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TGFβ1 induces age-related bone loss by promoting degradation of TNF receptor-associated factor 3 (TRAF3), levels of which decrease in murine and human bone during aging. We report that a subset of neutrophils (TGFβ1+CCR5+) is the major source of TGFβ1 in murine bone. Their numbers are increased in bone marrow (BM) of aged wild-type mice and adult mice with TRAF3 conditionally deleted in mesenchymal progenitor cells (MPCs), associated with increased expression in BM of the chemokine, CCL5, suggesting that TRAF3 in MPCs limits TGFβ1+CCR5+ neutrophil numbers in BM of young mice. During aging, TGFβ1-induced TRAF3 degradation in MPCs promotes NF-κB-mediated expression of CCL5 by MPCs, associated with higher TGFβ1+CCR5+ neutrophil numbers in BM where they induce bone loss. TGFβ1+CCR5+ neutrophils decreased bone mass in male mice. The FDA-approved CCR5 antagonist, maraviroc, reduced TGFβ1+CCR5+ neutrophil numbers in BM and increased bone mass in aged mice. 15-mon-old mice with TGFβRII specifically deleted in MPCs had lower numbers of TGFβ1+CCR5+ neutrophils in BM and higher bone volume than wild-type littermates. We propose that pharmacologic reduction of TGFβ1+CCR5+ neutrophil numbers in BM could treat or prevent age-related osteoporosis. Age-related osteoporosis is known to be dependent on TGFβ1 signalling. Here the authors show that a subset of neutrophils (identified by TGFβ1+CCR5+) increase during aging in mouse bone marrow resulting in bone loss, while a CCR5 antagonist can reduce the neutrophil numbers and increase bone mass in aged mice. [ABSTRACT FROM AUTHOR]

Microvesicles (MVs) are recognized as an important class of cell‐to‐cell messengers. Although the properties of MVs are increasingly documented, the mechanisms regulating MV biogenesis remain debated. Myofibroblasts are a key cellular component of wound healing and have been shown to produce MVs upon stimulation with serum. However, the mediator(s) responsible for the observed effect of serum on MV release have yet to be identified. To isolate the molecule(s) of interest, serum proteins were sequentially separated using chromatography, selective precipitation, and electrophoresis. MV production was assessed throughout the purification and after stimulation of myofibroblasts with two potent purified molecules. α‐2‐Macroglobulin (A2M) was thereby found to dose‐dependently stimulate MV release. We confirmed the presence of the A2M receptor, low‐density lipoprotein receptor‐related protein‐1 (LRP1), on myofibroblasts. Inhibition of LRP1 resulted in a significant decrease in MV production. Together, our results suggest that A2M positively regulates MV shedding through the activation of LRP1 on myofibroblasts. α‐2‐Macroglobulin positively regulates microvesicle shedding through the activation of low‐density lipoprotein receptor‐related protein‐1 on myofibroblasts. [ABSTRACT FROM AUTHOR]

Our laboratory has developed a technique to reconstruct in vitro tissue from human cells using the self-assembly tissue-engineering method, which utilizes the ability of fibroblasts to deposit the matrix they secrete. The time necessary for tissue construction, several weeks, is a drawback for many clinical uses. We hypothesized that the addition of laminaran can increase the deposition of matrix, speeding up the production of the tissue. Laminaran was isolated from the brown seaweed Saccharina longicruris harvested in Canada and its structure was evaluated. Laminaran is a small molecular weight polysaccharide composed of linear glucose chains. Monolayer-cultured human skin fibroblasts were cultured in the presence of laminaran with ascorbate for 7 or 35 days to produce a dermis. Treatment did not induce any variation in the growth rate or alpha smooth muscle actin content but it did increase the deposition of collagen I in a dose-dependent manner. After 35 days, the reconstructed dermal thickness was increased when laminaran was added, and collagen I deposition and MMP activity were also significantly increased. Thus, laminaran can be used to increase the rate of production of reconstructed self-assembled dermis and can also potentially be used in cosmetic or therapeutic creams to stimulate matrix production. [ABSTRACT FROM AUTHOR]