Immunomodulation of Acellular Dermal Matrix Through Interleukin 4 Enhances Vascular Infiltration.

BACKGROUND: Acellular dermal matrix (ADM) supported implant-based reconstruction remains the most commonly performed mode of reconstruction after breast cancer. Acellular dermal matrix clinical usage has reported benefits but requires rapid and efficient vascular and cellular incorporation into the recipient to have the best outcomes. Orderly transition from M1 to M2 macrophage phenotypic profile, coordinated in part by interleukin 4 (IL-4), is an important component of vascular stabilization and remodeling. Using the ADM substrate as a delivery device for immunomodulation of macrophage phenotype holds the potential to improve integration. METHODS: Interleukin 4 was adsorbed onto ADM samples and drug elution curves were measured. Next, experimental groups of 8 C57BL/6 mice had 5-mm ADM discs surgically placed in a dorsal window chamber with a vascularized skin flap on one side and a plastic cover slip on the other in a model of implant-based breast reconstruction. Group 1 consisted of IL-4 (5 µg) adsorbed into the ADM preoperatively and group 2 consisted of an untreated ADM control. Serial gross examinations were performed with histology at day 21 for markers of vascularization, mesenchymal cell infiltration, and macrophage lineage. RESULTS: Drug elution curves showed sustained IL-4 release for 10 days after adsorption. Serial gross examination showed similar rates of superficial vascular investment of the ADM beginning at the periphery by day 14 and increasing through day 21. Interleukin-4 treatment led to significantly increased CD31 staining of vascular endothelial cells within the ADM over the control group (P < 0.05) at 21 days. Although vimentin staining did not indicate a significant increase in fibroblasts overall, IL-4 did result in a significant increase in expression of α-smooth muscle actin. The expression of macrophage phenotype markers Arginase1 and iNOS present within the ADM were not significantly affected by IL-4 treatment at the day 21 time point. CONCLUSIONS: Acellular dermal matrix has the potential to be used for immunomodulatory cytokine delivery during the timeframe of healing. Using implanted ADM as a delivery vehicle to drive IL-4 mediated angiogenesis and vascular remodeling significantly enhanced vascularity within the ADM substrate.

Cross-linking effects of carbodiimide, oxidized chitosan oligosaccharide and glutaraldehyde on acellular dermal matrix of basa fish (Pangasius bocourti).

Basa acellular dermal matrix (BADM) has advantages in the preparation of oral prosthetic membranes. In order to prepare high-quality BADM, a suitable cross-linking agent is necessary. In this study, acellular dermal matrix was prepared from basa fish skin and then cross-linked with carbodiimide (EDC), oxidized chitosan oligosaccharide (OCOS) and glutaraldehyde (GA), respectively. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), histological staining, DNA electrophoresis and the limulus amoebocyte lysate chromogenic assay were used to detect the structure and properties of BADM. The compatibility of BADM was detected by implantation in vivo and cell experiments. The results showed that the majority of the cellular and DNA in BADM were removed. The endotoxin was not be detected. Furthermore, the structure of BADM was not destroyed. The mechanical and anti-degraded properties of BADM were promoted obviously after cross-linking. The thermal shrinkage temperatures of wet and dry EDC-BADM (BADM cross-linked by carbodiimide) were increased by 39.22 °C and 18.27 °C, respectively, compared with that of the uncross-linked BADM. In addition, the EDC-BADM had good biocompatibility and cytocompatibility. In conclusion, carbodiimide can improve the properties of BADM, which has potential application in the field of biomaterials.

Supercritical Carbon Dioxide-decellularized Porcine Acellular Dermal Matrix combined with Autologous Adipose-derived Stem Cells: Its Role in Accelerated Diabetic Wound Healing.

