Uncontrolled fibrosis via excess deposition of extracellular matrix (ECM) is a hallmark of hypertrophic scars and keloids. A decellularized ECM biomaterial from porcine small intestinal submucosa (SIS; Biodesign or BioD, Cook Biotech, Inc.) is widely used in clinical applications for tissue repair. The objective of the current study was to test the effects of BioD scaffolds, as compared with collagen constructs, on normal human skin (nFB) and keloid fibroblasts (kFBs). Immortalized human dermal fibroblasts (hFBs) and human keloid fibroblasts (hKFs) were utilized for all experiments. Cells were cultured either on BioD membranes or on collagen gel (used as a control). To investigate pro-fibrotic signaling pathways, real-time quantitative PCR (qPCR), ELISA, and gene knockdown studies were conducted on cultured cells. ECM gene expression array revealed that BioD significantly attenuated (p < 0.05) the expression of thrombospondin-1 and fibronectin-1, two drivers of fibrosis in nFB as well as kFB. BioD-repressed thrombospondin-1 and fibronectin-1 gene expression manifested as significant downregulation (n = 5–6; p < 0.05) of both proteins in nFB and kFB. The levels of latent transforming-growth factor (LAP-TGFβ-1) were markedly reduced (n = 5; p < 0.05) in both nFB and kFB cultured on BioD, but not the other constructs. Knockdown of FN1 using siRNA significantly attenuated (n = 5, p < 0.05) pro-fibrotic responses, including expression of Col1A1 and the levels of LAP-TGFβ-1 in nFB, suggesting that downregulation of FN1 by BioD is one of the primary underlying mechanisms of attenuated pro-fibrotic responses in keloid fibroblasts. This study reports that a decellularized ECM scaffold may significantly attenuate pro-fibrotic responses in both normal and keloid fibroblasts via TSP1 and FN1-dependent mechanisms.

BACKGROUND/AIM:Decellularized extracellular matrix (ECM) acts as a depot for biochemical factors when conditioned by the growth of cells that are subsequently removed, and in the case of tumors, this ECM depot is known as the matrisome. This study was undertaken to determine whether a tissue-engineered matrisome could be used as an antigenic depot to stimulate protective immunity against tumor regrowth and metastasis following surgical reduction of the tumor.MATERIALS AND METHODS:Using two transplanted tumor cell models, the PAIII rat model of prostate cancer and the B16F1 mouse model of melanoma, mice were administered either media (control), a suspension of inactivated tumor cells, extracellular matrix (SIS), or a matrisome engineered through growth and removal of tumor cells on SIS that was then implanted either directly onto the resected tumor bed or at an anatomical site distant to the tumor bed. Tumor weights were determined at 21 days (rats) and at 17 days (mice), and the number of metastatic foci on the lungs were enumerated at 21 days in rats.RESULTS:Data showed that for both PAIII and B16F1 tumors, mean PAIII and B16F1 tumor weights were significantly reduced for vaccinated animals compared to controls. Furthermore, significantly fewer metastatic foci from PAIII tumors were present on the lungs in vaccinated rats compared to controls.CONCLUSION:Antigens within the tissue-engineered matrisome stimulated an inhibitory response to tumor growth; this strategy should be explored further as a means of cancer immunotherapy.

