The use of urinary bladder matrix in the treatment of trauma and combat casualty wound care

Reconstruction and Regeneration of Composite Fingertip Injuries Using Acellular Bladder Matrix

Purpose

Traumatic fingertip amputations are one of the most encountered injuries in the emergency department requiring evaluation by a hand surgeon. Current management strategies vary widely. We describe the use of acellular urinary bladder matrix (UBM) in complex distal fingertip injuries involving bone, soft tissue, and nailbed.

Methods

A prospective cohort of 47 patients with proximal fingertip amputations (36 Allen zone III and 15 Allen zone IV) underwent UBM application with resultant fingertip regeneration. Patients received the first application in the operating room. Subsequent applications were reapplied weekly in the clinic setting until fibrinous granulation tissue was observed (average 2.5 total applications). Patients performed daily dressing changes until regeneration was achieved.

Results

The average time to regeneration was 8.4 weeks. The mean length deficit compared to the contralateral fingertip was 3.6 mm for zone 3 and 4.8 mm for zone 4 injuries. The static 2-point discrimination of the injured fingertip was 1.2 mm less sensitive compared to the contralateral uninjured finger in zone 3 injuries and 1.1 mm in the zone 4 cohort. Overall patient satisfaction measured on a 10-point Likert scale was 9.5. Seven complications were observed: 5 hook nail deformities, one bony exostosis requiring surgical excision, and one case of pyogenic granuloma.

Conclusion

Application of UBM is a reliable way to promote composite regeneration of Allen III-IV fingertip injuries. Its use resulted in excellent patient satisfaction with minimal complications encountered. Urinary bladder matrix should be considered for use in the treatment of proximal fingertip amputations.

Level of Evidence

Therapeutic IV.

A Novel UBM/SIS Composite Biological Scaffold for 2-Year Abdominal Defect Repairing and Strength Recovery in Canine Model

Biological scaffolds are widely utilized in hernia treatment due to their exceptional pro-regenerative properties, which mitigate scar formation. However, serious complications occurred, caused by inflammatory response, premature degradation, and mechanical failure. Consequently, improvements of the biological scaffold are necessary to mitigate these risks. In this study, a novel biological scaffold integrating basement membrane-containing urinary bladder matrix (UBM) and small intestinal submucosa (SIS) is developed, and its safety and effectiveness are assessed in comparison to a commercial SIS (c-SIS) scaffold. The introduction of UBM as top surface layers significantly promotes cell adhesion, facilitating rapid formation of isolated regeneration zone. Proteomic analysis has demonstrated a more efficient decellularization of the UBM/SIS scaffold, which subsequently mitigates inflammation in murine models, and promotes the polarization of macrophages toward the pro-healing M2 phenotype in a rat model of abdominal wall muscle defect. Furthermore, a two-year repair trial is conducted on a full-thickness abdominal wall muscle defect in canine model and confirmed that the UBM/SIS scaffold exhibits reduced seroma occurrences and enhanced tissue repair performances. Overall, the efficacy of this novel biological scaffold suggests its potential to minimize hernia recurrence in clinical practice and mitigate patient suffering from severe inflammatory responses.

Dermal Substitute Integra for the Treatment of Mammalian Bite Injuries of Nose: a New Reconstructive Ladder

Background

Bite injuries affecting the nose are uncommon occurrences characterized by their intricate nature and potential for severe complications. These injuries, inflicted by animals such as dogs and cats, and occasionally by humans, often result in traumatic nasal defects, with the lower third of the nose being the most affected area. Current reconstructive options for nasal defects include full-thickness skin grafts, local or regional flaps, and composite grafts. The traditional reconstructive ladder serves as a valuable guide for surgeons, outlining a continuum of treatment options from simpler to more complex interventions. Advancements in reconstructive technologies, such as the introduction of dermal substitutes, have reshaped the decision-making process, ushering in a new era of facial reconstruction.

Methods

In this context, dermal substitutes have emerged as promising adjuncts in nasal reconstruction, drawing from their success in burn surgery. Notably, the bilayered dermal substitute Integra has demonstrated efficacy in promoting wound healing and facilitating tissue regeneration. By harnessing the regenerative potential of Integra, plastic surgeons can address specific nasal defects arising from bite injuries with greater precision and improved outcomes.

Results

This study aims to present a case series of patients with bite injuries to the nose, showcasing the successful application of Integra dermal substitute in conjunction with secondary full-thickness skin grafting.

Conclusions

Through a retrospective analysis of patient demographics, injury characteristics, surgical interventions, and postoperative outcomes, we seek to underscore the utility of this combined approach in achieving optimal functional and aesthetic results. We aim to contribute to the evolving paradigm of nasal reconstruction.

