Influence of Irradiation on Capsules of Silicone Implants Covered with Acellular Dermal Matrix in Mice.

BACKGROUND: In advanced breast cancer, radiotherapy is recommended as adjuvant therapy following breast reconstructive surgery. This inevitably led to growing concerns over possible complications of radiotherapy on implants. In this experimental animal study, we investigated the utility of acellular dermal matrix (ADM) wraps around implants as preventive management for radiotherapy complications. METHODS: Black mice (C57NL6; n = 32) were assigned to groups that either received radiation or did not: groups A and B underwent surgery using implants without radiotherapy; while groups C and D underwent surgery using implants with radiotherapy for one and three months, respectively. The hemispheric silicone implants with an 0.8-cm-diameter were inserted on the left back of each mouse, and implants wrapped by ADM were inserted on the right back. The Clinic 23EX LINAC model was used for irradiation at 10 Gy. The samples were evaluated by gross assessment, histological analysis, immunohistochemical analysis, and the Western blotting test. RESULTS: The H&E staining analysis showed that membrane thickness is smallest in group A, followed by groups C, D, and B. In a Masson trichrome histological analysis, collagen fibers became less dense and more widespread over time in the groups that received an ADM. Immunohistochemistry findings were similarly constant. However, the expression of TGF-ß1 was increased in the irradiated groups, whereas it was decreased in the non-irradiated groups as observed over time. CONCLUSIONS: Radiotherapy was shown to increase risk factors for capsular contracture, including inflammatory response, pseudoepithelium, thinning of membrane, and TGF-ß1 expression over time; however, the accompanying framework using an ADM as a barrier between implant and tissue was shown to be effective in alleviating these risks. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Transplanted fibroblasts proliferate in host bronchial tissue and enhance bronchial anastomotic healing in a rodent model.

INTRODUCTION: Healing of airway anastomoses after preoperative irradiation can be a significant clinical problem. The augmentation of bronchial anastomoses with a fibroblast-seeded human acellular dermis (hAD) was shown to be beneficial, although the underlying mechanism remained unclear. Therefore, in this study we investigated the fate of the fibroblasts transplanted to the scaffold covering the anastomosis. MATERIAL AND METHODS: 32 Fisher rats underwent surgical anastomosis of the left main bronchus. In a 2 × 2 factorial design, they were randomized to receive preoperative irradiation of 20 Gy and augmentation of the anastomosis with a fibroblast-seeded transplant. Fibroblasts from subcutaneous fat of Fischer-344 rat were transduced retrovirally with tdTomato for cell tracking. After 7 and 14 days, animals were sacrificed and cell concentration of transplanted and nontransplanted fibroblasts in the hAD as well as in the bronchial tissue was measured using RT-PCR. RESULTS: Migration of transplanted fibroblasts from dermis to bronchus were demonstrated in both groups, irradiated and nonirradiated. In the irradiated groups, there was a cell count of 7 × 104 ± 1 × 104 tomato+-fibroblasts in the bronchial tissue at day 7, rising to 1 × 105 ± 1 × 104 on day 14 (p <0.0001). Tomato+-cell concentration in hAD increased from 6 × 103 ± 1 × 103 at day 7 to 6 × 104 ± 1 × 104 at day 14 (p <0.0001). In the nonirradiated groups, tomato+-cell concentration in bronchus was 4 × 103 ± 1 × 103 on day 7 and 4 × 103 ± 1 × 103 at day 14. In the hAD tomato+ cell concentration rising from 1 × 104 ± 1 × 103 at day 7 to 2 × 104 ± 3 × 103 cells at day 14 (p = 0.0028). CONCLUSIONS: Transplanted fibroblasts in the irradiated groups proliferate and migrate into the irradiated host bronchial tissue, but not in the nonirradiated groups.

In-vivo quantification of the revascularization of a human acellular dermis seeded with EPCs and MSCs in co-culture with fibroblasts and pericytes in the dorsal chamber model in pre-irradiated tissue.

