Faculty Bibliography

Aseptic loosening is a major complication of prosthetic joint surgery, characterized by chronic inflammation, pain, and osteolysis surrounding the bone-implant interface. Progranulin (PGRN) is known to have anti-inflammatory action by binding to Tumor Necrosis Factor (TNF) receptors and antagonizing TNFalpha. Here we report that titanium particles significantly induced PGRN expression in RAW264.7 cells and also in a mouse air-pouch model of inflammation. PGRN-deficiency enhanced, whereas administration of recombinant PGRN effectively inhibited, titanium particle-induced inflammation in an air pouch model. In addition, PGRN also significantly inhibited titanium particle-induced osteoclastogenesis and calvarial osteolysis in vitro, ex vivo and in vivo. Mechanistic studies demonstrated that the inhibition of PGRN on titanium particle induced-inflammation is primarily via neutralizing the titanium particle-activated TNFalpha/NF-kappaB signaling pathway and this is evidenced by the suppression of particle-induced IkappaB phosphorylation, NF-kappaB p65 nuclear translocation, and activity of the NF-kappaB-specific reporter gene. Collectively, these findings not only demonstrate that PGRN plays an important role in inhibiting titanium particle-induced inflammation, but also provide a potential therapeutic agent for the prevention of wear debris-induced inflammation and osteolysis.

KCNQ (voltage-gated K(+) channel family 7 (Kv7)) channels control cellular excitability and underlie the K(+) current sensitive to muscarinic receptor signaling (the M current) in sympathetic neurons. Here we show that the novel anti-epileptic drug retigabine (RTG) modulates channel function of pore-only modules (PMs) of the human Kv7.2 and Kv7.3 homomeric channels and of Kv7.2/3 heteromeric channels by prolonging the residence time in the open state. In addition, the Kv7 channel PMs are shown to recapitulate the single-channel permeation and pharmacological specificity characteristics of the corresponding full-length proteins in their native cellular context. A mutation (W265L) in the reconstituted Kv7.3 PM renders the channel insensitive to RTG and favors the conductive conformation of the PM, in agreement to what is observed when the Kv7.3 mutant is heterologously expressed. On the basis of the new findings and homology models of the closed and open conformations of the Kv7.3 PM, we propose a structural mechanism for the gating of the Kv7.3 PM and for the site of action of RTG as a Kv7.2/Kv7.3 K(+) current activator. The results validate the modular design of human Kv channels and highlight the PM as a high-fidelity target for drug screening of Kv channels.

Hair thinning and loss are prominent aging phenotypes but have an unknown mechanism. We show that hair follicle stem cell (HFSC) aging causes the stepwise miniaturization of hair follicles and eventual hair loss in wild-type mice and in humans. In vivo fate analysis of HFSCs revealed that the DNA damage response in HFSCs causes proteolysis of type XVII collagen (COL17A1/BP180), a critical molecule for HFSC maintenance, to trigger HFSC aging, characterized by the loss of stemness signatures and by epidermal commitment. Aged HFSCs are cyclically eliminated from the skin through terminal epidermal differentiation, thereby causing hair follicle miniaturization. The aging process can be recapitulated by Col17a1 deficiency and prevented by the forced maintenance of COL17A1 in HFSCs, demonstrating that COL17A1 in HFSCs orchestrates the stem cell-centric aging program of the epithelial mini-organ.

Complex regulatory networks regulate stem cell behavior and contributions to tissue growth, repair, and homeostasis. A full understanding of the networks controlling stem cell self-renewal and differentiation, however, has not yet been realized. To systematically dissect these networks and identify their components, we performed an unbiased, transcriptome-wide in vivo RNAi screen in female Drosophila germline stem cells (GSCs). Based on characterized cellular defects, we classified 646 identified genes into phenotypic and functional groups and unveiled a comprehensive set of networks regulating GSC maintenance, survival, and differentiation. This analysis revealed an unexpected role for ribosomal assembly factors in controlling stem cell cytokinesis. Moreover, our data show that the transition from self-renewal to differentiation relies on enhanced ribosome biogenesis accompanied by increased protein synthesis. Collectively, these results detail the extensive genetic networks that control stem cell homeostasis and highlight the intricate regulation of protein synthesis during differentiation.

Formyl peptide receptor 1 (FPR1) targeting multimodal probe cFLFLFK-MHI-DOTA for leukocyte based inflammation imaging is described. The compound consists of three domains, (a) cFLFLF peptide for FPR1 recognition and binding for activated leukocyte, (b) heptamethine cyanine dye (MHI) for near infrared fluorescence (NIRF) detection and imaging, and (c) metal chelator DOTA ligand that could form complex with a radiometal for nuclear (PET/SPECT) imaging or with a paramagnetic metal for MRI imaging. Detailed synthesis, characterization and in vitro evaluation are reported. The availability of dual mode inflammation imaging probe would allow in vivo gross level imaging of inflammation foci as well as ex vivo microscopic level cellular imaging for role played by innate immune cells in inflamed tissue.

White adipose tissue (WAT) is essential for maintaining metabolic function, especially during obesity. The intronic microRNAs miR-33a and miR-33b, located within the genes encoding sterol-regulatory element-binding proteins, SREBP-2 and SREBP-1 respectively, are transcribed in concert with their host genes and function alongside them to regulate cholesterol, fatty acid, and glucose metabolism. SREBP-1 is highly expressed in mature WAT and plays a critical role in promoting in-vitro adipocyte differentiation. It is unknown whether miR-33b is induced during or involved in adipogenesis. This is in part due to loss of miR-33b in rodents, precluding in-vivo assessment of the impact of miR-33b using standard mouse models. This work demonstrates that miR-33b is highly induced upon differentiation of human pre-adipocytes, along with SREBP-1. We further report that miR-33b is an important regulator of adipogenesis, as inhibition of miR-33b enhanced lipid droplet accumulation. Conversely, overexpression of miR-33b impaired pre-adipocyte proliferation, and reduced lipid droplet formation and the induction of PPARgamma target genes during differentiation. These effects may be mediated by targeting of HMGA2, CDK6 and other predicted miR-33b targets. Together, these findings demonstrate a novel role of miR-33b in the regulation of adipocyte differentiation, with important implications for the development of obesity and metabolic disease.