Histopathologic Analysis of a Recalcitrant Calcaneal Wound Treated Using a Synthetic Hybrid-scale Fiber Matrix

Traditionally, full-thickness wounds with exposed structures are treated with flap coverage or dermal regenerative templates. Most dermal regenerative templates are biologic in origin, but recently synthetic options have become available. One such product is a synthetic hybrid-scale fiber matrix (SHSFM). In this case, SHSFM was used to treat a recalcitrant calcaneal wound. After the wound granulated, it was biopsied, and histopathologic analysis was conducted. A 16-year-old woman involved in a motor vehicle collision sustained multiple traumatic injuries which were stabilized. Postoperatively, she developed a calcaneal infection and associated wound, which developed into a chronic, nonhealing wound. Failed treatments included removal of hardware, multiple debridements, and advanced wound therapies. An SHSFM was then trialed, which led to granulation of the wound without infection. Despite wound healing, the patient subsequently elected to undergo a below-the-knee amputation due to pain and functional disability from posttraumatic ankle arthritis. The heel was biopsied at the time of amputation for analysis. Pathologists noted excellent granulation tissue formation and complete coverage of the wound surface area and 75% of the wound depth, which included epithelialization and decreasing inflammation at wound edges. Collagen deposition and numerous interspersed blood vessels were present. Foreign material and bacteria were absent. No osteomyelitis was observed. This analysis provided the opportunity to investigate the in vivo regenerate from a novel synthetic SHSFM. Given the uniqueness and challenges presented in this case, the usage of this relatively new product warrants further investigation with larger populations and assorted wound etiologies.

Urinary bladder matrix for lower extremity split-thickness skin graft donor site

Split-thickness skin grafts (STSG) are commonly used to treat soft-tissue defects. Harvesting a STSG creates an additional partial thickness wound at the donor site which must be managed. Many dressings are commercially available for the management of STSG donor sites; however, there is no evidence-based consensus on optimal dressing for site management. Urinary bladder matrix (UBM) is an extracellular matrix that acts as a structural support for tissue remodeling and provides molecular components for repair. Common clinical applications of UBM include coverage of deep wounds, burns, and irradiated skin. Skin grafting from the lower extremities poses a challenge due to the increased dermal tension. UBM-based reconstruction is an alternative method of managing lower extremity skin graft donor sites. This case study demonstrates the use of UBM in the reconstruction of a STSG donor site of the anterolateral thigh, which resulted in satisfactory healing, no pain, and excellent cosmetic and functional outcomes.

Incubation with porcine urinary bladder matrix yields a late-stage wound transcriptome in endothelial cells and keratinocytes isolated from both diabetic and non-diabetic subjects

Proper wound closure requires the functional coordination of endothelial cells (ECs) and keratinocytes. In the late stages of wound healing, keratinocytes become activated and ECs promote the maturation of nascent blood vessels. In diabetes mellitus, decreased keratinocyte activation and impaired angiogenic action of ECs delay wound healing. Porcine urinary bladder matrix (UBM) improves the rate of wound healing, but the effect of exposure to UBM under diabetic conditions remains unclear. We hypothesized that keratinocytes and ECs isolated from both diabetic and non-diabetic donors would exhibit a similar transcriptome representative of the later stages of wound healing following incubation with UBM. Human keratinocytes and dermal ECs isolated from non-diabetic and diabetic donors were incubated with and without UBM particulate. RNA-Seq analysis was performed to identify changes in the transcriptome of these cells associated with exposure to UBM. While diabetic and non-diabetic cells exhibited different transcriptomes, these differences were minimized following incubation with UBM. ECs exposed to UBM exhibited changes in the expression of transcripts suggesting an increase in the endothelial-mesenchymal transition (EndoMT) associated with vessel maturation. Keratinocytes incubated with UBM demonstrated an increase in markers of activation. Comparison of the whole transcriptomes with public datasets suggested increased EndoMT and keratinocyte activation following UBM exposure. Both cell types exhibited loss of pro-inflammatory cytokines and adhesion molecules. These data suggest that application of UBM may accelerate healing by promoting a transition to the later stages of wound healing. This healing phenotype is achieved in cells isolated from both diabetic and non-diabetic donors.

Research progress of biomaterials and innovative technologies in urinary tissue engineering

Substantial interests have been attracted to multiple bioactive and biomimetic biomaterials in recent decades because of their ability in presenting a structural and functional reconstruction of urinary tissues. Some innovative technologies have also been surging in urinary tissue engineering and urological regeneration by providing insights into the physiological behavior of the urinary system. As such, the hierarchical structure and tissue function of the bladder, urethra, and ureter can be reproduced similarly to the native urinary tissues. This review aims to summarize recent advances in functional biomaterials and biomimetic technologies toward urological reconstruction. Various nanofirous biomaterials derived from decellularized natural tissues, synthetic biopolymers, and hybrid scaffolds were developed with desired microstructure, surface chemistry, and mechanical properties. Some growth factors, drugs, as well as inorganic nanomaterials were also utilized to enhance the biological activity and functionality of scaffolds. Notably, it is emphasized that advanced approaches, such as 3D (bio) printing and organoids, have also been developed to facilitate structural and functional regeneration of the urological system. So in this review, we discussed the fabrication strategies, physiochemical properties, and biofunctional modification of regenerative biomaterials and their potential clinical application of fast-evolving technologies. In addition, future prospective and commercial products are further proposed and discussed.

