The performance of silk scaffolds in a rat model of augmentation cystoplasty

Abstract

The diverse processing plasticity of silk-based biomaterials offers a versatile platform for understanding the impact of structural and mechanical matrix properties on bladder regenerative processes. Three distinct groups of 3-D matrices were fabricated from aqueous solutions of Bombyx mori silk fibroin either by a gel spinning technique (GS1 and GS2 groups) or a solvent-casting/salt-leaching method in combination with silk film casting (FF group). SEM analyses revealed that GS1 matrices consisted of smooth, compact multi-laminates of parallel-oriented silk fibers while GS2 scaffolds were composed of porous (pore size range, 5–50µm) lamellar-like sheets buttressed by a dense outer layer. Bi-layer FF scaffolds were comprised of porous foams (pore size, ~400 µm) fused on their external face with a homogenous, nonporous silk film. Silk groups and small intestinal submucosa (SIS) matrices were evaluated in a rat model of augmentation cystoplasty for 10 weeks of implantation and compared to cystotomy controls. Gross tissue evaluations revealed the presence of intra-luminal stones in all experimental groups. The incidence and size of urinary calculi was the highest in animals implanted with gel spun silk matrices and SIS with frequencies ≥57% and stone diameters of 3–4mm. In contrast, rats augmented with FF scaffolds displayed substantially lower rates (20%) and stone size (2mm), similar to the levels observed in controls (13%, 2mm). Histological (hematoxylin and eosin, Masson's trichrome) and immunohistochemical (IHC) analyses showed comparable extents of smooth muscle regeneration and contractile protein (α-smooth muscle actin and SM22α) expression within defect sites supported by all matrix groups similar to controls. Parallel evaluations demonstrated the formation of a transitional, multi-layered urothelium with prominent uroplakin and p63 protein expression in all experimental groups. De novo innervation and vascularization processes were evident in all regenerated tissues indicated by Fox3-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. In comparison to other biomaterial groups, cystometric analyses at 10 weeks post-op revealed that animals implanted with the FF matrix configuration displayed superior urodynamic characteristics including compliance, functional capacity, as well as spontaneous non voiding contractions consistent with control levels. Our data demonstrate that variations in scaffold processing techniques can influence the in vivo functional performance of silk matrices in bladder reconstructive procedures.

The use of bi-layer silk fibroin scaffolds and small intestinal submucosa matrices to support bladder tissue regeneration in a rat model of spinal cord injury

“…Aqueous SF solutions were prepared from B. mori silkworm cocoons using published procedures [25] and utilized to construct a bi-layer SF matrix using methods previously described [24]. Briefly, an SF solution (8% wt/vol) was poured into a rectangular casting vessel and dried in a laminar flow hood at room temperature for 48 h to achieve formation of an SF film.…”

“…Bi-layer silk fibroin (SF) scaffolds derived from Bombyx mori silkworm cocoons as well as porcine small intestinal submucosa have been previously shown to promote defect consolidation and mediate functional voiding in non-diseased animal models of bladder augmentation [18–24]. These matrices, therefore, represent potential candidates for neurogenic bladder repair; however their performance in the setting of neuropathogenic disease is currently unknown.…”

Genitourinary System

“…Biomaterials used for scaffolding include both synthetic and naturally derived materials, and they are designed to provide structural support to maintain the overall shape of bladder and a favorable microenvironment for cell growth. Synthetic biomaterials such as polylactic-co-glycolic acid (PLGA) have been evaluated as scaffolds for bladder applications, and their suitability for supporting cells has been excellent in study results to date [42,43]. PLGA coated with collagen or fibrin has shown biocompatibility and supported cell growth and differentiation.…”

<I>In Vitro</I> and <I>In Vivo</I> Evaluation of Pectin/Copper Exchanged Faujasite Composite Membranes

“…3 The polymeric suspension is poured onto molds and once the solvent gets evaporated, a homogenous membrane of composite material consisting of particles embedded in a polymer matrix will be formed, which can be gently peeled off from the surface of molds and stored in desiccator. 4 Composite membranes embedded with micro and nanoparticles are gaining lot of importance in the biomedical field. Liu et al, have reported increased proliferation and differentiation of pre-osteoblasts on nanostructured polypyrrole membrane.…”