Proteomics identifies multipotent and low oncogenic risk stem cells of the spleen.

The adult spleen harbors a population of naturally occurring multipotent stem cells of non-lymphoid lineage (CD45-). In animal models, these splenic stem cells can directly or indirectly contribute to regeneration of bone, inner ear, cranial nerves, islets, hearts and salivary glands. Here we characterize the CD45- stem cell proteome to determine its potential broader multipotency versus its protection from malignant transformation. Using state-of-the-art proteomics and in vivo testing, we performed functional analyses of unique proteins of CD45- (non-lymphoid) splenic stem cells, as compared with CD45+ (lymphoid) cells. CD45- stem cell-specific proteins were identical to those in iPS, including OCT3/4, SOX2, KLF4, c-MYC and NANOG. They also expressed Hox11, Gli3, Wnt2, and Adam12, the benchmark transcription factors of embryonic stem cells. These transcription factors were functional because their mRNA was upregulated in the spleen in association with ongoing damage to the pancreas and salivary glands, organs to which they normally contribute stem cells. We also show low likelihood of malignant transformation. Our proteomic and functional analyses reveals that naturally occurring CD45- stem cells of the spleen are the first-ever candidates for naturally occurring population of embryonic and iPS cells with low oncogenic risk. Given their presence in normal humans and mice, splenic stem cells are poised for translational research.

Tissue engineered cartilage "bioshell" protective layer for subcutaneous implants.

OBJECTIVE: One current technique to reconstruct an ear for microtia involves the use of a high density polyethylene auricular implant; however, the implant can extrude if not covered in a temporoparietal fascia flap. Theoretically, an autologous tissue engineered cartilage "bioshell" protective coating around a permanent biocompatible implant might reduce potential extrusion to avoid the flap requirement. We hypothesized that if subjected to intentional exposure, a bioshell coating over an implant would provide enhanced wound healing. METHODS: Six sheets of high density polyethylene and six sheets of 24 carat pure gold wire-mesh measuring 19 mm x 25 mm were implanted subcutaneously in an immunocompetent swine model. Half of each implant group were coated with chondrocytes (50-70 million cells/cm(3)) which were suspended in Pluronic F-127 30% hydrogel; the remaining implants without chondrocytes were used as controls. At 10 weeks post-implantation, partial implant exposure via excision of overlying skin was performed to simulate extrusion and the sites were allowed to heal secondarily. RESULTS: All (6/6) of bioshell implants achieved wound closure after exposure by the seventh post-operative day; controls achieved closure at approximately 10 days. Bioshell neocartilage was evaluated and confirmed histologically using hematoxylin and eosin and safranin O stains. Histochemically, neocartilage approximated native cartilage with 60% glycosaminoglycans content. CONCLUSION: A 'proof-of-principle' tissue engineered bioshell around subcutaneous high density polyethylene and gold implants generated an elastic neocartilage coating, elicited a low inflammatory reaction, and was associated with 30% faster wound healing.