Biomaterials-based immunomodulation enhances survival of murine vascularized composite allografts

Vascularized composite allotransplantation (VCA) is a restorative option for patients suffering from severe tissue defects not amenable to conventional reconstruction. However, the toxicities associated with life-long multidrug immunosuppression to enable allograft survival and induce immune tolerance largely limit the broader application of VCA. Here, we investigate the potential of targeted immunomodulation using CTLA4-Ig combined with a biological porcine-derived extracellular matrix (ECM) scaffold that elicits a pro-regenerative Th2 response to promote allograft survival and regulate the inflammatory microenvironment in a stringent mouse orthotopic hind limb transplantation model (BALB/c to C57BL/6). The median allograft survival time (MST) increased significantly from 15.0 to 24.5 days (P = 0.0037; Mantel-Cox test) after adding ECM to the CTLA4-Ig regimen. Characterization of the immune infiltration shows a pro-regenerative phenotype prevails over those associated with inflammation and rejection including macrophages (F4/80^hi+CD206^hi+MHCII^low), eosinophils (F4/80^lowSiglec-F⁺), and T helper 2 (Th2) T cells (CD4⁺IL-4⁺). This was accompanied by an increased expression of genes associated with a Type 2 polarized immune state such as Il4, Ccl24, Arg1 and Ym1 within the graft. Furthermore, when ECM was applied along with a clinically relevant combination of CTLA4-Ig and Rapamycin, allograft survival was prolonged from 33.0 to 72.5 days (P = 0.0067; Mantel-Cox test). These studies implicate the clinical exploration of combined regimens involving local application of pro-regenerative, immunomodulatory biomaterials in surgical wound sites with targeted co-stimulatory blockade to reduce adverse effects of immunosuppression and enhance graft survival in VCA.

Characterizing the inherent activity of urinary bladder matrix for adhesion, migration, and activation of fibroblasts as compared with collagen-based synthetic scaffold

The mechanism of action underlying the intriguing prominent bioactivity of urinary bladder matrix (UBM) for in situ tissue regeneration of soft tissue defects remains to be elucidated. It is speculated that the activity of UBM for cell adhesion, migration, and activation is inherent. The bioactivity of UBM for in situ tissue regeneration and its relation with the structure and intact soluble components of UBM were investigated in comparison to a collagen-based scaffold, PELNAC (PEL). We isolated the soluble component of the two materials with urea buffer, and evaluated the respective effect of these soluble components on the in vitro adhesion and migration of L929 fibroblasts. The spatiotemporal pattern of endogenous-cell ingrowth into the scaffolds and cell activation were investigated using a model of murine subcutaneous implantation. UBM is more capable of promoting the adhesion, migration, and proliferation of fibroblasts than PEL in a serum-independent manner. In vivo, as compared with PEL, UBM exhibits significantly enhanced activity for fast endogenous cell ingrowth and produces a more prominent pro-regenerative and pro-remodeling microenvironment by inducing the expression of TGF-β1, VEGF, MMP-9, and murine type I collagen. Overall, our results suggest the prominent bioactivity of UBM for in situ tissue regeneration is inherent.

Urinary Bladder Matrix Grafting Versus Flap Coverage for Acute or Infected Wound Defects in Patients With Orthopaedic Trauma

OBJECTIVES

Urinary bladder matrix (UBM) grafting of acute or infected wound defects has been reported to be successful in small case series. The purpose of this study was to compare the outcomes of UBM grafting with flap coverage.

DESIGN

This is a retrospective comparative study.

SETTING

Level-1 trauma center.

PATIENTS

Orthopaedic trauma patients with wound defects not amenable to primary closure or skin grafting.

INTERVENTION

Wound coverage with UBM grafting (n = 26) by orthopaedic trauma surgeons versus flap coverage (n = 26) by microvascular-trained plastic surgeons.

MAIN OUTCOME MEASUREMENTS

Primary wound coverage success, complications, returns to the operating room, hospital length of stay, and time to wound healing.

RESULTS

The UBM group was more likely to have an American Society of Anesthesiologist class ≥3 (58% vs. 23%, P = 0.02), a foot/ankle wound (77% vs. 12%, P < 0.001), an infected wound defect (81% vs. 50%, P = 0.03), and smaller defects (21 vs. 100 cm 2 , P = 0.02). UBM grafting resulted in a longer time to wound healing (6 vs. 2 months, P = 0.002) and a shorter hospital length of stay (2 vs. 14 days, P < 0.0001). UBM and flap groups had similarly high rates of failure of primary wound coverage (31% vs. 31%; P = 1.0), complications (46% vs. 62%, P = 0.4), and returns to the operating room (46% vs. 65%; P = 0.2). All 3 acute traumatic wounds undergoing UBM grafting concurrently with fracture fixation experienced graft failure and osteomyelitis.

