Chronic and recurring pressure ulcers (PUs) create an unmet need for predictive biomarkers. In this work, we examine the panniculus carnosus, a thin cutaneous muscle, traditionally considered vestigial in humans, and ask whether the panniculus may play a role in the chronicity and reinjury of heel PUs. To determine whether humans have a panniculus muscle layer at the heel, we dissected eight cadavers. To assess the influence of the panniculus layer on PU, we performed computational simulations of supine weight bearing. Finally, we assessed panniculus regeneration in fluorescent mice. Results show a panniculus layer present in all cadavers examined. Simulations show a thin layer of panniculus muscle causes a dramatic decrease in the volume of soft tissue experiencing high strain and stress, compared to a heel without a panniculus. Importantly, in the mouse model, the panniculus fails to regenerate after PU, even when other cutaneous layers had fully regenerated. Our work shows that the panniculus is able to redistribute load around the heel bone, which might allow it to prevent PUs. Moreover, it is highly susceptible to incomplete regeneration after PU. Poor panniculus regeneration after PU might be a predictive anatomical biomarker for recurrence, and this biomarker should be evaluated prospectively in future clinical trials.

Imaging Fourier-transform spectroscopy (IFTS) is a powerful method for biological hyperspectral analysis based on various imaging modalities, such as fluorescence or Raman. Since the measurements are taken in the Fourier space of the spectrum, it can also take advantage of compressed sensing strategies. IFTS has been readily implemented in high-throughput, high-content microscope systems based on wide-field imaging modalities. However, there are limitations in existing wide-field IFTS designs. Non-common-path approaches are less phase-stable. Alternatively, designs based on the common-path Sagnac interferometer are stable, but incompatible with high-throughput imaging. They require exhaustive sequential scanning over large interferometric path delays, making compressive strategic data acquisition impossible. In this paper, we present a novel phase-stable, near-common-path interferometer enabling high-throughput hyperspectral imaging based on strategic data acquisition. Our results suggest that this approach can improve throughput over those of many other wide-field spectral techniques by more than an order of magnitude without compromising phase stability.

BackgroundConfetti fluorescence and other multi-color genetic labelling strategies are useful for observing stem cell regeneration and for other problems of cell lineage tracing. One difficulty of such strategies is segmenting the cell boundaries, which is a very different problem from segmenting color images from the real world. This paper addresses the difficulties and presents a superpixel-based framework for segmentation of regenerated muscle fibers in mice.ResultsWe propose to integrate an edge detector into a superpixel algorithm and customize the method for multi-channel images. The enhanced superpixel method outperforms the original and another advanced superpixel algorithm in terms of both boundary recall and under-segmentation error. Our framework was applied to cross-section and lateral section images of regenerated muscle fibers from confetti-fluorescent mice. Compared with “ground-truth” segmentations, our framework yielded median Dice similarity coefficients of 0.92 and higher.ConclusionOur segmentation framework is flexible and provides very good segmentations of multi-color muscle fibers. We anticipate our methods will be useful for segmenting a variety of tissues in confetti fluorecent mice and in mice with similar multi-color labels.Electronic supplementary materialThe online version of this article (doi:10.1186/s12918-016-0372-2) contains supplementary material, which is available to authorized users.

Pressure injuries are classified as chronic wounds, but the reasons for poor healing are not well understood, such as whether impairments are due to comorbidities and bacteria. Chronic vascular ulcers have pathologies caused by extracellular release of hemoglobin, so we questioned whether muscle pressure injuries (mPI) would have intrinsic pathologies due to extracellular myoglobin (Mb), and whether iron chelation therapy could improve them. Healthy mice in specific-pathogen-free conditions received pressure injuries. Cohorts were Mb-/- versus Mb+/+ in elderly 20-month-olds, or adult Mb+/+ 5-month-olds treated with saline versus iron chelator (subcutaneous deferoxamine, DFO). For comparison, healthy control regeneration was created using cardiotoxin injection. Unlike acute injuries, the wound bed of mPI displayed failure of phagocytosis at day 3, accompanied by high accumulation of iron, oxidative damage, and a lack of viable immune cells. The necrotic tissue was later expelled as slough (eschar). Mb-knockout mPI had undetectable levels of iron, low oxidative stress (p<0.05), greater immune infiltration (230%, p<0.05), 4-fold decreased marker for extracellular traps (p<0.01), and 50% smaller area of tissue death. Similar to knockout, injecting DFO after wounding caused improvement in oxidative stress (2-fold, p<0.05), extracellular trap marker (4-fold, p<0.01), and diameter of tissue killed (35%, p<0.05). In other words, tissue margins could be protected from dying. At later timepoints, DFO-treated wounds had higher levels of viable immune infiltrate (p<0.05), greater extent of muscle regeneration (46% smaller diameter of gap, p<0.01), and superior myofiber morphology (p<0.0001). We conclude that myoglobin iron from mPI causes oxidative stress and delayed infiltration, despite a lack of infection. Remarkably, tissue viability could be salvaged by post-injury treatment with subcutaneous injections of an FDA-approved iron chelator. This work also sheds light on how a hostile wound microenvironment impairs myogenesis and morphogenesis.