Outcomes of adult urethroplasty with commercially available acellular matrix

Partial decellularization eliminates immunogenicity in tracheal allografts

There is currently no suitable autologous tissue to bridge large tracheal defects. As a result, no standard of care exists for long-segment tracheal reconstruction. Tissue engineering has the potential to create a scaffold from allografts or xenografts that can support neotissue regeneration identical to the native trachea. Recent advances in tissue engineering have led to the idea of partial decellularization that allows for the creation of tracheal scaffolds that supports tracheal epithelial formation while preserving mechanical properties. However, the ability of partial decellularization to eliminate graft immunogenicity remains unknown, and understanding the immunogenic properties of partially decellularized tracheal grafts (PDTG) is a critical step toward clinical translation. Here, we determined that tracheal allograft immunogenicity results in epithelial cell sloughing and replacement with dysplastic columnar epithelium and that partial decellularization creates grafts that are able to support an epithelium without histologic signs of rejection. Moreover, allograft implantation elicits CD8+ T-cell infiltration, a mediator of rejection, while PDTG did not. Hence, we establish that partial decellularization eliminates allograft immunogenicity while creating a scaffold for implantation that can support spatially appropriate airway regeneration.

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.

Decellularized xenografts in regenerative medicine: From processing to clinical application

Decellularized xenografts are an inherent component of regenerative medicine. Their preserved structure, mechanical integrity and biofunctional composition have well established them in reparative medicine for a diverse range of clinical indications. Nonetheless, their performance is highly influenced by their source (ie species, age, tissue) and processing (ie decellularization, crosslinking, sterilization and preservation), which govern their final characteristics and determine their success or failure for a specific clinical target. In this review, we provide an overview of the different sources and processing methods used in decellularized xenografts fabrication and discuss their effect on the clinical performance of commercially available decellularized xenografts.

Bioscaffold-Induced Brain Tissue Regeneration

Brain tissue lost after a stroke is not regenerated, although a repair response associated with neurogenesis does occur. A failure to regenerate functional brain tissue is not caused by the lack of available neural cells, but rather the absence of structural support to permit a repopulation of the lesion cavity. Inductive bioscaffolds can provide this support and promote the invasion of host cells into the tissue void. The putative mechanisms of bioscaffold degradation and its pivotal role to permit invasion of neural cells are reviewed and discussed in comparison to peripheral wound healing. Key differences between regenerating and non-regenerating tissues are contrasted in an evolutionary context, with a special focus on the neurogenic response as a conditio sine qua non for brain regeneration. The pivotal role of the immune system in biodegradation and the formation of a neovasculature are contextualized with regeneration of peripheral soft tissues. The application of rehabilitation to integrate newly forming brain tissue is suggested as necessary to develop functional tissue that can alleviate behavioral impairments. Pertinent aspects of brain tissue development are considered to provide guidance to produce a metabolically and functionally integrated de novo tissue. Although little is currently known about mechanisms involved in brain tissue regeneration, this review outlines the various components and their interplay to provide a framework for ongoing and future studies. It is envisaged that a better understanding of the mechanisms involved in brain tissue regeneration will improve the design of biomaterials and the methods used for implantation, as well as rehabilitation strategies that support the restoration of behavioral functions.

A roadmap for promoting endogenous in situ tissue restoration using inductive bioscaffolds after acute brain injury

The regeneration of brain tissue remains one of the greatest unsolved challenges in medicine and by many is considered unfeasible. Indeed, the adult mammalian brain does not regenerate tissue, but there is ongoing endogenous neurogenesis, which is upregulated after injury and contributes to tissue repair. This endogenous repair response is a conditio sine que non for tissue regeneration. However, scarring around the lesion core and cavitation provide unfavorable conditions for tissue regeneration in the brain. Based on the success of using extracellular matrix (ECM)-based bioscaffolds in peripheral soft tissue regeneration, it is plausible that the provision of an inductive ECM-based hydrogel inside the volumetric tissue loss can attract neural cells and create a de novo viable tissue. Following perturbation theory of these successes in peripheral tissues, we here propose 9 perturbation parts (i.e. requirements) that can be solved independently to create an integrated series to build a functional and integrated de novo neural tissue. Necessities for tissue formation, anatomical and functional connectivity are further discussed to provide a new substrate to support the improvement of behavioral impairments after acute brain injury. We also consider potential parallel developments of this tissue engineering effort that can support therapeutic benefits in the absence of de novo tissue formation (e.g. structural support to veterate brain tissue). It is envisaged that eventually top-down inductive "natural" bioscaffolds composed of decellularized tissues (i.e. ECM) will be replaced by bottom-up synthetic designer hydrogels that will provide very defined structural and signaling properties, potentially even opening up opportunities we currently do not envisage using natural materials.