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Barmpatsalou V, Rodler A, Jacobson M, Karlsson EML, Pedersen BL, Bergström CAS. Development and validation of a porcine artificial colonic mucus model reflecting the properties of native colonic mucus in pigs. Eur J Pharm Sci 2023; 181:106361. [PMID: 36528165 DOI: 10.1016/j.ejps.2022.106361] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/12/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022]
Abstract
Colonic mucus plays a key role in colonic drug absorption. Mucus permeation assays could therefore provide useful insights and support rational formulation development in the early stages of drug development. However, the collection of native colonic mucus from animal sources is labor-intensive, does not yield amounts that allow for routine experimentation, and raises ethical concerns. In the present study, we developed an in vitro porcine artificial colonic mucus model based on the characterization of native colonic mucus. The structural properties of the artificial colonic mucus were validated against the native secretion for their ability to capture key diffusion patterns of macromolecules in native mucus. Moreover, the artificial colonic mucus could be stored under common laboratory conditions, without compromising its barrier properties. In conclusion, the porcine artificial colonic mucus model can be considered a biorelevant way to study the diffusion behavior of drug candidates in colonic mucus. It is a cost-efficient screening tool easily incorporated into the early stages of drug development and it contributes to the implementation of the 3Rs (refinement, reduction, and replacement of animals) in the drug development process.
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Affiliation(s)
- Vicky Barmpatsalou
- The Swedish Drug Delivery Center, Department of Pharmacy, Uppsala University, Box 580, SE-751 23, Uppsala, Sweden
| | - Agnes Rodler
- The Swedish Drug Delivery Center, Department of Pharmacy, Uppsala University, Box 580, SE-751 23, Uppsala, Sweden; The Swedish Drug Delivery Center, Department of Medicinal Chemistry, Uppsala University, Box 574, SE-751 23, Uppsala, Sweden
| | - Magdalena Jacobson
- Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Sciences, Swedish University of Agricultural Sciences, Box 7054, SE-750 07, Uppsala, Sweden
| | - Eva Marie-Louise Karlsson
- Oral Product Development, Pharmaceutical Technology & Development, Operations, AstraZeneca, Gothenburg, Sweden
| | - Betty Lomstein Pedersen
- Product Development & Drug Delivery, Global Pharmaceutical R&D, Ferring Pharmaceuticals A/S, Amager Strandvej 405, Kastrup 2770, Denmark
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2
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Advances in Oral Drug Delivery Systems: Challenges and Opportunities. Pharmaceutics 2023; 15:pharmaceutics15020484. [PMID: 36839807 PMCID: PMC9960885 DOI: 10.3390/pharmaceutics15020484] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/20/2023] [Accepted: 01/25/2023] [Indexed: 02/05/2023] Open
Abstract
The oral route is the most preferred route for systemic and local drug delivery. However, the oral drug delivery system faces the harsh physiological and physicochemical environment of the gastrointestinal tract, which limits the bioavailability and targeted design of oral drug delivery system. Innovative pharmaceutical approaches including nanoparticulate formulations, biomimetic drug formulations, and microfabricated devices have been explored to optimize drug targeting and bioavailability. In this review, the anatomical factors, biochemical factors, and physiology factors that influence delivering drug via oral route are discussed and recent advance in conventional and novel oral drug delivery approaches for improving drug bioavailability and targeting ability are highlighted. We also address the challenges and opportunities of oral drug delivery systems in future.
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3
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Wu H, Huang R, Fan J, Luo N, Yang X. Low potassium disrupt intestinal barrier and result in bacterial translocation. Lab Invest 2022; 20:309. [PMID: 35794599 PMCID: PMC9258207 DOI: 10.1186/s12967-022-03499-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/24/2022] [Indexed: 11/10/2022]
Abstract
Abstract
Background
Bacterial translocation was observed in critical illness and patients with chronic diseases such as liver cirrhosis and chronic kidney disease (CKD). Hypokalemia is a common complication in these diseases. Whether low potassium diet may increase intestinal permeability and result in bacterial translocation lack of evidence. The present study was aimed to investigate the potential effects of LK on intestinal permeability.
