Histological assessment of cellular half-life in tissues in vivo

Modeling treatment of diabetic wounds with oxygen therapy and senolytic drug

Diabetic wounds are common in patients with type 2 diabetes; they are ischemic and inflammatory, and difficult to heal without intervention. Hyperbaric oxygen therapy (HBOT) is a standard treatment, but its effectiveness is limited to a subset of the aging population. Senescent fibroblasts, a hallmark of aging, impair wound healing, and senolytic drugs, like quercetin (Q), which target senescent cells, may improve healing. In this study, we developed a mathematical model that defines biological aging through two parameters, η and [Formula: see text], that decline with age. These parameters reflect the biological age of an individual, where η represents fibroblast proliferation and [Formula: see text] represents the production of the angiogenetic protein VEGF. Our model predicts that treatment with only HBOT achieves wound closure, within normal expectable time, for patients with a limited subset pairs of [Formula: see text], and this subset is increased to a larger subset by combining Q with HBOT. The two subsets of [Formula: see text] are determined explicitly by simulations of the model. To make these results applicable in clinical setting, one will have to relate the aging parameters η and [Formula: see text] to tangible marks of biological-aging factors.

Vascular function in the aging human brain during muscle exertion

To determine how brain oxygenation is stably maintained during advancing age, cerebral oxygenation and hemoglobin were measured real-time at 10 Hz using near-infrared spectroscopy (NIRS) at rest (30 seconds) and during a 10-repeated handgrip strength test (30 seconds) for 834 adults (M/F = 45/55%) aged 20-88 y. The amplitude of cerebral hemodynamic fluctuation was reflected by converting 300 values of % oxygen saturation and hemoglobin of each 30-second phase to standard deviation as indicatives of brain oxygenation variability (BOV) and brain hemodynamic variability (BHV) for each participant. Both BOV (+21-72%) and BHV (+94-158%) increased during the maximal voluntary muscle exertions for all age levels (α < 0.05), suggesting an increased vascular recruitment to maintain oxygen homeostasis in the brain. Intriguingly, BHV was >100 folds for both resting and challenged conditions (α < 0.001) in >80% of adults aged above 50 y despite similar BOV compared with young age counterparts, indicating a huge cost of amplifying hemodynamic oscillation to maintain a stable oxygenation in the aging brain. Since vascular endothelial cells are short-lived, our results implicate a hemodynamic compensation to emergence of daily deficits in replacing senescent endothelial cells after age 50 y.

Reduced stem cell aging in exercised human skeletal muscle is enhanced by ginsenoside Rg1

Background: Stem cell aging, characterized by elevated p16^INK4a expression, decreases cell repopulating and self-renewal abilities, which results in elevated inflammation and slow recovery against stress.

Methods: Biopsied muscles were analyzed at baseline and 24 h after squat exercise in 12 trained men (22 ± 2 y). Placebo (PLA) and immunostimulant Rg1 (5 mg) were supplemented 1 h before a squat exercise, using a double-blind counterbalanced crossover design.

Results: Perceived exertion at the end of resistance exercise session was significantly lowered after Rg1 supplementation. Exercise doubled endothelial progenitor cells (EPC) (p < 0.001) and decreased p16^INK4a mRNA to 50% of baseline (d = 0.865, p < 0.05) in muscle tissues, despite p16^INK4a+ cell and beta-galactosidase⁺ (ß-Gal⁺) cell counts being unaltered. Rg1 further lowered p16INK4a mRNA to 35% of baseline with greater effect size than the PLA level (d = 1.302, p < 0.01) and decreased myeloperoxidase (MPO) mRNA to 39% of baseline (p < 0.05). A strong correlation between MPO and p16^INK4a expression in muscle tissues was observed (r = 0.84, p < 0.001).

Conclusion: EPC in skeletal muscle doubled 1 d after an acute bout of resistance exercise. The exercised effects in lowering EPC aging and tissue inflammation were enhanced by immunostimulant Rg1, suggesting the involvement of immune stimulation on EPC rejuvenation.

