Local FK506 implants in non-human primates to prevent early acute rejection in vascularized composite allografts.

BACKGROUND: Previous vascularized composite allograft (VCA) studies from our laboratory have shown that topical FK506 delivery in non-human primates (NHPs) was limited by inadequate dermal penetration and rejection persisted. Herein, we report the first utilization of FK506 via subcutaneously implanted discs to mitigate VCA rejection in NHPs. METHODS: Full major histocompatibility complex (MHC)-mismatched NHP pairs underwent partial-face VCA and FK506 disc implantation along the suture line. All allotransplants were maintained post-operatively for two months on the FK506 discs, methylprednisolone, mycophenolate mofetil, and supplemented with intramuscular FK506 if necessary. Group 1 (n=4) was used for optimization of the implant, while Group 2 (n=3) underwent delayed bone marrow transplantation (DBMT) after two months. VCA skin biopsies and peripheral blood samples were obtained for serial assessment of rejection and mixed chimerism by histopathology and flow cytometry respectively. RESULTS: In Group 1, two technical failures occurred. Of the remaining two NHPs, one developed supratherapeutic levels of FK506 (50-120 ng/mL) and had to be euthanized on postoperative day (POD) 12. Reformulation of the implant resulted in stable FK506 levels (20-30 ng/mL) up to POD12 when further intramuscular (IM) FK506 injections were necessitated. In Group 2, two NHPs survived to undergo conditioning and one successfully developed chimerism at 2-3 weeks post-DBMT (96-97% granulocytes and 7-11% lymphocytes of recipient-origin). However, all three NHPs had to be terminated from study at POD64, 77 and 86 due to underlying post-transplant lymphoproliferative disorder. All VCAs remained rejection-free up to study endpoint otherwise. CONCLUSIONS: This study shows preliminary results of local FK506 implants in potentially mitigating VCA acute rejection for tolerance protocols based on mixed chimerism approach.

A step toward engineering thick tissues: Distributing microfibers within 3D printed frames.

Microfiber mats for tissue engineering scaffolds support cell growth, but are limited by poor cell infiltration and nutrient transport. Three-dimensional printing, specifically fused deposition modeling (FDM), can rapidly produce customized constructs, but macroscopic porosity resulting from low resolution reduces cell seeding efficiency and prevents the formation of continuous cell networks. Here we describe the fabrication of hierarchical scaffolds that integrate a fibrous microenvironment with the open macropore structure of FDM. Biodegradable tyrosine-derived polycarbonate microfibers were airbrushed iteratively between layers of 3D printed support structure following optimization. Confocal imaging showed layers of airbrushed fiber mats supported human dermal fibroblast growth and extracellular matrix development throughout the scaffold. When implanted subcutaneously, hierarchical scaffolds facilitated greater cell infiltration and tissue formation than airbrushed fiber mats. Fibronectin matrix assembled in vitro throughout the hierarchical scaffold survived decellularization and provided a hybrid substrate for recellularization with mesenchymal stromal cells. These results demonstrate that by combining FDM and airbrushing techniques we can engineer customizable hierarchical scaffolds for thick tissues that support increased cell growth and infiltration.

Designing Biomaterials for 3D Printing.

Three-dimensional (3D) printing is becoming an increasingly common technique to fabricate scaffolds and devices for tissue engineering applications. This is due to the potential of 3D printing to provide patient-specific designs, high structural complexity, rapid on-demand fabrication at a low-cost. One of the major bottlenecks that limits the widespread acceptance of 3D printing in biomanufacturing is the lack of diversity in "biomaterial inks". Printability of a biomaterial is determined by the printing technique. Although a wide range of biomaterial inks including polymers, ceramics, hydrogels and composites have been developed, the field is still struggling with processing of these materials into self-supporting devices with tunable mechanics, degradation, and bioactivity. This review aims to highlight the past and recent advances in biomaterial ink development and design considerations moving forward. A brief overview of 3D printing technologies focusing on ink design parameters is also included.

Phosphorus reclamation through hydrothermal carbonization of animal manures.

Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from large farms was investigated as a scenario for the reclamation of phosphate for agricultural use and mitigation of the negative environmental impact of phosphate pollution. Hydrothermal reaction conditions were identified for poultry, swine, and cattle manures that resulted in hydrochar yields of 50-60% for all three manures, and >90% of the total phosphorus present in these systems was contained in the hydrochars as precipitated phosphate salts. Phosphate recovery was achieved in yields of 80-90% by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Phosphate recovery was achieved in yields of 81-87% based on starting manures by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Swine and cattle manures produced hydrochars with combustion energy contents comparable to those of high-end sub-bituminous coals.