Advanced Imaging Techniques for Investigation of Acellular Dermal Matrix Biointegration

Acellular dermal matrix imaging features in breast reconstructive surgery: a pictorial review

Acellular dermal matrices (ADMs) are biological engineered tissues, which may provide an immunologically inert scaffold in breast reconstruction. Since the literature on imaging features of ADMs is limited, radiologists must be aware of the common imaging appearances of ADM, to differentiate normal conformation from residual or recurrent disease. Our purpose is to review the current role of ADMs in implant-based breast reconstruction, describing the normal imaging findings at ultrasound, mammography, and MRI also considering the possible changes over time. In this pictorial essay, we reviewed imaging features of ADMs described in the literature and we reported our experience in patients who underwent reconstructive surgery with human or animal ADM for newly diagnosed breast cancer.

The Bridging Effect of Artificial Dermis on Reconstruction of Skin Avulsion Injury

Skin avulsion wounds are expected to be swollen and tense after trauma, and skin perfusion can be compromised after primary closure, resulting in wound dehiscence and poor healing. The artificial dermis (AD) serves as a dermal regeneration template that is used to heal skin defects with secondary intention. Therefore, the aim of this study is to evaluate the effect of AD application on traumatic skin avulsion injuries compared to conventional primary closure. A retrospective cohort of 20 patients with skin avulsion injuries were included the study: ten patients were treated with AD and ten patients were managed with primary closure. When compared to the primary closure group, AD group had a shorter average healing time (58.40 ± 26.94 days V 65.50 ± 46.45 days) and significantly higher flap viability (92.00 ± 13.17% V 78.00 ± 13.98%; p = .03). In conclusion, AD is a promising material for the treatment of skin avulsion injury and produces better clinical results.

Clinical observation on healing of tarsal plate defect after reconstruction with xenogeneic acellular dermal matrix

Objective

To evaluate the safety, function, and cosmetic outcome of eyelid reconstruction using a xenogeneic acellular dermal matrix as a tarsal plate replacement in the repair of 50 to 100% eyelid defects following excision of large malignant tumours.

Methods

A retrospective, non-comparative, interventional study of 21 eyes was performed over 26 months. Fourteen patients were female and seven were male. In all cases, a xenogeneic acellular dermal matrix was used for total or subtotal replacement of the tarsal plate. The central vertical height of the palpebral fissure was measured immediately after eyelid margin incision and at 1 and 6 months postoperatively.

Results

In patients who underwent surgery, the mean palpebral fissure height (PFH) was not significantly different between immediately and 1 month after incision (8.10 ± 0.562 mm vs 8.17 ± 0.577 mm, respectively; P > 0.05). After 6 months, PFH was 8.26 ± 0.605 mm, which was significantly different from that immediately after incision (P < 0.05). After 6 months of follow-up, all patients had a good aesthetic appearance after eyelid reconstruction, with no obvious graft dissolution or rejection, normal eyelid activity, and normal opening, closing, and lifting function. None of the 21 patients experienced tumour recurrence during postoperative follow-up.

Conclusion

The xenogeneic acellular dermal matrix was a successful tarsal plate replacement. This material is readily available, and a second surgical site is avoided. The xenogeneic acellular dermal matrix is considered a promising alternative material for tarsal replacement in future generations.