Background: Clinically useful biomaterials are derived from xenogeneic extracellular matrices, but extensive processes often used to remove all residual DNA are detrimental to their proper biological function. We hypothesized that deliberate and repeated injection of DNA extracted from clinically implantable, xenogeneic extracellular matrices might elicit an immune response in a well-established murine model that could ultimately lead to altered extracellular matrix remodeling. Methods: DNA was purified from unprocessed porcine extracellular matrices and processed extracellular matrices before sterilization (aseptic) and after sterilization. Groups of 10 mice were injected with these 3 purified DNAs and 3 controls: (1) DNA from E. coli; (2) DNA from unprocessed porcine extracellular matrices combined with interleukin-12 and methylated bovine serum albumin and emulsified in incomplete Freund's adjuvant; and (3) buffered saline. Immunizations occurred every 2 weeks for a total of 3 injections. Local cytokines and systemic anti-DNA antibodies were quantified 3 and 7 days after final injection. Results: The DNA extracted from unprocessed, aseptic, or sterilized porcine extracellular matrices failed to elicit a rejection response, and only with significant, proinflammatory adjuvant activation could such a response be seen. Without the adjuvants, biomaterial-derived DNA resulted in a mild accommodation cytokine response locally and no systemic anti-DNA antibody expression even at doses approximately 100-fold larger than would be clinically likely via extracellular matrix implantation. Conclusion: The immunological safety of porcine extracellular matrix biomaterials appears not to be related to DNA residues present. Such biomaterials need not be extensively processed, likely leading to detrimental changes in their bioactivity, solely in an effort to remove the mammalian DNA.

Wound healing is a complex natural process that involves the recruitment of cells, the renewal of tissue composition, and the reinforcement of structural tissue architecture. Following ischemic injury or chronic disease, wound healing is delayed, and can often result in chronic inflammation or permanent morbidity. Tissue engineering strategies to harness the wound healing process include the use of naturally derived extracellular matrix (ECM) scaffolds with inherent bioactivity to both passively facilitate and actively direct healing toward a successful resolution. As the body heals, the properly designed ECM scaffold is gradually remodeled and integrated into the body, leaving behind organized tissue that provides long-term strength. Herein we explain the interplay of the ECM (i.e., its complex composition and bioactivity) with the cells of the body throughout the process of tissue remodeling, thus explaining how even a tissue-engineered xenograft material can direct the body to restore itself.

Each year hundreds of new biomedical devices and therapies are developed to attempt to solve unmet medical needs. However, many fail due to unforeseen challenges of complex ethical, regulatory, and societal issues. We propose that a number of these issues can be effectively transformed into drivers of innovation for medical solutions if ethical analysis is considered early, iteratively, and comprehensively in the research and development process.

BACKGROUND Paracrine factors secreted by adipose-derived stem cells can be captured, fractionated, and concentrated to produce therapeutic factor concentrate (TFC). The present study examined whether TFC effects could be enhanced by combining TFC with a biological matrix to provide sustained release of factors in the target region. MATERIAL AND METHODS Unilateral hind limb ischemia was induced in rabbits. Ischemic limbs were injected with either placebo control, TFC, micronized small intestinal submucosa tissue (SIS), or TFC absorbed to SIS. Blood flow in both limbs was assessed with laser Doppler perfusion imaging. Tissues harvested at Day 48 were assessed immunohistochemically for vessel density; in situ hybridization and quantitative real-time PCR were employed to determine miR-126 expression. RESULTS LDP ratios were significantly elevated, compared to placebo control, on day 28 in all treatment groups (p=0.0816, p=0.0543, p=0.0639, for groups 2-4, respectively) and on day 36 in the TFC group (p=0.0866). This effect correlated with capillary density in the SIS and TFC+SIS groups (p=0.0093 and p=0.0054, respectively, compared to placebo). A correlation was observed between miR-126 levels and LDP levels at 48 days in SIS and TFC+SIS groups. CONCLUSIONS A single bolus administration of TFC and SIS had early, transient effects on reperfusion and promotion of ischemia repair. The effects were not additive. We also discovered that TFC modulated miR-126 levels that were expressed in cell types other than endothelial cells. These data suggested that TFC, alone or in combination with SIS, may be a potent therapy for patients with CLI that are at risk of amputation.

