplantation of microencapsulated cells expressing VEGF improves angiogenesis in implanted xenogeneic acellular dermis on wound

BACKGROUND

Cell-based gene therapy using cells that express angiogenic factors is an alternative technique for therapeutic angiogenesis in transplantation of xenogeneic acellular dermis matrix (ADM). However, immune rejection is a substantial obstacle to implantation of genetically engineered allogeneic or xenogeneic cells.

OBJECTIVE

To evaluate application of microencapsulated cells that express vascular endothelial growth factor (VEGF) in xenogeneic ADM transplants to improve wound angiogenesis and healing.

MATERIALS AND METHODS

NIH3T3 cells were genetically modified to secrete VEGF and enveloped in semipermeable microcapsules. Microencapsulated VEGF-NIH3T3 cells were implanted in defects on the dorsa of guinea pigs with xenogeneic ADM and autologous split-thickness skin grafts. Cell structure and microencapsulation were observed at microscopy, and expression of VEGF was detected using an enzyme-linked immunosorbent assay (ELISA) and immunochemistry. Extent of angiogenesis in the ADM and the survival rate of the composite skin were evaluated after 2 weeks. In addition, expression of human VEGF and CD31 in the implanted acellular dermis was assessed, and microvessel density was calculated.

RESULTS

Microencapsulated VEGF-expressing NIH3T3 cells were prepared successfully, and demonstrated proliferation and viability, and expressed VEGF both in vitro and in vivo. Extent of angiogenesis and survival rate of the composite skin containing the microencapsulated VEGF-expressing cells were significantly greater than in controls. Microencapsulated VEGF-expressing NIH3T3 cells augmented early angiogenesis in ADM implanted on wound and improved healing.

CONCLUSION

Microencapsulated xenogeneic cell-based gene therapy may be a novel approach to therapeutic angiogenesis in transplantation of xenogeneic ADM skin.

Use of Homologous Acellular Dermal Matrix for Abdominal Wall Reconstruction in Rats

Homologous acellular dermal matrix graft (HADMG) has been used for the reconstructions of bowel, bladder, or urethra, but its suitability in the reconstruction of abdominal wall has not been tested. Therefore an experimental study was performed to evaluate the use of HADMG for the reconstruction of abdominal wall defects in weanling rats. Thirty weanling Wistar rats were used. A patch of abdominal wall 20 x 20 mm in dimension was removed. The defects were reconstructed with HADMGs that were derived from rat skin and prepared through a detergent enzymatic method. The reconstructed abdominal walls were evaluated as hernia rate and graft take ratio, excised and prepared for histological examination at 21 (n = 10), 40 (n = 10), and 90 (n = 10) days postoperation. The healing of repaired abdominal walls was uneventful. Histological evaluation demonstrated the migration of fibroblasts and neovascularization within the HADMG. Hernia in four rats were developed at 90 days. Neither significant wound contraction nor inflammation was seen at 21, 40, and 90 days after surgery in wounds receiving HADMGs. Thus, the use of a HADMG for reconstructing the abdominal wall in weanling rats has not given rise to any complications. HADMG has progressively remodeled into fibrous tissue. It appears to represent an important alternative substitute for the reconstruction of abdominal wall.

Preparation of laser micropore porcine acellular dermal matrix for skin graft: an experimental study

In our previous study, we used composite grafts consisting of meshed porcine acellular dermal matrix (PADM) and thin split-thickness autologous epidermis to cover full thickness burn wounds in clinical practice. However, a certain degree of contraction might occur because the distribution of dermal matrix was not uniform in burn wound. In this study, we prepare a composite skin graft consisting of PADM with the aid of laser to improve the quality of healing of burn wound.

METHODS

PADM was prepared by the trypsin/Triton X-100 method. Micropores were produced on the PADM with a laser punch. The distance between micropores varied from 0.8, 1.0, 1.2 to 1.5mm. Full thickness defect wounds were created on the back of 144 SD rats. The rats were randomly divided into six groups: micropore groups I-IV in which the wound were grafted with PADM with micropores, in four different distances, respectively and split-thickness autograft; mesh group rats received meshed PADM graft and split-thickness autograft; control group received simple split-thickness autografting. The status of wound healing was histologically observed at regular time points after surgery. The wound healing rate and contraction rate were calculated.