Acellular Dermal Matrix Favorably Modulates the Healing Response after Surgery

SUMMARY

When first described for breast reconstruction, the presence of acellular dermal matrices (ADM) was associated with increased seroma formation and infection. However, clinical safety data has gradually improved with surgeon experience to an acceptable outcomes profile of ADM-assisted reconstruction when compared to submuscular implant coverage. In fact, ADM use potentially decreases capsular contracture rates and facilitates expansion for staged pre-pectoral breast reconstruction. Due to new regulatory requirements, the collection of unbiased, well-powered pre-market approval data summarizing long-term clinical outcomes will be essential over the coming years to understand the clinical performance of ADM usage in breast reconstruction.Currently, we can highlight the physiologic benefits of ADM use in breast reconstruction by evaluating the components of surgical wound healing that are favorably augmented by the implanted collagen substrate. ADM takes advantage of the wound healing cascade to incorporate into the patient's tissues - a process that requires a coordinated inflammatory infiltrate and angiogenesis. The presence of ADM augments and modulates the wound healing process to its advantage by simultaneously increasing the invasion of appropriate cellular constituents to facilitate expeditious healing and accelerate angiogenesis. Herein, we summarize the wound healing literature to demonstrate the mechanisms ADM use to biointegrate and the literature in which cellular constituents and soluble growth factors are upregulated in the presence of ADM. Lastly, we use our experimental observations of ADM incorporation to corroborate the literature.

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.

Biologics and acellular dermal matrices in head and neck reconstruction: A comprehensive review

Acellular dermal matrices (ADMs) have been studied extensively in the literature and have gained popularity for various reconstructive and aesthetic purposes. ADMs are composed of a basement membrane and acellular dermal layer of collagen and provide a platform for mucosal epithelization and neovascularization. Combining dermal collagen and essential growth factors allows ADMs to support adequate wound healing and bolster soft-tissue repairs. These dermal matrices can be derived from human cadaveric donor skin (allogenic) or mammalian donor sources (xenogeneic). These dermal substitutes provide the benefit of reducing or eliminating the need for autologous tissue grafts and subsequently minimize donor site morbidity. Many ADMs are currently available in the market, each with variations in processing, manufacturing, storage, preparation, and use. The literature validating ADMs in the head and neck for both cosmetic and reconstructive purposes is evolving rapidly. This review aims to provide an up-to-date and comprehensive overview of the principles of acellular dermal matrices (ADMs), the different types of ADMs, and evaluate common indications, techniques, and outcomes pertaining to select anatomic sites in the head and neck reconstruction.

Rabbit as an animal model for the study of biological grafts in pelvic floor dysfunctions

The aims of this study were to evaluate the feasibility of the New Zealand White (NZW) rabbit for studying implanted biomaterials in pelvic reconstructive surgery; and to compare the occurrence of graft-related complications of a commercial polypropylene (PP) mesh and new developed human dermal matrix implanted at vaginal and abdominal level. 20 white female NZW rabbits were randomized into two groups, experimental group (human acellular dermal matrices-hADM-graft) and control group (commercial PP graft). In each animal, grafts were surgically implanted subcutaneously in the abdominal wall and in the vaginal submucosa layer for 180 days. The graft segments were then removed and the surgical and clinical results were analyzed. The main surgical challenges during graft implantation were: (a) an adequate vaginal exposure while maintaining the integrity of the vaginal mucosa layer; (b) to keep aseptic conditions; (c) to locate and dissect the breast vein abdominal surgery; and (d) to withdraw blood samples from the ear artery. The most abnormal findings during the explant surgery were found in the PP group (33% of vaginal mesh extrusion) in comparison with the hADM group (0% of vaginal graft extrusion), p = 0.015. Interestingly, macroscopic observation showed that the integration of the vaginal grafts was more common in the hADM group (40%) than in the PP group, in which the vaginal mesh was identified in 100% of the animals (p = 0.014). The NZW rabbit is a good model for assessing materials to be used as grafts for pelvic reconstructive surgery and vaginal surgery. Animals are easily managed during the procedures, including surgical intervention and vaginal mucosa approach. Additionally, hADM is associated with fewer clinical complications, as well as better macroscopic tissue integration, compared to PP mesh.

The Biointegration of a Porcine Acellular Dermal Matrix in a Novel Radiated Breast Reconstruction Model

BACKGROUND

Ideal acellular dermal matrices (ADM) for breast reconstruction exhibit native extracellular matrix (ECM) structure to allow rapid biointegration and appropriate mechanical properties for desired clinical outcomes. In a novel in vivo model of irradiated breast reconstruction, we describe the cellular and vascular ingrowth of Artia, a porcine product chemically prepared to mimic the biomechanics of human ADM, with retained natural ECM structure to encourage cellular ingrowth.