CONCLUSION

UBM grafting is an effective alternative to flap coverage for small traumatic or infected wounds but should be avoided in acute traumatic wounds undergoing fracture fixation.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Co-Graft of Acellular Dermal Matrix and Split Thickness Skin Graft-A New Reconstructive Surgical Method in the Treatment of Hidradenitis Suppurativa

Hidradenitis suppurativa is a chronic disease that significantly reduces patients' quality of life. Patients are chronically treated with systemic therapies, which are often ineffective. Surgical treatment for severe cases of hidradenitis suppurativa is one option for affected patients. Surgical treatment has its limitations, and wound closure may be particularly problematic. This requires the use of reconstructive techniques. The methods of choice for wound closure are split-thickness skin grafts or local flaps reconstructions. However, each method has its limitations. This is a presentation of a new reconstructive surgical method in hidradenitis suppurativa surgery: the use of a co-graft of Acellular dermal matrix and split thickness skin graft as a novel method in wound closure after wide excisions, based on two cases. The results of this method are very promising: we achieved very fast wound closure with good aesthetic results regarding scar formation. In this paper, we used several examinations: laser speckle analysis, cutometer tests, and health-related quality of life (QoL) questionnaire to check the clinical impact of this method. Our initial results are very encouraging. ADM with STSG as a co-graft could be widely used in reconstructive surgery. This is a preliminary study, which should be continued in further, extended research.

Single-layer acellular porcine bladder matrix as graft in corporoplasty for ventral curvature in pediatric proximal hypospadias repair: an initial experience

BACKGROUND

Single-layer ACellࣨ Cytalࣨ matrix (ACell Inc, Columbia, MD) is a commercially available, acellular scaffold derived from porcine bladder epithelial basement membrane and tunica propria. We describe our initial experience using Cytalࣨ as corporal graft in pediatric patients who underwent correction of ventral curvature in proximal hypospadias repair.

METHODS

A retrospective review of a single-institution, four surgeon hypospadias database was performed between January 2020 and December 2021. Outcomes assessed were postoperative recurrent ventral curvature, corporal diverticulum, scarring on corporoplasty site on physical exam, and parental reports of atypical adverse effects.

RESULTS

Ten males underwent correction of ventral curvature with Cytalࣨ as corporal graft for correction of ventral curvature were identified. All completed planned operations. Median age was 18.6 months (IQR 14.6-27.0). Median follow up was 14.1 months (IQR 8.9-16.5). Mean ventral curvature after degloving was 80 ± 50 degrees. All patients had straight erections. Nine of the 10 patients had straight erections verified at a subsequent artificial erection test at least 6 months from the corporoplasty (90%). The remaining patient underwent a double face onlay-tube-onlay transverse island preputial flap as a single-stage hypospadias repair and did not require any additional procedures. He had straight erections per parental history. None developed corporal diverticulum or demonstrated induration at site of corporoplasty on physical exam. There were no parental reports of atypical adverse systemic effects.

CONCLUSIONS

In the short term, single-layer Cytalࣨ is effective as corporal graft for correction of ventral curvature in proximal hypospadias repairs without incurring additional donor site morbidity.

Urinary Bladder Matrix Grafting: A Simple and Effective Alternative to Flap Coverage for Wounds in High-Risk Orthopaedic Trauma Patients

SUMMARY

Complex traumatic and/or infected wounds and their sequelae are a significant burden for high-volume trauma centers. Local or free flap coverage options are well described; however, they may be high risk in poor hosts with multiple comorbidities and active infections. In addition, flap coverage can result in delays in wound coverage depending on specialist availability. Porcine urinary bladder matrix grafting has been shown to be a simple definitive wound coverage option that can be performed without delay in multiple patient populations for wounds that would otherwise require flap coverage. The purpose of this article was to describe a technique for urinary bladder matrix grafting and report on a series of orthopaedic trauma patients treated with this technique.

Tissue Engineering in Skin Substitute

Thermal injuries may cause significant damage to large areas of the skin. Extensive and deep burn wounds require specialized therapy. The optimal method in the strategy of treating extensive, full thickness burns (III°) is the use of autologous split thickness skin grafts STSG (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalized patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017). The main limitation of that method is the inadequate amount of healthy, undamaged skin (donor sites), which could be harvested and used as a graft. Moreover, donor sites are an additional wounds that require analgesic therapy, leave scars during the healing process and they are highly susceptible to infection (1-6). It must be emphasized that in terms of the treatment of severe, deep and extensive burns, and there should be no doubt that the search for a biocompatible skin substitute that would be able to replace autologous STSG is an absolute priority. The above-mentioned necessitates the search for new treatment methods of severe burn wounds. Such methods could consider the preparation and application of bioengineered, natural skin substitutes. At present, as the clinical standard considered by the physicians may be use of available biological skin substitutes, e.g., human allogeneic skin, in vitro cultured skin cells, acellular dermal matrix ADM and revitalized ADMs, etc. (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalised patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017; Łabuś et al. FebJ Biomed Mater Res B Appl Biomater 106:726-733, 2018).

