An introduction to stem cells

1998 saw the publication of two papers describing the growth in vitro of human embryonic stem (ES) cells derived either from the inner cell mass (ICM) of the early blastocyst or the primitive gonadal regions of early aborted fetuses. Work on murine ES cells over many years had already established the amazing flexibility of ES cells, essentially able to differentiate into almost all cells that arise from the three germ layers. The realization of such pluripotentiality (see below) has, of course, resulted in the field of stem cell research going into overdrive, the establishment of many new biotechnology companies (http://www.stemcellresearchnew.com/catalog1677.html), and a genuine belief that stem cell research will deliver a revolution in terms of how we treat cardiovascular disease, neurodegenerative disease, cancer, diabetes, and the like. However, many people believe that early human embryos should be accorded the same status as any sentient being and thus their 'harvesting' for stem cells is morally unjustifiable. With this in mind, other sources of malleable stem cells have been sought. In the adult, organ formation and regeneration was thought to occur through the action of organ- or tissue-restricted stem cells (i.e. haematopoietic stem cells giving rise to all the cells of the blood, neural stem cells making neurons, astrocytes, and oligodendrocytes). However, it is now believed that stem cells from one organ system, for example the haematopoietic compartment can develop into the differentiated cells within another organ system, such as the liver, brain or kidney. Thus, certain adult stem cells may turn out be as malleable as ES cells and so also be useful in regenerative medicine. This brief overview summarizes the important attributes of tissue-based stem cells and clarifies the terms used.     

Anxiety Treatment and Targeted Sleep Enhancement to Address Sleep Disturbance in Pre/Early Adolescents with Anxiety

Sleep disturbance is prevalent in anxious youth and prospectively predicts poor emotional adjustment in adolescence. Study 1 examined whether anxiety treatment improves subjective and objective sleep disturbance in anxious youth. Study 2 examined whether a sleep intervention called Sleeping TIGERS can further improve sleep following anxiety treatment. Study 1 examined 133 youth (ages 9–14; 56% female; 11% ethnic/racial minority) with generalized, social, or separation anxiety over the course of anxiety treatment (cognitive behavioral treatment or client-centered treatment). Sleep-related problems (parent-, child-report) and subjective (diary) and objective (actigraphy) sleep patterns were assessed across treatment in an open trial design. Study 2 included 50 youth (ages 9–14; 68% female; 10% ethnic/racial minority) who continued to report sleep-related problems after anxiety treatment and enrolled in an open trial of Sleeping TIGERS. Pre- and postassessments duplicated Study 1 and included the Focal Interview of Sleep to assess sleep disturbance. Study 1 demonstrated small reductions in sleep problems and improvements in subjective sleep patterns (diary) across anxiety treatment, but outcomes were not deemed clinically significant, and 75% of youth stayed above clinical cutoff. Study 2 showed clinically significant, large reductions in sleep problems and small changes in some subjective sleep patterns (diary). Anxiety treatment improves, but does not resolve, sleep disturbance in peri-pubertal youth, which may portend risk for poor emotional adjustment and mental health. The open trial provides preliminary support that Sleeping TIGERS can improve sleep in anxious youth to a clinically significant degree.     

Y chromosome deletions in azoospermic and severely oligozoospermic men undergoing intracytoplasmic sperm injection after testicular sperm extraction

