3D Bioprintable Hypoxia-Mimicking PEG-Based Nano Bioink for Cartilage Tissue Engineering.

As hypoxia plays a significant role in the formation and maintenance of cartilage tissue, aiming to develop native hypoxia-mimicking tissue engineering scaffolds is an efficient method to treat articular cartilage (AC) defects. Cobalt (Co) is documented for its hypoxic-inducing effects in vitro by stabilizing the hypoxia-inducible factor-1α (HIF-1α), a chief regulator of stem cell fate. Considering this, we developed a novel three-dimensional (3D) bioprintable hypoxia-mimicking nano bioink wherein cobalt nanowires (Co NWs) were incorporated into the poly(ethylene glycol) diacrylate (PEGDA) hydrogel system as a hypoxia-inducing agent and encapsulated with umbilical cord-derived mesenchymal stem cells (UMSCs). In the current study, we investigated the impact of Co NWs on the chondrogenic differentiation of UMSCs in the PEGDA hydrogel system. Herein, the hypoxia-mimicking nano bioink (PEGDA+Co NW) was rheologically optimized to bioprint geometrically stable cartilaginous constructs. The bioprinted 3D constructs were evaluated for their physicochemical characterization, swelling-degradation behavior, mechanical properties, cell proliferation, and the expression of chondrogenic markers by histological, immunofluorescence, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) methods. The results disclosed that, compared to the control (PEGDA) group, the hypoxia-mimicking nano bioink (PEGDA+Co NW) group outperformed in print fidelity and mechanical properties. Furthermore, live/dead staining, double-stranded DNA (dsDNA) content, and glycosaminoglycans (GAGs) content demonstrated that adding low amounts of Co NWs (<20 ppm) into PEGDA hydrogel system supported UMSC adhesion, proliferation, and differentiation. Histological and immunofluorescence staining of the PEGDA+Co NW bioprinted structures revealed the production of type 2 collagen (COL2) and sulfated GAGs, rendering it a feasible option for cartilage repair. It was further corroborated by a significant upregulation of the hypoxia-mediated chondrogenic and downregulation of the hypertrophic/osteogenic marker expression. In conclusion, the hypoxia-mimicking hydrogel system, including PEGDA and Co2+ ions, synergistically directs the UMSCs toward the chondrocyte lineage without using expensive growth factors and provides an alternative strategy for translational applications in the cartilage tissue engineering field.

A Tete - a - tete of benign, borderline and malignant fibrohistiocytic tumor.

Dermatofibrosarcoma protruberans is a relatively uncommon slow growing, locally aggressive fibrous tumor of the skin. It has a prospensity of progressing to fibrosarcomatous change in 5% of the cases. We present a case of a 56 yr old male with presented to the outpatient department of surgery, Sri Siddhartha Medical College, Tumkur with a chest swelling in 2013. FNAC was inconclusive and the mass was excised. On histopathology, areas of benign fibrohistiocytic tumor, dermatofibrosarcoma protruberans and fibrosarcomatous dermatofibrosarcoma were identified in the same tumor. Immunohistochemistry confirmed the diagnosis of DFSP with fibrosarcomatous change. Although, transformed DFSP is more aggressive, the prognosis is influenced by the extent of excision and with wide excision, there may be little increased risk for recurrence and metastasis over that of conventional DFSP.

Intra articular synovial lipoma of the right tarsometatarsal joint- a rare case report.

Intra articular synovial lipomas are very rare and only few cases have been reported till now. We are reporting a rare case of intra articular synovial lipoma of the tarsometatarsal joint in the right foot in a 38-year-old male who presented with dull aching pain in the plantar aspect of the foot while walking. The lesion was resected and subjected to histopathological examination, which showed well defined lobules of mature adipocytes separated by thin fibrous septa and covered by synovial lining. Immunohistochemistry with S100 antigen showed membrane positivity. A diagnosis of intra articular synovial lipoma of the tarsometatarsal joint of the right foot was made. Our English literature search failed to yield any information regarding the occurrence of synovial lipoma in small joints and our case may be the first of its kind.