Broader implementation of cell-based therapies has been hindered by the logistics associated with the expansion of clinically relevant cell numbers ex vivo. To overcome this limitation, Wilson Wolf Manufacturing developed the G-Rex, a cell culture flask with a gas-permeable membrane at the base that supports large media volumes without compromising gas exchange. Although this culture platform has recently gained traction with the scientific community due to its superior performance when compared with traditional culture systems, the limits of this technology have yet to be explored. In this study, we investigated multiple variables including optimal seeding density and media volume, as well as maximum cell output per unit of surface area. Additionally, we have identified a novel means of estimating culture growth kinetics. All of these parameters were subsequently integrated into a novel G-Rex “M” series, which can accommodate these optimal conditions. A multicenter study confirmed that this fully optimized cell culture system can reliably produce a 100-fold cell expansion in only 10 days using 1L of medium. The G-Rex M series is linearly scalable and adaptable as a closed system, allowing an easy translation of preclinical protocols into the good manufacturing practice.

Background The T cell suppressive property of bone marrow derived mesenchymal stromal cells (MSCs) has been considered a major mode of action and basis for their utilization in a number of human clinical trials. However, there is no well-established reproducible assay to measure MSC-mediated T cell suppression. Methods At the University of Wisconsin-Madison Production Assistance for Cellular Therapy (PACT) Center we developed an in vitro quality control T cell suppression immunopotency assay (IPA) which utilizes anti-CD3 and anti-CD28 antibodies to stimulate T cell proliferation. We measured MSC-induced suppression of CD4+ T cell proliferation at various effector to target cell ratios using defined peripheral blood mononuclear cells and in parallel compared to a reference standard MSC product. We calculated an IPA value for suppression of CD4+ T cells for each MSC product. Results Eleven MSC products generated at three independent PACT centers were evaluated for cell surface phenotypic markers and T cell suppressive properties. Flow cytometry results demonstrated typical MSC cell surface marker profiles. There was significant variability in the level of suppression of T cell proliferation with IPA values ranging from 27% to 88%. However, MSC suppression did not correlate with HLA-DR expression. Discussion We have developed a reproducible immunopotency assay to measure allogeneic MSC-mediated suppression of CD4+ T cells. Additional studies may be warranted to determine how these in vitro assay results may correlate with other immunomodulatory properties of MSCs, in addition to evaluating the ability of this assay to predict in vivo efficacy.

Objective The goal of this study was to assess the immunogenicity and antigenicity of StrataGraft skin tissue in a randomized phase I/II clinical trial for the temporary management of full-thickness skin loss. Summary Background Data StrataGraft skin tissue consists of a dermal equivalent containing human dermal fibroblasts and a fully-stratified, biologically active epidermis derived from NIKS cells, a pathogen-free, long-lived, consistent, human keratinocyte progenitor. Methods Traumatic skin wounds often require temporary allograft coverage to stabilize the wound bed until autografting is possible. StrataGraft and cadaveric allograft were placed side-by-side on 15 patients with full-thickness skin defects for one week prior to autografting. Allografts were removed from the wound bed and examined for allogeneic immune responses. Immunohistochemistry and indirect immunofluorescence were used to assess tissue structure and cellular composition of allografts. In vitro lymphocyte proliferation assays, chromium-release assays, and development of antibodies were used to examine allogeneic responses. Results One week after patient exposure to allografts, there were no differences in the numbers of T or B lymphocytes or Langerhans cells present in StrataGraft skin substitute compared to cadaver allograft, the standard of care. Importantly, exposure to StrataGraft skin substitute did not induce the proliferation of patient peripheral blood mononuclear cells to NIKS keratinocytes or enhance cell-mediated lysis of NIKS keratinocytes in vitro. Similarly, no evidence of antibody generation targeted to the NIKS keratinocytes was seen. Conclusions These findings indicate that StrataGraft tissue is well-tolerated and not acutely immunogenic in patients with traumatic skin wounds. Notably, exposure to StrataGraft did not increase patient sensitivity toward or elicit immune responses against the NIKS keratinocytes. We envision this novel skin tissue technology will be widely used to facilitate the healing of traumatic cutaneous wounds.

Background-Large wounds often require temporary allograft placement to optimize the wound bed and prevent infection until permanent closure is feasible. We developed and clinically tested a second-generation living human skin substitute (StrataGraft). StrataGraft provides both a dermis and a fully-stratified, biologically-functional epidermis generated from a pathogen-free, long-lived human keratinocyte progenitor cell line, Neonatal Immortalized KeratinocyteS (NIKS).