Y chromosome deletions encompassing the AZFc region have been reported in 13% of azoospermic men and 7% of severely oligozoospermic men. We examined the impact of these Y deletions on the severity of testicular defects in 51 azoospermic men undergoing intracytoplasmic sperm injection (ICSI) after testicular sperm extraction (TESE) and 30 men with severe oligozoospermia undergoing ICSI after ejaculation of spermatozoa. In addition, five azoospermic patients shown previously to have Y chromosome deletions underwent histological evaluation of their previously obtained testis biopsy specimens. A further 27 azoospermic men underwent TESE-ICSI, but not Y chromosome DNA testing. Ten of 51 azoospermic men (20%) who underwent TESE-ICSI and Y-DNA testing were found to be deleted for portions of the Y chromosome AZFc region. Of these 10, five had spermatozoa retrievable from the testis, and in two cases the wives became pregnant. Of the 41 azoospermic men with no Y chromosome deletion, 22 (54%) had spermatozoa retrievable from the testis, and in 12 cases (29%) the wives became pregnant. Four of 30 (13%) severely oligozoospermic patients were found to be deleted for AZFc and in three (75%) of these pregnancy was achieved. The other 26 severely oligozoospermic couples who had no AZFc deletions underwent ICSI, and 12 (46%) have an ongoing or delivered pregnancy. The embryo implantation rate was not significantly different for azoospermic (22%), oligozoospermic (16%), Y-deleted (14%) or Y-intact (18%) men. Of the total of 19 infertile men who had Y chromosome deletions, 14 had deletions within Y chromosome intervals 6D-6F, in the AZFc region. Twelve of those 14 had some spermatozoa (however few in number) in the ejaculate or testis. Five of the Y-deleted men had deletions that extended more proximally on the Y chromosome, and in none of these could any spermatozoa be observed in either ejaculate or testis. These results support the concept that, in azoospermic or oligozoospermic men with Y chromosome deletions limited to intervals 6D-6F (AZFc), there are generally very small numbers of testicular or ejaculated spermatozoa. Larger Y deletions, including and extending beyond the AZFc region and encompassing more Y genes, tend to be associated with a total absence of testicular spermatozoa. In those cases where spermatozoa were retrieved, the presence of Y deletions had no obvious impact on fertilization or pregnancy rate.      

Improved oocyte quality is obtained with follicle stimulating hormone alone than with follicle stimulating hormone/human menopausal gonadotrophin combination

The aim of this study was to compare the efficacy of pure follicle stimulating hormone (FSH) with that of FSH/human menopausal gonadotrophin (HMG) combination in downregulated cycles. A total of 357 patients was evaluated retrospectively. Sixty percent of patients in the FSH group and 55% in the FSH/HMG group were new; the others were repeat patients. Ovulation was suppressed with leuprolide acetate in all patients, followed by either FSH (n = 218) or FSH/HMG (n = 119). There was no difference in patients' age, infertility factors, number of ampoules used, length of stimulation, oestradiol levels on day of human chorionic gonadotrophin (HCG) administration, number of oocytes recovered or the number of embryos transferred. Also, nuclear maturity at aspiration and fertilization rates were not different between the two groups. FSH stimulation resulted in a significantly higher percentage of mature oocytes that showed the typical 'mature' morphological characteristics (P < 0.0001). The clinical pregnancy rates per transfer were 40 and 28% in patients stimulated with pure FSH and FSH/HMG respectively (P < 0.05). The significantly higher number of immature oocytes matured in vitro in the FSH/HMG group (P = 0.001) suggests a possible effect on in-vitro maturation, due to luteinizing hormone present in HMG. The difference in mature oocyte quality may be an important determinant in the higher pregnancy rates for the FSH- stimulated patients.      

Elevation of serum sex hormone-binding globulin in females with fulminant hepatitis B virus infection

Amongst adults exposed to the hepatitis B virus (HBV), the infection pursues a fulminant course more frequently in females, while conversely a chronic carrier state is more frequent in males. Because of these differences in sex ratio, we investigated the relationship between the outcome of HBV infection and serum concentrations of sex hormone-binding globulin (SHBG), a circulating glycoprotein that exerts an important influence on the balance of free sex hormones. SHBG levels were significantly elevated in females with fulminant HBV infection compared to females with either uncomplicated acute or chronic HBV infection (P less than .05 and P less than .001, respectively). That this was not a nonspecific effect of fulminant hepatitis was confirmed by the significantly higher levels in this group than in age-matched females with fulminant hepatitis unrelated to HBV (P less than .05). In contrast, four of 15 female HBsAg carriers had SHBG values in the male range, and these included three of four patients who had acquired HBV as adults. SHBG levels were normal in all male groups. These results suggested that for adults the hormonal environment may be important in determining the course of HBV infection.     

