ABSTRACT
While young muscle is capable of restoring the original architecture of damaged myofibers, aged muscle displays a markedly reduced regeneration. We show that expression of the "anti-aging" protein, α-Klotho, is up-regulated within young injured muscle as a result of transient Klotho promoter demethylation. However, epigenetic control of the Klotho promoter is lost with aging. Genetic inhibition of α-Klotho in vivo disrupted muscle progenitor cell (MPC) lineage progression and impaired myofiber regeneration, revealing a critical role for α-Klotho in the regenerative cascade. Genetic silencing of Klotho in young MPCs drove mitochondrial DNA (mtDNA) damage and decreased cellular bioenergetics. Conversely, supplementation with α-Klotho restored mtDNA integrity and bioenergetics of aged MPCs to youthful levels in vitro and enhanced functional regeneration of aged muscle in vivo in a temporally-dependent manner. These studies identify a role for α-Klotho in the regulation of MPC mitochondrial function and implicate α-Klotho declines as a driver of impaired muscle regeneration with age.
Subject(s)
Aging/genetics , DNA, Mitochondrial/genetics , Mitochondria/genetics , Muscle, Skeletal/metabolism , Myoblasts/metabolism , Receptors, Cell Surface/genetics , Stem Cells/metabolism , Aging/metabolism , Aging/pathology , Animals , DNA Methylation , DNA, Mitochondrial/metabolism , Epigenesis, Genetic , Gene Expression Regulation, Developmental , Glucuronidase , Klotho Proteins , Mice , Mice, Inbred C57BL , Mice, Knockout , Mitochondria/metabolism , Muscle, Skeletal/pathology , Myoblasts/pathology , Promoter Regions, Genetic , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Receptors, Cell Surface/antagonists & inhibitors , Receptors, Cell Surface/metabolism , Regeneration/genetics , Signal Transduction , Stem Cells/pathologyABSTRACT
BACKGROUND: Human herpesviruses (HHVs) 6 and 7 are recently discovered betaherpesviruses. Although HHV-6 has been associated with disordered hematopoiesis in bone marrow transplant recipients, little information is available on the presence of both viruses in the bone marrow from healthy subjects. METHODS: We detected HHV-6 and HHV-7 DNA by means of polymerase chain reaction in bone marrow and peripheral blood samples from 18 healthy subjects who underwent total hip arthroplasty. RESULTS: Genomic HHV-6 and HHV-7 DNA were detected in 11% and 67% of the blood samples, respectively, and in 28% and 50% of the bone marrow samples, respectively. CONCLUSIONS: Both viruses may be present in the bone marrow without hematopoiesis disorder and can be transmitted through bone marrow infusion. Therefore, the causative role of these two viruses in some bone marrow diseases cannot be inferred simply from the detection of their genome in bone marrow by means of polymerase chain reaction.
Subject(s)
Bone Marrow/virology , Herpesvirus 6, Human/isolation & purification , Herpesvirus 7, Human/isolation & purification , Adult , Aged , Arthroplasty, Replacement, Hip , Bone Marrow/chemistry , DNA, Viral/analysis , DNA, Viral/blood , Female , Genome, Viral , Herpesvirus 6, Human/genetics , Herpesvirus 7, Human/genetics , Humans , Male , Middle Aged , Polymerase Chain Reaction , Reference ValuesABSTRACT
We had previously described six distinct alleles of the glycoprotein B (gB) gene of human herpesvirus 7 (HHV-7). The genetic changes corresponding to these alleles did not affect gB gene transcription or translation in in vitro assays. The study of distinct HHV-7-positive human samples showed preferential associations of some gB alleles with some alleles of two other genes, distantly located on the HHV-7 genome, coding for the phosphoprotein p100 (p100) and the major capsid protein (MCP). Two allele combinations, corresponding to 44 and 31% of the samples studied, respectively, were interpreted as the genetic signatures of two major prototype HHV-7 variants.
Subject(s)
Alleles , Genes, Viral , Genetic Variation , Herpesviridae Infections/virology , Herpesvirus 7, Human/genetics , Capsid/genetics , Humans , Phosphoproteins/genetics , Polymorphism, Genetic , Protein Biosynthesis , Transcription, Genetic , Viral Envelope Proteins/geneticsABSTRACT
As for other herpesviruses, glycoprotein B (gB) of human herpesvirus 7 (HHV-7) is believed to play a major role in virus infection and as a target of the host immunogenic response. Using nested PCR, we amplified the whole HHV-7 gB gene from 108 human peripheral blood mononuclear cell samples and studied its variability. By means of restriction fragment length polymorphism (RFLP) analysis, three distinct patterns, designated I, II, and III, were defined and detected at frequencies of 93, 5, and 2%, respectively. Determination of the nucleotide sequence allowed us to recognize five critical positions in the gB gene with six specific combinations of point changes at these positions. These combinations were gB alleles A, B, C, D, E, and F. Alleles D and E corresponded to RFLP patterns II and III, respectively, while the other four alleles corresponded to RFLP pattern I. Identical gB alleles were detected in serial samples as well as in paired samples of blood and saliva from the same individuals, except for one case. In contrast, the distribution of gB alleles differed according to the geographical origin of the human samples: C was the most frequent allele in both African and Caribbean samples, whereas F was the most frequent allele in European ones. Although none of the allele-specific nucleotide changes induced any modification at the protein level, the definition of gB alleles provided convenient viral markers for the study of both HHV-7 infections and human population genetics.