Urinary bladder matrix scaffolds improve endometrial regeneration in a rat model of intrauterine adhesions

Intrauterine adhesions caused by damage to the basal layer of the endometrium have a serious impact on women's fertility. Currently, there is no effective treatment to promote the regeneration of the endometrium. Urinary bladder matrix (UBM) is a derivative extracellular matrix biomaterial that has a complete basement membrane and provides a basis for the body to achieve complete self-functional repair. In this study, UBM was transplanted into the uterine horns of intrauterine adhesions in Sprague-Dawley rats to test whether UBM could improve endometrial regeneration in rats with intrauterine adhesions. Thicker endometria, increased numbers of glands, fewer fibrotic areas and increased proliferation of cells and blood vessels were found in the UBM group compared to the injury group. Transplantation of UBM reduced the mRNA levels of proinflammatory cytokines (tumor necrosis factor α) and increased those of anti-inflammatory cytokines (basic fibroblast growth factor) compared to the injury group. In the UBM group, the mRNA expression of endometrial receptivity factors (leukemia inhibitory factor and integrin αVβ₃) was higher than that in the injury group, but it was lower than that in the normal group and the sham-operated group. More embryos were seen in the UBM group than in the injury group, although the UBM group had fewer embryos than the normal and sham-operated groups. Therefore, UBM may contribute to endometrial regeneration and may improve endometrial receptivity and fertility.

Urinary Bladder Matrix Does Not Improve Tenogenesis in an In Vitro Equine Model

Extracellular matrix (ECM) is responsible for tendon strength and elasticity. Healed tendon ECM lacks structural integrity, leading to reinjury. Porcine urinary bladder matrix (UBM) provides a scaffold and source of bioactive proteins to improve tissue healing, but has received limited attention for treating tendon injuries. The objective of this study was to evaluate the ability of UBM to induce matrix organization and tenogenesis using a novel in vitro model. We hypothesized that addition of UBM to tendon ECM hydrogels would improve matrix organization and cell differentiation. Hydrogels seeded with bone marrow cells (n = 6 adult horses) were cast using rat tail tendon ECM ± UBM, fixed under static tension and harvested at 7 and 21 days for construct contraction, cell viability, histology, biochemistry, and gene expression. By day 7, UBM constructs contracted significantly from baseline, whereas control constructs did not. Both control and UBM constructs contracted significantly by day 21. In both groups, cells remained viable over time and changed from round and randomly oriented to elongated along lines of tension with visible compaction of the ECM. There were no differences over time or between treatments for nuclear aspect ratio, DNA, or glycosaminoglycan content. Decorin, matrix metalloproteinase 13, and scleraxis expression increased significantly over time, but not in response to UBM treatment. Mohawk expression was constant over time. Cartilage oligomeric matrix protein expression decreased over time in both groups. Using a novel ECM hydrogel model, substantial matrix organization and cell differentiation occurred; however, the addition of UBM failed to induce greater matrix organization than tendon ECM alone. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1848-1859, 2019.

Modulation of inflammation in wounds of diabetic patients treated with porcine urinary bladder matrix

Aim: To determine if porcine urinary bladder matrix (UBM) treatment is associated with modulation of wound inflammation in diabetic patients. Patients & methods: mRNA associated with M1 and M2 macrophages were measured in wounds of diabetic and nondiabetic patients pre- and post-treatment with UBM and an M1:M2 score was calculated. Results: Wound tissue from diabetic subjects exhibited elevated M1:M2 scores compared with nondiabetic patients, suggesting a greater pro-inflammatory state prior to treatment. Post-treatment, there was significantly greater reduction in the magnitude of the individual M1:M2 scores in the diabetic patients resulting in similar levels in both groups of patients. Conclusions: UBM may assist in diabetic wound healing by restoring an inflammatory state similar to that of nondiabetic patients.

The Collagen Suprafamily: From Biosynthesis to Advanced Biomaterial Development

Collagen is the oldest and most abundant extracellular matrix protein that has found many applications in food, cosmetic, pharmaceutical, and biomedical industries. First, an overview of the family of collagens and their respective structures, conformation, and biosynthesis is provided. The advances and shortfalls of various collagen preparations (e.g., mammalian/marine extracted collagen, cell-produced collagens, recombinant collagens, and collagen-like peptides) and crosslinking technologies (e.g., chemical, physical, and biological) are then critically discussed. Subsequently, an array of structural, thermal, mechanical, biochemical, and biological assays is examined, which are developed to analyze and characterize collagenous structures. Lastly, a comprehensive review is provided on how advances in engineering, chemistry, and biology have enabled the development of bioactive, 3D structures (e.g., tissue grafts, biomaterials, cell-assembled tissue equivalents) that closely imitate native supramolecular assemblies and have the capacity to deliver in a localized and sustained manner viable cell populations and/or bioactive/therapeutic molecules. Clearly, collagens have a long history in both evolution and biotechnology and continue to offer both challenges and exciting opportunities in regenerative medicine as nature's biomaterial of choice.

