Johannes Nathanael Lieberkühn (1711-1756): luminary eighteenth century anatomist and his illuminating discovery of intestinal glands

Johannes Nathanael Lieberkühn was a prodigious anatomist whose meticulous experiments and precise detailing helped in comprehending the microscopic anatomy of digestive system during early part of eighteenth century. Notably, his inventions in the field of microscopy aptly complemented his quest for anatomical knowledge at microscopic level. He designed a reflector (Lieberkühn reflector) which enhanced the amount of focussed light leading to bright illumination of tissue specimen. He invented the solar microscope which provided excellent resolution of minute anatomical details. Lieberkühn discovered the digestive juice secreting tubular glands (glands of Lieberkühn) present at the base of intestinal villi producing epithelial invaginations (crypts of Lieberkühn). He also described the intricate juxtaposition of blood vessels in relation to a single intestinal villi. Moreover, through empirically designed experimental set up, Lieberkühn was able to demonstrate the flow of lymph from intestinal villi to collecting lymphatic vessels. Also, his grandiose collection of laboratory specimens involving vascular anatomy are a testimony of his untiring efforts in academia. His contributions were seminal in comprehending the anatomy of digestive system and paved the way for future revelations. His work unveiled the enormous scope of microanatomy in medical science and catalysed the advent of histological staining methods a century later.

Intestine-inspired wrinkled MXene microneedle dressings for smart wound management

Composite MXene-based materials are prone to crack propagation, thus limiting their tensile properties. Numerous efforts have been devoted to removing material constraints and fabricating unitary MXene elastic films. Here, for the first time, inspired by the intestinal wrinkles and villi structure, we presented a ductile, biologically friendly, and highly conductive MXene-based microneedle (MMN) dressing composed of stacked MXene film and superfine microneedle arrays through a simple stretching and laser engraving strategy for wound healing. By utilizing photothermal responsive MXene, periodic porous structures, and a temperature-responsive polymer to construct the MMN dressing, the system can act as an effective route for facilitating controllable drug delivery controlled by near-infrared (NIR) irradiation. In addition, superior conductivity imparts them with the capacity to realize continuous and steady monitoring of motion sensing. The practical performance further demonstrated that the versatile MMN dressing showed obvious therapeutic efficacy in vivo animal wound models. Thus, it is believed that MMN dressings with biomimetic structures, controllable drug release, and conductive pathways will open a new chapter for wound management and widen other practical applications in biomedical fields, such as artificial tendons and soft robotics. STATEMENT OF SIGNIFICANCE: MXene-based materials have been demonstrated as critical tools in advancing our understanding of wound healing. However, the rapid crack propagation is a constraint on their tensile properties. Here, inspired by the intestinal wrinkles and villi structure, a single-step method has also been discussed to present a MXene-based microneedle dressing composed of unitary MXene elastic film and superfine microneedle arrays. At the same time, the dressing with biomimetic structures, controllable drug release, and conductive pathways has prospects in intelligent wound management and varieties of related biomedical fields.

Epithelial-Mesenchymal Interactions for the Development of Intestinal Villi

Small intestine has a structure called villi that increases the mucosal surface area for nutrient absorption. Intricate and tight epithelial-mesenchymal interactions are required for villi development. These interactions are regulated by signaling molecules, physical forces, and epithelial deformation. Signaling molecules include hedgehog (Hh), bone morphogenetic protein (BMP) and Wnt ligands. The Hh ligand is expressed from the epithelium and binds to the underlying mesenchymal cells, resulting in aggregation into mesenchymal clusters. The clusters express BMP and Wnt ligands to control its size and spacing between clusters. The clusters then form villi. Despite the fact that the villi formation is studied extensively, we do not have a complete understanding. In addition, the recent study shows there is a great relationship between the overexpression of the Hh signal and development of cancer in the gastrointestinal tract. Therefore, signaling between epithelial and mesenchymal cells and their physical interactions will be discussed on this review.