Aerobic exercise induces tumor suppressor p16INK4a expression of endothelial progenitor cells in human skeletal muscle

Aerobic exercise induces oxidative stress and DNA damage, nevertheless, lowers cancer incidence. It remains unclear how genetic stability is maintained under this condition. Here, we examined the dynamic change of the tumor suppressor p16^INK4a in cells of skeletal muscle among young men following 60-min of aerobic cycling at 70% maximal oxygen consumption (V̇O_2max). Rg1 (5 mg, an immunostimulant ginsenoside) and placebo (PLA) were supplemented 1 h before exercise. Data from serial muscle biopsies shows unchanged p16^INK4a+ cells after exercise followed by a considerable increase (+21-fold) in vastus lateralis muscle 3 h later. This increase was due to the accumulation of endothelial progenitor cells (p16^INK4a+/CD34⁺) surrounding myofibers and other infiltrated nucleated cells (p16^INK4a+/CD34^-) in necrotic myofibers. During the Rg1 trial, acute increases of p16^INK4a+ cells in the muscle occurred immediately after exercise (+3-fold) and reversed near baseline 3 h later. Rg1 also lowered IL-10 mRNA relative to PLA 3 h after exercise. Post-exercise increases in VEGF mRNA and CD163⁺ macrophages were similar for PLA and Rg1 trials. Conclusion: The marked increases in p16^INK4a protein expression of endothelial progenitor cells in skeletal muscle implicates a protective mechanism for maintaining genetic stability against aerobic exercise. Rg1 accelerates resolution of the exercise-induced stress response.

Mathematical Model of Chronic Dermal Wounds in Diabetes and Obesity

Chronic dermal-wound patients frequently suffer from diabetes type 2 and obesity; without treatment or early intervention, these patients are at risk of amputation. In this paper, we identified four factors that impair wound healing in these populations: excessive production of glycation, excessive production of leukotrient, decreased production of stromal derived factor (SDF-1), and insulin resistance. We developed a mathematical model of wound healing that includes these factors. The model consists of a system of partial differential equations, and it demonstrates how these four factors impair the closure of the wound, by reducing the oxygen flow into the wound area and by blocking the transition from pro-inflammatory macrophages to anti-inflammatory macrophages. The model is used to assess treatment by insulin injection and by oxygen infusion.

Tamoxifen activity against Plasmodium in vitro and in mice

BACKGROUND

Tamoxifen is an oestrogen receptor modulator that is widely used for the treatment of early stage breast cancer and reduction of recurrences. Tamoxifen is also used as a powerful research tool for controlling gene expression in the context of the Cre/loxP site-specific recombination system in conditional mutant mice.

METHODS

To determine whether the administration of tamoxifen affects Plasmodium growth and/or disease outcome in malaria, in vitro studies assessing the effect of tamoxifen and its active metabolite 4-hydroxytamoxifen on Plasmodium falciparum blood stages were performed. Tamoxifen effects were also evaluated in vivo treating C57/B6 mice infected with Plasmodium berghei (ANKA strain), which is the standard animal model for the study of cerebral malaria.

RESULTS

Tamoxifen and its active metabolite, 4-hydroxytamoxifen, show activity in vitro against P. falciparum (16.7 to 5.8 µM IC50, respectively). This activity was also confirmed in tamoxifen-treated mice infected with P. berghei, which show lower levels of parasitaemia and do not develop signs of cerebral malaria, compared to control mice. Mice treated with tamoxifen for 1 week and left untreated for an additional week before infection showed similar parasitaemia levels and signs of cerebral malaria as control untreated mice.

CONCLUSIONS

Tamoxifen and its active metabolite, 4-hydroxytamoxifen, have significant activity against the human parasite P. falciparum in vitro and the rodent parasite P. berghei in vivo. This activity may be useful for prevention of malaria in patients taking this drug chronically, but also represents a major problem for scientists using the conditional mutagenic Cre/LoxP system in the setting of rodent malaria. Allowing mice to clear tamoxifen before starting a Plasmodium infection allows the use the Cre/LoxP conditional mutagenic system to investigate gene function in specific tissues.

Aged cells in human skeletal muscle after resistance exercise

It remains unclear how exercise, as an entropic event, brings benefit against human aging. Here we examined longitudinal changes of p16^Ink4a+ senescent cells in skeletal muscle of young men (aged 22.5±1.7 y) before and after resistance exercise (0 h and 48 h) with multiple biopsies at two different protein availabilities: low protein (14%) and isocaloric high protein (44%) supplemented conditions. Immunohistochemistry analysis of muscle cross-sections using p16^Ink4a and CD34 antibodies confirmed that the detected senescent cells were endothelial progenitor cells. Leukocyte infiltration into skeletal muscle increased during resistance exercise. The senescent cells in muscle decreased (-48%, P < 0.01) after exercise for 48 h. Low protein supplementation resulted in greater infiltrations of both CD68⁺ phagocytic macrophage and leukocyte, further decreased p16^Ink4a+ senescent cells (-73%, P < 0.001), and delayed increases in regenerative CD163⁺ macrophage in skeletal muscle, compared with high protein supplemented condition. Significant gain in muscle mass after 12 weeks of training occurred only under high protein supplemented condition.

