Pavel Klein

Solid-state photocrosslinking of hyaluronan microfibres

Hyaluronan (HA) was chemically modified to a photocurable derivative by the acylation with a mixed anhydride of trans-cinnamic acid and characterized by UV, IR and 2D NMR spectroscopy. Photocurable HA was processed to a microfibrous structure by wet-spinning technology. Water solubility of otherwise water-soluble HA microfibres was reduced significantly by the solid-state photocrosslinking. We also investigated that the nature of polymer structure had a great impact to a final crosslink ratio. The analysis of the mechanical properties showed higher ultimate tensile strength and increased rigidity of the photocrosslinked fibres in comparison to the untreated ones. Moreover all tested materials are regarded as biocompatible according to the tests of cell viability, phototoxicity and enzymatic degradability, which make them suitable candidates for numerous biomedical applications.

Endogenously produced hydrogen sulfide is involved in porcine oocyte maturation in vitro.

Hydrogen sulfide, one of three known gasotransmitters, is involved in physiological processes, including reproductive functions. Oocyte maturation and surrounding cumulus cell expansion play an essential role in female reproduction and subsequent embryonic development. Although the positive effects of exogenous hydrogen sulfide on maturing oocytes are well known, the role of endogenous hydrogen sulfide, which is physiologically released by enzymes, has not yet been described in oocytes. In this study, we observed the presence of Cystathionine β-Synthase (CBS), Cystathionine γ-Lyase (CTH) and 3-Mercaptopyruvate Sulfurtransferase (3-MPST), hydrogen sulfide-releasing enzymes, in porcine oocytes. Endogenous hydrogen sulfide production was detected in immature and matured oocytes as well as its requirement for meiotic maturation. Individual hydrogen sulfide-releasing enzymes seem to be capable of substituting for each other in hydrogen sulfide production. However, meiosis suppression by inhibition of all hydrogen sulfide-releasing enzymes is not irreversible and this effect is a result of M-Phase/Maturation Promoting Factor (MPF) and Mitogen-Activated Protein Kinase (MAPK) activity inhibition. Futhermore, cumulus expansion expressed by hyaluronic acid (HA) production is affected by the inhibition of hydrogen sulfide production. Moreover, quality changes of the expanded cumuli are indicated. These results demonstrate hydrogen sulfide involvement in oocyte maturation as well as cumulus expansion. As such, hydrogen sulfide appears to be an important cell messenger during mammalian oocyte meiosis and adequate cumulus expansion.

Chondrocyte Cultivation in Hyaluronan-Tyramine Cross-Linked Hydrogel

The application of chondrocyte-seeded hydrogels, such as tyramine-substituted hyaluronan, is a highly promising strategy for damaged cartilage treatments. The rheological characteristics of hyaluronan-tyramine derivative scaffold were determined together with the hydrogel swelling, the water uptake, and the morphological characterization. The chondrocytes seeded in hyaluronan-tyramine hydrogel were viable and expressed markers typical for differentiated chondrocytes with no signs of hypertrophy or extensive expression of matrix metalloproteinases. The lyophilized unseeded hyaluronan-tyramine scaffolds were also implantated into trochlea osteochondral defects in rabbits. In conclusion, the hyaluronan-tyramine derivative was proven to be advisable material as a scaffold for cartilage reconstitution. GRAPHICAL ABSTRACT

A simple method for assessing hyaluronic acid production by cumulus-oocyte complexes

The cumulus expansion of cumulus-oocyte complex (COC) is an essential regulating process of oocyte maturation and as such it is a possible biomarker of the in vitro maturing oocytes quality. Cumulus expansion is usually assessed by non-invasive methods based on visual evaluation with many inaccuracies. On the other hand, analytical measurement of the quantity of hyaluronic acid (HA), the most abundant compound of expanded cumuli, is one of possible methods to evaluate cumulus expansion precisely. Therefore, this study aimed to verify the applicability of HA analysis for evaluating the cumulus expansion and testing oocyte maturation. The COCs were cultured in modified M199 medium for 8–48 h. The samples for the HA analysis were prepared on an 8-hour time scale, and HA retained in COCs was measured using a spectrophotometric method adapted for this purpose. We observed an increasing quantity of HA during the in vitro cultivation. A comparison with expanded COCs’ classification or expansion area proved the proposed method of HA analysis suitable for the evaluation of cumulus expansion in vitro. Our findings consider the quantity of HA-expressed cumulus expansion to be a valuable marker of COC quality enabling an adequate oocyte meiotic stage estimation.

Cumulus Cell Expansion, Its Role in Oocyte Biology and Perspectives of Measurement: A Review

Abstract Cumulus expansion of the cumulus-oocyte complex is necessary for meiotic maturation and acquiring developmental competence. Cumulus expansion is based on extracellular matrix synthesis by cumulus cells. Hyaluronic acid is the most abundant component of this extracellular matrix. Cumulus expansion takes place during meiotic oocyte maturation under in vivo and in vitro conditions. Quantification and measurement of cumulus expansion intensity is one possible method of determining oocyte quality and optimizing conditions for in vitro cultivation. Currently, subjective methods of expanded area and more exact cumulus expansion measurement by hyaluronic acid assessment are available. Among the methods of hyaluronic acid measurement is the use of radioactively labelled synthesis precursors. Alternatively, immunological and analytical methods, including enzyme-linked immunosorbent assay (ELISA), spectrophotometry, and high-performance liquid chromatography (HPLC) in UV light, could be utilized. The high sensitivity of these methods could provide a precise analysis of cumulus expansion without the use of radioisotopes. Therefore, the aim of this review is to summarize and compare available approaches of cumulus expansion measurement, respecting special biological features of expanded cumuli, and to suggest possible solutions for exact cumulus expansion analysis.

A porcine model of skin wound infected with a polybacterial biofilm

Abstract A clinically relevant porcine model of a biofilm-infected wound was established in 10 minipigs. The wounds of six experimental animals were infected with a modified polymicrobial Lubbock chronic wound biofilm consisting of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Bacillus subtilis. Four animals served as uninfected controls. The wounds were monitored until they had healed for 24 days. The biofilm persisted in the wounds up to day 14 and significantly affected healing. The control to infected healed wound area ratios were: 45%/21%, 66%/37%, and 90%/57% on days 7, 10 and 14, respectively. The implanted biofilm prolonged inflammation, increased necrosis, delayed granulation and impaired development of the extracellular matrix as seen in histological and gene expression analyses. This model provides a therapeutic one-week window for testing of anti-biofilm treatments and for research on the pathogenesis of wound infections in pig that is clinically the most relevant animal wound healing model.

Sugar and nutritional extremism

ABSTRACT For many, sugar represents a threat to their health, a perception that is driven by increase in the prevalence of obesity, diabetes, and metabolic disorders, which directly or indirectly is connected with the consumption of sugar. However, is sugar to blame for this health crisis, or are sedentary lifestyle and unhealthy diet equally important? Today, sugars and fats are being targeted for restriction or even prohibition. Should we get rid of sugar altogether and/or does it merit a reprieve? Is the effort to “outlaw” sugars a symptom of nutritional extremism that can be as harmful as any other type of extremism?