Methods
Grade 8-week-old male Bal B/C mice were randomly placed either on a normal potassium (NK) mouse chow or a low potassium (LK) diet for 28 days. Intestinal permeability and expression of tight junction proteins were compared between the two groups.
Results
Compared with the NK group, the mice in LK group had significantly lower serum potassium level, increased levels of plasmas endotoxin and plasma d-lactate. The bacterial translocation was higher and in occurred mainly in mesenteric lymph nodes (MLN), liver and spleen. The pathologic change of small intestine was obvious with thinner villus lamina propria, shorter crypt depth and thinner intestinal wall. Slight increases in the expression of proteins and mRNA levels of both claudin-1 and claudin-2 were observed in LK group.
Conclusions
Low potassium diet could increase intestinal permeability and thereby lead to bacterial translocation, which was suspected to result from impaired intestinal epithelial barrier and biological barrier.
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4
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Zhang Y, Wu P, Jeantet R, Dupont D, Delaplace G, Chen XD, Xiao J. How motility can enhance mass transfer and absorption in the duodenum: Taking the structure of the villi into account. Chem Eng Sci 2020. [DOI: 10.1016/j.ces.2019.115406] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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5
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Lentle RG. Deconstructing the physical processes of digestion: reductionist approaches may provide greater understanding. Food Funct 2018; 9:4069-4084. [PMID: 30011345 DOI: 10.1039/c8fo00722e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
I provide a broad overview of the physical factors that govern intestinal digestion i.e. the admixture of food particles in digesta with secreted enzymes and the subsequent mass transfer of liberated nutrients from the surfaces of particles to the gut wall, with a view to outlining the quantitative work that is required to determine the relative importance of these factors in the digestion of particular foods. I first discuss what is known of the mechanical forces generated by contraction of the walls of the various segments of the gut and the level of diffusive, and advective mixing that it generates within the lumen. I then discuss the particular physical effects that may limit the digestion of solid, physically and/or chemically homogenous and heterogeneous food particles, notably capillarity, porosity, poro-elastic flow and compaction and their likely effects on diffusive and convective mass transfer at particulate surfaces. Similarly, I discuss mucins and morphology on mass transfer of nutrients to the gut wall i.e. the mucosa.
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Affiliation(s)
- R G Lentle
- Digestive Biomechanics Group, College of Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
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6
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Waigh TA. Advances in the microrheology of complex fluids. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:074601. [PMID: 27245584 DOI: 10.1088/0034-4885/79/7/074601] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
New developments in the microrheology of complex fluids are considered. Firstly the requirements for a simple modern particle tracking microrheology experiment are introduced, the error analysis methods associated with it and the mathematical techniques required to calculate the linear viscoelasticity. Progress in microrheology instrumentation is then described with respect to detectors, light sources, colloidal probes, magnetic tweezers, optical tweezers, diffusing wave spectroscopy, optical coherence tomography, fluorescence correlation spectroscopy, elastic- and quasi-elastic scattering techniques, 3D tracking, single molecule methods, modern microscopy methods and microfluidics. New theoretical techniques are also reviewed such as Bayesian analysis, oversampling, inversion techniques, alternative statistical tools for tracks (angular correlations, first passage probabilities, the kurtosis, motor protein step segmentation etc), issues in micro/macro rheological agreement and two particle methodologies. Applications where microrheology has begun to make some impact are also considered including semi-flexible polymers, gels, microorganism biofilms, intracellular methods, high frequency viscoelasticity, comb polymers, active motile fluids, blood clots, colloids, granular materials, polymers, liquid crystals and foods. Two large emergent areas of microrheology, non-linear microrheology and surface microrheology are also discussed.
