Skin substitutes with noncultured autologous skin cell suspension heal porcine full-thickness wounds in a one-stage procedure.

Clinical application of skin substitute is typically a two-stage procedure with application of skin substitute matrix to the wound followed by engraftment of a split-thickness skin graft (STSG). This two-stage procedure requires multiple interventions, increasing the time until the wound is epithelialised. In this study, the feasibility of a one-stage procedure by combining bioengineered collagen-chondroitin-6-sulfate (DS1) or decellularised fetal bovine skin substitute (DS2) with autologous skin cell suspension (ASCS) in a porcine full-thickness wound healing model was evaluated. Twelve full-thickness excisional wounds on the backs of pigs received one of six different treatments: empty; ASCS; DS1 with or without ASCS; DS2 with or without ASCS. The ASCS was prepared using a point-of-care device and was seeded onto the bottom side of DS1, DS2, and empty wounds at 80 000 cells/cm2 . Wound measurements and photographs were taken on days 0, 9, 14, 21, 28, 35, and 42 post-wounding. Histological analysis was performed on samples obtained on days 9, 14, 28, and 42. Wounds in the empty group or with ASCS alone showed increased wound contraction, fibrosis, and myofibroblast density compared with other treatment groups. The addition of ASCS to DS1 or DS2 resulted in a marked increase in re-epithelialisation of wounds at 14 days, from 15 ± 11% to 71 ± 20% (DS1 vs DS1 + ASCS) or 28 ± 14% to 77 ± 26 (DS2 vs DS2 + ASCS) despite different mechanisms of tissue regeneration employed by the DS used. These results suggest that this approach may be a viable one-stage treatment in clinical practice.

Sequential gelation of tyramine-substituted hyaluronic acid hydrogels enhances mechanical integrity and cell viability.

Tyramine-substituted hyaluronic acid (HA-Tyr) hydrogels formed by the oxidative coupling reaction of hydrogen peroxide (H2O2) and horseradish peroxidase (HRP) have been used for cellular encapsulation and protein delivery. Crosslinking density and gelation time can be tuned by altering the H2O2 and HRP concentrations. Previous studies using HA-Tyr constructs report significant mechanical degradation after 21 days of culture. In this work, exogenous supplementation of HRP after initial gelation resulted in superior mechanical properties in acellular hydrogels and improved viability and proliferation in cell-laden constructs. Swelling of the acellular hydrogels was prevented in the samples receiving exogenous HRP. Monolayer studies showed no negative effect of relevant HRP concentrations on the viability of human adipose-derived stem cells (hASCs) and improved the viability of hASCs cultured with HRP and H2O2 compared to H2O2 alone. Taken together, this study demonstrates that HA-Tyr hydrogel properties could be modified by exogenous supplementation of HRP to tune scaffold degradation and improve cell viability by mitigating the negative effects of oxidative stress.

Hybrid hyaluronic acid hydrogel/poly(ɛ-caprolactone) scaffold provides mechanically favorable platform for cartilage tissue engineering studies.

Hybrid scaffolds for cartilage tissue engineering provide the potential for high stiffness properties in tension and compression while exhibiting the viscoelastic response found in hydrogels and native cartilage tissue. We investigate the impact of a hybrid scaffold fabricated from a hyaluronic acid (HA)-based hydrogel combined with porous poly(ε-caprolactone) (PCL) material formed by a particulate leaching method to study dedifferentiated chondrocyte response. The material properties of the hybrid scaffold showed mean Young's moduli in tension which were similar to human articular cartilage but not statistically different between the hybrid and porous PCL scaffolds at 2.02 and 2.07 MPa, respectively. For both the hybrid and porous PCL control scaffolds in compression at low loading frequencies (<1 Hz) and 10% strain peak amplitude the Young's moduli are not statistically distinct. However, at frequencies in the range of normal human gait from 1 to2 Hz, hybrid scaffolds exhibit significantly (p < 0.01) increased loss moduli indicating additional contribution of the viscous phase to stiffness. Dedifferentiated chondrocytes seeded onto the scaffolds exhibited a rounded morphology in hybrid scaffolds however ECM protein expression levels of collagen type I, collagen type II, and aggrecan are not different from the PCL control scaffolds. These results provide a model platform to investigate cell response to mechanical and chemical cues in a hybrid scaffold system with mechanical properties similar to human cartilage that does not contribute to differentiation in order to identify the appropriate design and development parameters to promote formation of extracellular matrix and investigate chondrocyte scaffold interactions.