Live Tissue Imaging to Elucidate Mechanical Modulation of Stem Cell Niche Quiescence.

The periosteum, a composite cellular connective tissue, bounds all nonarticular bone surfaces. Like Velcro, collagenous Sharpey's fibers anchor the periosteum in a prestressed state to the underlying bone. The periosteum provides a niche for mesenchymal stem cells. Periosteal lifting, as well as injury, causes cells residing in the periosteum (PDCs) to change from an immobile, quiescent state to a mobile, active state. The physical cues that activate PDCs to home to and heal injured areas remain a conundrum. An understanding of these cues is key to unlocking periosteum's remarkable regenerative power. We hypothesized that changes in periosteum's baseline stress state modulate the quiescence of its stem cell niche. We report, for the first time, a three-dimensional, high-resolution live tissue imaging protocol to observe and characterize ovine PDCs and their niche before and after release of the tissue's endogenous prestress. Loss of prestress results in abrupt shrinkage of the periosteal tissue. At the microscopic scale, loss of prestress results in significantly increased crimping of collagen of periosteum's fibrous layer and a threefold increase in the number of rounded nuclei in the cambium layer. Given the body of published data describing the relationships between stem cell and nucleus shape, structure and function, these observations are consistent with a role for mechanics in the modulation of periosteal niche quiescence. The quantitative characterization of periosteum as a stem cell niche represents a critical step for clinical translation of the periosteum and periosteum substitute-based implants for tissue defect healing. Stem Cells Translational Medicine 2017;6:285-292

In vivo local co-delivery of recombinant human bone morphogenetic protein-7 and pamidronate via poly-D, L-lactic acid

The effects of bone anabolic agents such as bone morphogenetic proteins (BMPs) have the potential to be augmented by co-treatment with an anti-catabolic such as a bisphosphonate. We hypothesised that the effects of bisphosphonates on BMP-induced bone anabolism would be dose dependent, and we aimed to test this in a small animal model. Agents were delivered locally using a biodegradable poly-d, l-lactic-acid (PDLLA) polymer delivery system. Recombinant human BMP-7 (25 µg) was tested with a range of doses of the bisphosphonate pamidronate (0.02 mg, 0.2 mg and 2 mg local PAM; 0.3 mg/kg and 3 mg/kg thrice-weekly systemic PAM) versus BMP-7 alone. Polymer pellets were surgically implanted in the hind limbs of female C57BL6/J mice (8-10 week) and ectopic bone nodules were harvested at 3 and 8 weeks post-operatively. At 3 weeks, local low dose PAM (0.02 mg) induced a 102% increase in rhBMP-7 induced bone volume (p<0.01) as measured by miroCT, and this was comparable to systemic PAM (0.3 mg/kg thrice-weekly). In contrast, local high dose PAM (2 mg) resulted in a 97% decrease in bone volume (p<0.01). Radiography and histology indicated that the polymer vehicle was still largely present at 8 weeks indicating inefficient biodegradation. This is the first study to validate the utility of local co-delivery of BMP/bisphosphonate via biodegradable polymer and supports the continued refinement of more advanced bioresorbable delivery systems for clinical applications

Rapid cell culture and pre-clinical screening of a transforming growth factor-beta (TGF-beta) inhibitor for orthopaedics

BACKGROUND: Transforming growth factor-beta (TGF-beta) and bone morphogenetic proteins (BMPs) utilize parallel and related signaling pathways, however the interaction between these pathways in bone remains unclear. TGF-beta inhibition has been previously reported to promote osteogenic differentiation in vitro, suggesting it may have a capacity to augment orthopaedic repair. We have explored this concept using an approach that represents a template for the testing of agents with prospective orthopaedic applications. METHODS: The effects of BMP-2, TGF-beta1, and the TGF-beta receptor (ALK-4/5/7) inhibitor SB431542 on osteogenic differentiation were tested in the MC3T3-E1 murine pre-osteoblast cell line. Outcome measures included alkaline phosphatase staining, matrix mineralization, osteogenic gene expression (Runx2, Alp, Ocn) and phosphorylation of SMAD transcription factors. Next we examined the effects of SB431542 in two orthopaedic animal models. The first was a marrow ablation model where reaming of the femur leads to new intramedullary bone formation. In a second model, 20 microg rhBMP-2 in a polymer carrier was surgically introduced to the hind limb musculature to produce ectopic bone nodules. RESULTS: BMP-2 and SB431542 increased the expression of osteogenic markers in vitro, while TGF-beta1 decreased their expression. Both BMP-2 and SB431542 were found to stimulate pSMAD1 and we also observed a non-canonical repression of pSMAD2. In contrast, neither in vivo system was able to provide evidence of improved bone formation or repair with SB431542 treatment. In the marrow ablation model, systemic dosing with up to 10 mg/kg/day SB431542 did not significantly increase reaming-induced bone formation compared to vehicle only controls. In the ectopic bone model, local co-administration of 38 microg or 192 microg SB431542 did not increase bone formation. CONCLUSIONS: ALK-4/5/7 inhibitors can promote osteogenic differentiation in vitro, but this may not readily translate to in vivo orthopaedic applications

Coupled modeling of storm surge and coastal inundation: A case study in New York City during Hurricane Sandy

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/In this paper we describe a new method of modeling coastal inundation arising from storm surge by coupling a widely used storm surge model (ADCIRC) and an urban flood inundation model (FloodMap). This is the first time the coupling of such models is implemented and tested using real events. The method offers a flexible and efficient procedure for applying detailed ADCIRC storm surge modeling results along the coastal boundary (with typical resolution of ∼100 m) to FloodMap for fine resolution inundation modeling (< 5 m). The coastal inundation during Hurricane Sandy was simulated at both the city (New York City) and sub-regional (lower Manhattan) scales with various resolutions. Results obtained from the ADCIRC and coupled ADCIRC -FloodMap simulations were compared with the recorded (High Water Marks) and derived (inundation extent based on the planar method) data from FEMA. At the city scale, coupled ADCIRC -FloodMap modeling demonstrates improved prediction over ADCIRC modeling alone for both the extent and depth of inundation. The advantage of the coupled model is further illustrated in the sub-regional modeling, using a mesh resolution of 3 m which is substantially finer than the inland mesh resolution used by ADCIRC (> 70 m). In further testing, we explored the effects of mesh resolution and roughness specification. Results agree with previous studies that fine resolution is essential for capturing intricate flow paths and connectivity in urban topography. While the specification of roughness is more challenging for urban environments, it may be empirically optimized. The successful coupling of ADCIRC and FloodMap models for fine-resolution coastal inundation modeling unlocks the potential for undertaking large numbers of probabilistically-based synthetic surge events for street-level risk analysis

What Drives Household Recovery After Disasters? A Case Study of New York City After 2012 Hurricane Sandy

Community recovery from disasters depends on how its subunits, such as households, fare. But the current knowledge on this topic is fragmented and undervalues a household’s agency for action, which can result in narrowly designed, and sometimes counterproductive, recovery plans and aid policies. In this article, we examine various internal and contextual characteristics of households to answer the question, what factors influence household recovery the most and how? Using logistical regression analysis on random sample survey data collected from households affected by the 2012 Hurricane Sandy in New York City, NY, we discuss the influence of various socioeconomic factors, knowledge and availability of external aid, and neighborhood condition on a household’s perception of their own recovery. We conclude with three lessons on community participation, recovery financing, and community restoration for recovery managers to ensure disaster recovery plans are comprehensive and build local capacity to recover