Diabetes mellitus (DM) causes impaired wound healing by affecting one or more of the biological mechanisms of hemostasis, inflammation, proliferation, and remodeling and a large number of cell types, extracellular components, growth factors, and cytokines. Interventions targeted toward these mechanisms might accelerate the wound healing process. To evaluate the wound healing efficacy of supercritical carbon dioxide (scCO2)-decellularized porcine acellular dermal matrix (ADM) combined with autologous adipose-derived stem cells (ASCs) in streptozotocin (STZ)-induced DM rats. DM was induced by injecting rats with STZ; dorsal full-thickness skin (5 × 5 cm2) was created and treated with and without ASCs-scCO2-treated ADM to evaluate the wound healing rate through histological examination, fluorescence microscopic observation, and immunohistochemical analysis. In the present study, complete decellularization of the porcine dermal matrix was achieved through scCO2. Isolation of ASCs was conducted and evaluated using CD29+/CD31-/CD45-/CD90+ markers in flow cytometry, which indicated that more than 90% of cells were ASCs. The percentage of cells labeled with CD29+ and CD90+ was found to be 97.50% and 99.69%, respectively. The wound healing rate increased in all groups relative to the group with the DM wound without treatment. DM wound treated with ADM-ASCs showed significantly higher (p < 0.01) wound healing rate than DM wound without treatment. ADM-ASC-treated rats showed significantly increased epidermal growth factor, Ki67, and prolyl 4-hydroxylase and significantly decreased CD45 compared with the group with the DM wound without treatment. The intervention comprising ADM decellularized from porcine skin by using scCO2 and ASCs was proven to improve diabetic wound healing. ADM-ASCs had a positive effect on epidermal regeneration, anti-inflammation, collagen production and processing, and cell proliferation; thus, it accelerated wound healing.

Protection by Glycerol, Sucrose and Trehalose for Acellular Human Dermis Against Gamma Irradiation Damage at -78.5°C.

BACKGROUND: Glycerol, sucrose and trehalose are used as protectants for membrane, protein, cell and tissue preservation. The undercooled state (glassy or rubbery) of their solutions may also offer protection for protein, cells and tissues against radiation damage upon sterilization. OBJECTIVE: The study aimed to examine the protective effects of glycerol, sucrose and trehalose on cryopreserved acellular human dermis against gamma irradiation damage. MATERIALS AND METHODS: Acellular human dermis was cryopreserved at -80°C in glycerol, sucrose and trehalose solutions or their combinations with a base citrate-phosphate buffer (pH 6.0). Cryopreserved acellular dermis was then subjected to 13 kGy gamma irradiation at -78.5°C, and radiation damage was assessed by histological evaluation. RESULTS: Freeze and thaw alone do not alter the structure of acellular dermis, but gamma irradiation at -78.5°C results in significant structural changes in acellular dermis, including the formation of large holes, the damage of collagen fibers and the loss of overall dermis tissue histology. The incorporation of glycerol, sucrose and trehalose into cryopreservation solutions reduces gamma irradiation-induced tissue structural damage considerably. When used alone, trehalose (0.5 M) provided better protection against gamma irradiation damage than did sucrose (0.5 M) and glycerol (1.0 M). When used in combination, the glycerol and trehalose combination provides the best tissue protection. Significant donor-to-donor variation exists in tissue damage after gamma irradiation. For donor dermis that is less sensitive to gamma irradiation damage, glycerol, sucrose or trehalose alone is able to provide good protection. However, for more sensitive donor dermis, only the glycerol and trehalose combination is able to provide sufficient tissue protection. CONCLUSION: Glycerol, sucrose and trehalose protects cryopreserved acellular human dermis against gamma irradiation damage. Cryopreservation solutions can be optimized to permit tissues for gamma sterilization to increase the safety human tissue implants.

Nanofiber-acellular dermal matrix as a bilayer scaffold containing mesenchymal stem cell for healing of full-thickness skin wounds.

Full-thickness skin defect is one of the main clinical problems, which cannot be repaired spontaneously. The aim of this study was to evaluate the feasibility of combining nanofibers with ADM as a bilayer scaffold for treatment of full-thickness skin wounds in a single-step procedure. The nanofibrous polycaprolactone/fibrinogen scaffolds were fabricated by electrospinning. Subsequently, mesenchymal stem cells were isolated from rat adipose tissues and characterized by flow cytometry. Cell adhesion, proliferation, and the epidermal differentiation potential of adipose-derived stem cells (ADSCs) on nanofibrous scaffolds were investigated by scanning electron microscopy (SEM), alamarBlue, and real-time PCR, respectively. In animal studies, full-thickness excisional wounds were created on the back of rats and treated with following groups: ADM, ADM-ADSCs, nanofiber, nanofiber-ADSCs, bilayer, and bilayer-ADSCs. In all groups, wounds were harvested on days 14 and 21 after treatment to evaluate re-epithelialization, blood vessel density, and collagen content. The results indicated that ADSCs seeded on ADM, nanofiber, and bilayer scaffolds can promote re-epithelialization, angiogenesis, and collagen remodeling in comparison with cell-free scaffolds. In conclusion, nanofiber-ADSCs showed the best results for re-epithelialization (according to histological scoring), average blood vessel density (92.7 ± 6.8), and collagen density (87.4 ± 4.9%) when compared to the control and other experimental groups.