We present a game theoretic framework that models strategic interactions among humans and things that are assumed to be interconnected by a social-technological network, as in an internet of humans and things (IOHT). Often a pair of agents in the network interacts in order for an informed sender-agent to signal an uninformed receiver-agent to take an action that benefits each of the players; the benefits to the pair of agents are modeled by two separate utility functions, both depending on the sender"™s private information, the signal exchanged, and the receiver"™s revealed (and also possibly unrevealed) action. In general, the two agents"™ utilities may not be aligned and may encourage deceptive behavior. For example, a sender, aware of his/her own private "state of ignorance", may seek useful information from a receiver who owns powerful computational resources to search a large corpus of webpages; the sender does so by sending a signal to the receiver in the form of a keyword. Obvious examples of deceptiveness here range from attempts to hide one"™s intentions to auctioning the keywords on an ad exchange through real-time bidding. A rather troublesome situation occurs when deceptions are employed to breach the security of the system, thus making the entire social-technological network unreliable. Earlier, we proposed a signaling-game-theoretic framework to alleviate this problem. This paper further enhances that framework by reconfiguring signals to possess more complex structures (epistatic signals to represent attack and defense options over a given set of vulnerabilities). We explore two augmentations to the original evolutionary signaling game by first enhancing mutation bias toward strategies performing well in previous populations and second allowing the parameters of the utility functions to depend on population preferences giving rise to a minority game with epistatic signaling. The resulting game systems are empirically studied through extensive computer simulation.

Significance: Chronic wounds remain a significant public health problem. Alterations in normal physiological processes caused by aging or diabetes lead to impaired tissue repair and the development of chronic and nonhealing wounds. Understanding the unique features of the wound environment will be required to develop new therapeutics that impact these disabling conditions. New drug-delivery systems (DDSs) may enhance current and future therapies for this challenging clinical problem. Recent Advances: Historically, physical barriers and biological degradation limited the efficacy of DDSs in wound healing. In aiming at improving and optimizing drug delivery, recent data suggest that combinations of delivery mechanisms, such as hydrogels, small molecules, RNA interference (RNAi), as well as growth factor and stem cell-based therapies (biologics), could offer exciting new opportunities for improving tissue repair. Critical Issues: The lack of effective therapeutic approaches to combat the significant disability associated with chronic wounds has become an area of increasing clinical concern. However, the unique challenges of the wound environment have limited the development of effective therapeutic options for clinical use. Future Directions: New platforms presented in this review may provide clinicians and scientists with an improved understanding of the alternatives for drug delivery in wound care, which may facilitate the development of new therapeutic approaches for patients.

OBJECTIVES: Dalbavancin, a semi-synthetic lipoglycopeptide, is characterized by a long plasma half-life, which allows weekly dosing. Dalbavancin may be a good treatment option for patients with deep sternal wound infections owing to its improved pharmacokinetic profile and antibacterial activity compared with currently used antibiotics. Here we evaluated the efficacy of 7 or 14 days of treatment with dalbavancin, compared with vancomycin and with saline, in reducing sternal bone MRSA counts in a rat Staphylococcus aureus deep sternal wound infection model. METHODS: A mid-sternal wound was surgically induced in anaesthetized rats. A clinical strain of MRSA was injected into the sternum to establish infection. Rats were treated intraperitoneally for 7 or 14 days with dalbavancin, vancomycin or saline. The number of cfu per gram of sternum or spleen tissue was determined using viable counts. The antibacterial efficacy was determined by the reduction in bacterial counts per gram of sternum or spleen tissue in each treatment group. RESULTS: Treatment with dalbavancin was superior to treatment with saline for 7 days (0.75 log reduction in bone cfu) or 14 days (>3 log reduction in bone cfu) and similar to treatment with vancomycin. Additionally, dalbavancin was also effective in reducing systemic dissemination of MRSA. CONCLUSIONS: Dalbavancin is effective in the treatment of MRSA rat sternal osteomyelitis.

BACKGROUND: Plasma-derived fractions have been used as an autologous source of growth factors; however, limited knowledge concerning their biologic effects has hampered their clinical application. In this study, the authors analyze the content and specific effect of both platelet-rich plasma (PRP) and platelet-poor plasma (PPP) on osteoblastic differentiation using primary cultures of human periodontal ligament stem cells (HPLSCs). METHODS: The authors evaluated the growth factor content of PRP and PPP using a proteome profiler array and enzyme-linked immunosorbent assay. HPLSCs were characterized by flow cytometry and differentiation assays. The effect of PRP and PPP on HPLSC bone differentiation was analyzed by quantifying calcium deposition after 14 and 21 days of treatment. RESULTS: Albeit at different concentrations, the two fractions had similar profiles of growth factors, the most representative being platelet-derived growth factor (PDGF) isoforms (PDGF-AA, -BB, and -AB), insulin-like growth factor binding protein (IGFBP)-2, and IGFBP-6. Both formulations exerted a comparable stimulus on osteoblastic differentiation even at low doses (2.5%), increasing calcium deposits in HPLSCs. CONCLUSIONS: PRP and PPP showed a similar protein profile and exerted comparable effects on bone differentiation. Further studies are needed to characterize and compare the effects of PPP and PRP on bone healing in vivo.