CONCLUSION

Rapid senescent cell clearance of human skeletal muscle during resistance exercise seems to associate with enhanced in situ phagocytosis. High protein availability accelerates resolution of muscle inflammation and promotes muscle increment after training.

Endothelial pyruvate kinase M2 maintains vascular integrity

The M2 isoform of pyruvate kinase (PKM2) is highly expressed in most cancer cells, and has been studied extensively as a driver of oncogenic metabolism. In contrast, the role of PKM2 in nontransformed cells is little studied, and nearly nothing is known of its role, if any, in quiescent cells. We show here that endothelial cells express PKM2 almost exclusively over PKM1. In proliferating endothelial cells, PKM2 is required to suppress p53 and maintain cell cycle progression. In sharp contrast, PKM2 has a strikingly different role in quiescent endothelial cells, where inhibition of PKM2 leads to degeneration of tight junctions and barrier function. Mechanistically, PKM2 regulates barrier function independently of its canonical activity as a pyruvate kinase. Instead, PKM2 suppresses NF-kB and its downstream target, the vascular permeability factor angiopoietin 2. As a consequence, loss of endothelial cell PKM2 in vivo predisposes mice to VEGF-induced vascular leak, and to severe bacteremia and death in response to sepsis. Together, these data demonstrate new roles of PKM2 in quiescent cells, and highlight the need for caution in developing cancer therapies that target PKM2.

Ginsenoside Rg1 supplementation clears senescence-associated β-galactosidase in exercising human skeletal muscle

Background

Ginsenoside Rg1 has been shown to clear senescence-associated beta-galactosidase (SA-β-gal) in cultured cells. It remains unknown whether Rg1 can influence SA-β-gal in exercising human skeletal muscle.

Methods

To examine SA-β-gal change, 12 young men (age 21 ± 0.2 years) were enrolled in a randomized double-blind placebo controlled crossover study, under two occasions: placebo (PLA) and Rg1 (5 mg) supplementations 1 h prior to a high-intensity cycling (70% VO_2max). Muscle samples were collected by multiple biopsies before and after cycling exercise (0 h and 3 h). To avoid potential effect of muscle biopsy on performance assessment, cycling time to exhaustion test (80% VO_2max) was conducted on another 12 participants (age 23 ± 0.5 years) with the same experimental design.

Results

No changes of SA-β-gal were observed after cycling in the PLA trial. On the contrary, nine of the 12 participants showed complete elimination of SA-β-gal in exercised muscle after cycling in the Rg1 trial (p < 0.05). Increases in apoptotic DNA fragmentation (PLA: +87% vs. Rg1: +133%, p < 0.05) and CD68⁺ (PLA: +78% vs. Rg1: +121%, p = 0.17) occurred immediately after cycling in both trials. During the 3-h recovery, reverses in apoptotic nuclei content (PLA: +5% vs. Rg1: −32%, p < 0.01) and increases in inducible nitrate oxide synthase and interleukin 6 mRNA levels of exercised muscle were observed only in the Rg1 trial (p < 0.01).

Conclusion

Rg1 supplementation effectively eliminates senescent cells in exercising human skeletal muscle and improves high-intensity endurance performance.

Cell proliferation assay – method optimisation for in vivo labeling of DNA in the rat forestomach

The study of cell proliferation is a useful tool in the fields of toxicology, pathophysiology and pharmacology. Cell proliferation and its degree can be evaluated using 5-bromo-2′-deoxyuridine which is incorporated into the newly synthesized DNA. The aim of this study was the optimization of subcutaneous application of 5-bromo-2′-deoxyuridine implantation for continuous and persistent marking of proliferating cells in the rat forestomach. 3-tert-Butyl-4-hydroxyanisole was used as the agent that ensures cell proliferation. In order to determine the optimal dose for proliferating cells labeling, 5-bromo-2′-deoxyuridine doses of 50 mg, 100 mg, 200 mg or 350 mg were implemented 2 days prior to sacrifice by flat-faced cylindrical matrices. Immunohistochemical analysis using 5-bromo-2′-deoxyuridine in situ detection kit was performed for the detection of 5-bromo-2′-deoxyuridine labeled cells. The results showed that for adult rats, the optimum 5-bromo-2′-deoxyuridine dose is 200 mg per animal for subcutaneous application. The here described manner of 5-bromo-2′-deoxyuridine in vivo labeling provides a simple, efficient, and reliable method for cell labeling, and at the same minimizes stress to animals.

