Human diseased arteries contain cells expressing leukocytic and embryonic stem cell markers

Profiling natural serum antibodies of non-human primates with a carbohydrate antigen microarray

BACKGROUND

Engineering of α-Galactosyltransferase gene-knockout pigs circumvented hyperacute rejection of pig organs after xenotransplantation in non-human primates. Overcoming this hurdle revealed the importance of non-α-Gal carbohydrate antigens in the immunobiology of acute humoral xenograft rejection.

METHODS

This study analyzed serum from seven naïve cynomolgus monkeys (blood type O/B/AB = 3/2/2) for the intensity of natural IgM and IgG signals using carbohydrate antigen microarray, which included historically reported α-Gal and non-α-Gal carbohydrate antigens with various modifications.

RESULTS

The median (range) of IgM and IgG signals were 12.71 (7.23-16.38) and 9.05 (7.23-15.90), respectively. The highest IgM and IgG signals with narrowest distribution were from mono- and disaccharides, followed by modified structures. Natural anti-α-Gal antibody signals were medium to high in IgM (11.2-15.9) and medium in IgG (8.5-11.6) spectra, and was highest with Lac core structure (Galα1-3Galβ1-4Glc, iGb3) and lowest with LacNAc core structure (Galα1-3Galβ1-4GlcNAc). Similar signal intensities (up to 15.8 in IgM and up to 11.8 in IgG) were observed for historically detected natural non-α-Gal antigens, which included Tn antigen, T antigen, GM2 glycolipid, and Sd^a antigen. The hierarchical clustering analysis revealed the presence of clusters of anti-A antibodies and was capable of distinguishing between the blood group B and AB non-human primates.

CONCLUSIONS

The results presented here provide the most comprehensive evaluation of natural antibodies present in cynomolgus monkeys.

The Effect of Recombinant Undercarboxylated Osteocalcin on Endothelial Dysfunction

Low circulating levels of undercarboxylated osteocalcin (ucOC) is associated with a higher risk of cardiovascular disease, yet whether ucOC has a direct effect on endothelium-dependent vasorelaxation, or in proximity to its postulated receptor, the class CG protein-coupled receptor (GPCR6A), in blood vessels remains unclear. Immunohistochemistry and proximity ligation assays were used to localize the presence of ucOC and GPRC6A and to determine the physical proximity (< 40 nm) in radial artery segments collected from patients undergoing coronary artery bypass surgery (n = 6) which exhibited calcification (determined by Von Kossa) and aorta from New Zealand white rabbits exhibiting atherosclerotic plaques. Endothelium-dependent vasorelaxation was assessed using cumulative doses of acetylcholine in vitro on abdominal aorta of rabbits fed a normal chow diet (n = 10) and a 4-week atherogenic diet (n = 9) pre-incubated with ucOC (10 ng/mL) or vehicle. Both ucOC and GPRC6A were localized in human and rabbit diseased-blood vessels. Proximity ligation assay staining demonstrated physical proximity of ucOC with GPRC6A only within plaques in rabbit arteries and the endothelium layer of rabbit arterioles. Endothelium-dependent vasorelaxation was impaired in atherogenic abdominal aorta compared to healthy aorta and ucOC attenuated this impairment. ucOC attenuated impaired endothelium-dependent vasorelaxation in rabbit abdominal aorta following an atherogenic diet, however, this effect may be independent of GPRC6A. It is important that future studies determine the underlying cellular mechanisms by which ucOC effects blood vessels as well as whether it can be used as a therapeutic agent against the progression of atherosclerosis.

Evidence for CD34/SMA positive cells in the left main coronary artery in atherogenesis

Regression of atherosclerosis is a key aspect of preventing further coronary artery disease and understanding which cell type forms smooth muscle cells in atherosclerotic fibrous caps will aid in reducing CAD. Atherogenesis is a complex interplay of cells migrating and proliferating into the vascular wall. CD34 positive hemapoetic stem cells are believed to not transform into vascular smooth muscle cells (SMC). The current study hypothesised that there would be no evidence for CD34(+)/α SMC actin(+) cells in atherosclerotic coronary arteries.

AIMS

To identify CD34+/α actin positive cells in the fibrous cap and wall of atherosclerotic plaques in the coronary artery.

METHODS

Male New Zealand White rabbits were fed a diet containing 0.5% cholesterol and 1% methionine for 4 weeks, then 9 weeks of normal diet to induce regression. Immunohistochemistry was used to detect CD34(+) haematopoietic progenitor cells and α SMC actin.

RESULTS

In the fibrous cap, the majority of cells were CD34(-)/α SMC actin(+) spindle shaped cells. However very rare populations of CD34(+)/α SMC actin(+) and CD34(+)/α SMC actin(-) cells were also present but these cells were not spindle shaped.

CONCLUSION

Our study found that CD34(+)/α SMC actin(-) spindle shaped cells were absent from the fibrous cap. Moreover, the predominant cell population were the vascular smooth muscle cells (CD34(-)/α SMC actin(+)) but (CD34(+)/α SMC actin(+)) cells were also present. This model could be used to understand the role of each SMC population subtype to hasten atherosclerotic regression in the coronary artery.