METHODS

Utilizing the murine dorsal skinfold model, Artia was implanted into 16 C57bl/6 mice. Eight of the mice received a single dose 35 Gy radiation to the skin, followed by 12 weeks to produce radiation fibrosis and 8 mice served as nonradiated controls. Real-time photoacoustic microscopy of vascular integration and oxygen saturation within the ADM were made over 14 days. At 21 days, vascular ingrowth (CD31), fibroblast scar tissue formation (alpha smooth-muscle actin α-SMA, vimentin), and macrophage function (M2/M1 ratio) were evaluated. Scanning electron microscopy images of Artia were produced to help interpret the potential orientation of cellular and vascular ingrowth.

RESULTS

Repeated photoacoustic microscopy imaging demonstrated vascular ingrowth increasing over 14 days, with a commensurate increase in oxygen saturation within both radiated and nonradiated ADM-albeit at an insignificantly lower rate in the radiated group. By day 21, robust CD31 staining was seen that was insignificantly greater in the nonradiated group. Of the fibroblast markers, vimentin expression was significantly greater in the radiated group (P < 0.05). Macrophage lineage phenotype was consistent with remodeling physiology in both radiated and nonradiated groups. Scanning electron microscopy demonstrated transversely organized collagen fibrils with natural porous ECM structure to allow cellular ingrowth.

CONCLUSIONS

Artia demonstrates appropriate biointegration, with increased oxygen saturation by 14 days, consistent with the performance of other collagen substrates in this model. Radiation fibrosis resulted in higher vimentin expression yet did not impact macrophage phenotype while only modestly decreasing Artia biointegration suggesting that ADM may have a role in reconstructive efforts in a radiated setting. Taken together with its enhanced biomechanics, this porcine ADM product is well poised to be clinically applicable to breast reconstruction.

Multimodal imaging for tumour characterization from micro- to macroscopic level using a newly developed dorsal chamber designed for long-term follow-up

Optical imaging of living animals is a unique method of studying the dynamics of physiological and pathological processes at a subcellular level. One-shot acquisitions at high resolution can be achieved on exteriorized organs before animal euthanasia. For longitudinal follow-up, intravital imaging can be used and involves imaging windows implanted in cranial, thoracic or dorsal regions. Several imaging window models exist, but none have proven to be applicable for long-term monitoring and most biological processes take place over several weeks. Moreover, none are compatible with multiple imaging modalities, meaning that different biological parameters cannot be assessed in an individual animal. We developed a new dorsal chamber that was well tolerated by mice (over several months) and allowed individual and collective cell tracking and behaviour analysis by optical imaging, ultrasound and magnetic resonance tomography. This new model broadens potential applications to areas requiring study of long-term biological processes, as in cancer research.

Histopathological Study of Meshed Versus Solid Sheet Acellular Dermal Matrices in a Porcine Model

BACKGROUND

Acellular dermal matrices (ADMs) are commonly used to support implant-based breast reconstruction. However, there is little comparative data on the incorporation process of different ADMs, and the value of meshing or fenestration versus solid sheet has not been established, although early clinical data suggest seroma rates may be reduced. This was a preclinical assessment of the incorporation process at optimal conditions in a pig model.

METHODS

SurgiMend and AlloDerm matrices were implanted in subcutaneous pockets on the backs of 15-week-old female pigs. Half of the samples were meshed 1:2.5; the remainder was grafted as a fenestrated (SurgiMend) or solid sheet (AlloDerm). Tissues were harvested at 3 months. Histological slides were prepared for hematoxylin and eosin staining, and Masson trichrome and immunostaining with anticollagen type I fluorescein isothiocyanate stain. Histological parameters (inflammation, giant cell reaction, neovascularization, fibroplasias, and scar tissue formation) were graded blindly on a scale of 0 (no reaction) to 3 (severe reaction).