INTRODUCTION: Transplantation of a cell-seeded graft may improve wound healing after radiotherapy. However, the survival of the seeded cells depends on a rapid vascularization of the graft. Co-culturing of adult stem cells may be a promising strategy to accelerate the vessel formation inside the graft. Thus, we compared the in vivo angiogenic potency of mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) using dorsal skinfold chambers and intravital microscopy. MATERIALS AND METHODS: Cells were isolated from rat bone marrow and adipose tissue and characterized by immunostaining and flow cytometry. Forty-eight rats received a dorsal skinfold chamber and were divided into 2 main groups, irradiated and non-irradiated. Each of these 2 groups were further subdivided into 4 groups: unseeded matrices, matrices + fibroblasts + pericytes, matrices + fibroblasts + pericytes + MSCs and matrices + fibroblasts + pericytes + EPCs. Vessel densities were quantified semi-automatically using FIJI. RESULTS: Fibroblasts + pericytes - seeded matrices showed a significantly higher vascular density in all groups with an exception of non-irradiated rats at day 12 compared to unseeded matrices. Co-seeding of MSCs increased vessel densities in both, irradiated and non-irradiated groups. Co-seeding with EPCs did not result in an increase of vascularization in none of the groups. DISCUSSION: We demonstrated that the pre-radiation treatment led to a significant decreased vascularization of the implanted grafts. The augmentation of the matrices with fibroblasts and pericytes in co-culture increased the vascularization compared to the non-seeded matrices. A further significant enhancement of vessel ingrowth into the matrices could be achieved by the co-seeding with MSCs in both, irradiated and non-irradiated groups.

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.

The effect of radiation on acellular dermal matrix and capsule formation in breast reconstruction: clinical outcomes and histologic analysis.

BACKGROUND: The authors compared clinical outcomes to determine whether acellular dermal matrix altered the capsular tissue architecture in irradiated and nonirradiated breasts following matrix-assisted expander reconstruction. METHODS: Part I included all 27 patients who underwent bilateral tissue expander reconstruction with acellular dermal matrix between 2007 and 2012 and subsequent unilateral radiation therapy. Part II included a subset of patients with capsular biopsy specimens taken at the time of implant exchange for histologic analysis. Specimens included irradiated and nonirradiated acellular dermal matrix and irradiated and nonirradiated native capsule. Clinical outcomes were analyzed in relation to capsule architecture and acellular dermal matrix performance. RESULTS: In part I, mean follow-up was 28 months. Grade III/IV contractures were identified in nine patients (all on the irradiated side), and 12 developed noncontracture complications (75 percent on the irradiated side). Nine patients were unable to continue with implant reconstruction and required salvage with autologous tissue. In part II, postirradiation biopsy specimens were taken of the peri-implant capsule in six patients at the time of secondary surgery. Elastin content and the total cellular infiltrate were significantly greater in the irradiated versus nonirradiated native capsules (p = 0.0015). Conversely, the irradiated matrix capsule was composed of similar amounts of cellular infiltrate and collagen as the nonirradiated matrix capsules and nonirradiated native capsules. Irradiated acellular dermal matrix showed the least amount of alpha-smooth actin staining but a similar number of blood vessels. CONCLUSION: Acellular dermal matrix appears to limit the elastosis and chronic inflammation seen in irradiated implant reconstructions and is potentially beneficial in these patients. 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.

Acellular dermal matrix in irradiated tissue expander/implant-based breast reconstruction: evidence-based review.

BACKGROUND: The benefits of acellular dermal matrix for breast reconstruction have been well described. However, its clinical impact for breast reconstruction in the setting of radiation therapy has not been well reported. METHODS: The MEDLINE and EMBASE databases were reviewed for articles published between January of 2005 and February of 2012 on breast reconstruction using acellular dermal matrix in the setting of radiation therapy. The authors also reviewed their institutional experience of consecutive patients who met these criteria between January of 2008 and October of 2011. RESULTS: Thirteen articles were identified for review: three animal studies on acellular dermal matrix and 10 with level III evidence of its use in humans. The 10 clinical studies included 246 irradiated patients. The M. D. Anderson experience included 30 irradiated acellular dermal matrix patients for a total of 276 irradiated patients evaluated in this review. Use of acellular dermal matrix in implant-based breast reconstruction in the setting of radiation therapy did not predispose to higher infection or overall complication rates or prevent bioprosthetic mesh incorporation. However, the rate of mesh incorporation may be slowed. Its use allowed for increased intraoperative saline fill volumes, which improved aesthetic outcomes and allowed patients to awake from surgery with a formed breast. CONCLUSIONS: Use of acellular dermal matrix for implant-based breast reconstruction does not appear to increase or decrease the risk of complications, but it might provide psychological and aesthetic benefits. Multicenter or single-center randomized controlled trials that provide high-quality, level I evidence are warranted.