Human skin cells that express stage-specific embryonic antigen 3 associate with dermal tissue regeneration

Stage-specific embryonic antigen 3 (SSEA3) is a glycosphingolipid that has previously been used to identify cells with stem cell-like, multipotent, and pluripotent characteristics. A rare subpopulation of SSEA3-expressing cells exists in the dermis of adult human skin. These SSEA3-expressing cells undergo a significant increase in cell number in response to injury, suggesting a possible role in regeneration. These SSEA3-expressing regeneration-associated (SERA) cells were derived through primary cell culture, purified by fluorescence-activated cell sorting (FACS), and characterized. Longer in vitro culture of the primary skin cells led to lower SSEA3 expression stability after FACS-based purification, suggesting that the current culture conditions may need to be optimized to permit the large-scale expansion of SERA cells. The SERA cells demonstrated a global transcriptional state that was most similar to bone marrow- and fat-derived mesenchymal stem cells (MSCs), and the highest expressing SSEA3-expressing cells co-expressed CD105 (clone 35). However, while a rare population of MSCs was observed in primary human skin cell cultures that could differentiate into adipocytes, osteoblasts, or chondrocytes, SERA cells did not possess this differentiation capacity, suggesting that there are at least two different rare subpopulations in adult human skin primary cultures. The identification, efficient purification, and large-scale expansion of these rare subpopulations (SERA cells and MSCs) from heterogeneous adult human skin primary cell cultures may have applications for future patient-specific cellular therapies.

Reinterpretation of evidence advanced for neo-oogenesis in mammals, in terms of a finite oocyte reserve

The central tenet of ovarian biology, that the oocyte reserve in adult female mammals is finite, has been challenged over recent years by proponents of neo-oogenesis, who claim that germline stem cells exist in the ovarian surface epithelium or the bone marrow. Currently opinion is divided over these claims, and further scrutiny of the evidence advanced in support of the neo-oogenesis hypothesis is warranted - especially in view of the enormous implications for female fertility and health. This article contributes arguments against the hypothesis, providing alternative explanations for key observations, based on published data. Specifically, DNA synthesis in germ cells in the postnatal mouse ovary is attributed to mitochondrial genome replication, and to DNA repair in oocytes lagging in meiotic progression. Lines purported to consist of germline stem cells are identified as ovarian epithelium or as oogonia, from which cultures have been derived previously. Effects of ovotoxic treatments are found to negate claims for the existence of germline stem cells. And arguments are presented for the misidentification of ovarian somatic cells as de novo oocytes. These clarifications, if correct, undermine the concept that germline stem cells supplement the oocyte quota in the postnatal ovary; and instead comply with the theory of a fixed, unregenerated reserve. It is proposed that acceptance of the neo-oogenesis hypothesis is erroneous, and may effectively impede research in areas of ovarian biology. To illustrate, a novel explanation that is consistent with orthodox theory is provided for the observed restoration of fertility in chemotherapy-treated female mice following bone marrow transplantation, otherwise interpreted by proponents of neo-oogenesis as involving stimulation of endogenous germline stem cells. Instead, it is proposed that the chemotherapeutic regimens induce autoimmunity to ovarian antigens, and that the haematopoietic chimaerism produced by bone marrow transplantation circumvents activation of an autoreactive response, thereby rescuing ovarian function. The suggested mechanism draws from animal models of autoimmune ovarian disease, which implicate dysregulation of T cell regulatory function; and from a surmised role for follicular apoptosis in the provision of ovarian autoantigens, to sustain self-tolerance during homeostasis. This interpretation has direct implications for fertility preservation in women undergoing chemotherapy.

Carbohydrate engineered cells for regenerative medicine

Carbohydrates are integral components of the stem cell niche on several levels; proteoglycans are a major constituent of the extracellular matrix (ECM) surrounding a cell, glycosoaminoglycans (GAGs) help link cells to the ECM and the neighboring cells, and small but informationally-rich oligosaccharides provide a "sugar code" that identifies each cell and provides it with unique functions. This article samples roles that glycans play in development and then describes how metabolic glycoengineering - a technique where monosaccharide analogs are introduced into the metabolic pathways of a cell and are biosynthetically incorporated into the glycocalyx - is overcoming many of the long-standing barriers to manipulating carbohydrates in living cells and tissues and is becoming an intriguing new tool for tissue engineering and regenerative medicine.

Co-localization of angiotensin-converting enzyme 2-, octomer-4- and CD34-positive cells in rabbit atherosclerotic plaques

Angiotensin‐converting enzyme 2 (ACE2) is a novel enzyme with possible implications in the treatment of blood pressure disorders. Recent evidence suggests that an upregulation of ACE2 can be stimulated by all‐trans retinoic acid (at‐RA); however, at‐RA also affects regulation of the stem‐cell marker octomer‐4 (Oct‐4) and thus cellular differentiation. We have previously shown that smooth muscle cells and macrophages present within rabbit atherosclerotic plaques are positive for ACE2, Oct‐4 and the haematopoietic stem‐cell marker CD34. Thus, to provide evidence that possible at‐RA treatment could affect both plaque cellular biology (via effects on cellular differentiation) and blood pressure (via ACE2), it is vital to show that cells with atherosclerotic plaques co‐express all three markers. Thus, we sought to provide evidence that a subset of cells within atherosclerotic plaques is positive for ACE2, Oct‐4 and CD34. We used New Zealand White rabbits that were fed a control diet supplemented with 0.5% cholesterol plus 1% methionine for 4 weeks and then allowed to consume a normal diet for 10 weeks. Immunohistochemistry was performed by standard techniques. We report that ACE2, Oct‐4 and CD34 were all present within atherosclerotic plaques. Although macrophages were positive for all three markers, spindle‐shaped cells in the media did not show all three markers. The endothelium overlying normal arterial wall showed positive Oct‐4 and ACE2 immunoreactivity, but CD34 immunoreactivity was patchy, indicating that such cells might not have fully differentiated. It is concluded that cells in atherosclerotic plaques express co‐express ACE2, Oct‐4 and CD34. Further studies aimed at establishing the effects of all‐trans retinoic acid on blood pressure and atherosclerotic cell differentiation are warranted.