Identity of tendon stem cells – how much do we know?

Tendon stem cells are multi‐potent adult stem cells with broad differentiation plasticity that render them of great importance in cell‐based therapies for the repair of tendons. We called them tendon‐derived stem cells (TDSCs) to indicate the tissue origin from which the stem cells were isolated in vitro. Based on the work of other sources of MSCs and specific work on TDSCs, some properties of TDSCs have been characterized / implicated in vitro. Despite these findings, tendon stem cells remained controversial cells. This was because MSCs residing in different organs, although very similar, were not identical cells. There is evidence of differences in stem cell‐related properties and functions related to tissue origins. Similar to other stem cells, tendon stem cells were identified and characterized in vitro. Their in vivo identities, niche (both anatomical locations and regulators) and roles in tendons were less understood. This review aims to summarize the current evidence of the possible anatomical locations and niche signals regulating the functions of tendon stem cells in vivo. The possible roles of tendon stem cells in tendon healing and non‐healing are presented. Finally, the potential strategies for understanding the in vivo identity of tendon stem cells are discussed.     

Regulation of cell proliferation, apoptosis, and carcinogenesis by activin

The aim of this review is to provide insight into the molecular mechanisms by which activin A modulates cell proliferation, apoptosis, and carcinogenesis in vitro and in vivo. Activin A, a member of the TGFbeta superfamily, has various effects on diverse biological systems, including cell growth inhibition in many cell types. However, the mechanism(s) by which activin exerts its inhibitory effects are not yet understood. This review highlights activin's effects on activin receptors and signaling pathway, modulation of activin signaling, and regulation of cell proliferation and apoptosis by activin. Based on the experiences of all the authors, we emphasized cell cycle inhibitors such as p16 and p21 and regulators of apoptosis such as p53 and members of the bcl-2 family. Aside from activin's inhibition of cell proliferation and enhancement of apoptosis, other newly developed methods for molecular studies of apoptosis by activin were briefly presented that support the role of activin as an inhibitor of carcinogenesis and cancer progression. These methods include subtractive hybridization based on covalent bonding, a simple and accurate means to determine molecular profile of as few as 20 cells based on an RNA-PCR approach, and a messenger RNA-antisense DNA interference phenomenon (D-RNAi), resulting in a long-term gene knockout effects.     

The clinical significance of thymidine kinase 1 measurement in serum of breast cancer patients using anti-TK1 antibody

The activity of total thymidine kinase in serum (S-TK) has been used as a tumor maker for decades. To date such activity has been determined using [125]I-iodo-deoxyuridine as a substrate. The aim of this study was to develop a new, antibody-based technique for the measurement of cytoplasmic thymidine kinase (TK1) in serum. Both mono- and polyclonal antibodies against S-TK1 were used in dot blot assay. S-TK1 was characterized by SDS and IEF techniques. Sixty-five breast cancer patients were studied, including 17 preoperative and 38 postoperative tumor-free patients and 10 patients with metastases to the lymph nodes (N1-2). They were compared to patients with benign tumors (n=21) and healthy volunteers (n=11). S-TK1 was low (0-1.0 pM) in healthy volunteers, while in preoperative patients the level was increased 6-110-fold. Significant differences were observed between preoperative patients and healthy volunteers (p=0.005), preoperative patients and patients with benign tumors (p<0.001), and preoperative patients and postoperative patients without metastases (p<0.001). No significant difference was observed between preoperative patients and postoperative patients with metastases (p=0.191). The S-TK activity in preoperative patients was also high in serum, but no decrease was observed following surgery. In conclusion, the anti-TK1 antibody could be a good marker for monitoring the response of breast cancer patients to therapy.     

Effects of precursors on serially propagated Digitalis lanata leaf and root cultures

Serially propagated Digitalis lanata leaf and root cultures established from germinated seeds were studied for digoxin production. Leaf cultures were grown and maintained in a medium containing benzyl adenine, and root cultures in the same medium with indoleacetic acid. A consistently high digoxin content, as determined by radio-immunoassay, is present in the leaf culture (9.0 mg % dry wt) and in root culture (1.9 mg % dry wt) as compared to unorganized cells (0.06 mg % dry wt). Leaf liquid cultures grew very rapidly as compared to the root cultures and the unorganized cell suspension cultures. The concentration of digoxin increased in both leaf and root cultures by adding to the medium either sodium glycocholate, cholesteryl acetate, or progesterone. Smilageninacetate increased the digoxin content of root cultures but not that of leaf cultures. Lanosterol and 5β-androstan-3,17-dione did not significantly increase the concentration of digoxin. Deoxycholic acid was toxic to the tissues studied.     

