Biology subjects

So, P. T.

Publications and source records attributed to So, P. T..

5 recordsLinked to original sources

bioRxiv2024

In Vivo Optical Clearing of Mammalian Brain

Established methods for imaging the living mammalian brain have, to date, taken the brains optical properties as fixed; we here demonstrate that it is possible to modify the optical properties of the brain itself to significantly enhance at-depth imaging while preserving native physiology. Using a small amount of any of several biocompatible materials to raise the refractive index of solutions superfusing the brain prior to imaging, we could increase several-fold the signals from the deepest cells normally visible and, under both one-photon and two-photon imaging, visualize cells previously too dim to see. The enhancement was observed for both anatomical and functional fluorescent reporters across a broad range of emission wavelengths. Importantly, visual tuning properties of cortical neurons in awake mice, and electrophysiological properties of neurons assessed ex vivo, were not altered by this procedure.

bioengineering↗

bioRxiv2023

Contributions of individual satellite cells to muscle regeneration assessed using a confetti mouse model

Insufficient regeneration is implicated in muscle pathologies, but much remains unknown about the regenerative output of individual muscle stem cells, called satellite cells (SCs). Prior work showed that individual SCs contribute to regeneration of more than one muscle fiber ("fiber-crossing") after full-muscle damage. We investigated whether fiber-crossing also occurred in peripheral regions of a localized muscle injury. To assess fiber-crossing with a minimum number of mice, we used lineage tracing with confetti fluorescence, and developed a novel stochastic modeling method to interpret the ambiguity of multi-color fluorescent lineage tags. Microscopy of the regenerated muscle showed that adjacent fibers often expressed the same-colored tags. Computational analysis concluded that the observed color patches would be extremely unlikely to occur by chance unless SCs contributed myonuclei to multiple adjacent fibers (26-33% of SCs contributing to at most 1-2 additional fibers). Interestingly, these results were similar across the different regions studied, suggesting that severe destruction is not required for fiber-crossing. Our method to assess fiber-crossing may be useful for future study of gene and cell therapies that use fiber-crossing to aid muscle regeneration.

physiology↗

bioRxiv2023

Multiphoton imaging of glucose, galactose, and fructose-induced formation of fluorescent advanced glycation end products in tissues

Blood glucose and HbA1c, intermediate glycation products of hemoglobin, remain the two clinical biomarkers for monitoring disease progression in diabetics. However, the formation of advanced glycation end products (AGEs) has been implicated in diabetic pathogenesis and the use of AGEs in tissues as long-term glycemic markers may be of value in the clinical setting. Therefore, it is necessary to understand how different tissue constituents respond to dietary monosaccharides. In this study, we studied the in vitro rate of fluorescent AGEs (fAGEs) formation with multiphoton microscopy in different porcine tissues (aorta, cornea, kidney, dermis, and tendon). These tissues were treated with D-glucose, D-galactose, and D-fructose, three primary monosaccharides found in human diets. We found that the use of D-fructose resulted in the highest glycation rate, followed by D-galactose and then D-glucose. Moreover, compared to non-collagen tissue constituents such as elastic fibers and cells, the rate of tissue glycation was consistently higher in collagen, suggesting that collagen is a more sensitive target for fAGE formation. However, we also found that collagen in different tissues exhibits different rates of fAGE formation, with slower rates observed in tightly packed tissues such as cornea and tendon. Our study suggests that for fAGE to be developed into a long-term glycemic biomarker, loosely organized collagen tissues located in the proximity of vasculature may be the best targets.

biophysics↗

bioRxiv2022

Myoglobin-derived iron causes phagocyte dysfunction, wound enlargement, and impaired regeneration in pressure injuries of muscle

The reasons for poor healing of pressure injuries are poorly understood. Vascular ulcers are worsened by extracellular release of hemoglobin, so we examined the impact of myoglobin (Mb) iron in murine muscle pressure injuries (mPI). Tests used Mb-knockout or treatment with deferoxamine iron chelator (DFO). Unlike acute injuries from cardiotoxin, mPI regenerated poorly with a lack of viable immune cells, persistence of dead tissue (necro-slough), and abnormal deposition of iron. However, Mb-knockout or DFO-treated mPI displayed a reversal of the pathology: decreased tissue death, decreased iron deposition, decrease in markers of oxidative damage, and higher numbers of intact immune cells. Subsequently, DFO treatment improved myofiber regeneration and morphology. We conclude that myoglobin iron contributes to tissue death in mPI. Remarkably, a large fraction of muscle death in untreated mPI occurred later than, and was preventable by, DFO treatment, even though treatment started 12 hours after pressure was removed. This demonstrates an opportunity for post-pressure prevention to salvage tissue viability.

molecular biology↗

bioRxiv2022

Label-free three-photon imaging of intact human cerebral organoids: tracking early events in brain development and deficits in Rett Syndrome

Human cerebral organoids are unique in their development of progenitor-rich zones akin to ventricular zones from which neuronal progenitors differentiate and migrate radially. Analyses of cerebral organoids thus far have been performed in sectioned tissue or in superficial layers due to their high scattering properties. Here, we demonstrate label-free three-photon imaging of whole, uncleared intact organoids ([~]2 mm depth) to assess early events of early human brain development. Optimizing a custom-made three-photon microscope to image intact cerebral organoids generated from Rett Syndrome patients, we show defects in the ventricular zone volumetric structure of mutant organoids compared to isogenic control organoids. Long-term imaging live organoids reveals that shorter migration distances and slower migration speeds of mutant radially migrating neurons are associated with more tortuous trajectories. Our label-free imaging system constitutes a particularly useful platform for tracking normal and abnormal development in individual organoids, as well as for screening therapeutic molecules via intact organoid imaging.

neuroscience↗