Dynamics of 5-methylcytosine and 5-hydroxymethylcytosine during pronuclear development in equine zygotes produced by ICSI

Background: Global epigenetic reprogramming is considered to be essential during embryo development to establish totipotency. In the classic model first described in the mouse, the genome-wide DNA demethylation is asymmetric between the paternal and the maternal genome. The paternal genome undergoes ten-eleven translocation (TET)-mediated active DNA demethylation, which is completed before the end of the first cell cycle. Since TET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine, the latter is postulated to be an intermediate stage toward DNA demethylation. The maternal genome, on the other hand, is protected from active demethylation and undergoes replication-dependent DNA demethylation. However, several species do not show the asymmetric DNA demethylation process described in this classic model, since 5-methylcytosine and 5-hydroxymethylcytosine are present during the first cell cycle in both parental genomes. In this study, global changes in the levels of 5-methylcytosine and 5-hydroxymethylcytosine throughout pronuclear development in equine zygotes produced in vitro were assessed using immunofluorescent staining. Results: We were able to show that 5-methylcytosine and 5-hydroxymethylcytosine both were explicitly present throughout pronuclear development, with similar intensity levels in both parental genomes, in equine zygotes produced by ICSI. The localization patterns of 5-methylcytosine and 5-hydroxymethylcytosine, however, were different, with 5-hydroxymethylcytosine homogeneously distributed in the DNA, while 5-methylcytosine tended to be clustered in certain regions. Fluorescence quantification showed increased 5-methylcytosine levels in the maternal genome from PN1 to PN2, while no differences were found in PN3 and PN4. No differences were observed in the paternal genome. Normalized levels of 5-hydroxymethylcytosine were preserved throughout all pronuclear stages in both parental genomes. Conclusions: In conclusion, the horse does not seem to follow the classic model of asymmetric demethylation as no evidence of global DNA demethylation of the paternal pronucleus during the first cell cycle was demonstrated. Instead, both parental genomes displayed sustained and similar levels of methylation and hydroxymethylation throughout pronuclear development

Eigenschappen en toekomstperspectieven van mesenchymale stamcellen bij honden

The therapeutic use of canine mesenchymal stem cells (cMSC) is rapidly expanding. MSC are stromal cells, which show multipotent stem cell properties in vitro. They possess trophic, immunoregulatory, antimicrobial and hematopoiesis-supportive properties. Moreover, injected MSC are able to migrate to sites of hypoxia and inflammation. Recently, more evidence has become available showing that MSC may originate from pericytes. Different microenvironments as well as non-standardized methods for their isolation and expansion lead to heterogeneous cell populations. Further research is essential in order to use these promising therapies without restrictions in dogs

Twisting of mummified remains around the umbilical cord as a potential risk of delayed twin reduction in the mare

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The lack of a representative tendinopathy model hampers fundamental mesenchymal stem cell research

Overuse tendon injuries are a major cause of musculoskeletal morbidity in both human and equine athletes, due to the cumulative degenerative damage. These injuries present significant challenges as the healing process often results in the formation of inferior scar tissue. The poor success with conventional therapy supports the need to search for novel treatments to restore functionality and regenerate tissue as close to native tendon as possible. Mesenchymal stem cell (MSC)-based strategies represent promising therapeutic tools for tendon repair in both human and veterinary medicine. The translation of tissue engineering strategies from basic research findings, however, into clinical use has been hampered by the limited understanding of the multifaceted MSC mechanisms of action. In vitro models serve as important biological tools to study cell behavior, bypassing the confounding factors associated with in vivo experiments. Controllable and reproducible in vitro conditions should be provided to study the MSC healing mechanisms in tendon injuries. Unfortunately, no physiologically representative tendinopathy models exist to date. A major shortcoming of most currently available in vitro tendon models is the lack of extracellular tendon matrix and vascular supply. These models often make use of synthetic biomaterials, which do not reflect the natural tendon composition. Alternatively, decellularized tendon has been applied, but it is challenging to obtain reproducible results due to its variable composition, less efficient cell seeding approaches and lack of cell encapsulation and vascularization. The current review will overview pros and cons associated with the use of different biomaterials and technologies enabling scaffold production. In addition, the characteristics of the ideal, state-of-the-art tendinopathy model will be discussed. Briefly, a representative in vitro tendinopathy model should be vascularized and mimic the hierarchical structure of the tendon matrix with elongated cells being organized in a parallel fashion and subjected to uniaxial stretching. Incorporation of mechanical stimulation, preferably uniaxial stretching may be a key element in order to obtain appropriate matrix alignment and create a pathophysiological model. Together, a thorough discussion on the current status and future directions for tendon models will enhance fundamental MSC research, accelerating translation of MSC therapies for tendon injuries from bench to bedside

Toepassingen van mesenchymale stamcellen bij het paard: huidige stand van zaken

Mesenchymal stem cells (MSC) are adult stem cells, which are capable of self-renewal and restricted differentiation into multiple organ-specific cell types. The significant therapeutic potential of MSC arises from their ability to promote tissue regeneration, prevent pathological scar formation, modulate immune responses and regulate inflammation. At present, MSC are mainly used in veterinary medicine to treat musculoskeletal injuries. Nevertheless, they may as well play a role in the treatment of several non-orthopedic diseases, such as immune-mediated, ischemic, inflammatory and neurological diseases. The treatment efficiency of MSC therapy can be influenced by the number of MSC which is used to treat the horse, the way the MSC are administered and the timing of the treatment. Moreover, there are advantages as well as disadvantages correlated to the use of autologons versus allogeneic MSC. The use of MSC in the treatment of equine injury has exciting potential. However; more fundamental research and well-designed clinical trials remain mandatory in order to safeguard the optimal routine clinical use of these valuable equine MSC at the patients' benefit

