Biostable electrospun microfibrous scaffolds mitigate hypertrophic scar contraction in an immune-competent murine model.

Burn injuries in the United States account for over one million hospital admissions per year, with treatment estimated at four billion dollars. Of severe burn patients, 30-90% will develop hypertrophic scars (HSc). In this study, we evaluate the impact of an elastomeric, randomly-oriented biostable polyurethane (PU) scaffold on HSc-related outcomes. In vitro, fibroblast-seeded PU scaffolds contracted significantly less and demonstrated fewer αSMA(+) myofibroblasts compared to fibroblast-seeded collagen lattices. In a murine HSc model, collagen coated PU (ccPU) scaffolds significantly reduced HSc contraction as compared to untreated control wounds and wounds treated with the clinical standard of care. Our data suggest that electrospun ccPU scaffolds meet the requirements to reduce HSc contraction including reduction of in vitro HSc related outcomes, diminished scar stiffness, and reduced scar contraction. While clinical dogma suggests treating severe burn patients with rapidly biodegrading skin equivalents, our data suggest that a more long-term scaffold may possess merit in reducing HSc. STATEMENT OF SIGNIFICANCE: In severe burns treated with skin grafting, between 30% and 90% of patients develop hypertrophic scars (HSc). There are no therapies to prevent HSc, and treatments are marginally effective. This work is the first example we are aware of which studies the impact of a permanent electrospun elastomer on HSc contraction in a murine model that mimics the human condition. Collagen coated polyurethane scaffolds decrease αSMA+ myofibroblast formation in vitro, prevent stiffening of scar tissue, and mitigate HSc contraction. Unlike current standards of care, electrospun, polyurethane scaffolds do not lose architecture over time. We propose that the future bioengineering strategy of mitigating HSc contraction should consider a long-term elastomeric matrix which persists within the wound bed throughout the remodeling phase of repair.

Mitigation of hypertrophic scar contraction via an elastomeric biodegradable scaffold.

Hypertrophic scar (HSc) occurs in 40-70% of patients treated for third degree burn injuries. Current burn therapies rely upon the use of bioengineered skin equivalents (BSEs), which assist in wound healing but do not prevent HSc contraction. HSc contraction leads to formation of a fixed, inelastic skin deformity. We propose that BSEs should maintain their architecture in the wound bed throughout the remodeling phase of repair to prevent HSc contraction. In this work we study a degradable, elastomeric, randomly oriented, electrospun micro-fibrous scaffold fabricated from the copolymer poly(l-lactide-co-ε-caprolactone) (PLCL). PLCL scaffolds displayed appropriate elastomeric and tensile characteristics for implantation beneath a human skin graft. In vitro analysis using human dermal fibroblasts demonstrated that PLCL scaffolds decreased myofibroblast formation as compared to an in vitro HSc contraction model. Using a validated immune-competent murine HSc contraction model, we found that HSc contraction was significantly greater in animals treated with standard of care, Integra, as compared to those treated with collagen coated-PLCL (ccPLCL) scaffolds. Finally, wounds treated with ccPLCL were significantly less stiff than control wounds at d30 in vivo. Together, these data suggest that scaffolds which persist throughout the remodeling phase of repair may represent a clinically translatable method to prevent HSc contraction.

The effect of substrate topography on direct reprogramming of fibroblasts to induced neurons.

Cellular reprogramming holds tremendous potential for cell therapy and regenerative medicine. Recently, fibroblasts have been directly converted into induced neurons (iNs) by overexpression of the neuronal transcription factors Ascl1, Brn2 and Myt1L. Hypothesizing that cell-topography interactions could influence the fibroblast-to-neuron reprogramming process, we investigated the effects of various topographies on iNs produced by direct reprogramming. Final iN purity and conversion efficiency were increased on micrograting substrates. Neurite branching was increased on microposts and decreased on microgratings, with a simplified dendritic arbor characterized by the reduction of MAP2(+) neurites. Neurite outgrowth increased significantly on various topographies. DNA microarray analysis detected 20 differentially expressed genes in iNs reprogrammed on smooth versus microgratings, and quantitative PCR (qPCR) confirmed the upregulation of Vip and downregulation of Thy1 and Bmp5 on microgratings. Electrophysiology and calcium imaging verified the functionality of these iNs. This study demonstrates the potential of applying topographical cues to optimize cellular reprogramming.