Synergistic Effects of Acetyl-l-Carnitine and Adipose-Derived Stromal Cells on Improving Regenerative Capacity of Acellular Nerve Allograft in Sciatic Nerve Defect.

The combination of decellularized nerve allograft and adipose-derived stromal cells (ASCs) represents a good alternative to nerve autograft for bridging peripheral nerve defects by providing physical guidance and biologic cues. However, the regeneration outcome of acellular nerve allograft (ANA) is often inferior to autograft. Therefore, we hypothesized that acetyl-l-carnitine (ALCAR) treatment and implantation of ASC-embedded ANA would work synergistically to promote nerve regeneration. Seventy rats were randomly allocated into seven experimental groups (n = 10), including the healthy control group, sham surgery group, autograft group, ANA group, ANA + ASCs group, ANA + ALCAR group (50 mg/kg for 2 weeks), and ANA + ASCs + ALCAR (50 mg/kg for 2 weeks) group. All grafts were implanted to bridge long-gap (10-mm) sciatic nerve defects. Functional, electrophysiological, and morphologic analysis was conducted during the experimental period. We found that ALCAR potentiated the survival and retention of transplanted ASCs and upregulated the expression of neurotrophic factor mRNAs in transplanted grafts. Sixteen weeks following implantation in the rat, the ANA supplemented by ASCs was capable of supporting reinnervation across a 10-mm sciatic nerve gap, with results close to that of the autografts in terms of functional, electrophysiological, and histologic assessments. Results demonstrated that ALCAR treatment improved regenerative effects of ANA combined with ASCs on reconstruction of a 10-mm sciatic nerve defect in rat comparable to those of autograft.

CXCR4 antagonist delivery on decellularized skin scaffold facilitates impaired wound healing in diabetic mice by increasing expression of SDF-1 and enhancing migration of CXCR4-positive cells.

C-X-C chemokine receptor type 4 (CXCR4) is an alpha-chemokine receptor specific for stromal cell-derived factor 1 (SDF-1 also called CXCL12). The antagonist of CXCR4 can mobilize CD34+ cells and hematopoietic stem cells from bone marrow within several hours, and it has an efficacy on diabetes ulcer through acting on the SDF-1/CXCR4 axis. In this study, we investigated for the first time whether the antagonist of CXCR4 (Plerixafor/AMD3100) delivered on acellular dermal matrix (ADM) may accelerate diabetes-impaired wound healing. ADM scaffolds were fabricated from nondiabetic mouse skin through decellularization processing and incorporated with AMD3100 to construct ADM-AMD3100 scaffold. Full-thickness cutaneous wound in streptozotocin (STZ)-induced diabetic mice were treated with ADM, AMD3100, or ADM-AMD3100. 21 days after treatment, wound closure in ADM-AMD3100-treated mice was more complete than ADM group and AMD3100 group, and it was accompanied by thicker collagen formation. Correspondingly, diabetic mice treated with ADM-AMD3100 demonstrated prominent neovascularization (higher capillary density and vascular smooth muscle actin), which were accompanied by up-regulated mRNA levels of SDF-1 and enhanced migration of CXCR4 in the granulation tissue. Our results demonstrate that ADM scaffold provide perfect niche for loading AMD3100 and ADM-AMD3100 is a promising method for diabetic wound healing mainly by increasing expression of SDF-1 and enhancing migration of CXCR4-positive cells.

Collagen-Elastin and Collagen-Glycosaminoglycan Scaffolds Promote Distinct Patterns of Matrix Maturation and Axial Vascularization in Arteriovenous Loop-Based Soft Tissue Flaps.