Frequency and ethnic distribution of the common DHCR7 mutation in Smith‐Lemli‐Opitz syndrome

Smith‐Lemli‐Opitz syndrome (SLOS) is an inherited multiple malformation syndrome caused by enzymatic deficiency of 3β‐hydroxysterol‐Δ⁷‐reductase (DHCR7). SLOS is thought to be most common among European Caucasians, with an incidence of 1 in 20,000 to 1 in 30,000 births. To define the carrier rate and ethnic distribution of SLOS, we screened DNA samples from 2,978 unrelated individuals for the most common SLOS mutation (IVS8‐1G→C). Twenty‐four heterozygotes of the IVS8‐1G→C mutation were detected in 2,978 individuals of European Caucasian and Black backgrounds. For European Caucasians, the carrier rate for SLOS may be as high as 1 in 30, suggesting an incidence of 1 in 1,700 to 1 in 13,400. This high number is supported by the recent observation of newborn and prenatal incidence of 1 in 22,000 in the Caucasian population. Ours is the first report of the IVS8‐1G→C mutation in persons of African ancestry. Published 2001 Wiley‐Liss, Inc.     

Endocardial infiltrates in human heart transplants: a serial biopsy analysis comparing four immunosuppression protocols

Endocardial mononuclear cell infiltrates were studied in 2,350 consecutive biopsies from 172 patients over a period ranging from 4 to 16 months post cardiac transplantation. The patients, otherwise unselected, were equally subdivided into four groups based upon the specific type of maintenance immunosuppression used. This was to allow for comparison of the effects of four separate commonly used recipient immunosuppression protocols, which could potentially influence the characteristics of the infiltrates. With azathiaprine-corticosteroid immunosuppression, endocardial infiltrates in otherwise normal biopsies were exceedingly rare, very minor, and invariably unifocal. Mild and moderate rejection were associated with a highly significant stepwise increase in incidence, prominence, and multifocality of endocardial infiltrates. In contrast, with each of the three cyclosporine-based recipient immunosuppression protocols which were evaluated, approximately 15% of biopsies with no evidence of rejection were associated with endocardial infiltrates. There was a wide range of variation in the prominence of the endocardial infiltrates present. Multifocal infiltrates were frequently encountered, the incidence of which was exclusively dependent upon the specific cyclosporine-based immunosuppression protocol used. With mild and with moderate rejection there was a significant stepwise increase in overall biopsy incidence of all endocardial infiltrates in each of the three groups, although there was no variation in relative prominence of the infiltrates, or in incidence of multifocality when biopsies without rejection were compared. The presence of conspicuous vascular spaces within endocardial infiltrates and significant extension of the infiltrates into the adjacent myocardium, with or without associated myofiber necrosis, were characteristic features of the most prominent endocardial infiltrates in all three cyclosporine-based immunosuppression groups. This constellation of changes has sometimes been referred to as "Quilty" effect. The relative incidence with which these particular features were encountered in association with endocardial infiltrates did not vary with rejection category of the biopsies. This study has shown that the presence of all forms of endocardial infiltrates, in the absence of concomitant rejection, is a characteristic manifestation of cyclosporine-based recipient immunosuppression, regardless of the specific protocol and cyclosporine dosage schedule. Under azathiaprine-based immunosuppression, endocardial infiltrates are almost invariably associated with rejection. It is postulated that cyclosporine-related endocardial mononuclear cell infiltration, in the absence of overt rejection, may result from a low level alloimmune response secondary to fluctuations in cyclosporine drug levels or related factors, and that the incidence with these infiltrates occur can be augmented during acute rejection episodes when the strength of the recipient immune response is magnified.