Phenotypic variation in skeletal traits and diseases is the product of genetic and environmental factors. Epigenetic mechanisms include information-containing factors, other than DNA sequence, that cause stable changes in gene expression and are maintained during cell divisions. They represent a link between environmental influences, genome features, and the resulting phenotype. The main epigenetic factors are DNA methylation, posttranslational changes of histones, and higher-order chromatin structure. Sometimes non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are also included in the broad term of epigenetic factors. There is rapidly expanding experimental evidence for a role of epigenetic factors in the differentiation of bone cells and the pathogenesis of skeletal disorders, such as osteoporosis and osteoarthritis. However, different from genetic factors, epigenetic signatures are cell-and tissue-specific and can change with time. Thus, elucidating their role has particular difficulties, especially in human studies. Nevertheless, epigenomewide association studies are beginning to disclose some disease-specific patterns that help to understand skeletal cell biology and may lead to development of new epigenetic-based biomarkers, as well as new drug targets useful for treating diffuse and localized disorders. Here we provide an overview and update of recent advances on the role of epigenomics in bone and cartilage diseases.Besides chromatin-related marks and structure, non-coding RNAs (ncRNAs) are also frequently included among the mechanisms of epigenetic control. (8) They are classified as small RNAs (<200 nucleotides) and long RNAs (>200 nucleotides). The best-known subset of small RNAs are microRNAs (miRNAs, 18 to 25 nucleotides), which inhibit protein synthesis by binding to the 3 0 -untranslated region of target mRNAs. Long non-coding RNAs (lncRNAs) modulate the activity of both nearby genes and distant genes by a variety of mechanisms. For instance, they often serve as scaffolds for transcription factors and other molecules involved in initiation of transcription, including Box 1. Epigenomics-Related TermsChromatin: The complex of DNA and its packaging molecules. The core of the chromatin is the nucleosome, which consists of an octamer of 4 histones around which 147 bp of DNA is wrapped around.Chromosome conformation capture and Hi-C: Techniques used to map the spatial (3D) organization of the chromatin in the nucleus. Chromosome conformation capture (3C) quantifies the number of interactions between a given loci and the rest of the genome. In Hi-C, all genomic interaction between all genomic regions are quantified.CTCF: CCCTC-binding factor, highly conserved zinc finger protein involved in diverse genomic regulatory functions, including transcriptional activation/repression, insulation, imprinting, and X-chromosome inactivation, through mediating the formation of chromatin loops. DNA methyl-transferases (DNMTs): Family of enzymes responsible for the methylation of DNA. DNMT1...

The clinical spectrum of hypophosphatasia (HPP) is broad and variable within families. Along severe infantile forms, adult forms with mild manifestations may be incidentally discovered by the presence of low alkaline phosphatase (ALP) activity in serum. However, it is still unclear whether individuals with persistently low levels of ALP, in the absence of overt manifestations of HPP, have subclinical abnormalities of bone remodeling or bone mass. The aim of this study was to obtain a better understanding of the skeletal phenotype of adults with low ALP by analyzing bone mineral density (BMD), bone microarchitecture (trabecular bone score, TBS), and bone turnover markers (P1NP and ß-crosslaps). We studied 42 individuals with persistently low serum ALP. They showed lower levels of P1NP (31.4 ± 13.7 versus 48.9 ± 24.4 ng/ml; p = 0.0002) and ß-crosslaps (0.21 ± 0.17 versus 0.34 ± 0.22 ng/ml, p = 0.0015) than individuals in the control group. There were no significant differences in BMD, bone mineral content, or TBS. These data suggest that individuals with hypophosphatasemia have an overall reduction of bone turnover, even in the absence of overt manifestations of HPP or low BMD. We evaluated bone mineral density (BMD), bone microarchitecture, and bone turnover markers in patients with low serum levels of alkaline phosphatase. Our results show that these patients have low bone remodeling even in the absence of BMD abnormalities, thus supporting the recommendation of avoiding antiresorptives such as bisphosphonates in these subjects.

Background. The clinical and epidemiological data of the recent outbreak of monkeypox (MPX) differ from previous reports. One difference is the epidemiological profile; the disease mainly affects a subgroup of MSM (men who have sex with men) with high-risk sexual behaviors, frequently persons living with human immunodeficiency virus (PLHIV). Methods. In this observational analysis, all patients with PCR (polymerase chain reaction)-confirmed MPX attending an Infectious Diseases and Tropical Medicine Unit in Gran Canaria (Spain) between May and July 2022 were considered. Results. In total, 42 men were included; 88% were identified as MSM, with a median age of 40 years. Only 43% were born in Spain. All the patients had systemic symptoms and skin lesions. The distribution of lesions was more frequent in the genital/anal region, and the involvement of hands and feet was less common. Fever and lymphadenopathies were less frequent than in other series. Other unusual manifestations were proctitis, pharyngitis and penile–scrotal edema. Half of the patients had other associated infections (mainly STIs, sexually transmitted infections), and 60% of the monkeypox patients had PLHIV (People Living with HIV). When comparing the clinical characteristics between HIV-positive and -negative patients, we found three main differences: (i) a higher frequency of perioral lesions, (ii) a higher frequency of pharyngitis and (iii) a higher number of sexually transmitted infections in HIV-positive patients. Conclusions. The clinical findings in this outbreak of MPX had great variability in presentation. Several clinical differences were found in PLHIV-coinfected patients.