INTRODUCTION: Autologous free flaps are the criterion standard for reconstructions of complex soft tissue defects; however, they are limited by donor-site morbidities. The arteriovenous (AV) loop model enables the generation of soft tissue constructs based on acellular dermal matrices with a functional microvasculature and minimal donor site morbidity. The ideal scaffold for AV loop-based tissue engineering has not been determined. METHODS: AV loops were placed into subcutaneous isolation chambers filled with either a collagen-elastin scaffold or a collagen-glycosaminoglycan scaffold in the thighs of rats. Matrix elasticity, neoangiogenesis, cell migration, and proliferation were compared after 14 and 28 days. RESULTS: Mean vessel count and area had increased in both matrices at 28 compared with 14 days. Collagen-elastin matrices showed a higher mean vessel count and area compared with collagen-glycosaminoglycan matrices at 14 days. At 28 days, a more homogeneous vascular network and higher cell counts were observed in collagen-elastin matrices. Collagen-glycosaminoglycan matrices, however, exhibited less volume loss at day 28. CONCLUSIONS: Collagen-based scaffolds are suitable for soft tissue engineering in conjunction with the AV loop technique. These scaffolds exhibit distinct patterns of angiogenesis, cell migration, and proliferation and may in the future serve as the basis of tissue-engineered free flaps as an individualized treatment concept for critical wounds.

Acellular dermal matrix loading with bFGF achieves similar acceleration of bone regeneration to BMP-2 via differential effects on recruitment, proliferation and sustained osteodifferentiation of mesenchymal stem cells.

New generation of barrier membranes has been developed, which not only act as barriers but also as delivery devices to release specific growth factors. This study observed biological behaviors of bone morrow mesenchymal stem cells (BMMSCs) pretreated by bFGF or BMP-2 in vitro and evaluated differential bone regeneration process induced by bFGF and BMP-2 loaded acellular dermal matrix (ADM) membrane using critical-size rat calvarial defect model in vivo. The results showed that the proliferation capability of BMMSCs pretreated by bFGF was stronger than that by BMP-2, while there was temporally differential effect of bFGF and BMP-2 pretreatment on MSC osteogenic differentiation potentials. During healing process of rat calvarial defects, 2-fold more CD34-/CD90+ MSCs in group of bFGF-ADM was observed than in any other treatment group at 2weeks. However, there were similar amount of new bone formation and expression of osteopotin in newly-formed bone tissue in groups of bFGF- and BMP-2-ADM at 8weeks, which were more than those in ADM alone and blank control. Taken together, bFGF-ADM guided similar bone regeneration to BMP-2 through more efficient recruitment of MSCs, and moreover, BMMSCs pretreated by bFGF showed stronger proliferation at 1-5days and osteogenic differentiation potentials at 14days compared with BMP-2 pretreatment.

Evaluation of the Antimicrobial Efficacy of a Novel Rifampin/Minocycline-Coated, Noncrosslinked Porcine Acellular Dermal Matrix Compared With Uncoated Scaffolds for Soft Tissue Repair.

Background Despite meticulous aseptic technique and systemic antibiotics, bacterial colonization of mesh remains a critical issue in hernia repair. A novel minocycline/rifampin tyrosine-coated, noncrosslinked porcine acellular dermal matrix (XenMatrix AB) was developed to protect the device from microbial colonization for up to 7 days. The objective of this study was to evaluate the in vitro and in vivo antimicrobial efficacy of this device against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. Methods XenMatrix AB was compared with 5 existing uncoated soft tissue repair devices using in vitro methods of zone of inhibition (ZOI) and scanning electron microscopy (SEM) at 24 hours following inoculation with MRSA or E coli These devices were also evaluated at 7 days following dorsal implantation and inoculation with MRSA or E coli (60 male New Zealand white rabbits, n = 10 per group) for viable colony-forming units (CFU), abscess formation and histopathologic response, respectively. Results In vitro studies demonstrated a median ZOI of 36 mm for MRSA and 16 mm for E coli for XenMatrix AB, while all uncoated devices showed no inhibition of bacterial growth (0 mm). SEM also demonstrated no visual evidence of MRSA or E coli colonization on the surface of XenMatrix AB compared with colonization of all other uncoated devices. In vivo XenMatrix AB demonstrated complete inhibition of bacterial colonization, no abscess formation, and a reduced inflammatory response compared with uncoated devices. Conclusion We demonstrated that XenMatrix AB possesses potent in vitro and in vivo antimicrobial efficacy against clinically isolated MRSA and E coli compared with uncoated devices.

The impact of chemotherapy and radiation therapy on the remodeling of acellular dermal matrices in staged, prosthetic breast reconstruction.

