Serum miRNA Signatures Are Indicative of Skeletal Fractures in Postmenopausal Women With and Without Type 2 Diabetes and Influence Osteogenic and Adipogenic Differentiation of Adipose Tissue-Derived Mesenchymal Stem Cells In Vitro

Standard DXA measurements, including Fracture Risk Assessment Tool (FRAX) scores, have shown limitations in assessing fracture risk in Type 2 Diabetes (T2D), underscoring the need for novel biomarkers and suggesting that other pathomechanisms may drive diabetic bone fragility. MicroRNAs (miRNAs) are secreted into the circulation from cells of various tissues proportional to local disease severity and were recently found to be crucial to bone homeostasis and T2D. Here, we studied, if and which circulating miRNAs or combinations of miRNAs can discriminate best fracture status in a well-characterized study of diabetic bone disease and postmenopausal osteoporosis (n = 80 postmenopausal women). We then tested the most discriminative and most frequent miRNAs in vitro. Using miRNA-qPCR-arrays, we showed that 48 miRNAs can differentiate fracture status in T2D women and that several combinations of four miRNAs can discriminate diabetes-related fractures with high specificity and sensitivity (area under the receiver-operating characteristic curve values [AUCs], 0.92 to 0.96; 95% CI, 0.88 to 0.98). For the osteoporotic study arm, 23 miRNAs were fracture-indicative and potential combinations of four miRNAs showed AUCs from 0.97 to 1.00 (95% CI, 0.93 to 1.00). Because a role in bone homeostasis for those miRNAs that were most discriminative and most present among all miRNA combinations had not been described, we performed in vitro functional studies in human adipose tissue-derived mesenchymal stem cells to investigate the effect of miR-550a-5p, miR-188-3p, and miR-382-3p on osteogenesis, adipogenesis, and cell proliferation. We found that miR-382-3p significantly enhanced osteogenic differentiation (p < 0.001), whereas miR-550a-5p inhibited this process (p < 0.001). Both miRNAs, miR-382-3p and miR-550a-5p, impaired adipogenic differentiation, whereas miR-188-3p did not exert an effect on adipogenesis. None of the miRNAs affected significantly cell proliferation. Our data suggest for the first time that miRNAs are linked to fragility fractures in T2D postmenopausal women and should be further investigated for their diagnostic potential and their detailed function in diabetic bone. © 2016 American Society for Bone and Mineral Research.

Circulating microRNAs as novel biomarkers for bone diseases - Complex signatures for multifactorial diseases?

Biomarkers are essential tools in clinical research and practice. Useful biomarkers must combine good measurability, validated association with biological processes or outcomes, and should support clinical decision making if used in clinical practice. Several types of validated biomarkers have been reported in the context of bone diseases. However, because these biomarkers face certain limitations there is an interest in the identification of novel biomarkers for bone diseases, specifically in those that are tightly linked to the disease pathology leading to increased fracture-risk. MicroRNAs (miRNAs) are the most abundant RNA species to be found in cell-free blood. Encapsulated within microvesicles or bound to proteins, circulating miRNAs are remarkably stable analytes that can be measured using gold-standard technologies such as quantitative polymerase-chain-reaction (qPCR). Nevertheless, the analysis of circulating miRNAs faces several pre-analytical as well as analytical challenges. From a biological view, there is accumulating evidence that miRNAs play essential roles in the regulation of various biological processes including bone homeostasis. Moreover, specific changes in miRNA transcription levels or miRNA secretory levels have been linked to the development and progression of certain bone diseases. Only recently, results from circulating miRNAs analysis in patients with osteopenia, osteoporosis and fragility fractures have been reported. By comparing these findings to studies on circulating miRNAs in cellular senescence and aging or muscle physiology and sarcopenia, several overlaps were observed. This suggests that signatures observed during osteoporosis might not be specific to the pathophysiology in bone, but rather integrate information from several tissue types. Despite these promising first data, more work remains to be done until circulating miRNAs can serve as established and robust diagnostic tools for bone diseases in clinical research, clinical routine and in personalized medicine.

Secreted microvesicular miR-31 inhibits osteogenic differentiation of mesenchymal stem cells

Damage to cells and tissues is one of the driving forces of aging and age-related diseases. Various repair systems are in place to counteract this functional decline. In particular, the property of adult stem cells to self-renew and differentiate is essential for tissue homeostasis and regeneration. However, their functionality declines with age (Rando, 2006). One organ that is notably affected by the reduced differentiation capacity of stem cells with age is the skeleton. Here, we found that circulating microvesicles impact on the osteogenic differentiation capacity of mesenchymal stem cells in a donor-age-dependent way. While searching for factors mediating the inhibitory effect of elderly derived microvesicles on osteogenesis, we identified miR-31 as a crucial component. We demonstrated that miR-31 is present at elevated levels in the plasma of elderly and of osteoporosis patients. As a potential source of its secretion, we identified senescent endothelial cells, which are known to increase during aging in vivo (Erusalimsky, 2009). Endothelial miR-31 is secreted within senescent cell-derived microvesicles and taken up by mesenchymal stem cells where it inhibits osteogenic differentiation by knocking down its target Frizzled-3. Therefore, we suggest that microvesicular miR-31 in the plasma of elderly might play a role in the pathogenesis of age-related impaired bone formation and that miR-31 might be a valuable plasma-based biomarker for aging and for a systemic environment that does not favor cell-based therapies whenever osteogenesis is a limiting factor.