The use of degradable materials is required to address current performance and functionality shortcomings from biologically-derived tissues and non-resorbable synthetic materials used for hernia mesh repair applications. Herein a series of degradable l-valine-co-l-phenylalanine poly(ester urea) (PEU) copolymers were investigated for soft-tissue repair. Poly[(1-VAL-8)0.7-co-(1-PHE-6)0.3] showed the highest uniaxial mechanical properties (332.5 ± 3.5 MPa). Additionally, l-valine-co-l-phenylalanine poly(ester urea)s were blade coated on small intestine submucosa extracellular matrix (SIS-ECM) and found to enhance the burst test mechanical properties of SIS-ECM in composite films (force at break between 102.6 ± 6.5-151.4 ± 11.3 N). Free standing films of l-valine-co-l-phenylalanine PEUs were found to have superior extension at break when compared to SIS-ECM (averages between 1.2 and 1.9 cm and 1.2 cm respectively). Fibroblast (L-929) spreading, proliferation, and improved attachment over control were observed without toxicity in vitro, while a reduced inflammatory response at both 7 and 14 days post-implant was observed for poly[(1-VAL-8)⁠0.7-co-(1-PHE-6)⁠0.3] when compared to polypropylene in an in vivo rat hernia model. These results support the use of PEU copolymers as free-standing films or as composite materials in soft-tissue applications for hernia-repair.

Templates inserted into surgical wounds strongly influence the healing responses in humans. The science of these templates, in the form of extracellular matrix biomaterials, is rapidly evolving and improving as the natural interactions with the body become better understood.

A major problem in cancer research is the lack of a tractable model for delayed metastasis. Herein we show that cancer cells suppressed by SISgel, a gel-forming normal ECM material derived from Small Intestine Submucosa (SIS), in flank xenografts show properties of suppression and re-activation that are very similar to normal delayed metastasis and suggest these suppressed cells can serve as a novel model for developing therapeutics to target micrometastases or suppressed cancer cells. Co-injection with SISgel suppressed the malignant phenotype of highly invasive J82 bladder cancer cells and highly metastatic JB-V bladder cancer cells in nude mouse flank xenografts. Cells could remain viable up to 120 days without forming tumors and appeared much more highly differentiated and less atypical than tumors from cells co-injected with Matrigel. In 40% of SISgel xenografts, growth resumed in the malignant phenotype after a period of suppression or dormancy for at least 30 days and was more likely with implantation of 3 million or more cells. Ordinary Type I collagen did not suppress malignant growth, and tumors developed about as well with collagen as with Matrigel. A clear signal in gene expression over different cell lines was not seen by transcriptome microarray analysis, but in contrast, Reverse Phase Protein Analysis of 250 proteins across 4 cell lines identified Integrin Linked Kinase (ILK) signaling that was functionally confirmed by an ILK inhibitor. We suggest that cancer cells suppressed on SISgel could serve as a model for dormancy and re-awakening to allow for the identification of therapeutic targets for treating micrometastases.

Extracellular matrix (ECM) is an essential component of every tissue in our bodies, but it has been relatively misunderstood for decades. More recently, knowledge regarding the role of the ECM in biology and in medicine has been significantly expanded, and its study has greatly added to the world of regenerative medicine in a real and practical sense. This chapter seeks to address the concepts of in situ tissue engineering through the provision of an ECM as scaffold for regrowth of functional tissue. Whether harvesting and decellularizing an ECM from a tissue source or building it de novo, the many variables encountered in tissue processing affect the physicochemical aspects of the ECM material, the results achieved after in vivo implantation, and the resulting clinical utility of the implants made from such materials. Further more, even the most robust ECM materials are affected by procedural and patient-related variables that together affect clinical outcomes for tissue reconstructions with ECM. Advanced biomaterials that consist, either wholly or partially, of ECMs can form the basis for many therapeutic modalities, but clinical medicine must play a role in defining the procedures and the patients that will best benefit from these materials in the future

Abdominal wall defects and tissue loss that result from traumatic injury, surgical resection, failure of abdominal closures (i.e., incisional hernias) or ventral hernias are a common clinical problem. Currently, the repair of these tissue defects represents a reconstructive challenge to surgeons. The goal of abdominal wall reconstruction is to restore and maintain a functional abdominal wall. This article reviews the current and potential tissue engineering strategies for the repair of abdominal wall defects and suggests some innovative approaches for the translation to the clinical setting.