Complete horizontal skin cell resurfacing and delayed vertical cell infiltration into porcine reconstructive tissue matrix compared to bovine collagen matrix and human dermis

Preventing postoperative adhesions after hand tendon repair using acellular dermal matrix

AIMS

Postoperative tendon adhesions contribute to functional disability and reconstructive failure. In this study, we present the long-term outcomes of a prospective study in which acellular dermal matrix (ADM) was used to prevent postoperative adhesion after tendon injury.

METHODS

The study was conducted between March 2014 and February 2017. Patients, aged 19-65 years, with an acute single flexor tendon injury in zones 1 or 2, distal to the palmar digital crease were candidates for the study. Patients were allocated to either an ADM treatment group or a control group without ADM treatment.

RESULTS

A total of 37 patients were enrolled in the study: 21 patients in the ADM group and 16 patients in the control group. At six months after surgery, the range of motion in the proximal interphalangeal joint was 81.0±5.1 degrees in the ADM group and 75.8±6.9 degrees in the control group. The range of motion in the distal interphalangeal joint was 79.9±7.1 in the ADM group and 71.2±5.7 degrees in the control group, with significant difference (p=0.03 and p<0.05, respectively). In addition, the total active motion was higher in the ADM group than in the control group. The patients' scores on the Patient Satisfaction Questionnaire were also significantly different, with higher satisfaction scores in the ADM group (p=0.02). The minimal follow-up period was six months.

CONCLUSION

The use of ADM after tendon repair has the potential to significantly improve the outcome of tendon surgery in terms of range of motion.

DECLARATION OF INTEREST

None of the authors has any financial interest in the products, devices, or drugs mentioned in this article.

[Suitability of biological acellular dermal matrices as a skin replacement]

INTRODUCTION

 Tissue defects are associated with loss of epidermal and dermal components of the skin. For full-thickness tissue defects, dermal equivalents are useful to enable rapid wound closure. Split-thickness skin grafts are associated with loss of tissue elasticity resulting in scar contractures that can impair joint mobility. Synthetic collagen matrices and allogeneic acellular dermal matrices (ADM) are commercially available and could serve as skin tissue replacement. The aim of this study was to investigate whether ADM of different dermal layers or bioartificial matrices can serve as cutaneous replacement. For this purpose, cellular migration, differentiation and the inflammatory reaction were studied in an established ex vivo skin organ model.

MATERIALS AND METHODS

 Human split-thickness skin grafts were transplanted onto ADM (Epiflex, DIZG, Berlin, Germany), de-epidermized dermis (DED) or an artificial collagen-elastin matrix (Matriderm, Dr. Suwelack, Billerbeck, Germany). Epithelial migration was studied using an established skin culture model at the air-liquid interface. In addition, the effect of tissue from different dermal compartments, e. g. papillar and reticular dermis, on epithelial migration was compared. Epithelial resurfacing and differentiation of matrices as well as the inflammatory reaction were studied using histological, immunohistochemical and biochemical analyses.

RESULTS AND CONCLUSION

 Significantly more epithelial outgrowth area was found on DED (2.54 mm ± 0.43 mm, mean ± SEM) compared to papillary ADM (1.32 mm ± 0.44 mm, p = 0.039), to reticular ADM (no horizontal growth, p < 0.0001) and collagen-elastin matrix (0.78 mm ± 0.11 mm, p = 0.0056) measured by fluorescence microscopy over 10 days presumably due to the presence of pro-migratory basement membrane residues on DED. Reepithelialization was significantly higher (p < 0.002) on papillary dermis compared to ADM of reticular origin. In contrast to the biological matrices, a complete horizontal penetration was found in the macroporous collagen-elastin matrix. Pro-inflammatory mediators varied depending on the human skin donor and matrix. In summary, the biochemical structure of the matrix' surface and its origin influenced the epithelial behaviour with regard to migration, differentiation and inflammatory response.

Is Transgenic Porcine Skin as Good as Allogeneic Skin for Regenerative Medicine? Comparison of Chosen Properties of Xeno- and Allogeneic Material

BACKGROUND

Burn treatment is associated with the need of dressing large cutaneous defects. There is a need of alternative search for the allogeneic skin as a source of grafting for a clinical use. Such sources include animals. For many years, porcine skin was used as a biological dressing for wounds or donor's fields, or residual fields after skin grafting. Current studies aim to minimize immunogenicity, inter alia, through the decellularization process.

MATERIALS AND METHODS

The decellularization methods and porcine skin resettlement of human keratinocytes and fibroblasts were evaluated. The mechanical properties of the dressings and their influence on the viability, apoptosis, population doubling, and cell cycle of keratinocytes and fibroblasts were examined. The inheritance of cell antigens responsible for histocompatibility on the human keratinocyte and fibroblast surface in the cultures incubated with examined variants of dressings from porcine skin were analyzed.

RESULTS

The most effective acellularization method is trypsinization. Morphology of the cell remained proper and stable during the whole experiment. In both fibroblast and keratinocyte cultures, the highest number of apoptotic cells was observed when samples were incubated with allogeneic skin. In the keratinocyte cultures, the highest number of live cells was observed when incubated with porcine transgenic acellular dermal matrix. The acellular matrices influence the increase of population doubling of keratinocytes in the cultures.