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Affiliation(s)
- Thomas Andrew Waigh
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK. Photon Science Institute, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK
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Lim YF, de Loubens C, Love RJ, Lentle RG, Janssen PWM. Flow and mixing by small intestine villi. Food Funct 2016; 6:1787-95. [PMID: 25968481 DOI: 10.1039/c5fo00285k] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Flow and mixing in the small intestine are multi-scale processes. Flows at the scale of the villi (finger-like structures of ≈500 μm length) are poorly understood. We developed a three-dimensional lattice-Boltzmann model to gain insight into the effects of villous movements and the rheology of digesta on flow, mixing and absorption of nutrients at the periphery of the intestinal lumen. Our model simulated the hydrodynamic consequences of villi movements that resulted from folding of the mucosa during longitudinal contractions. We found that cyclic approximation and separation of groups of villi generated laminar eddies at the edges of the group and augmented mass transfers in the radial direction between the inter-villous space and the intestinal lumen which improved the absorption of nutrients and mixing at the periphery of the lumen. This augmentation was greater with highly diffusible nutrients and with high levels of shear-thinning (pseudoplasticity) of the fluid. We compared our results with bulk flows simulations done by previous workers and concluded that villous movements during longitudinal contractions is a major radial mixing mechanism in the small intestine and increases mixing and absorption around the mucosa despite adverse rheology.
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Affiliation(s)
- Y F Lim
- Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North, New Zealand.
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8
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Nanoparticle delivery and particle diffusion in confined and complex environments. J Drug Deliv Sci Technol 2015. [DOI: 10.1016/j.jddst.2015.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Fox CB, Kim J, Le LV, Nemeth CL, Chirra HD, Desai TA. Micro/nanofabricated platforms for oral drug delivery. J Control Release 2015; 219:431-444. [PMID: 26244713 DOI: 10.1016/j.jconrel.2015.07.033] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/29/2015] [Accepted: 07/30/2015] [Indexed: 12/18/2022]
Abstract
The oral route of drug administration is most preferred due to its ease of use, low cost, and high patient compliance. However, the oral uptake of many small molecule drugs and biotherapeutics is limited by various physiological barriers, and, as a result, drugs suffer from issues with low solubility, low permeability, and degradation following oral administration. The flexibility of micro- and nanofabrication techniques has been used to create drug delivery platforms designed to address these barriers to oral drug uptake. Specifically, micro/nanofabricated devices have been designed with planar, asymmetric geometries to promote device adhesion and unidirectional drug release toward epithelial tissue, thereby prolonging drug exposure and increasing drug permeation. Furthermore, surface functionalization, nanotopography, responsive drug release, motion-based responses, and permeation enhancers have been incorporated into such platforms to further enhance drug uptake. This review will outline the application of micro/nanotechnology to specifically address the physiological barriers to oral drug delivery and highlight technologies that may be incorporated into these oral drug delivery systems to further enhance drug uptake.
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Affiliation(s)
- Cade B Fox
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Jean Kim
- UC Berkeley & UCSF Graduate Program in Bioengineering, UCSF Mission Bay Campus, San Francisco, CA 94158, USA
| | - Long V Le
- UC Berkeley & UCSF Graduate Program in Bioengineering, UCSF Mission Bay Campus, San Francisco, CA 94158, USA
| | - Cameron L Nemeth
- UC Berkeley & UCSF Graduate Program in Bioengineering, UCSF Mission Bay Campus, San Francisco, CA 94158, USA
| | - Hariharasudhan D Chirra
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Tejal A Desai
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA; UC Berkeley & UCSF Graduate Program in Bioengineering, UCSF Mission Bay Campus, San Francisco, CA 94158, USA.
