In vivo growth of a bioengineered internal anal sphincter: comparison of growth factors for optimization of growth and survival

Abstract

Purpose-Our laboratory has developed and implanted a novel bioengineered internal anal sphincter (IAS) to treat anal incontinence. Fibroblast growth factor-2 (FGF-2) has been used in mice; however, the optimal growth factor for successful IAS implantation is unclear. This study compares several growth factors in order to optimize IAS viability and functionality.Methods-Bioengineered IAS rings were implanted subcutaneously into the dorsum of wildtype C57Bl/6 mice, with an osmotic pump dispensing FGF-2, vascular endothelial growth factor (VEGF), or platelet-derived growth factor (PDGF) (n = 4 per group). Control mice received IAS implants but no growth factor. The IAS was harvested approximately 25 days post-implantation. Tissue was subjected to physiologic testing, then histologically analyzed. Muscle phenotype was confirmed by immunofluorescence.Results-All implants supplemented with growth factors maintained smooth muscle phenotype. Histological scores, blood vessel density and muscle fiber thickness were all markedly better with growth factors. Neovascularization was comparable between the three growth factors. Basal tonic force of the constructs was highest with VEGF or PDGF.Conclusion-All growth factors demonstrated excellent performance. As our ultimate goal is clinical implantation, our strong results with PDGF, a drug approved for use in the United States and the European Union, pave the way for translating bioengineered IAS implantation to the clinical realm.

The effect of scaffold macroporosity on angiogenesis and cell survival in tissue-engineered smooth muscle

“…Even the strongest tissue-engineered muscles are much weaker than normal muscle, suggesting the need for thicker scaffolds, which will further increase the need for rapid vascular infiltration and better mimic of the multi-layered intestine [1,33,40,41]. Furthermore, survival and maturity of intestinal smooth muscle cells (SMCs) in vivo is accompanied by angiogenesis [42,43], suggesting that a pro-angiogenic biomaterial may enable the development of a mature smooth muscle.…”

Cell and organ bioengineering technology as applied to gastrointestinal diseases

“…Bioengineered IAS has been successfully implanted into mice 123. Isolated sphincter smooth muscles were grown into rings (see figure 5).…”

“…The enteric neurons formed synapses with the smooth muscle cells. This IAS tissue with neural innervation also responded to stimulation with neurotransmitters with the appropriate physiological responses 123. IAS also has been bioengineered using human anal sphincter smooth cells 136.…”

Stem cell transplantation in neurodegenerative disorders of the gastrointestinal tract: future or fiction?

“…ENSC can also be delivered intraperitoneally and may be able to home in to the gut by as yet unidentified cues 87. Recent studies show that transplantation of ENSC embedded in artificial or bioengineered materials, scaffolds or tissues can also offer viable alternatives to injection of cells into the diseased tissue 88. Finally, intravascular delivery of NSC, which has been tried in the treatment of CNS disorders, is also a feasible route of delivery for the treatment of ENS disorders 89.…”