Feasibility, tolerance, and safety of intravenous infusions of allogeneic mesenchymal stem cell (MSC) therapy in lung transplant recipients with bronchiolitis obliterans syndrome (BOS) are not well established. MSCs were manufactured, cryopreserved, transported to our facility, thawed, and infused into nine recipients with moderate BOS (average drop in forced expiratory volume in 1 second was 56.8% ± 3.2% from post‐transplant peak) who were refractory to standard therapy and not candidates for retransplant. Cells were viable and sterile prior to infusion. Patients received a single infusion of either 1 (n = 3), 2 (n = 3), or 4 (n = 3) million MSCs per kg. Patients were medically evaluated before; during; and at 24 hours, 1 week, and 1 month after infusion for evidence of infusion‐related adverse events and tolerance of therapy. Vital signs, pulmonary function test results, Borg Dyspnea Index, and routine laboratory data were recorded. Vital signs and O2 saturation did not significantly change during or up to 2 hours after MSC infusion. There were no significant changes in gas exchange variables, pulmonary function test results, or laboratory values at 1, 7, and 30 days postinfusion compared with preinfusion values. Infusion of MSCs in patients with BOS was feasible, safe, and well tolerated and did not produce any significant adverse changes in clinical, functional, or laboratory variables during or up to 30 days after infusion. Manufacturing, transport, and administration of intravenous, allogeneic bone marrow‐derived MSCs in doses from 1 to 4 million MSCs per kg is safe in lung transplant recipients with BOS. Stem Cells Translational Medicine 2018;7:161–167

To study three-dimensional (3D) cryo-imaging to measure cell biodistribution and clearance after intravenous infusion, the authors established a lung injury model in rats. Human mesenchymal stem cells (hMSCs) labeled with QTracker were infused via jugular vein. Organs were cryopreserved, followed by 3D cryo-imaging. At 60 minutes, 82 ± 9.7% of cells were detected, and at day 2, 0.06% of cells were detected. hMSCs were retained primarily in the liver, with fewer detected in lungs and spleen.

When skin is compromised, a cascade of signals initiates the rapid repair of the epidermis to prevent fluid loss and provide defense against invading microbes. During this response, keratinocytes produce host defense peptides that have antimicrobial activity against a diverse set of pathogens. Using non-viral vectors we have genetically modified the novel, non-tumorigenic, pathogen-free human keratinocyte progenitor cell line (NIKS) to express the human cathelicidin host defense peptide in a tissue-specific manner. NIKS skin tissue that expresses elevated levels of cathelicidin possesses key histological features of normal epidermis and displays enhanced antimicrobial activity against bacteria in vitro. Moreover, in an in vivo infected burn wound model, this tissue results in a two log reduction in a clinical isolate of multidrug-resistant Acinetobacter baumannii. Taken together, these results suggest this genetically engineered human tissue could be applied to burns and ulcers to counteract bacterial contamination and prevent infection.

Introduction CD133+ cells confer angiogenic potential and may be beneficial for the treatment of critical limb ischemia (CLI). However, patient selection, blinding methods and endpoints for clinical trials is challenging. We hypothesized that bilateral intramuscular administration of cytokine mobilized CD133+ cells in ambulatory patients with refractory CLI would be feasible and safe. Methods In this double-blind, randomized, sham-controlled trial, subjects received subcutaneous injections of granulocyte colony stimulating factor (10 mcg/kg/d) for 5 days, followed by leukapheresis, and intramuscular administration of 50-400 million sorted CD133+ cells delivered into both legs. Control subjects received normal saline injections, sham leukapheresis and intramuscular injection of placebo buffered solution. Subjects were followed for 1 year. An aliquot of CD133+ cells was collected from each subject to test for genes associated with cell senescence. Results 70 subjects were screened, of whom 10 were eligible. Subject enrollment was suspended due to a high rate of mobilization failure in subjects randomized to treatment. Of 10 subjects enrolled (7 randomized to treatment, 3 randomized to control), there were no differences in serious adverse events at 12 months and blinding was preserved. There were non-significant trends toward improved amputation free survival, 6 minute walk distance, walking impairment questionnaire and quality of life in subjects randomized to treatment. Successful CD133+ mobilizers expressed fewer senescence associated genes compared to poor mobilizers. Conclusion Bilateral administration of autologous CD133+ cell in ambulatory CLI subjects was safe and blinding was preserved. However, poor mobilization efficiency combined with high CD133+ senescence suggests futility in this approach.