Advances in addressing full-thickness skin defects: a review of dermal and epidermal substitutes

full-thickness skin defects remain a reconstructive challenge. Novel regenerative modalities can aid in addressing these defects. A literature review of currently available dermal and epidermal regenerates was performed. The mechanism and application for each skin substitute was analyzed to provide a guide for these modalities. Available epidermal substitutes include autografts and allografts and may be cultured or noncultured. Dermal regenerate templates exist in biologic and synthetic varieties that differ in the source animal and processing. Epidermal and dermal skin substitutes are promising adjunctive tools for addressing certain soft tissue defects and have improved outcomes in reconstructive procedures. The following article provides a comprehensive review of the biologic materials available and the types of complex wounds amenable to their use.

Evaluation of tissue engineering products for the management of neuropathic diabetic foot ulcers: an interim analysis

OBJECTIVE

The objective of this prospective, multicentre clinical study is to assess the application of MatriStem MicroMatrix (MSMM) and MatriStem Wound Matrix (MSWM) (porcine urinary bladder derived extracellular matrix) compared with Dermagraft (DG) (human fibroblast-derived dermal substitute) for the management of non-healing diabetic foot ulcers (DFUs).

METHOD

A randomised, multicentre study was conducted at thirteen centers throughout the US. It was designed to evaluate the incidence of ulcer closure, rate of ulcer healing, wound characteristics, patient quality of life, cost-effectiveness, and recurrence. Those subjects whose DFUs decreased in size by ≤30% or increased by ≤50% during the standard of care (SOC) phase were randomised into the treatment phase of the study. The study evaluated complete wound closure by eight weeks with weekly device application. A two-week post treatment SOC phase followed the treatment phase for any wounds that did not heal by the end of eight weeks, and wound closure was also evaluated at the end of that period. Ulcer recurrence at 6 months post-treatment was evaluated in the subjects that showed wound healing by the end of the post-treatment SOC phase. Standard adjunctive therapy, including debridement, saline irrigation and foot off-loading, was provided to both arms during the four-week screening period, after which eligible subjects were randomised in a 1:1 ratio, to either the MatriStem (MS) or DG treatment arm. This study was developed to evaluate the hypothesis that the wound outcomes observed after wound management with MS were non-inferior to those of DG after eight weeks. The authors present the planned interim results of this study after one half of the projected enrolment was completed.

RESULTS

There were 95 subjects consented and entered into the SOC four-week screening phase of the trial and 56 were randomised into the treatment phase. At the planned interim analysis, there was a significantly lower cost per subject and significant improvement in patient quality of life for the subjects treated with MS compared with those managed with DG. However, there was not a statistically significant difference found during the analysis of the interim data between the two study groups for rate of wound healing or number of subjects with complete wound closure.

CONCLUSION

The data from this interim analysis show that MSMM and MSWM provide results for healing DFUs that are similar to the results obtained for DG at a significant quality of life and economic advantage.

DECLARATION OF INTEREST

The opinions expressed are those of the authors and not necessarily those of the Department of Veterans Affairs or the United States Government. T.W. Gilbert is employed as the Chief Science Officer and is a stockholder in ACell, Inc., which commercializes MatriStem Wound Matrix and MicroMatrix. None of the other authors have a conflict of interest to declare.

Comparison of in vivo remodeling of urinary bladder matrix and acellular dermal matrix in an ovine model

Aim: Biologically derived surgical graft materials come from a variety of sources with varying mechanical properties. This study aimed to evaluate the host response and mechanical performance of two extracellular matrix devices in a large animal preclinical model. Materials & methods: Bilateral defects were created in the fascia lata of sheep and repaired with either an acellular dermal matrix (ADM) or urinary bladder matrix (UBM). After 1 or 3 months, the repair site was explanted for histological and mechanical analysis. Results & conclusion: Despite pre-implantation mechanical differences, both UBM and ADM demonstrated similar mechanical performance at 3 months. However, UBM was completely remodeled into site-appropriate tissue by 3 months, while ADM showed limited tissue incorporation.

Retrorectus repair of incisional ventral hernia with urinary bladder matrix reinforcement in a long-term porcine model

Aim: Not all biologically derived materials elicit the same host response when used for reinforcement of ventral hernia repairs. This study aimed to evaluate the remodeling characteristics of the abdominal wall following reinforcement with urinary bladder matrix (UBM) in a large animal preclinical model of ventral hernia repair. Materials & methods: Midline defects in 36 Yucatan minipigs were reinforced with UBM-derived surgical devices using a classic Rives–Stoppa–Wantz approach, and compared with primary repair controls. After 3 or 8 months, the abdominal wall was explanted for histological and mechanical analysis. Results & conclusion: All UBM-derived surgical devices were completely resorbed within 8 months and facilitated deposition of vascularized, biomechanically functional connective tissue in the retrorectus plane, with no evidence of hernia formation.