Gelokaliseerde steatitis als complicatie na dystokie bij een merrie

In this article, a case of localized steatitis is reported at the level of the perivaginal adipose tissue after dystocia in a mare. Although the mare initially recovered well postpartum, she died a few days later. At the second consultation, a knobby bump was present at both sides of the vaginal wall on vaginal examination. The intravaginal opening of these bumps was associated with the outflow of pus containing yellow-brown pieces of necrotic adipose tissue. Later on, steatitis at the level of the ligamentae vesicae and a bladder rupture were also observed at necropsy. These disorders probably accelerated the clinical symptoms resulting in shock. Generally, two types of steatitis are differentiated: localized and generalized steatitis. While only one fat depot is affected in the localized form, the disease involves several fat depots in the generalized form. Localized steatitis at the level of the perivaginal adipose tissue has not yet been described in the horse

Equine tenocyte seeding on gelatin hydrogels improves elongated morphology

(1) Background: Tendinopathy is a common injury in both human and equine athletes. Representative in vitro models are mandatory to facilitate translation of fundamental research into successful clinical treatments. Natural biomaterials like gelatin provide favorable cell binding characteristics and are easily modifiable. In this study, methacrylated gelatin (gel-MA) and norbornene-functionalized gelatin (gel-NB), crosslinked with 1,4-dithiotreitol (DTT) or thiolated gelatin (gel-SH) were compared. (2) Methods: The physicochemical properties (H-1-NMR spectroscopy, gel fraction, swelling ratio, and storage modulus) and equine tenocyte characteristics (proliferation, viability, and morphology) of four different hydrogels (gel-MA, gel-NB85/DTT, gel-NB55/DTT, and gel-NB85/SH75) were evaluated. Cellular functionality was analyzed using fluorescence microscopy (viability assay and focal adhesion staining). (3) Results: The thiol-ene based hydrogels showed a significantly lower gel fraction/storage modulus and a higher swelling ratio compared to gel-MA. Significantly less tenocytes were observed on gel-MA discs at 14 days compared to gel-NB85/DTT, gel-NB55/DTT and gel-NB85/SH75. At 7 and 14 days, the characteristic elongated morphology of tenocytes was significantly more pronounced on gel-NB85/DTT and gel-NB55/DTT in contrast to TCP and gel-MA. (4) Conclusions: Thiol-ene crosslinked gelatins exploiting DTT as a crosslinker are the preferred biomaterials to support the culture of tenocytes. Follow-up experiments will evaluate these biomaterials in more complex models

Characterization and profiling of immunomodulatory genes of equine mesenchymal stromal cells from non-invasive sources

Introduction: Mesenchymal stromal cells (MSCs) have been extensively studied for their promising capabilities in regenerative medicine. Although bone marrow is the best-known source for isolating equine MSCs, non-invasive alternative sources such as umbilical cord blood (UCB), umbilical cord matrix (UCM), and peripheral blood (PB) have also been reported. Methods: Equine MSCs from three non-invasive alternative sources were isolated from six individual mares (PB) and their foals (UCB and UCM) at parturition. To minimize inter-horse variability, the samples from the three sources were matched within the same mare and for UCB and UCM even within the same foal from that specific mare. The following parameters were analyzed: (i) success rate of isolation, (ii) proliferation capacity, (iii) tri-lineage differentiation ability, (iv) immunophenotypical protein, and (v) immunomodulatory mRNA profiles. Linear regression models were fit to determine the association between the source of MSCs (UCB, UCM, PB) and (i) the moment of first observation, (ii) the moment of first passage, (iii) cell proliferation data, (iv) the expression of markers related to cell immunogenicity, and (v) the mRNA profile of immunomodulatory factors, except for hepatocyte growth factor (HGF) as no normal distribution could be obtained for the latter variable. To evaluate the association between the source of MSCs and the mRNA expression of HGF, the non-parametric Kruskal-Wallis test was performed instead. Results: While equine MSCs could be isolated from all the UCB and PB samples, isolation from UCM was successful in only two samples because of contamination issues. Proliferation data showed that equine MSCs from all three sources could be easily expanded, although UCB-derived MSCs appeared significantly faster in culture than PB- or UCM-derived MSCs. Equine MSCs from both UCB and PB could be differentiated toward the osteo-, chondro-, and adipogenic lineage, in contrast to UCM-derived MSCs in which only chondro-and adipogenic differentiation could be confirmed. Regardless of the source, equine MSCs expressed the immunomodulatory genes CD40, CD80, HGF, and transforming growth factor-beta (TGF beta). In contrast, no mRNA expression was found for CD86, indoleamine 2,3-dioxygenase (IDO), and tumor necrosis factor-alpha (TNF alpha). Conclusions: Whereas UCM seems less feasible because of the high contamination risks and low isolation success rates, UCB seems a promising alternative MSC source, especially when considering allogeneic MSC use

Ovarian teratoma in the mare: a review and two cases

A 4-year-old Belgian Warmblood mare suffering from pelvic flexure impaction was diagnosed with a teratoma of the left ovary. The enlarged ovary was identified several days after treatment of the impaction. Surgical removal of the affected ovary was performed and histo pathological examination confirmed the presence of a teratoma. The features of another ovarian teratoma, which was an accidental finding at slaughter, are also described