Asa C. Black

Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis derived from fetal, adult, and geriatric donors

This study details the profile of 13 cell surface cluster differentiation markers on human reserve stem cells derived from connective tissues. Stem cells were isolated from the connective tissues of dermis and skeletal muscle derived from fetal, mature, and geriatric humans. An insulin/dexamethasone phenotypic bioassay was used to determine the identity of the stem cells from each population. All populations contained lineage‐committed myogenic, adipogenic, chondrogenic, and osteogenic progenitor stem cells as well as lineage‐uncommitted pluripotent stem cells capable of forming muscle, adipocytes, cartilage, bone, fibroblasts, and endothelial cells. Flow cytometric analysis of adult stem cell populations revealed positive staining for CD34 and CD90 and negative staining for CD3, CD4, CD8, CD11c, CD33, CD36, CD38, CD45, CD117, Glycophorin‐A, and HLA DR‐II. Anat Rec 264:51–62, 2001.

Clonogenic analysis reveals reserve stem cells in postnatal mammals: I. Pluripotent mesenchymal stem cells

Clonal populations of lineage‐uncommitted pluripotent mesenchymal stem cells have been identified in prenatal avians and rodents. These cells reside in the connective tissue matrices of many organs and tissues. They demonstrate extended capabilities for self‐renewal and the ability to differentiate into multiple separate tissues within the mesodermal germ line. This study was designed to determine whether such cells are present in the connective tissues of postnatal mammals. This report describes a cell clone derived by isolation from postnatal rat connective tissues, cryopreservation, extended propagation, and serial dilution clonogenic analysis. In the undifferentiated state, this clone demonstrates a high nuclear‐to‐cytoplasmic ratio and extended capacity for self‐renewal. Subsequent morphological, histochemical, and immunochemical analysis after the induction of differentiation revealed phenotypic markers characteristic of multiple cell types of mesodermal origin, such as skeletal muscle, smooth muscle, fat cells, cartilage, and bone. These results indicate that this clone consists of pluripotent mesenchymal stem cells. This report demonstrates that clonal populations of reserve stem cells are present in mammals after birth. Potential roles for such cells in the maintenance, repair, and regeneration of mesodermal tissues are discussed. Anat Rec 263:350–360, 2001.

Adult-derived stem cells and their potential for use in tissue repair and molecular medicine.

This report reviews three categories of precursor cells present within adults. The first category of precursor cell, the epiblast‐like stem cell, has the potential of forming cells from all three embryonic germ layer lineages, e.g., ectoderm, mesoderm, and endoderm. The second category of precursor cell, the germ layer lineage stem cell, consists of three separate cells. Each of the three cells is committed to form cells limited to a specific embryonic germ layer lineage. Thus the second category consists of germ layer lineage ectodermal stem cells, germ layer lineage mesodermal stem cells, and germ layer lineage endodermal stem cells. The third category of precursor cells, progenitor cells, contains a multitude of cells. These cells are committed to form specific cell and tissue types and are the immediate precursors to the differentiated cells and tissues of the adult. The three categories of precursor cells can be readily isolated from adult tissues. They can be distinguished from each other based on their size, growth in cell culture, expressed genes, cell surface markers, and potential for differentiation. This report also discusses new findings. These findings include the karyotypic analysis of germ layer lineage stem cells; the appearance of dopaminergic neurons after implantation of naive adult pluripotent stem cells into a 6‐hydroxydopamine‐lesioned Parkinsons model; and the use of adult stem cells as transport mechanisms for exogenous genetic material. We conclude by discussing the potential roles of adult‐derived precursor cells as building blocks for tissue repair and as delivery vehicles for molecular medicine.

Bioactive factors affect proliferation and phenotypic expression in progenitor and pluripotent stem cells

Progenitor and pluripotent stem cells reside within connective tissue compartments. They are also present in granulation tissue. This study examined the effects of treating these two cell populations with eight bioactive factors. Cells were assayed for DNA content as a measure of proliferation and for tissue‐specific phenotypic markers as measures of lineage progression and lineage commitment. Platelet‐derived endothelial growth factor and insulin‐like growth factor‐II did not induce proliferation in either population. However, dexamethasone, insulin, insulin‐like growth factor‐I, muscle morphogenetic protein, platelet‐derived growth factor‐AA, and platelet‐derived growth factor‐BB stimulated proliferation in one or both cell populations. Platelet‐derived growth factor‐BB was the most potent stimulator of proliferation in either population. Phenotypic expression markers were induced in the progenitor cells by insulin, insulin‐like growth factor‐I, insulin‐like growth factor‐II, dexamethasone, and muscle morphogenetic protein. However, only dexamethasone and muscle morphogenetic protein induced phenotypic expression markers in the pluripotent cells. Platelet‐derived endothelial cell growth factor, platelet‐derived growth factor‐AA, and platelet‐derived growth factor‐BB did not induce phenotypic expression markers in progenitor or pluripotent cells. This study suggests the potential for using progenitor and pluripotent cells as an in vitro model to ascertain the effects of various bioactive factors on stem cells potentially involved in tissue maintenance and repair.