Peroral administration of 5-bromo-2-deoxyuridine in drinking water is not a reliable method for labeling proliferating S-phase cells in rats

In rodents, peroral (p.o.) administration of 5-bromo-2'-deoxyuridine (BrdU) dissolved in drinking water is a widely used method for labeling newly formed cells over a prolonged time-period. Despite the broad applicability of this method, the pharmacokinetics of BrdU in rats or mice after p.o. administration remains unknown. Moreover, the p.o. route of administration may be limited by the relatively low amount of BrdU consumed over 24h and the characteristic drinking pattern of rats, with water intake being observed predominantly during the dark phase. Therefore, we investigated the reliability of staining proliferating S-phase cells with BrdU after p.o. administration (1mg/ml) to rats using both in vitro and in vivo conditions. Flow cytometric analysis of tumor cells co-cultivated with sera from experimental animals exposed to BrdU dissolved in drinking water or 25% orange juice revealed that the concentration of BrdU in the blood sera of rats throughout the day was below the detection limits of our assay. Ingested BrdU was only sufficient to label approximately 4.2±0.3% (water) or 4.2±0.3% (25% juice) of all S-phase cells. Analysis of data from in vivo conditions indicates that only 7.6±3.3% or 15.5±2.3% of all S-phase cells in the dentate gyrus of the hippocampus was labeled in animals administered drinking water containing BrdU during the light and dark phases of the day. In addition, the intensity of BrdU-positive nuclei in animals receiving p.o. administration of BrdU was significantly lower than in control animals intraperitoneally injected with BrdU. Our data indicate that the conventional approach of p.o. administration of BrdU in the drinking water to rats provides strongly inaccurate information about the number of proliferating cells in target tissues. Therefore other administration routes, such as osmotic mini pumps, should be considered for labeling of proliferating cells over a prolonged time-period.

Hematopoietic bone marrow cells participate in endothelial, but not epithelial or mesenchymal cell renewal in adult rats

The extent to which bone marrow (BM) contributes to physiological cell renewal is still controversial. Using the marker human placental alkaline phosphatase (ALPP) which can readily be detected in paraffin and plastic sections by histochemistry or immunohistochemistry, and in ultrathin sections by electron microscopy after pre-embedding staining, we examined the role of endogenous BM in physiological cell renewal by analysing tissues from lethally irradiated wild-type inbred Fischer 344 (F344) rats transplanted (BMT) with unfractionated BM from ALPP-transgenic F344 rats ubiquitously expressing the marker. Histochemical, immunohistochemical and immunoelectron microscopic analysis showed that the proportion of ALPP(+) capillary endothelial cells (EC) profoundly increased from 1 until 6 months after BMT in all organs except brain and adrenal medulla. In contrast, pericytes and EC in large blood vessels were ALPP(-) . Epithelial cells in kidney, liver, pancreas, intestine and brain were recipient-derived at all time-points. Similarly, osteoblasts, chondrocytes, striated muscle and smooth muscle cells were exclusively of recipient origin. The lack of mesenchymal BM-derived cells in peripheral tissues prompted us to examine whether BMT resulted in engraftment of mesenchymal precursors. Four weeks after BMT, all haematopoietic BM cells were of donor origin by flow cytometric analysis, whereas isolation of BM mesenchymal stem cells (MSC) failed to show engraftment of donor MSC. In conclusion, our data show that BM is an important source of physiological renewal of EC in adult rats, but raise doubt whether reconstituted irradiated rats are an apt model for BM-derived regeneration of mesenchymal cells in peripheral tissues.

Extending the knowledge in histochemistry and cell biology

Central to modern Histochemistry and Cell Biology stands the need for visualization of cellular and molecular processes. In the past several years, a variety of techniques has been achieved bridging traditional light microscopy, fluorescence microscopy and electron microscopy with powerful software-based post-processing and computer modeling. Researchers now have various tools available to investigate problems of interest from bird's- up to worm's-eye of view, focusing on tissues, cells, proteins or finally single molecules. Applications of new approaches in combination with well-established traditional techniques of mRNA, DNA or protein analysis have led to enlightening and prudent studies which have paved the way toward a better understanding of not only physiological but also pathological processes in the field of cell biology. This review is intended to summarize articles standing for the progress made in "histo-biochemical" techniques and their manifold applications.

State-of-the-art technologies, current opinions and developments, and novel findings: news from the field of histochemistry and cell biology

Investigations of cell and tissue structure and function using innovative methods and approaches have again yielded numerous exciting findings in recent months and have added important data to current knowledge, inspiring new ideas and hypotheses in various fields of modern life sciences. Topics and contents of comprehensive expert reviews covering different aspects in methodological advances, cell biology, tissue function and morphology, and novel findings reported in original papers are summarized in the present review.