Therapeutic potential of follistatin to promote tissue regeneration and prevent tissue fibrosis

Upregulation of follistatin and low apoptotic activity in intraductal oncocytic papillary neoplasm of the pancreatobiliary system

Intraductal oncocytic papillary neoplasm (IOPN) is a rare intraductal tumor of the pancreatobiliary system. Currently, little is known about its distinct characteristics, unlike intraductal papillary mucinous neoplasms (IPMN) and intraductal papillary neoplasms of the bile duct (IPNB). The present study compared 22 IOPNs (18 pancreatic and 4 biliary) with those of 61 IPMNs/8 IPNBs. IOPNs were classified into pure and combined types, depending on the coexistence of IPMN/IPNB. Multiple gene expression analysis (nCounter system) was performed, and hierarchical clustering analysis separated IOPNs(n = 4) and IPMNs(n = 3)/ IPNBs(n = 3), and pathway score analysis supported the result. Volcano plot identified follistatin (FST) as the most upregulated mRNA in IOPN in comparison to the gastric subtype (log2 fold change of 5.34) and the intestinal subtype (that of 5.81) of IPMN/IPNB. The expression of FST in IOPN was also high in quantitative polymerase chain reaction and immunohistochemical analysis. We also found lower apoptotic activity in IOPN, particularly in pure type, compared to high-grade or invasive IPMN/IPNB using immunohistochemistry for cleaved caspase 3. But, combined type IOPN was more similar to IPMN/IPNB than pure IOPN. In conclusion, we proved that IOPN, particularly pure IOPN, is distinct from IPMN/IPNB in FST mRNA overexpression and exhibits lower apoptotic activity.

Follistatin and the Breast Implant Capsule

Supplemental Digital Content is available in the text.

Background:

Breast capsular contracture remains an elusive problem faced by plastic surgeons and is the leading long-term complication after breast implantation. Follistatin (Fst) is a protein with known anti-inflammatory and antifibrotic properties and has the potential to limit the severity of diseases associated with inflammation and fibrosis such as capsular contracture. The aim of this study was to examine the effect of Fst288 on capsular fibrosis around silicone implants in a mouse model.

Methods:

BALB/c mice were implanted subcutaneously with untreated silicone implants (baseline control). In the experimental group, immediately after silicone implant insertion, the implant pocket received either a single injection of 1 µg Fst288 or normal saline (internal control). The animals were killed at 3, 5, 7, 14, 28, and 90 days after surgery, and serum, implants, and the surrounding tissue were removed for histological and immunohistochemical analyses.

Results:

Fst288 treatment resulted in significant decreases in capsule thickness at 28 days (P < 0.05) and 3 months (P < 0.001), decreased collagen production at 14 days (P < 0.05) and 3 months (P < 0.01), decreased angiogenesis at 3 months (P < 0.001), decreased α-smooth muscle actin levels at 3 months (P < 0.05), and a decrease in the number of CD45+ cells at days 5 (P < 0.05) and 7 (P < 0.01), respectively, when compared with control implants.

Conclusions:

A single injection of Fst288 at the time of silicone implant insertion into the mice results in a significant reduction in pericapsular inflammation and capsular fibrosis.

Substantial Increases Occur in Serum Activins and Follistatin during Lung Transplantation

Background

Lung transplantation exposes the donated lung to a period of anoxia. Re-establishing the circulation after ischemia stimulates inflammation causing organ damage. Since our published data established that activin A is a key pro-inflammatory cytokine, we assessed the roles of activin A and B, and their binding protein, follistatin, in patients undergoing lung transplantation.

Methods

Sera from 46 patients participating in a published study of remote ischemia conditioning in lung transplantation were used. Serum activin A and B, follistatin and 11 other cytokines were measured in samples taken immediately after anaesthesia induction, after remote ischemia conditioning or sham treatment undertaken just prior to allograft reperfusion and during the subsequent 24 hours.

Results

Substantial increases in serum activin A, B and follistatin occurred after the baseline sample, taken before anaesthesia induction and peaked immediately after the remote ischemia conditioning/sham treatment. The levels remained elevated 15 minutes after lung transplantation declining thereafter reaching baseline 2 hours post-transplant. Activin B and follistatin concentrations were lower in patients receiving remote ischemia conditioning compared to sham treated patients but the magnitude of the decrease did not correlate with early transplant outcomes.