Bridging the Gap: Engineered Porcine-derived Urinary Bladder Matrix Conduits as a Novel Scaffold for Peripheral Nerve Regeneration

PURPOSE

This study aims to compare engineered nerve conduits constructed from porcine-derived urinary bladder matrix (UBM) with the criterion-standard nerve autografts, for segmental loss peripheral nerve repairs.

METHODS

Forty-eight Sprague-Dawley rats were divided into 2 groups. All underwent a 10-mm sciatic nerve gap injury. This was repaired using either (1) reverse autograft-the 10-mm cut segment was oriented 180 degrees and used to coapt the proximal and distal stumps or (2) UBM conduit-the 10-mm nerve gap was bridged with UBM conduit. Behavior assessments such as sciatic function index and foot fault asymmetry scores were performed weekly. At 3- or 6-week time endpoints, the repaired nerves and bilateral gastrocnemius/soleus muscles were harvested from each animal. Nerves were evaluated using immunohistochemistry for motor and sensory axon staining and with diffusion tensor imaging. The net wet muscle weights were calculated to assess the degree of muscle atrophy.

RESULTS

The UBM group demonstrated significantly improved foot fault asymmetry scores at 2 and 4 weeks, whereas there was no difference in sciatic function index. The net muscle weights were similar between both groups. Motor axon counts proximal/inside/distal to the conduit/graft were similar between UBM conduits and reverse autografts, whereas sensory axon counts within and distal to the conduit were significantly higher than those of the autograft at 6 weeks. Sensory axonal regeneration seemed to be adherent to the inner surface of the UBM conduit, whereas it had a scattered appearance in autografts. Diffusion tensor imaging parameters between groups were similar.

CONCLUSIONS

Urinary bladder matrix conduits prove to be at least similar to nerve autografts for the repair of peripheral nerve injuries with a short gap. The matrix perhaps serves as a scaffold to augment sensory nerve growth.

CLINICAL RELEVANCE

In a clinical setting, UBM may eliminate the donor site morbidity and increased operative time associated with nerve autografting.

Extracellular Matrix Applications in the Treatment of Open Fractures With Complex Wounds and Large Soft Tissue Defects

Use of biologic scaffolds such as extracellular matrix (ECM) is a promising trend in the treatment of complex wounds in orthopedic trauma patients. In this clinical series we describe the technique of the successful application of porcine urinary bladder ECM products in the treatment of open fractures of the extremities with complex wounds and large soft tissue defects. The clinical outcomes demonstrated that even in challenging cases where local flap coverage of bone or neurovascular structures is not possible, sequential xenograft implantation allowed us to achieve a stable soft tissue envelope. Different forms of ECM products are easy to apply in the presence of orthopedic hardware. In certain wounds, complete closure can be achieved even without subsequent skin grafting. We recommend relatively earlier application of xenograft.

Intra-articular Injection of Urinary Bladder Matrix Reduces Osteoarthritis Development

Micronized porcine urinary bladder matrix (UBM) is an extracellular matrix biomaterial that has immunomodulatory and pro-regenerative properties. The objective of this study was to assess the ability of UBM to alter disease progression in a mouse model of post-traumatic osteoarthritis (OA). Ten-week-old wild-type C57BL/6 male mice underwent anterior cruciate ligament transection (ACLT) to induce OA. Two weeks after ACLT, UBM (50 mg/mL) or saline was injected into the mouse joint. At 4 and 8 weeks post-ACLT, cartilage integrity was assessed using OARSI scoring of histology, pain was evaluated, and joints were harvested for quantitative RT-PCR analysis of cartilage-specific and inflammatory gene expression. UBM-treated animals showed improved cartilage integrity at 4 and 8 weeks and reduced pain at 4 weeks compared to saline-injected mice. Animals injected with UBM expressed higher levels of genes encoding structural cartilage proteins, such as collagen2α1 and aggrecan, as well as anti-inflammatory cytokines, including interleukins 10 and 4. UBM decreased cartilage degeneration in the murine ACLT model of OA, which may be due to reduced inflammation in the joint and maintenance of high expression levels of proteoglycans.