RESULTS

The wound healing rate in micropore groups I and II was not statistically different from that in control group, but was significantly higher than that in mesh group 6 weeks after grafting. The wound healing rate in micropore groups III and IV was lower than that in mesh and control groups 4 and 6 weeks after grafting. The wound contraction rate in micropore groups I and II was remarkably lower than that in control group 4 and 6 weeks after surgery and it was significantly much lower than that in mesh group 6 weeks after surgery. Histological examination revealed good epithelization, regularly arranged collagenous fibers and integral structure of basement membrane.

CONCLUSION

Laser micropore PADM (0.8 or 1.0mm in distance) grafting in combination with split-thickness autografting can improve wound healing. The PADM with laser micropores in 1.0mm distance is the better choice.

Cytokine production following experimental implantation of xenogenic dermal collagen and polypropylene grafts in mice

AIM

We earlier showed that xenogenic Pelvicol (Bard, Olen, Belgium) implants induce a lesser inflammatory response than Prolene (Johnson and Johnson, Dilbeek, Belgium). The purpose of this study was to determine cytokine profiles in the host immune responses to Pelvicol in a mouse model. The hypothesis was that Pelvicol would induce a "T-helper2" (Th2) rather than T-helper1 (Th1) type of inflammatory response.

METHODS

Mice were implanted subcutaneously with Pelvicol or Prolene and the graft sites were harvested at 3 to 28 days. Histopathology was done and cytokine levels were determined by immunohistochemistry and RT-PCR. Flow cytometry was used to identify which cell population contributed to the observed cytokine production profiles.

RESULTS

Pelvicol induced a decreased inflammation and displayed an increase in IL-10 and TGF-beta, but reduce of TNF-alpha and IFN-gamma, indicating a Th2 type dominated response as examined by immunohistochemistry and RT-PCR. Flow cytometry showed that the monocytes/maceophages were the main cell population responsible for production of these cytokines. Monocytes/maceophages from Pelvicol explants showed upregulated expression of IL-10 while Prolene explants expressed TNF-alpha.

CONCLUSION

Pelvicol induced a Th2 type cytokine-dominated immune response after subcutaneous implantation in mice.

The effect of gelatin–chondroitin sulfate–hyaluronic acid skin substitute on wound healing in SCID mice

Tissue-engineered skin substitutes provided a feasibility to overcome the shortage of skin autograft by culturing keratinocytes and dermal fibroblasts in vitro. In this study, we applied bi-layer gelatin-chondrointin-6-sulfate-hyaluronic acid (gelatin-C6S-HA) biomatrices onto the severe combined immunodeficiency (SCID) mice to evaluate its effect on promoting wound healing. Human foreskin keratinocytes and dermal fibroblasts were cultured with reconstructed skin equivalent (rSE) for 7 days. The rSE was then grafted to the dorsum of SCID mice to evaluate its biocompatibility by histologic and immunohistochemistry analysis. The results showed that human epidermis were well-developed with the expression of differentiated markers and basement membrane-specific proteins at 4 weeks. After implantation, the percentages of skin graft take were satisfactory, while cell-seeded group was better than non-cell-seeded one. The basement membrane proteins including laminin, type IV collagen, type VII collagen, integrin alpha6, and integrin beta4 were all detected at the dermal-epidermal junction, which showed a continuous structure in the 4 weeks after grafting. This bi-layer gelatin-C6S-HA skin substitute not only has positive effect on promoting wound healing, but also has high rate of graft take. This rSE would have the potential to be applied on the extensively and deeply burned patients who suffer from severe skin defect in the near future.

Outcomes of allogenic acellular matrix therapy in treatment of diabetic foot wounds: an initial experience

The purpose of this study was to evaluate outcomes of persons with UT grade 2A neuropathic diabetic foot wounds treated with an acellular matrix. Data were abstracted for 17 consecutive patients with diabetes--76.5% males, aged 61.5 +/- 8.5 years with a mean glycated haemoglobin of 9.2 +/- 2.2% presenting for care at a large, multidisciplinary wound care centre. All patients received surgical debridement for their diabetic foot wounds and were placed on therapy consisting of a single application of an acellular matrix graft (GraftJacket; Wright Medical Technologies, Arlington, TN, USA) with dressing changes taking place weekly. Outcomes evaluated included time to complete wound closure and proportion of patients achieving wound closure in 20 weeks. Acellular matrix therapy was used as initial therapy and was sutured or stapled in place under a silicone-based non adherent dressing. Therapy was then followed by a moisture-retentive dressing until complete epithelialisation. In total, 82.4% of wounds measuring a mean 4.6 +/- 3.2 cm(2) healed in the 20-week evaluation period. For those that healed in this period, healing took place in a mean 8.9 +/- 2.7 weeks. We conclude that a regimen consisting of moist wound healing using an acellular matrix dressing may be a useful adjunct to appropriate diabetic foot ulcer care for deep, non-infected, non-ischaemic wounds. We await the completion of further trials in this area to confirm or refute this initial assessment.