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10
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Bajka BH, Rigby NM, Cross KL, Macierzanka A, Mackie AR. The influence of small intestinal mucus structure on particle transport ex vivo. Colloids Surf B Biointerfaces 2015; 135:73-80. [PMID: 26241918 DOI: 10.1016/j.colsurfb.2015.07.038] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 07/14/2015] [Accepted: 07/15/2015] [Indexed: 12/17/2022]
Abstract
Mucus provides a barrier to bacteria and toxins while allowing nutrient absorption and waste transport. Unlike colonic mucus, small intestinal mucus structure is poorly understood. This study aimed to provide evidence for a continuous, structured mucus layer and assess the diffusion of different sized particles through it. Mucus structure was assessed by histology and immunohistochemistry. Ultra-structure was assessed by scanning electron microscopy. Tracking of 100 nm and 500 nm latex beads was conducted using ex vivo porcine mucus. The porcine jejunum and ileum were filled with mucus. Layered MUC2 staining was visible throughout the small intestine, covering villus tips. Scanning electron microscopy showed net-like mucin sheets covering villi (211 ± 7 nm pore diameter). Particle tracking of 100 nm latex beads, showed no inhibition of diffusion through mucus while 500 nm beads displayed limited diffusion. These results suggest a continuous mucus layer exists throughout the small intestine, which is highly stratified adjacent to the epithelium. The network observed is consistent with previous observations and correlates with stratified MUC2 staining. Mucin pore size is consistent with free diffusion of 100 nm and limited diffusion of 500 nm particles. Small Intestinal mucus structure has important implications for drug delivery systems and prevention and treatment of conditions like mucositis and inflammatory bowel disease.
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Affiliation(s)
| | - Neil M Rigby
- Institute of Food Research, Norwich, Norfolk, UK
| | | | - Adam Macierzanka
- Institute of Food Research, Norwich, Norfolk, UK; Department of Fats and Detergents Technology, Faculty of Chemistry, Gdansk University of Technology, Narutowicza 11/12, 80-952 Gdansk, Poland
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11
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A review of mixing and propulsion of chyme in the small intestine: fresh insights from new methods. J Comp Physiol B 2015; 185:369-87. [PMID: 25648621 DOI: 10.1007/s00360-015-0889-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 01/05/2015] [Accepted: 01/17/2015] [Indexed: 01/18/2023]
Abstract
The small intestine is a convoluted flexible tube of inconstant form and capacity through which chyme is propelled and mixed by varying patterns of contraction. These inconstancies have prevented quantitative comparisons of the manner in which contractile activity engenders mixing of contained chyme. Recent quantitative work based on spatiotemporal mapping of intestinal contractions, macro- and micro-rheology, particle image velocimetry and real-time modelling has provided new insights into this process. Evidence indicates that the speeds and patterns of the various types of small intestinal contraction are insufficient to secure optimal mixing and enzymatic digestion over a minimal length of intestine. Hence particulate substrates and soluble nutrients become dispersed along the length of the lumen. Mixing within the lumen is not turbulent but results from localised folding and kneading of the contents by contractions but is augmented by the inconstant spatial disposition of the contractions and their component contractile processes. The latter include inconstancies in the sites of commencement and the directions of propagation of contraction in component groups of smooth muscle cells and in the coordination of the radial and circular components of smooth muscle contraction. Evidence suggests there is ongoing augmentation of mixing at the periphery of the lumen, during both the post-prandial and inter-meal periods, to promote flow around and between adjacent villi. This results largely from folding of the relatively inelastic mucosa during repeated radial and longitudinal muscular contraction, causing chyme to be displaced by periodic crowding and separation of the tips of the relatively rigid villi. Further, micro-rheological studies indicate that such peripheral mixing may extend to the apices of enterocytes owing to discontinuities in the mobile mucus layer that covers the ileal mucosa.
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12
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The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine. Rev Physiol Biochem Pharmacol 2015; 168:59-118. [PMID: 26345415 DOI: 10.1007/112_2015_24] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.