Decellularized Matrix and Supplemental Fat Grafting Leads to Regeneration following Traumatic Fingertip Amputation

Decellularized scaffold materials are capable of regenerating missing tissues when utilized under appropriate conditions. Fat grafting also has reported advantages in revitalizing damaged tissue beds. This report details a case of traumatic fingertip amputation treated with a combination of decellularized materials in conjunction with fat grafting, resulting in a supple and functional reconstruction of the affected digit. After traumatic fingertip amputation, a patient was initially treated with decellularized porcine urinary bladder matrix powder. As a second stage, the healed tip scar tissue was reexcised, and a second application of powder was applied. As a third stage, the tip scar tissue was reexcised and a decellularized bilayer was sewn into the soft tissues of the debrided tip, resulting in an improved soft tissue envelope. As a final stage, the restored fingertip soft tissue envelope was fat grafted for additional bulk. Patient underwent treatment every other day with decellularized porcine urinary bladder matrix (powder and bilayer) and was able to reasonably regenerate the traumatic fingertip soft tissue envelope. This resulted in an envelope that was further enhanced with fat grafting. The resulting digit was sensate with maintained length, and possessed a more normal appearance than would be achieved by healing by secondary intention, or local flap or graft coverage. Decellularized materials can be utilized in conjunction with fat grafting to treat traumatic fingertip amputations in select patients. This combination approach is able to achieve a sensate fingertip and regain length lost in the affected digit. Additionally, we describe a novel technique that can be employed to maximize the amount of soft tissue regenerated by the decellularized products.

Changing paradigms in lower extremity reconstruction in war-related injuries

BACKGROUND

Ballistic high-energy trauma has substantially increased the severity of non-fatal extremity injuries incurred in modern warfare. Expedient medical care, refinement in surgical techniques, and soft tissue coverage have brought about a paradigm shift in the management of lower extremity wounds during the last decade with an increased emphasis on limb salvage.

METHODS

A literature-based study was conducted to analyze reconstructive modalities based on the location, depth, and severity of wounds, as well as mechanism of injury, concomitant vascular injuries and open fractures, choice of flap, timing of definitive reconstruction, and complications.

RESULTS

Extremity injuries account for over 60 % of injuries in the recent conflicts in Iraq and Afghanistan, with the majority secondary to explosive devices. The severity of these injuries is profound compared with civilian registries, and conventional injury scoring systems have failed to accurately predict outcomes in combat trauma. The mainstay of treatment is serial debridement, negative pressure therapy, fracture stabilization, and treatment of concomitant injuries by the forward medical teams with subsequent definitive reconstruction after transport to an advanced military treatment facility. Autologous reconstruction with free tissue transfer and pedicled flaps remains the primary modality for soft tissue coverage in limb salvage. Adjunct innovative modalities, such as external tissue expansion, dermal substitutes, and regenerative matrices, have also been successfully utilized for limb salvage.

CONCLUSION

Lower extremity injuries account for the vast majority of injuries in modern warzones. Explosive devices represent the most common mechanism of injury, with blast impact leading to extensive soft tissue injuries necessitating complex reconstructive strategies. Serial debridement, negative pressure therapy, and autologous reconstruction with free tissue transfer and pedicled flaps remain the mainstay of treatment in recent conflicts.

Porcine acellular lung matrix for wound healing and abdominal wall reconstruction: A pilot study

Surgical wound healing applications require bioprosthetics that promote cellular infiltration and vessel formation, metrics associated with increased mechanical strength and resistance to infection. Porcine acellular lung matrix is a novel tissue scaffold known to promote cell adherence while minimizing inflammatory reactions. In this study, we evaluate the capacity of porcine acellular lung matrix to sustain cellularization and neovascularization in a rat model of subcutaneous implantation and chronic hernia repair. We hypothesize that, compared to human acellular dermal matrix, porcine acellular lung matrix would promote greater cell infiltration and vessel formation. Following pneumonectomy, porcine lungs were processed and characterized histologically and by scanning electron microscopy to demonstrate efficacy of the decellularization. Using a rat model of subcutaneou implantation, porcine acellular lung matrices (n = 8) and human acellular dermal matrices (n = 8) were incubated in vivo for 6 weeks. To evaluate performance under mechanically stressed conditions, porcine acellular lung matrices (n = 7) and human acellular dermal matrices (n = 7) were implanted in a rat model of chronic ventral incisional hernia repair for 6 weeks. After 6 weeks, tissues were evaluated using hematoxylin and eosin and Masson’s trichrome staining to quantify cell infiltration and vessel formation. Porcine acellular lung matrices were shown to be successfully decellularized. Following subcutaneous implantation, macroscopic vessel formation was evident. Porcine acellular lung matrices demonstrated sufficient incorporation and showed no evidence of mechanical failure after ventral hernia repair. Porcine acellular lung matrices demonstrated significantly greater cellular density and vessel formation when compared to human acellular dermal matrix. Vessel sizes were similar across all groups. Cell infiltration and vessel formation are well-characterized metrics of incorporation associated with improved surgical outcomes. Porcine acellular lung matrices are a novel class of acellular tissue scaffold. The increased cell and vessel density may promote long-term improved incorporation and mechanical properties. These findings may be due to the native lung scaffold architecture guiding cell migration and vessel formation. Porcine acellular lung matrices represent a new alternative for surgical wound healing applications where increased cell density and vessel formation are sought.