The Anabolic Androgenic Steroid Nandrolone Decanoate Disrupts Redox Homeostasis in Liver,Heart and Kidney of Male Wistar Rats

The abuse of anabolic androgenic steroids (AAS) may cause side effects in several tissues. Oxidative stress is linked to the pathophysiology of most of these alterations, being involved in fibrosis, cellular proliferation, tumorigenesis, amongst others. Thus, the aim of this study was to determine the impact of supraphysiological doses of nandrolone decanoate (DECA) on the redox balance of liver, heart and kidney. Wistar male rats were treated with intramuscular injections of vehicle or DECA (1 mg.100 g⁻¹ body weight) once a week for 8 weeks. The activity and mRNA levels of NADPH Oxidase (NOX), and the activity of catalase, glutathione peroxidase (GPx) and total superoxide dismutase (SOD), as well as the reduced thiol and carbonyl residue proteins, were measured in liver, heart and kidney. DECA treatment increased NOX activity in heart and liver, but NOX2 mRNA levels were only increased in heart. Liver catalase and SOD activities were decreased in the DECA-treated group, but only catalase activity was decreased in the kidney. No differences were detected in GPx activity. Thiol residues were decreased in the liver and kidney of treated animals in comparison to the control group, while carbonyl residues were increased in the kidney after the treatment. Taken together, our results show that chronically administered DECA is able to disrupt the cellular redox balance, leading to an oxidative stress state.     

Use of a large-scale Triticeae expressed sequence tag resource to reveal gene expression profiles in hexaploid wheat (Triticum aestivum L.).

The US Wheat Genome Project, funded by the National Science Foundation, developed the first large public Triticeae expressed sequence tag (EST) resource. Altogether, 116,272 ESTs were produced, comprising 100,674 5' ESTs and 15 598 3' ESTs. These ESTs were derived from 42 cDNA libraries, which were created from hexaploid bread wheat (Triticum aestivum L.) and its close relatives, including diploid wheat (T. monococcum L. and Aegilops speltoides L.), tetraploid wheat (T. turgidum L.), and rye (Secale cereale L.), using tissues collected from various stages of plant growth and development and under diverse regimes of abiotic and biotic stress treatments. ESTs were assembled into 18,876 contigs and 23,034 singletons, or 41,910 wheat unigenes. Over 90% of the contigs contained fewer than 10 EST members, implying that the ESTs represented a diverse selection of genes and that genes expressed at low and moderate to high levels were well sampled. Statistical methods were used to study the correlation of gene expression patterns, based on the ESTs clustered in the 1536 contigs that contained at least 10 5' EST members and thus representing the most abundant genes expressed in wheat. Analysis further identified genes in wheat that were significantly upregulated (p < 0.05) in tissues under various abiotic stresses when compared with control tissues. Though the function annotation cannot be assigned for many of these genes, it is likely that they play a role associated with the stress response. This study predicted the possible functionality for 4% of total wheat unigenes, which leaves the remaining 96% with their functional roles and expression patterns largely unknown. Nonetheless, the EST data generated in this project provide a diverse and rich source for gene discovery in wheat.     

Mitochondrial hydrogen peroxide production alters oxygen consumption in an oxygen-concentration-dependent manner

Metabolic responses of mammalian cells toward declining oxygen concentration are generally thought to occur when oxygen limits mitochondrial ATP production. However, at oxygen concentrations markedly above those limiting to mitochondria, several mammalian cell types display reduced rates of oxygen consumption without energy stress or compensatory increases in glycolytic ATP production. We used mammalian Jurkat T cells as a model system to identify mechanisms responsible for these changes in metabolic rate. Oxygen consumption was 31% greater at high oxygen (150–200 μM) compared to low oxygen (5–10 μM). Hydrogen peroxide was implicated in the response as catalase prevented the increase in oxygen consumption normally associated with high oxygen. Cell-derived hydrogen peroxide, predominately from the mitochondria, was elevated with high oxygen. Oxygen consumption related to intracellular calcium turnover was shown, through EDTA chelation and dantrolene antagonism of the ryanodine receptor, to account for 70% of the response. Oligomycin inhibition of oxygen consumption indicated that mitochondrial proton leak was also sensitive to changes in oxygen concentration. Our results point toward a mechanism in which changes in oxygen concentration influence the rate of hydrogen peroxide production by mitochondria, which, in turn, alters cellular ATP use associated with intracellular calcium turnover and energy wastage through mitochondrial proton leak.     

Evidence for the role of a trypsin-like enzyme in the hamster sperm acrosome reaction.

Acrosome reactions occurring in vitro in hamster sperm capacitated by bovine follicular fluid were severly inhibited by four synthetic trypsin inhibitors and by Zn2+. Three polypeptide trypsin inhibitors and a synthetic chymotrypsin inhibitor did not inhibit the acrosome reaction, and Ca2+ overcame the inhibition by Zn2+. These results suggest that a trypsin-like enzyme (possibly acrosin) plays a role in the acrosome reaction.