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Lim YF, Lentle RG, Janssen PWM, Williams MAK, de Loubens C, Mansel BW, Chambers P. Determination of villous rigidity in the distal ileum of the possum (Trichosurus vulpecula). PLoS One 2014; 9:e100140. [PMID: 24956476 PMCID: PMC4067314 DOI: 10.1371/journal.pone.0100140] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Accepted: 05/21/2014] [Indexed: 12/21/2022] Open
Abstract
We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV). Ileal villi were relatively rigid along their entire length (mean 550 µm), and exhibited no noticeable bending even at flow rates that exceeded calculated normal physiological shear stress (>0.5 mPa). However, movement of villus tips indicated that the whole rigid structure of a villus could pivot about the base, likely from laxity at the point of union of the villous shaft with the underlying mucosa. Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface. The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely. Together the findings indicate that mixing and absorption is likely to be confined to the tips of villi under conditions where the villi and intestinal wall are immobile and is unlikely to be greatly augmented by passive bending of the shafts of villi.
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Affiliation(s)
- Yuen Feung Lim
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
| | - Roger G. Lentle
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
- Riddet Institute, Massey University, Palmerston North, New Zealand
- * E-mail:
| | - Patrick W. M. Janssen
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
| | - Martin A. K. Williams
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
- Riddet Institute, Massey University, Palmerston North, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Clément de Loubens
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
| | - Bradley W. Mansel
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Paul Chambers
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Characterisation of mixing in the proximal duodenum of the rat during longitudinal contractions and comparison with a fluid mechanical model based on spatiotemporal motility data. PLoS One 2014; 9:e95000. [PMID: 24747714 PMCID: PMC3991651 DOI: 10.1371/journal.pone.0095000] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 03/21/2014] [Indexed: 11/28/2022] Open
Abstract
The understanding of mixing and mass transfers of nutrients and drugs in the small intestine is of prime importance in creating formulations that manipulate absorption and digestibility. We characterised mixing using a dye tracer methodology during spontaneous longitudinal contractions, i.e. pendular activity, in 10 cm segments of living proximal duodenum of the rat maintained ex-vivo. The residence time distribution (RTD) of the tracer was equivalent to that generated by a small number (8) of continuous stirred tank reactors in series. Fluid mechanical modelling, that was based on real sequences of longitudinal contractions, predicted that dispersion should occur mainly in the periphery of the lumen. Comparison with the experimental RTD showed that centriluminal dispersion was accurately simulated whilst peripheral dispersion was underestimated. The results therefore highlighted the potential importance of micro-phenomena such as microfolding of the intestinal mucosa in peripheral mixing. We conclude that macro-scale modeling of intestinal flow is useful in simulating centriluminal mixing, whereas multi-scales strategies must be developed to accurately model mixing and mass transfers at the periphery of the lumen.
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Lentle RG, Janssen PWM, Deloubens C, Lim YF, Hulls C, Chambers P. Mucosal microfolds augment mixing at the wall of the distal ileum of the brushtail possum. Neurogastroenterol Motil 2013; 25:881-e700. [PMID: 23941237 DOI: 10.1111/nmo.12203] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 07/19/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND Recent work suggests that mixing in the small intestine takes place in central luminal and peripheral compartments. However, while movements of villi have been described, the mechanisms by which peripheral mixing are engendered remain unclear. METHODS We examined the disposition and movement of mucosa and associated villi during contractions of the everted terminal ileum of the brushtail possum. We then simulated the effect of these movements on peripheral mixing. KEY RESULTS Compression of the intestinal mucosa by phasic longitudinal or radial contractions created short-lived microfolds, which were of similar scale to the attached villi. The packing density of the villous tips increased in the concavities and decreased on the crests of these microfolds. Simulations showed that these caused liquid digesta to be expelled from, or drawn into, intervillous spaces, significantly augmenting peripheral, but not bulk, luminal mixing. CONCLUSIONS & INFERENCES We describe a mechanism by which peripheral mixing may be engendered by mucosal microfolds without requiring the coordinated contraction of individual villi or groups of villi.
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Affiliation(s)
- R G Lentle
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
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