Micromolding-based encapsulation of mesenchymal stromal cells in alginate for intraarticular injection in osteoarthritis.

Osteoarthritis (OA) is an inflammatory joint disease that affects cartilage, subchondral bone, and joint tissues. Undifferentiated Mesenchymal Stromal Cells are a promising therapeutic option for OA due to their ability to release anti-inflammatory, immuno-modulatory, and pro-regenerative factors. They can be embedded in hydrogels to prevent their tissue engraftment and subsequent differentiation. In this study, human adipose stromal cells are successfully encapsulated in alginate microgels via a micromolding method. Microencapsulated cells retain their in vitro metabolic activity and bioactivity and can sense and respond to inflammatory stimuli, including synovial fluids from OA patients. After intra-articular injection in a rabbit model of post-traumatic OA, a single dose of microencapsulated human cells exhibit properties matching those of non-encapsulated cells. At 6 and 12 weeks post-injection, we evidenced a tendency toward a decreased OA severity, an increased expression of aggrecan, and a reduced expression of aggrecanase-generated catabolic neoepitope. Thus, these findings establish the feasibility, safety, and efficacy of injecting cells encapsulated in microgels, opening the door to a long-term follow-up in canine OA patients.

Human Liver-Derived Extracellular Matrix for the Culture of Distinct Human Primary Liver Cells.

The lack of robust methods to preserve, purify and in vitro maintain the phenotype of the human liver's highly specialized parenchymal and non-parenchymal cell types importantly hampers their exploitation for the development of research and clinical applications. There is in this regard a growing interest in the use of tissue-specific extracellular matrix (ECM) to provide cells with an in vitro environment that more closely resembles that of the native tissue. In the present study, we have developed a method that allows for the isolation and downstream application of the human liver's main cell types from cryopreserved material. We also isolated and solubilized human liver ECM (HL-ECM), analyzed its peptidomic and proteomic composition by mass spectrometry and evaluated its interest for the culture of distinct primary human liver cells. Our analysis of the HL-ECM revealed proteomic diversity, type 1 collagen abundance and partial loss of integrity following solubilization. Solubilized HL-ECM was evaluated either as a coating or as a medium supplement for the culture of human primary hepatocytes, hepatic stellate cells and liver sinusoidal endothelial cells. Whereas the solubilized HL-ECM was suitable for cell culture, its impact on the phenotype and/or functionality of the human liver cells was limited. Our study provides a first detailed characterization of solubilized HL-ECM and a first report of its influence on the culture of distinct human primary liver cells.

Post-resection treatment of glioblastoma with an injectable nanomedicine-loaded photopolymerizable hydrogel induces long-term survival.

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor. Despite available therapeutic options, the prognosis for patients with GBM remains very poor. We hypothesized that the intra-operative injection of a photopolymerizable hydrogel into the tumor resection cavity could sustain the release of the anti-cancer drug paclitaxel (PTX) encapsulated in poly (lactic-co-glycolic acid) (PLGA) nanoparticles and prevent GBM recurrence. The tumor was resected 13 days after implantation and a pre-gel solution composed of polyethylene glycol dimethacrylate (PEG-DMA) polymer, a photoinitiator and PTX-loaded PLGA nanoparticles (PTX PLGA-NPs) was injected into the tumor resection cavity. A solid gel filling the whole cavity was formed immediately by photopolymerization using a 400 nm light. PTX in vitro release study showed a burst release (11%) in the first 8 h and a sustained release of 29% over a week. In vitro, U87 MG cells were sensitive to PTX PLGA-NPs with IC50 level of approximately 0.010 µg/mL. The hydrogel was well-tolerated when implanted in the brain of healthy mice for 2 and 4 months. Administration of PTX PLGA-NPs-loaded hydrogel into the resection cavity of GBM orthotopic model lead to more than 50% long-term survival mice (150 days) compared to the control groups (mean survival time 52 days). This significant delay of recurrence is very promising for the post-resection treatment of GBM.

Author Correction: Stem cells from human apical papilla decrease neuro­inflammation and stimulate oligodendrocyte progenitor differentiation via activin­A secretion.

In the original publication, sixth author's surname was incorrectly published as "Llyod" instead of "Lloyd". The correct name should read as "Amy Lloyd".

Stem cells from human apical papilla decrease neuro-inflammation and stimulate oligodendrocyte progenitor differentiation via activin-A secretion.

Secondary damage following spinal cord injury leads to non-reversible lesions and hampering of the reparative process. The local production of pro-inflammatory cytokines such as TNF-α can exacerbate these events. Oligodendrocyte death also occurs, followed by progressive demyelination leading to significant tissue degeneration. Dental stem cells from human apical papilla (SCAP) can be easily obtained at the removal of an adult immature tooth. This offers a minimally invasive approach to re-use this tissue as a source of stem cells, as compared to biopsying neural tissue from a patient with a spinal cord injury. We assessed the potential of SCAP to exert neuroprotective effects by investigating two possible modes of action: modulation of neuro-inflammation and oligodendrocyte progenitor cell (OPC) differentiation. SCAP were co-cultured with LPS-activated microglia, LPS-activated rat spinal cord organotypic sections (SCOS), and LPS-activated co-cultures of SCOS and spinal cord adult OPC. We showed for the first time that SCAP can induce a reduction of TNF-α expression and secretion in inflamed spinal cord tissues and can stimulate OPC differentiation via activin-A secretion. This work underlines the potential therapeutic benefits of SCAP for spinal cord injury repair.