RESULTS

All explanted ADMs (SurgiMend, n = 23; AlloDerm, n = 20) were firmly incorporated within the host tissue. SurgiMend showed more fibroplasia (P = 0.029) compared with AlloDerm in meshed or solid sheet form. Meshed ADMs showed a trend toward increased inflammation (P = 0.074) and giant cell reaction (P = 0.053) compared with solid sheet/fenestrated ADM.

CONCLUSIONS

Meshing ADM may allow cells to populate matrices more rapidly, promoting integration compared with solid sheet ADMs. This study sets the histological basis for further clinical investigations, with the aim of demonstrating lower complication rates (and particularly reduced seroma formation) with meshed ADMs.

Acellular Dermal Matrices: Applications in Plastic Surgery

Modern advances in tissue engineering have transformed the plastic surgeon's management strategies across a wide variety of applications. Comprehension of the fundamentals of biologic constructs is critical to navigating the available armamentarium. It is essential that plastic surgeons become familiar with some of the existing methods for utilizing biologics as well as the advantages and limitations to their use. In this article, the authors describe the basic science of biologics with a focus on acellular dermal matrices (ADMs), and review the recent evidence behind their use for a variety of reconstructive and aesthetic purposes. The review is organized by system and examines the common indications, techniques, and outcomes pertaining to the application of ADMs in select anatomic areas. The final section briefly considers possible future directions for using biologics in plastic and reconstructive surgery.

Prosthetic Breast Reconstruction and Red Breast Syndrome: Demystification and a Review of the Literature

Supplemental Digital Content is available in the text.

Red breast syndrome (RBS) represents an inflammatory condition that rarely occurs in the setting of acellular dermal matrix use after prosthetic reconstruction. It is characterized by erythema or rubor that occurs directly over the ADM, and its appearance resembles that of a cellulitis. There have been many explanations with regard to etiology, but none have addressed the physiologic alterations leading to the onset and resolution of RBS. RBS is postulated to be the result of lymphatic disruption and is self-limiting. Resolution is postulated to be the result of angiolymphatic regeneration and the re-establishment of lymphatic flow within the mastectomy skin flap and the ADM, resulting in the clearance of inflammatory mediators responsible for the localized erythema.

A Histological Comparison of Two Human Acellular Dermal Matrix Products in Prosthetic-Based Breast Reconstruction

Background

Acellular dermal matrices (ADMs) are an integral component of breast reconstruction. The ideal matrix would be relatively immuno-inert, allow rapid vascularization, and be affordable. The purpose of this study was to histologically compare 2 commonly used ADM products.

Methods

This is a prospective histological study of 17 patients (20 breasts) following prosthetic-based breast reconstruction with ADM: Alloderm (LifeCell Corp, Branchburg, N.J.) or Cortiva (RTI Surgical, Alachua Fla.). Biopsies were taken from the dermal matrix and natural capsules surrounding the expander/implant during secondary surgery [Range, 72-694 days (mean, 217 days)]. Biopsy specimens were prepared via hematoxylin and eosin, Masson's trichrome, elastin, and transforming growth factor (TGF)-1 stains. Quantitative analysis of staining was performed with ImageJ software. The clinical outcome of each patient is analyzed in relation to capsule architecture and ADM performance.

Results

There were 7 breasts in the Alloderm group and 13 in the Cortiva group. Both groups had similar demographic, aesthetic results, and complication profiles. The TGF-1 staining demonstrated significantly lower levels in the Cortiva capsules (P = 0.0139). The percentage of elastin and collagen are similar in the Cortiva, Alloderm, and natural peri-implant capsules. The native capsules show a significantly greater number of blood vessels when compared with Cortiva and Alloderm (P = 0.0371 and P = 0.0347, respectively); however, there is no difference in vascular pattern between the 2 dermal matrices.

Discussion

Postoperatively, Cortiva demonstrates equal vascularity with less TGF-1 activation compared with Alloderm. The clinical success and complication profile were similar between the Alloderm and Cortiva patients.