Bioengineering and regeneration of gastrointestinal tissue: where are we now and what comes next?

Changes in the Gut Microbiota Composition during Implantation of Composite Scaffolds Based on Poly(3-hydroxybutyrate) and Alginate on the Large-Intestine Wall

The development of biopolymer scaffolds for intestine regeneration is one of the most actively developing areas in tissue engineering. However, intestinal regenerative processes after scaffold implantation depend on the activity of the intestinal microbial community that is in close symbiosis with intestinal epithelial cells. In this work, we study the impact of different scaffolds based on biocompatible poly(3-hydroxybutyrate) (PHB) and alginate (ALG) as well as PHB/ALG scaffolds seeded with probiotic bacteria on the composition of gut microbiota of Wistar rats. Implantation of PHB/ALG scaffolds on the large-intestine wall to close its injury showed that alpha diversity of the gut microbiota was not reduced in rats implanted with different PHB/ALG scaffolds except for the PHB/ALG scaffolds with the inclusion of Lactobacillus spheres (PHB/ALG-L). The composition of the gut microbiota of rats implanted with PHB/ALG scaffolds with probiotic bacteria or in simultaneous use of an antimicrobial agent (PHB/ALG-AB) differed significantly from other experimental groups. All rats with implanted scaffolds demonstrated shifts in the composition of the gut microbiota by individual operational taxonomic units. The PHB/ALG-AB construct led to increased abundance of butyrate-producing bacteria: Ileibacterium sp. dominated in rats with implanted PHB/ALG-L and Lactobacillus sp. and Bifidobacterium sp. dominated in the control group. In addition, the PHB/ALG scaffolds had a favourable effect on the growth of commensal bacteria. Thus, the effect of implantation of the PHB/ALG scaffold compared to other scaffolds on the composition of the gut microbiota was closest to the control variant, which may demonstrate the biocompatibility of this device with the microbiota.

Surgical Treatment of Short Bowel Syndrome—The Past, the Present and the Future, a Descriptive Review of the Literature

Short bowel syndrome (SBS) is a devastating disorder with both short- and long-term implications for patients. Unfortunately, the prevalence of SBS has doubled over the past 40 years. Broadly speaking, the etiology of SBS can be categorized as congenital or secondary, the latter typically due to extensive small bowel resection following diseases of the small intestine, e.g., necrotizing enterocolitis, Hirschsprung’s disease or intestinal atresia. As of yet, no cure exists, thus, conservative treatment, primarily parenteral nutrition (PN), is the first-line therapy. In some cases, weaning from PN is not possible and operative therapy is required. The invention of the longitudinal intestinal lengthening and tailoring (LILT or Bianchi) procedure in 1980 was a major step forward in patient care and spawned further techniques that continue to improve lives for patients with severe SBS (e.g., double barrel enteroplasty, serial transverse enteroplasty, etc.). With this review, we aim to provide an overview of the clinical implications of SBS, common conservative therapies and the development of operative techniques over the past six decades. We also provide a short outlook on the future of operative techniques, specifically with respect to regenerative medicine.

A systematic review of translation and experimental studies on internal anal sphincter for fecal incontinence

The complexity in the molecular mechanism of the internal anal sphincter (IAS) limits preclinical or clinical outcomes of fecal incontinence (FI) treatment. So far, there are no systematic reviews of IAS translation and experimental studies that have been reported. This systematic review aims to provide a comprehensive understanding of IAS critical role in FI. Previous studies revealed the key pathway for basal tone and relaxation of IAS in different properties as follows; calcium, Rho-associated, coiled-coil containing serine/threonine kinase, aging-associated IAS dysfunction, oxidative stress, renin-angiotensin-aldosterone, cyclooxygenase, and inhibitory neurotransmitters. Previous studies have reported improved functional outcomes of cellular treatment for regeneration of dysfunctional IAS, using various stem cells, but did not demonstrate the interrelationship between those results and basal tone or relaxation-related molecular pathway of IAS. Furthermore, these results have lower specificity for IAS-incontinence due to the included external anal sphincter or nerve injury regardless of the cell type. An acellular approach using bioengineered IAS showed a physiologic response of basal tone and relaxation response similar to human IAS. However, in both cellular and acellular approaches, the lack of human IAS data still hampers clinical application. Therefore, the IAS regeneration presents more challenges and warrants more advances.

Tissue engineering of the gastrointestinal tract: the historic path to translation

The gastrointestinal (GI) tract is imperative for multiple functions including digestion, nutrient absorption, and timely waste disposal. The central feature of the gut is peristalsis, intestinal motility, which facilitates all of its functions. Disruptions in GI motility lead to sub-optimal GI function, resulting in a lower quality of life in many functional GI disorders. Over the last two decades, tissue engineering research directed towards the intestine has progressed rapidly due to advances in cell and stem-cell biology, integrative physiology, bioengineering and biomaterials. Newer biomedical tools (including optical tools, machine learning, and nuanced regenerative engineering approaches) have expanded our understanding of the complex cellular communication within the GI tract that lead to its orchestrated physiological function. Bioengineering therefore can be utilized towards several translational aspects: (i) regenerative medicine to remedy/restore GI physiological function; (ii) in vitro model building to mimic the complex physiology for drug and pharmacology testing; (iii) tool development to continue to unravel multi-cell communication networks to integrate cell and organ-level physiology. Despite the significant strides made historically in GI tissue engineering, fundamental challenges remain including the quest for identifying autologous human cell sources, enhanced scaffolding biomaterials to increase biocompatibility while matching viscoelastic properties of the underlying tissue, and overall biomanufacturing. This review provides historic perspectives for how bioengineering has advanced over time, highlights newer advances in bioengineering strategies, and provides a realistic perspective on the path to translation.