BACKGROUND: An acellular dermal matrix will typically incorporate, in time, with the overlying mastectomy skin flap. This remodeling process may be adversely impacted in patients who require chemotherapy and radiation, which influence neovascularization and cellular proliferation. METHODS: Multiple biopsy specimens were procured from 86 women (n = 94 breasts) undergoing exchange of a tissue expander for a breast implant. These were divided by biopsy location: submuscular capsule (control) as well as superiorly, centrally, and inferiorly along the paramedian acellular dermis. Specimens were assessed for cellular infiltration, cell type, fibrous encapsulation, scaffold degradation, extracellular matrix deposition, neovascularization, mean composite remodeling score, and type I and III collagen. Patients were compared based on five oncologic treatment groups: no adjuvant therapy (untreated), neoadjuvant chemotherapy with or without radiation, and chemotherapy with or without radiation. RESULTS: Biopsy specimens were procured 45 to 1805 days after implantation and demonstrated a significant reduction in type I collagen over time. Chemotherapy adversely impacted fibrous encapsulation (p = 0.03). Chemotherapy with or without radiation adversely impacted type I collagen (p = 0.02), cellular infiltration (p < 0.01), extracellular matrix deposition (p < 0.04), and neovascularization (p < 0.01). Radiation exacerbated the adverse impact of chemotherapy for several remodeling parameters. Neoadjuvant chemotherapy also caused a reduction in type I (p = 0.01) and III collagen (p = 0.05), extracellular matrix deposition (p = 0.03), and scaffold degradation (p = 0.02). CONCLUSION: Chemotherapy and radiation therapy limit acellular dermal matrix remodeling. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Cross-linking in biomaterials: a primer for clinicians.

The purpose of this primer is to provide the clinical surgeon with a survey overview of the basic biochemistry of collagen and the methods and rationale of collagen cross-linking in the processing and preparation of bioprosthetics for surgical implantation. The author highlights the critical biologic factors, such as strength over time, integration, and rate, and type of remodeling, that are to an extent controllable by the cross-linking of collagen tissues so that clinicians may be better capable of understanding differences among the devices, which may be more applicable to their clinical indications.

Dermis acelular porcina (sus scrofa) cargada con antioxidantes de larrea divaricata / Porcine (sus scrofa) acellular dermis load with antioxidants from larrea divaricata

Con el objeto de cargar con antioxidantes de Larrea divaricata una dermis acelular porcina para propósitos terapéuticos, se determinó el contenido de polifenoles y antocianinas de extractos puros, aislados y absorbidos en una dermis acelular porcina. Los valores para polifenoles totales y antocianinas fueron: a) Larrea divaricata: 58,77 + 1,55 mg ácido gálico / 100 g peso fresco, 400,00 + 9,55 mg cianidina 3-glucósido / 100 g peso fresco, repectivamente, b) dermis acelular porcina: 8,86 + 0,55 mg ac. gállico / 100 g peso fresco y 0,10+ 0,00 mg cianidina 3-glucósido / 100 g peso fresco; respectivamente, c) Larrea divaricata absorbida en dermis acelular porcina 45,92 + 0,90 mg ácido gálico / 100 g peso fresco y 155,92 + 5,90 mg cianidina 3-glucósido / 100 g peso fresco, respectivamente. Nosotros concluimos que es posible tener una dermis acelular porcina cargada con antioxidantes de Larrea divaricata para propósitos médicos.

The aim of the study was to evaluate loading with antioxidants from Larrea divaricata a porcine acellular dermis for therapeutic purposes, poliphenols and anthocianins of pure extracts, isolated and absorbed in pig acellular dermis was evaluated. The following values (total polyphenols and anthocianins) were obtained: a) Larrea divaricata: 58,77 + 1,55 mg gallic acid / 100 g fresh weight; 400,95 + 9,55 mg cianydin 3- glucosyde / 100 g fresh weight; respectively; b) porcine acellular dermis: 8,86 + 0,55 mg gallic acid / 100 g fresh weight and 0,10+ 0,00 mg cianydin 3-glucosyde / 100 g fresh weight; respectively, c) L. divaricata absorbed in porcine acellular dermis: 45,92 + 0,90 mg gallic acid / 100 g fresh weight and 155,92 + 5,90 mg cianydin 3-glucosyde / 100 g fresh weight, respectively. We concluded that it is possible to get a porcine acellular dermis loaded with antioxidants from Larrea divaricata for medical purposes.