There are more than 2 million bone grafting procedures performed annually in US alone. Despite significant efforts, the repair of large segmental bone defects is a substantial clinical challenge which...

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Design and development of scaffold structures for osteochondral (OC) interface regeneration is a significant engineering challenge. Recent efforts are aimed at recapitulating the unique compositional and hierarchical structure of an OC interface. Conventional scaffold fabrication techniques often have limited design control and reproducibility, and the development of OC scaffolds with zonal hierarchy and structural integrity between zones is especially challenging. In this study, a series of multi-zonal and gradient structures were designed and fabricated using three-dimensional (3D) bioprinting. We developed OC scaffolds with bi-phasic and tri-phasic configurations to support the zonal structure of OC tissue, and gradient scaffold configurations to enable smooth transitions between the zones to more closely mimic a bone-cartilage interface. A biodegradable polymer, polylactic acid (PLA), was used for the fabrication of zonal/gradient scaffolds to provide mechanical strength and support OC function. The formation of the multi-zonal and gradient scaffolds was confirmed through SEM imaging and micro-CT scanning. Precisely controlled hierarchy with tunable porosity along the scaffold length established the formation of the bio-inspired scaffolds with different zones/gradient structure. In addition, we also developed a novel bioprinting method to selectively introduce cells into desired scaffold zones of the zonal/gradient scaffolds via concurrent printing of a cell-laden hydrogel within the porous template. Live/dead staining of the cell-laden hydrogel introduced in the cartilage zone showed uniform cell distribution with high cell viability. Overall, our study developed bio-inspired scaffold structures with structural hierarchy and mechanical integrity for bone-cartilage interface engineering.

Hand warts were studied in 160 butchers. Clinical and histological studies were performed in 190 warts and virological studies in 165 warts from 104 butchers. Since we found almost perfect correlation between the histological pattern and the type of infecting virus, it was possible to evaluate the virus types in a further 39 of 56 butchers without virological studies, on the basis of the histology of the warts. The most common infection was with HPV-2 (human papilloma virus) and HPV-7. Thirty-three butchers were infected with two types of viruses and three butchers with three HPVs. The morphology of warts varied considerably. The majority were similar to verrucae vulgares or verrucae planae. Some deep warts resembled myrmecia-type verrucae plantares. Often, several types of warts coexisted. Some clinical patterns were shown to be preferentially associated with distinct types of papillomaviruses: common warts with HPV-2, HPV-4, or HPV-7, plane and intermediate warts with HPV-3, HPV-10, HPV-28. HPV-7, previously identified for the first time in these butchers, was found to be associated with common warts or common wart-like, papillomatous lesions.