Development of optimized cytotoxicity assays for assessing the antitumor potential of CAR-T cells.

CAR-T cells are T cells expressing a chimeric antigen receptor (CAR) rendering them capable of killing tumor cells after recognition of a target antigen. CD19 CAR-T cells have revolutionized the treatment of hematological malignancies. Their function is typically assessed by cytotoxicity assays using human allogeneic cell lines expressing the target antigen CD19 such as Nalm-6. However, an alloreactive reaction is observed with these cells, leading to a CD19-independent killing. To address this issue, we developed a fluorescence microscopy-based potency assay using murine target cells to provide an optimized cytotoxicity assay with enhanced specificity towards CD19. Murine NIH/3T3 (3T3) fibroblast-derived cell line and EL4 T-cell lymphoma-derived cell line were used as targets (no xenoreactivity was observed after coculture with human T cells). 3T3 and EL4 cells were engineered to express eGFP (enhanced Green Fluorescent Protein) and CD19 or CD22 using retroviral vectors. CD19 CAR-T cells and non-transduced (NT) control T cells were produced from several donors. After 4 h or 24 h, alloreactive cytotoxicity against CD19+ Nalm-6-GFP cells and CD19- Jurkat-GFP cells was observed with NT or CAR-T cells. In the same conditions, CAR-T but not NT cells specifically killed CD19+ but not CD19- 3T3-GFP or EL4-GFP cells. Both microscope- and flow cytometry-based assays revealed as sensitive as impedance-based assay. Using flow cytometry, we could further determine that CAR-T cells had mostly a stem cell-like memory phenotype after contact with EL4 target cells. Therefore, CD19+ 3T3-GFP or EL4-GFP cells and fluorescence microscopy- or flow cytometry-based assays provide convenient, sensitive and specific tools to evaluate CAR-T cell function with no alloreactivity.

Syngeneic Transplantation of Rat Olfactory Stem Cells in a Vein Conduit Improves Facial Movements and Reduces Synkinesis after Facial Nerve Injury.

BACKGROUND: Posttraumatic facial paralysis is a disabling condition. Current surgical management by faciofacial nerve suture provides limited recovery. To improve the outcome, the authors evaluated an add-on strategy based on a syngeneic transplantation of nasal olfactory stem cells in a rat model of facial nerve injury. The main readouts of the study were the recording of whisking function and buccal synkinesis. METHODS: Sixty rats were allocated to three groups. Animals with a 2-mm facial nerve loss were repaired with a femoral vein, filled or not with olfactory stem cells. These two groups were compared to similarly injured rats but with a faciofacial nerve suture. Olfactory stem cells were purified from rat olfactory mucosa. Three months after surgery, facial motor performance was evaluated using video-based motion analysis and electromyography. Synkinesis was assessed by electromyography, using measure of buccal involuntary movements during blink reflex, and double retrograde labeling of regenerating motoneurons. RESULTS: The authors' study reveals that olfactory stem cell transplantation induces functional recovery in comparison to nontransplanted and faciofacial nerve suture groups. They significantly increase (1) maximal amplitude of vibrissae protraction and retraction cycles and (2) angular velocity during protraction of vibrissae. They also reduce buccal synkinesis, according to the two techniques used. However, olfactory stem cell transplantation did not improve axonal regrowth of the facial nerve, 3 months after surgery. CONCLUSIONS: The authors show here that the adjuvant strategy of syngeneic transplantation of olfactory stem cells improves functional recovery. These promising results open the way for a phase I clinical trial based on the autologous engraftment of olfactory stem cells in patients with a facial nerve paralysis.

Mapping of proteomic profile and effect of the spongy layer in the human amniotic membrane.

The graft of human amniotic membrane (HAM) contributes to the healing of corneal perforating ulcers and so to save a large number of eyes suffering of severe chemical burns. This biological material is used for the treatment of ocular surface diseases because of its capacity to reduce inflammation and promote a quicker wound healing. For clinical use, the HAM is denuded from its spongy layer, but this layer can be an important source of growth factors which promote re-epithelialization. The aim of our study is to provide a general view of protein expression of the HAM and the spongy layer and therefore to determine if the spongy layer and/or a specific part of HAM have a beneficial role in the process of wound healing in patients with corneal ulcers. For this study, human placentas were obtained from healthy women after vaginal delivery or caesarean section after signing the consent form. Mapping of protein expression is done by dividing the placenta in 2 equal parts, one with spongy layer and another without (conventional HAM). Each part is also divided in 3 zones depending on the distance from the umbilical cord. The proteomic analysis was done by ELISA, targeting growth factors (EGF, HGF, KGF, NGF and TGF-beta1) and pro inflammatory cytokine TNF-α in the HAM without spongy layer and in the spongy layer. In this study we observed significant difference in the total amount of protein extract between the different donors. We do not observe a significant difference in the growth factor level between the conventional HAM and the spongy layer. No variation was observed in the expression of HGF, KGF and NGF in different zone of HAM and neither between conventional HAM and spongy layer in each zone. (*p value < 0.05, **p value<0.01,***p value < 0.001). We do detect very low dose of TNF-α and no correlation with the amount of growth factors. In our study we demonstrated that keeping the spongy layer in conventional method of handling HAM can add more GF, and so probably have a positive affect the wound healing process. Variation in some growth factors expression has been observed between the placentas and therefore this may explain the variation in clinical results. No indicator for the selection of placentas with a higher rate of growth factor was found.