Evaluation of osteogenic and chondrogenic activities of prefabricated periallografts

Reconstruction of cartilage and bone defects has always been a challenging problem for the surgeon. Basic elements that are responsible for the repair process of these tissues are periost and perichondrium. Although several methods for the use of periost and perichondrium are proposed in the literature, the osteogenic and chondrogenic capacities of these tissues were shown to be the most important factor for a successful outcome. Bone and cartilage formation in acellular dermal matrix (ADM) prefabricated with periost and perichondrium was studied in 20 New Zealand rabbits. Morphologic and histologic evaluation and comparison of the newly formed tissues were evaluated. Four rabbits were excluded from the study because of infection, and specimens were obtained at 4, 6, 8, and 12 weeks after the study began from the remaining 16 rabbits. A gradual increase in bone and cartilage tissue formation through the 4th to 12th weeks was documented by reason of perichondrium and periost activation infiltrating into acellular dermal allografts. In view of the data obtained, it was concluded that periost or perichondrium prefabricated over ADM may be an alternative technique of cartilage and bone formation that may provide adequate tissue with elastic and osteo- and chondroconductive properties for the reconstruction of challenging defects.

Closure of Abdominal Wall Defects Using Acellular Dermal Matrix

BACKGROUND

After some abdominal surgical procedures, the abdominal wall defect may be too large for closure by tension-free approximation of the wound margins because of tissue loss or swelling of the abdominal viscera. A variety of absorbable and nonabsorbable prosthetic materials have been used for emergency abdominal wall reconstruction. Of these materials, polytetrafluoroethylene (PTFE) sheets have proved to be the most efficacious.

METHODS

This study compared the efficacy of allogenic acellular dermal matrix (ADM) and PTFE as prosthetic materials for wound closure in rats with surgical, full-thickness, 2 x 3-cm abdominal wounds. Healing was studied among animals with and those without experimentally induced peritonitis for 21 days after surgery.

RESULTS

Acellular dermal matrix became vascularized and incorporated into the wound bed and was partially or fully epithelialized without the need for skin grafting. As a result, little superficial bleeding was seen, and ADM effectively closed the wounds even in the presence of peritonitis. Wounds treated with ADM also showed a significant reduction in wound area (sterile:p < 0.001; contaminated:p < 0.05). In contrast, PTFE temporarily closed the wounds, but was not incorporated into them. It consequently evoked the formation of extensive underlying granulation tissue that showed significant superficial bleeding when the PTFE was removed. Very limited wound contraction occurred in PTFE-treated wounds, and some instances of evisceration and fistula formation were observed. Wounds treated with both types of material showed significant amounts of adhesion to visceral organs underlying the wound site.

CONCLUSIONS

Acellular dermal matrix exhibits a number of favorable features relative to PTFE for closing sterile or contaminated full-thickness abdominal wall defects.

Process development of an acellular dermal matrix (ADM) for biomedical applications

The object of this study was to compare the extent of decellularization at each critical step of processing porcine skin to produce an acellular dermal matrix (ADM) for biomedical applications. The results demonstrated that the removal of epidermis using treatment with 0.25% trypsin for 18 h and 0.1% sodium dodecyl sulfate (SDS) for 12 h at room temperature was beneficial for the subsequent treatment to remove cells in the dermal structure. Lengthy incubation in 0.25% trypsin (12 h) and then 560 units/l Dispase (12 h) at 25 degrees C of small pieces of porcine skin from which the epidermis had been removed efficiently removed cells and cellular components from the skin. Histological examinations revealed that the epidermis, dermal fibroblasts, and epidermal appendages were completely removed by these treatments, and the basic dermal architecture of collagen bundles was that of a loose meshwork. Examinations by TEM showed that the characteristics of collagen fibers in the ADM were retained after complete removal of cells present under optimal conditions defined in this study. SDS-PAGE and size-exclusion HPLC revealed that collagen fibers in the ADM were mostly type I and showed two typical component peaks identified as oligomers and monomers, respectively.