A new model of nerve injury in the rat reveals a role of Regulator of G protein Signaling 4 in tactile hypersensitivity.

Tactile hypersensitivity is one of the most debilitating symptoms of neuropathic pain syndromes. Clinical studies have suggested that its presence at early postoperative stages may predict chronic (neuropathic) pain after surgery. Currently available animal models are typically associated with consistent tactile hypersensitivity and are therefore limited to distinguish between mechanisms that underlie tactile hypersensitivity as opposed to mechanisms that protect against it. In this study we have modified the rat model of spared nerve injury, restricting the surgical lesion to a single peripheral branch of the sciatic nerve. This modification reduced the prevalence of tactile hypersensitivity from nearly 100% to approximately 50%. With this model, we here also demonstrated that the Regulator of G protein Signaling 4 (RGS4) was specifically up-regulated in the lumbar dorsal root ganglia and dorsal horn of rats developing tactile hypersensitivity. Intrathecal delivery of the RGS4 inhibitor CCG63802 was found to reverse tactile hypersensitivity for a 1h period. Moreover, tactile hypersensitivity after modified spared nerve injury was most frequently persistent for at least four weeks and associated with higher reactivity of glial cells in the lumbar dorsal horn. Based on these data we suggest that this new animal model of nerve injury represents an asset in understanding divergent neuropathic pain outcomes, so far unravelling a role of RGS4 in tactile hypersensitivity. Whether this model also holds promise in the study of the transition from acute to chronic pain will have to be seen in future investigations.

Transplantation of testicular tissue in alginate hydrogel loaded with VEGF nanoparticles improves spermatogonial recovery.

Transplantation of cryopreserved immature testicular tissue (ITT) is a promising strategy to restore fertility in young boys facing gonadotoxic treatments. However, up to now, limited spermatogonial recovery has been achieved in xenografting models used to evaluate the potential of cryopreserved tissue transplantation. When comparing avascular xenografts of cryopreserved and fresh human ITT into a mouse model, the number of spermatogonia was significantly reduced, regardless of the cryopreservation procedure used. To improve tissue engraftment, revascularization and hence spermatogonial survival, ITT was embedded in two types of hydrogel loaded with VEGF nanoparticles. Small pieces (±1mm(3)) of testicular tissue were grafted in NMRI mice as follows: grafted without encapsulation, grafted after encapsulation in fibrin, in alginate, in fibrin-VEGF-nanoparticle (NP) and in alginate-VEGF-NP. Non-grafted tissue served as control. After 5 and 21days of implantation, seminiferous tubule integrity, revascularization and spermatogonial recovery were evaluated by histology and immunohistochemistry. Seminiferous tubule integrity ranged from 13.3% to 39.6% and 42.7% to 68.7% on day 5 and day 21, respectively. Vascular density on day 5 was found to be higher in VEGF supplemented groups, regardless of the hydrogel used. Staining for phosphorylated VEGF receptor 2 and endothelial proliferation on day 5 was higher in all groups compared to non-grafted avascular controls. Spermatogonial recovery ranged between 14.8% and 27.3% on day 21 and was significantly higher in the alginate and alginate-VEGF-NP groups. The present study demonstrates the potential of alginate hydrogel loaded with nanoencapsulated growth factors to improve cryopreserved tissue engraftment.

Acylated and unacylated ghrelin binding to membranes and to ghrelin receptor: towards a better understanding of the underlying mechanisms.

The O-octanoylation of human ghrelin is a natural post-translational modification that enhances its binding to model membranes and could potentially play a central role in ghrelin biological activities. Here, we aimed to clarify the mechanisms that drive ghrelin to the membrane and hence to its receptor that mediates most of its endocrinological effects. As the acylation enhances ghrelin lipophilicity and that ghrelin contains many basic residues, we examined the electrostatic attraction and/or hydrophobic interactions with membranes. Using various liposomes and buffer conditions in binding, zeta potential and isothermal titration calorimetry studies, we found that whereas acylated and unacylated ghrelin were both electrostatically attracted towards the membrane, only acylated ghrelin penetrated into the headgroup and the lipid backbone regions of negatively charged membranes. The O-acylation induced a 120-fold increase in ghrelin local concentration in the membrane. However, acylated ghrelin did not deeply penetrate the membrane nor did it perturb its organisation. Conformational studies by circular dichroism and attenuated total reflection Fourier transformed infrared as well as in silico modelling revealed that both forms of ghrelin mainly adopted the same structure in aqueous, micellar and bilayer environments even though acylated ghrelin structure is slightly more α-helical in a lipid bilayer environment. Altogether our results suggest that membrane acts as a "catalyst" in acylated ghrelin binding to the ghrelin receptor and hence could explain why acylated and unacylated ghrelin are both full agonists of this receptor but in the nanomolar and micromolar range, respectively.