Muscle morphogenetic protein induces myogenic gene expression in Swiss‐3T3 cells

Myogenesis is thought to be regulated by the MyoD family of regulatory genes, which includes MyoD, myogenin, MRF‐4/myf‐6, and myf‐5. In situ hybridization studies of vertebrate skeletal muscle development have shown the colocalization of the MyoD family of regulatory genes to specific stages of muscle development. Although many studies have analyzed the regulatory role of these genes during myogenesis, there have been few reports dealing with the activation of these myogenic regulatory genes by exogenous agents. We have previously shown that muscle morphogenetic protein induces myogenesis in clonal populations of avian pluripotent stem cells. The current study was designed to examine the ability of muscle morphogenetic protein to induce myogenesis in a clonal population derived from the established fibroblastic Swiss‐3T3 cell line. Swiss‐3T3 cells were cloned to generate separate cell populations, tested for pluripotency, propagated through 690 cell doublings, retested for pluripotency, treated with muscle morphogenetic protein, and examined for the induction of gene expression using probes for the transcription products of MyoD and myogenin. Muscle morphogenetic protein induced the expression of mRNAs for MyoD and myogenin, suggesting a role for this compound as an exogenous activator of myogenesis.

Effects of prenatal ethanol exposure on the hippocampal neurochemistry of albino rats at 90 days of postnatal age

OBJECTIVE Our purpose was to test the hypothesis that prenatal ethanol exposure alters the hippocampal muscarinic cholinergic neurochemistry of albino rats. STUDY DESIGN Ethanol was administered in a liquid diet to pregnant albino Sprague-Dawley rats. Liquid diet control animals received the same diet in which ethanol was replaced by an isocaloric amount of maltose-dextrin. Chow-fed control animals were fed laboratory chow as desired. Progeny were killed at 90 days of age, and their hippocampi were analyzed for muscarinic cholinergic receptors by use of tritiated quinuclidinyl benzilate. RESULTS Prenatal ethanol exposure produced a statistically significant decrease in the number of muscarinic receptors in males. Similar trends were noted in females, but the results were not statistically significant. CONCLUSION Prenatal ethanol treatment caused long-lasting alterations in the muscarinic cholinergic receptors of the hippocampus in male rats.

Differentiation Potential of Adult Stem Cells

Stem cells are a subcategory of cells designated as “precursor” cells. Precursor cells provide the cellular building blocks to maintain the tissues and organs of the body throughout the life-span of an individual. Precursor cells also provide the cellular building blocks for tissue replacement and repair following injury. There are three basic categories of precursor cells: lineage-uncommitted pluripotent stem cells; germ layer lineage-committed ectodermal, mesodermal, and endodermal stem cells; and lineage-committed progenitor cells. These three categories of precursor cells are based on their life-span, the nature of their lineage commitment, their ability to form various differentiated cell types, and their programmed developmental lineage pattern (Fig. 1).

Primitive Stem Cells are Present in the Blood of Adult Equines and Increase with Moderate Exercise or Ingestion of the Cyanobacter, Aphanizomenon Flos-Aquae

Primitive stem cells have been discovered within the blood of adult mammals such as rodents, porcines, and humans. The current study addressed the issue of primitive stem cells in the blood of adult equines. Blood withdrawal by venipuncture from adult equines was performed following the guidelines of Fort Valley State University IACUC. Ten horses were used in this study: one Danish Oldenburg, three Standard breds and six Quarter Horses with age ranges of 5 – 20 years. The blood was processed for stem cell isolation and counting. All horses examined were noted to have circulating levels of primitive stem cells in their blood. Standard breds showed an increase of stem cell number with increasing age of the animals. In contrast, Quarter Horses showed an increase in stem cell number that paralleled an increase in the level of stress to the animal, regardless of age. All horses showed an increase in stem cell number in their blood after moderate exercise (10 minutes of cantering) and at time periods after ingestion of Aphanizomenon flos-aquae . These studies demonstrate the existence of primitive stem cells within adult equine blood. Larger sample sizes are needed to determine the significance of the effects of age, stress, trauma and ingested compounds on the number of circulating primitive adult stem cells in the blood of adult horses. Further studies are also needed to assess the applicability of using circulating primitive stem cells for the restoration and/or repair of tissues in the adult equine damaged by trauma or disease.