Conclusions

We propose that the increases in the serum activin A, B and follistatin result from a combination of factors; the acute phase response, the reperfusion response and the use of heparin-based anti-coagulants.

Interstitial Outburst of Angiogenic Factors During Skeletal Muscle Regeneration After Acute Mechanical Trauma

Angiogenesis is a key event during tissue regeneration, but the intimate mechanisms controlling this process are still largely unclear. Therefore, the cellular and molecular interplay along normal tissue regeneration should be carefully unveiled. To this matter, we investigated by xMAP assay the dynamics of some angiogenic factors known to be involved in tissue repair, such as follistatin (FST), Placental Growth Factor-2 (PLGF-2), epidermal growth factor (EGF), betacellulin (BTC), and amphiregulin (AREG) using an animal model that mimics acute muscle contusion injuries. In situ immunofluorescence was used for the evaluation and tissue distribution of their cellular sources. Tissue levels of explored factors increased significantly during degeneration and inflammatory stage of regeneration, peaking first week postinjury. However, except for PLGF-2 and EGF, their levels remained significantly elevated after the inflammatory process started to fade. Serum levels were significantly increased only after 24 h for AREG and EGF. Though, for all factors except FST, the levels in injured samples did not correlate with serum or contralateral tissue levels, excluding the systemic influence. We found significant correlations between the levels of EGF and AREG, BTC, FST and FST and AREG in injured samples. Interstitial cells expressing these factors were highlighted by in situ immunolabeling and their number correlated with measured levels dynamics. Our study provides evidence of a dynamic level variation along the regeneration process and a potential interplay between selected angiogenic factors. They are synthesized, at least partially, by cell populations residing in skeletal muscle interstitium during regeneration after acute muscle trauma.

Histone deacetylase inhibitors in the treatment of muscular dystrophies: epigenetic drugs for genetic diseases

Histone deacetylases inhibitors (HDACi) include a growing number of drugs that share the ability to inhibit the enzymatic activity of some or all the HDACs. Experimental and preclinical evidence indicates that these epigenetic drugs not only can be effective in the treatment of malignancies, inflammatory diseases and degenerative disorders, but also in the treatment of genetic diseases, such as muscular dystrophies. The ability of HDACi to counter the progression of muscular dystrophies points to HDACs as a crucial link between specific genetic mutations and downstream determinants of disease progression. It also suggests the contribution of epigenetic events to the pathogenesis of muscular dystrophies. Here we describe the experimental evidence supporting the key role of HDACs in the control of the transcriptional networks underlying the potential of dystrophic muscles either to activate compensatory regeneration or to undergo fibroadipogenic degeneration. Studies performed in mouse models of Duchenne muscular dystrophy (DMD) indicate that dystrophin deficiency leads to deregulated HDAC activity, which perturbs downstream networks and can be restored directly, by HDAC blockade, or indirectly, by reexpression of dystrophin. This evidence supports the current view that HDACi are emerging candidate drugs for pharmacological interventions in muscular dystrophies, and reveals unexpected common beneficial outcomes of pharmacological treatment or gene therapy.

Role of activin in bacterial infections: a potential target for immunointervention?

Severe bacterial infections such as sepsis and meningitis still kill or severely injure people despite the use of bactericidal antibiotics. Therefore, new strategies for a better therapy are needed. Activin A, a member of the TGF-β superfamily and its binding protein follistatin (FS) are released by various cell types during acute and chronic inflammatory processes. Until now, a clear definition of conditions in which activin A exerts either its pro- or anti-inflammatory functions is lacking. The activin/FS-system participates in the fine-tuning of the host’s inflammatory response upon infectious stimuli. This response is on the one hand necessary for fighting pathogens, but on the other hand can negatively affect the host. This article focuses on the role of activin A and FS in infection and after acute inflammatory stimuli. The therapeutic potentials of blocking or promoting activin actions are discussed.