Autologous Myoblasts for the Treatment of Fecal Incontinence: Results of a Phase 2 Randomized Placebo-controlled Study (MIAS).

OBJECTIVE: The aim of this study was to evaluate the efficacy of intrasphincteric injections of autologous myoblasts (AMs) in fecal incontinence (FI) in a controlled study. SUMMARY OF BACKGROUND DATA: Adult stem cell therapy is expected to definitively cure FI by regenerating damaged sphincter. Preclinical data and results of open-label trials suggest that myoblast therapy may represent a noninvasive treatment option. METHODS: We conducted a phase 2 randomized, double-blind, placebo-controlled study of intrasphincteric injections of AM in 24 patients. The study compared outcome after AM (n = 12) or placebo (n = 12) injection using Cleveland Clinic Incontinence (CCI), score at 6 and 12 months. Patients in the placebo group were eligible to receive frozen AM after 1 year. RESULTS: At 6 months, the median CCI score significantly decreased from baseline in both the AM (9 vs 15, P = 0.02) and placebo (10 vs 15, P = 0.01) groups. Hence, no significant difference was found between the 2 groups (primary endpoint) at 6 months. At 12 months, the median CCI score continued to ameliorate in the AM group (6.5 vs 15, P = 0.006), while effect was lost in the placebo group (14 vs 15, P = 0.35). Consequently, there was a higher response rate at 12 months in the treated than the placebo arm (58% vs 8%, P = 0.03). After delayed frozen AM injection in the placebo group, the response rate was 60% (6/10) at 12 months. CONCLUSIONS: Intrasphincteric AM injections in FI patients have shown tolerance, safety, and clinical benefit at 12 months despite a transient placebo effect at 6 months.

Restoration of anal sphincter function after myoblast cell therapy in incontinent rats.

Fecal incontinence (FI) remains a socially isolating condition with profound impact on quality of life for which autologous myoblast cell therapy represents an attractive treatment option. We developed an animal model of FI and investigated the possibility of improving sphincter function by intrasphincteric injection of syngeneic myoblasts. Several types of anal cryoinjuries were evaluated on anesthetized Fischer rats receiving analgesics. The minimal lesion yielding sustainable anal sphincter deficiency was a 90° cryoinjury of the sphincter, repeated after a 24-h interval. Anal sphincter pressure was evaluated longitudinally by anorectal manometry under local electrostimulation. Myoblasts were prepared using a protocol mimicking a clinical-grade process and further transduced with a GFP-encoding lentiviral vector before intrasphincteric injection. Experimental groups were uninjured controls, cryoinjured + PBS, and cryoinjured + myoblasts (different doses or injection site). Myoblast injection was well tolerated. Transferred myoblasts expressing GFP integrated into the sphincter and differentiated in situ into dystrophin-positive mature myofibers. Posttreatment sphincter pressures increased over time. At day 60, pressures in the treated group were significantly higher than those of PBS-injected controls and not significantly different from those of normal rats. Longitudinal follow-up showed stability of the therapeutic effect on sphincter function over a period of 6 months. Intrasphincteric myoblast injections at the lesion borders were equally as effective as intralesion administration, but an injection opposite to the lesion was not. These results provide proof of principle for myoblast cell therapy to treat FI in a rat model. This strategy is currently being evaluated in humans in a randomized double-blind placebo-controlled clinical trial.

Chromosomal instability but lack of transformation in human myoblast preparations.

Genetic alterations have recently been described as emerging during the culture of embryonic stem cells or induced pluripotent stem cells, raising concerns about their safety in future clinical use. Myoblasts are adult stem cells with important therapeutic potential that have been used in clinical trials for almost 20 years, but their genome integrity has not yet been established. Here we produced 10 human myoblast preparations and investigated their genomic stability. At the third passage, half of the preparations had a normal karyotype and half showed one to four alterations/30 metaphases. Chromosome 2 trisomy was found in 1-2/30 metaphases and/or 2/100 nuclei by FISH in 3/10 samples, and there was no other recurrent anomaly. When prolonging cultures, these erratic abnormalities were never associated with a growth advantage. Cellular senescence was manifested in all samples by growth arrest before passage 15. Expression of TERT was always negative. Molecular analysis of individual p53 transcripts did not reveal tumorigenic mutations. CGH array (10 samples) and exome sequencing (one sample) failed to detect copy number variations or accumulation of mutations, respectively. Myoblasts did not grow either in soft agar or in vivo after injection in immunodeficient mice. Hence, occasional genomic abnormalities may occur during myoblast culture but are not associated with risk of transformation.

TRPC expression in mesenchymal stem cells.

Transient receptor potential canonical (TRPC) channels are key players in calcium homeostasis and various regulatory processes in cell biology. Little is currently known about the TRPC subfamily members in mesenchymal stem cells (MSC), where they could play a role in cell proliferation. We report on the presence of TRPC1, 2, 4 and 6 mRNAs in MSC. Western blot and immunofluorescence staining indicate a membrane and intracellular distribution of TRPC1. Furthermore, the decrease in the level of TRPC1 protein caused by RNA interference is accompanied by the downregulation of cell proliferation. These results indicate that MSC express TRPC1, 2, 4 and 6 mRNA and that TRPC1 may play a role in stem cell proliferation.