Urine is a novel source of autologous mesenchymal stem cells for patients with epidermolysis bullosa

Background

Regenerative medicine is strictly dependent on stem cells as a source for a high diversity of somatic cells. However, the isolation of such from individuals suffering from severe genetic skin blistering diseases like epidermolysis bullosa (EB) is often associated with further organ damage.

Methods

Stem cells were isolated from 112 urine samples from 21 different healthy donors, as well as from 33 urine samples from 25 donors with EB. The cultivation of these cells was optimized by testing different media formulations and pre-coating of culture vessels with collagen. The identity of cells was confirmed by testing marker expression, differentiation potential and immune-modulatory properties.

Results

We provide here an optimized protocol for the reproducible isolation of mesenchymal stem cells from urine, even from small volumes as obtained from patients with EB. Furthermore, we offer a basic characterization of those urine-derived stem cells (USCs) from healthy donors, as well as from patients with EB, and demonstrate their potential to differentiate into chondrocytes, osteoblasts and adipocytes, as well as their immune-modulatory properties.

Conclusions

Thus, USCs provide a novel and non-invasive source of stem cells, which might be applied for gene-therapeutic approaches to improve medical conditions of patients with EB.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1686-7) contains supplementary material, which is available to authorized users.

Differentially circulating miRNAs after recent osteoporotic fractures can influence osteogenic differentiation

Osteoporosis is the consequence of altered bone metabolism resulting in the systemic reduction of bone strength and increased risk of fragility fractures. MicroRNAs (miRNAs) regulate gene expression on a post-transcriptional level and are known to take part in the control of bone formation and bone resorption. In addition, it is known that miRNAs are secreted by many cell types and can transfer "messages" to recipient cells. Thus, circulating miRNAs might not only be useful as surrogate biomarkers for the diagnosis or prognosis of pathological conditions, but could be actively modulating tissue physiology. Therefore, the aim of this study was to test whether circulating miRNAs that exhibit changes in recent osteoporotic fracture patients could be causally related to bone metabolism. In the first step we performed an explorative analysis of 175 miRNAs in serum samples obtained from 7 female patients with recent osteoporotic fractures at the femoral neck, and 7 age-matched female controls. Unsupervised cluster analysis revealed a high discriminatory power of the top 10 circulating miRNAs for patients with recent osteoporotic fractures. In total 6 miRNAs, miR-10a-5p, miR-10b-5p, miR-133b, miR-22-3p, miR-328-3p, and let-7g-5p exhibited significantly different serum levels in response to fracture (adjusted p-value<0.05). These miRNAs were subsequently analyzed in a validation cohort of 23 patients (11 control, 12 fracture), which confirmed significant regulation for miR-22-3p, miR-328-3p, and let-7g-5p. A set of these and of other miRNAs known to change in the context of osteoporotic fractures were subsequently tested for their effects on osteogenic differentiation of human mesenchymal stem cells (MSCs) in vitro. The results show that 5 out of 7 tested miRNAs can modulate osteogenic differentiation of MSCs in vitro. Overall, these data suggest that levels of specific circulating miRNAs change in the context of recent osteoporotic fractures and that such perturbations of "normal" levels might affect bone metabolism or bone healing processes.

The role of microRNAs in cellular senescence and age-related conditions of cartilage and bone

BACKGROUND AND PURPOSE

We reviewed the current state of research on microRNAs in age-related diseases in cartilage and bone.

METHODS

PubMed searches were conducted using separate terms to retrieve articles on (1) the role of microRNAs on aging and tissue degeneration, (2) specific microRNAs that influence cellular and organism senescence, (3) microRNAs in age-related musculoskeletal conditions, and (4) the diagnostic and therapeutic potential of microRNAs in age-related musculoskeletal conditions.

RESULTS

An increasing number of studies have identified microRNAs associated with cellular aging and tissue degeneration. Specifically in regard to frailty, microRNAs have been found to influence the onset and course of age-related musculoskeletal conditions such as osteoporosis, osteoarthritis, and posttraumatic arthritis. Both intracellular and extracellular microRNAs may be suitable to function as diagnostic biomarkers.

INTERPRETATION

The research data currently available suggest that microRNAs play an important role in orchestrating age-related processes and conditions of the musculoskeletal system. Further research may help to improve our understanding of the complexity of these processes at the cellular and extracellular level. The option to develop microRNA biomarkers and novel therapeutic agents for the degenerating diseases of bone and cartilage appears to be promising.

Secretion of microvesicular miRNAs in cellular and organismal aging

Changes of factors circulating in the systemic environment during human aging have been investigated for a long time. Only recently however, miRNAs have been found to be secreted into the systemic and tissue environments where they are protected from RNAses by either carrier proteins or by being packaged into microvesicles. These miRNAs are then taken up by recipient cells, changing the cellular behavior by the classical miRNA induced silencing of target mRNAs. The origin of circulating miRNAs, however, is in most instances unclear, but senescent cells emerge as a possible source of such secreted miRNAs. Since differences in the circulating miRNAs have been found in a variety of age-associated diseases, and accumulation of senescent cells in the elderly emerges as a possible detrimental factor in aging, it is well conceivable that these miRNAs might contribute to the functional decline observed during aging of organisms. Therefore, we here give an overview on current knowledge on microvesicular secretion of miRNAs, changes of the systemic and tissue environments during aging of cells and organisms. Finally, we summarize current knowledge on miRNAs that are found to be specific for age-associated diseases.