Serum follistatin in patients with prostate cancer metastatic to the bone

The clinical significance of circulating follistatin (FLST), an inhibitor of the multifunctional cytokine activin A (Act A), was investigated in patients with prostate cancer (PCa). The serum concentrations of this molecule were determined by an enzyme-linked immunosorbent assay (ELISA) in PCa patients with (M+) or without (M0) bone metastases, in patients with benign prostate hyperplasia (BPH) and in healthy subjects (HS). The effectiveness of FLST in detecting PCa patients with skeletal metastases was determined by the receiver operating characteristic (ROC) curve analysis. Serum FLST was significantly higher in PCa patients than in BPH patients (P = 0.001) or HS (P = 0.011). Conversely, in BPH patients, FLST levels resulted lower than in HS (P = 0.025). In cancer patients the serum concentrations of FLST significantly correlated with the presence of bone metastases (P = 0.0005) or increased PSA levels (P = 0.04). Interestingly, significant differences in the ratio between FLST and Act A serum concentrations (FLST/Act A) were observed between HS and BPH patients (P = 0.001) or PCa patients (P = 0.0005). Finally, ROC curve analysis, highlighted a sound diagnostic performance of FLST in detecting M+ patients (P = 0.0001). However, the diagnostic effectiveness of FLST did not result significantly superior to that of Act A or PSA. These findings suggest that FLST may be regarded as a potential, molecular target in the treatment of metastatic bone disease while its clinical role as soluble marker in the clinical management of PCa patients with bone metastases needs to be better defined.

Evaluation of systemic follistatin as an adjuvant to stimulate muscle repair and improve motor function in Pompe mice

Due to the lack of acid alpha-glucosidase (GAA) activity, Pompe mice develop glycogen storage pathology and progressive skeletal muscle dysfunction with age. Applying either gene or enzyme therapy to reconstitute GAA levels in older, symptomatic Pompe mice effectively reduces glycogen storage in skeletal muscle but provides only modest improvements in motor function. As strategies to stimulate muscle hypertrophy, such as by myostatin inhibition, have been shown to improve muscle pathology and strength in mouse models of muscular dystrophy, we sought to determine whether these benefits might be similarly realized in Pompe mice. Administration of a recombinant adeno-associated virus serotype 8 vector encoding follistatin, an inhibitor of myostatin, increased muscle mass and strength but only in Pompe mice that were treated before 10 months of age. Younger Pompe mice showed significant muscle fiber hypertrophy in response to treatment with follistatin, but maximal gains in muscle strength were achieved only when concomitant GAA administration reduced glycogen storage in the affected muscles. Despite increased grip strength, follistatin treatment failed to improve rotarod performance. These findings highlight the importance of treating Pompe skeletal muscle before pathology becomes irreversible, and suggest that adjunctive therapies may not be effective without first clearing skeletal muscle glycogen storage with GAA.

Identification of differentially expressed genes during proliferative response of the liver induced by follistatin

The liver mass is controlled strictly and maintained constant in normal and pathological situations. An exception is observed after an administration of follistatin, which induces proliferation in intact liver. In the present study, we identified genes differentially expressed in proliferating liver caused by overexpression of follistatin-288. Adenovirus vector encoding follistatin-288 (Ad-FS) or green fluorescent protein was injected intraperitoneally in rats. Changes in the liver weight, expression of follistatin and nuclear bromodeoxyuridine labeling were measured. Samples taken on day 5 and day 7 were used to prepare RNA for microarray analysis. The expression of the genes was confirmed by quantitative reverse transcriptase PCR. After the injection of Ad-FS follistatin mRNA peaked on day 3, which was followed by progressive increase in the protein expression. A peak in bromodeoxyuridine labeling was observed on day 7. Microarray data from day 5 and day 7 samples showed that follistatin modified the expression of 907 genes, of which 575 were overexpressed and 332 were downregulated taking into consideration a two fold change reference compared to control rats. In particular, significant increases and time related changes in gene expression after the Ad-FS injection were found in nine genes including growth differentiation factor 15 and fibroblast growth factor 21. This study confirmed that follistatin induced proliferation in intact liver, and identified candidate genes involved in follistatin-induced liver cell growth.