CONCLUSION

For routine acellurization, trypsinization was chosen as the most effective method with preservation of tissue properties.

Nano-mechanical mapping of interdependent cell and ECM mechanics by AFM force spectroscopy

Extracellular matrix (ECM), as a dynamic component of the tissue, influences cell behavior and plays an important role in cell mechanics and tissue homeostasis. Reciprocally, this three-dimensional scaffold is dynamically, structurally and mechanically modified by cells. In the field of biophysics, the independent role of cell and ECM mechanics has been largely investigated; however, there is a lack of experimental data reporting the interdependent interplay between cell and ECM mechanics, measured simultaneously. Here, using Atomic Force Microscopy (AFM) we have characterized five different decellularized matrices diverse in their topography, ECM composition and stiffness and cultured them with normal and pathological fibroblasts (scar and Dupuytren's). We investigated the change in topography and elasticity of these matrices due to cell seeding, by using AFM peak force imaging and mechanical mapping, respectively. We found normal fibroblasts soften these matrices more than pathological fibroblasts, suggesting that pathological fibroblasts are profoundly influencing tissue stiffening in fibrosis. We detected different ECM composition of decellularized matrices used here influences fibroblast stiffness, thus highlighting that cell mechanics not only depends on ECM stiffness but also on their composition. We used confocal microscopy to assess fibroblasts invasion and found pathological fibroblasts were invading the matrices deeper than normal fibroblasts.

The role of the microenvironment in the biophysics of cancer

During the last decades, cell mechanics has been recognized as a quantitative measure to discriminate between many physiological and pathological states of single cells. In the field of biophysics of cancer, a large body of research has been focused on the comparison between normal and cancer mechanics and slowly the hypothesis that cancer cells are softer than their normal counterparts has been accepted, even though in situ tumor tissue is usually stiffer than the surrounding normal tissue. This corroborates the idea that the extra-cellular matrix (ECM) has a critical role in regulating tumor cell properties and behavior. Rearrangements in ECM can lead to changes in cancer cell mechanics and in specific conditions the general assumption about cancer cell softening could be confuted. Here, we highlight the contribution of ECM in cancer cell mechanics and argue that the statement that cancer cells are softer than normal cells should be firmly related to the properties of cell environment and the specific stage of cancer cell progression. In particular, we will discuss that when employing cell mechanics in cancer diagnosis and discrimination, the chemical, the topographical and - last but not least - the mechanical properties of the microenvironment are very important.

In Vitro Evaluation of Scaffolds for the Delivery of Mesenchymal Stem Cells to Wounds

Mesenchymal stem cells (MSCs) have been shown to improve tissue regeneration in several preclinical and clinical trials. These cells have been used in combination with three-dimensional scaffolds as a promising approach in the field of regenerative medicine. We compare the behavior of human adipose-derived MSCs (AdMSCs) on four different biomaterials that are awaiting or have already received FDA approval to determine a suitable regenerative scaffold for delivering these cells to dermal wounds and increasing healing potential. AdMSCs were isolated, characterized, and seeded onto scaffolds based on chitosan, fibrin, bovine collagen, and decellularized porcine dermis. In vitro results demonstrated that the scaffolds strongly influence key parameters, such as seeding efficiency, cellular distribution, attachment, survival, metabolic activity, and paracrine release. Chick chorioallantoic membrane assays revealed that the scaffold composition similarly influences the angiogenic potential of AdMSCs in vivo. The wound healing potential of scaffolds increases by means of a synergistic relationship between AdMSCs and biomaterial resulting in the release of proangiogenic and cytokine factors, which is currently lacking when a scaffold alone is utilized. Furthermore, the methods used herein can be utilized to test other scaffold materials to increase their wound healing potential with AdMSCs.

Simultaneous dermal matrix and autologous split-thickness skin graft transplantation in a porcine wound model: a three-dimensional histological analysis of revascularization

Despite the popularity of a simultaneous application of dermal matrices and split-thickness skin grafts, scarce evidence exists about the process of revascularization involved. In this study, we aimed at analyzing the progression of revascularization by high-resolution episcopic microscopy (HREM) in a porcine excisional wound model. Following the surgical procedure creating 5 × 5 cm(2) full-thickness defects on the back, one area was covered with an autologous split-thickness skin graft alone (control group), the other with a collagen-elastin dermal matrix plus split-thickness skin graft (dermal matrix group). Two skin biopsies per each group and location were performed on day 5, 10, 15, and 28 postoperatively and separately processed for H&E as well as HREM. The dermal layer was thicker in the dermal matrix group vs. control on day 5 and 28. No differences were found for revascularization by conventional histology. In HREM, the dermal matrix did not appear to decelerate the revascularization process. The presence of the dermal matrix could be distinguished until day 15. By day 28, the structure of the dermal matrix could no longer be delineated and was replaced by autologous tissue. As assessed by conventional histology and confirmed by HREM, the revascularization process was comparable in both groups, notably with regard to the vertical ingrowth of sprouting vessels. The presented technique of HREM is a valuable addition for analyzing small vessel sprouting in dermal matrices in the future.