Quiescent mouse embryonic C3H͞10T 1 ⁄2 cells are more resistant to different proapoptotic stimuli than are these cells in the exponential phase of growth. However, the exponentially growing 10T 1 ⁄2 cells are resistant to inhibitors of RNA or protein synthesis, whereas quiescent cells die upon these treatments. Conditioned medium from quiescent 10T 1 ⁄2 cells possesses anti-apoptotic activity, suggesting the presence of protein(s) that function as an inhibitor of the apoptotic program. Using differential display technique, we identified and cloned a cDNA designated sarp1 (secreted apoptosis-related protein) that is expressed in quiescent but not in exponentially growing 10T 1 ⁄2 cells. Hybridization studies with sarp1 revealed two additional family members. Cloning and sequencing of sarp2 and sarp3 revealed 38% and 40% sequence identity to sarp1, respectively. Human breast adenocarcinoma MCF7 cells stably transfected with sarp1 or infected with SARP1-expressing adenovirus became more resistant, whereas cells transfected with sarp2 displayed increased sensitivity to different proapoptotic stimuli. Expression of sarp family members is tissue specific. sarp mRNAs encode secreted proteins that possess a cysteine-rich domain (CRD) homologous to the CRD of frizzled proteins but lack putative membrane-spanning segments. Expression of SARPs modifies the intracellular levels of ␤-catenin, suggesting that SARPs interfere with the Wnt-frizzled proteins signaling pathway.

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Idiopathic pulmonary fibrosis (IPF) is a poorly understood progressive disease characterized by the accumulation of scar tissue in the lung interstitium. A hallmark of the disease is areas of injury to type II alveolar epithelial cells with attendant accumulation of fibroblasts in areas called fibroblastic foci. In an effort to better characterize the lung fibroblast phenotype in IPF patients, we isolated fibroblasts from patients with IPF and looked for activation of signaling proteins, which could help explain the exaggerated fibrogenic response in IPF. We found that IPF fibroblasts constitutively expressed increased basal levels of SPARC, plasminogen activator inhibitor-1 (PAI-1), and active ␤-catenin compared with control cells. Control of basal PAI-1 expression in IPF fibroblasts was regulated by SPARCmediated activation of Akt, leading to inhibition of glycogen synthase kinase-3␤ and activation of ␤-catenin. Additionally, IPF fibroblasts (but not control fibroblasts) were resistant to plasminogen-induced apoptosis and were sensitized to plasminogen-mediated apoptosis by inhibition of SPARC or ␤-catenin. These findings uncover a newly discovered regulatory pathway in IPF fibroblasts that is characterized by elevated SPARC, giving rise to activated ␤-catenin, which regulates expression of downstream genes, such as PAI-1, and confers an apoptosisresistant phenotype. Disruption of this pathway may represent a novel therapeutic target in IPF.

No abstract

Objectives: Platelet-rich plasma (PRP) has been has been used to augment tissue repair and regeneration after musculoskeletal injury. However, there is increasing clinical evidence that PRP, and related blood products, do not show a consistent clinical effect. The purpose of this study is to compare the effects of non-neutrophil containing PRP (LP-PRP), modified LP-PRP (Mod LP-PRP) where TGF-β1 and myostatin (MSTN) were depleted, and platelet poor plasma (PPP) on human skeletal muscle myoblast (HSMM) differentiation. Our hypothesis was that LP-PRP would lead to myoblast proliferation, not differentiation, while modifications of PRP preparations will increase myoblast differentiation, which is necessary for skeletal muscle regeneration. Methods: Blood was simultaneously processed from eight healthy human donors to create LP-PRP, Mod-LP-PRP, PPP and second spin (ss) PRP and Mod-PRP groups. Mod-PRP was created using antibodies attached to sterile beads to remove TGF-β1 and MSTN. The biologics were then individually added to human skeletal muscle myoblasts (HSMM) and were analyzed over four days. Analysis for induction into myoblast proliferation and differentiation pathways included Western blot and RT-PCR, as well as confocal microscopy to assess for polynucleated myotubule formation. Results: LP-PRP treatment lead to increased myoblast proliferation compared to PPP (1.01 x 106 vs 5.1 x 105 cells), but showed no evidence differentiation into muscle cells either by myotubule formation or via inducing myosin heavy chain (MHC) RNA compared to negative controls (0.1x fold change; p>0.05). TGF-β1 and MSTN were successfully depleted in Mod-PRP, but this modification did little to improve myoblast differentiation (0.2x fold change MHC RNA vs control; p>0.05). Application of PPP to cultures induced myoblast differentiation that included visible multinucleated myotubule formation and MHC induction compared to negative controls (9.8x fold change; p<0.05). A second centrifugal spin (removes platelets) lead to a significant increase in myoblast differentiation in PRP and Mod-PRP preparations, similar to the level of PPP and the 2% horse serum positive control (8.0x vs 6.7x vs 9.8x vs 6.0x fold increase in MHC RNA, respectively; all p<0.05 compared to LP-PRP, Mod-LP-PRP and negative controls). Western blot and RT-PCR analyses confirmed that MSTN and TGF-β1 were further depleted in all groups, including Mod-LP-PRP, that were subjected to a second spin. Conclusion: PPP, and PRP preparations subjected to a second spin to remove platelets, lead to induction of myoblast cells into the muscle differentiation pathway, while unmodified PRP lead to induction into the proliferation pathway. These results indicate that traditionally formulated PRP should not be used to induce muscle regeneration. Laboratory evidence suggests that platelet poor plasma (PPP) or LP-PRP subjected to a second spin to remove platelets should be used to stimulate myoblast differentiation, which is necessary for skeletal muscle regeneration. Clinical studies will...

An autologous source of stem cells can now be harvested using a simple arthroscopic technique that will allow orthopaedic surgeons easier access to progenitor cells for regenerative procedures.

A characteristic of dysregulated wound healing in IPF is fibroblastic-mediated damage to lung epithelial cells within fibroblastic foci. In these foci, TGF-β and other growth factors activate fibroblasts that secrete growth factors and matrix regulatory proteins, which activate a fibrotic cascade. Our studies and those of others have revealed that Akt is activated in IPF fibroblasts and it mediates the activation by TGF-β of pro-fibrotic pathways. Recent studies show that mTORC2, a component of the mTOR pathway, mediates the activation of Akt. In this study we set out to determine if blocking mTORC2 with MLN0128, an active site dual mTOR inhibitor, which blocks both mTORC1 and mTORC2, inhibits lung fibrosis. We examined the effect of MLN0128 on TGF-β-mediated induction of stromal proteins in IPF lung fibroblasts; also, we looked at its effect on TGF-β-mediated epithelial injury using a Transwell co-culture system. Additionally, we assessed MLN0128 in the murine bleomycin lung model. We found that TGF-β induces the Rictor component of mTORC2 in IPF lung fibroblasts, which led to Akt activation, and that MLN0128 exhibited potent anti-fibrotic activity in vitro and in vivo. Also, we observed that Rictor induction is Akt-mediated. MLN0128 displays multiple anti-fibrotic and lung epithelial-protective activities; it (1) inhibited the expression of pro-fibrotic matrix-regulatory proteins in TGF-β-stimulated IPF fibroblasts; (2) inhibited fibrosis in a murine bleomycin lung model; and (3) protected lung epithelial cells from injury caused by TGF-β-stimulated IPF fibroblasts. Our findings support a role for mTORC2 in the pathogenesis of lung fibrosis and for the potential of active site mTOR inhibitors in the treatment of IPF and other fibrotic lung diseases.

Female athletes with higher circulating relaxin levels may be more susceptible to ACL injury.