Analytical assay validation for acute myeloid leukemia measurable residual disease assessment by multiparametric flow cytometry.

BACKGROUND: Measurable residual disease (MRD) assessed by multiparametric flow cytometry (MFC) has gained importance in clinical decision-making for acute myeloid leukemia (AML) patients. However, complying with the recent In Vitro Diagnostic Regulations (IVDR) in Europe and Food and Drug Administration (FDA) guidance in the United States requires rigorous validation prior to their use in investigational clinical trials and diagnostics. Validating AML MRD-MFC assays poses challenges due to the unique underlying disease biology and paucity of patient specimens. In this study, we describe an experimental framework for validation that meets regulatory expectations. METHODS: Our validation efforts focused on evaluating assay accuracy, analytical specificity, analytical and functional sensitivity (limit of blank (LoB), detection (LLoD) and quantitation (LLoQ)), precision, linearity, sample/reagent stability and establishing the assay background frequencies. RESULTS: Correlation between different MFC methods was highly significant (r = 0.99 for %blasts and r = 0.93 for %LAIPs). The analysis of LAIP specificity accurately discriminated from negative control cells. The assay demonstrated a LoB of 0.03, LLoD of 0.04, and LLoQ of 0.1%. Precision experiments yielded highly reproducible results (Coefficient of Variation <20%). Stability experiments demonstrated reliable measurement of samples up to 96 h from collection. Furthermore, the reference range of LAIP frequencies in non-AML patients was below 0.1%, ranging from 0.0% to 0.04%. CONCLUSION: In this manuscript, we present the validation of an AML MFC-MRD assay using BM/PB patient specimens, adhering to best practices. Our approach is expected to assist other laboratories in expediting their validation activities to fulfill recent health authority guidelines.

Neoadjuvant Pembrolizumab and High-Dose IFNα-2b in Resectable Regionally Advanced Melanoma.

PURPOSE: Neoadjuvant immunotherapy may improve the clinical outcome of regionally advanced operable melanoma and allows for rapid clinical and pathologic assessment of response. We examined neoadjuvant pembrolizumab and high-dose IFNα-2b (HDI) therapy in patients with resectable advanced melanoma. PATIENTS AND METHODS: Patients with resectable stage III/IV melanoma were treated with concurrent pembrolizumab 200 mg i.v. every 3 weeks and HDI 20 MU/m2/day i.v., 5 days per week for 4 weeks, then 10 MU/m2/day subcutaneously 3 days per week for 2 weeks. Definitive surgery followed, as did adjuvant combination immunotherapy, completing a year of treatment. Primary endpoint was safety of the combination. Secondary endpoints included overall response rate (ORR), pathologic complete response (pCR), recurrence-free survival (RFS), and overall survival (OS). Blood samples for correlative studies were collected throughout. Tumor tissue was assessed by IHC and flow cytometry at baseline and at surgery. RESULTS: A total of 31 patients were enrolled, and 30 were evaluable. At data cutoff (October 2, 2019), median follow-up for OS was 37.87 months (range, 33.2-43.47). Median OS and RFS were not reached. Radiographic ORR was 73.3% [95% confidence interval (CI): 55.5-85.8], with a 43% (95% CI: 27.3-60.1) pCR rate. None of the patients with a pCR have had a recurrence. HDI and pembrolizumab were discontinued in 73% and 43% of patients, respectively. Correlative analyses suggested that intratumoral PD-1/PD-L1 interaction and HLA-DR expression are associated with pCR (P = 0.002 and P = 0.008, respectively). CONCLUSIONS: Neoadjuvant concurrent HDI and pembrolizumab demonstrated promising clinical activity despite high rates of treatment discontinuation. pCR is a prognostic indicator.See related commentary by Menzies et al., p. 4133.

Multimarker scores of Th1 and Th2 immune cellular profiles in peripheral blood predict response and immune related toxicity with CTLA4 blockade and IFNα in melanoma.

Neoadjuvant therapy with ipilimumab in combination with high dose IFNα was evaluated in patients with locally/regionally advanced melanoma in a previously reported clinical trial [NCT01608594]. In this study, peripheral immune cell profiling was performed in order to investigate the underlying mechanisms of tumor immune susceptibility and resistance. Peripheral blood mononuclear cells (PBMCs) from treated patients (N = 28) were collected at baseline and then at 6-weeks, 3-months and 12-months. High complexity (14-color) flow cytometry, designed to detect key immunological biomarkers was used to evaluate the frequencies of immune cell subsets. Statistical significance was determined using R-package employing Kruskal's test. We found that higher levels of Th1 cells at baseline (defined as CD45RA- CCR6- CXCR3+ CCR4-) correlated with the preoperative radiological response (p = 0.007) while higher Th2 cells (defined as CD45RA- CCR6- CXCR3- CCR4+) were associated with progressive disease (p = 0.009). A multimarker score consisting of higher levels of Th1 cells and CD8+ central memory T-cells was associated with pathologic complete response (pCR) (p = 0.041) at surgical resection. On the other hand, high TIM3 expression on T-cells correlated with gross viable tumor (p = 0.047). With regard to immune related toxicity, higher levels of phenotypically naive (defined as CCR7+CD45RA+) and effector memory (defined as CCR7-CD45RO+) CD8+ T-cells (p = 0.014) or lower levels of Th2 cells were associated with lower toxicity (p = 0.024). Furthermore, a multimarker score consisting of higher CD19+ and CD8+ cells was associated with lower toxicity (p = 0.0014). In conclusion, our study yielded mechanistic insights related to the immune impact of CTLA4 blockade and IFNα and potential biomarkers of immune response and toxicity.

Development of a combined radiation and full thickness burn injury minipig model to study the effects of uncultured adipose-derived regenerative cell therapy in wound healing.

PURPOSE: To develop an approach that models the cutaneous healing that occurs in a patient with full thickness thermal burn injury complicated by total body radiation exposure sufficient to induce sub-lethal prodromal symptoms. An assessment of the effects of an autologous cell therapy on wound healing on thermal burn injury with concomitant radiation exposure was used to validate the utility of the model. METHODS: Göttingen minipigs were subjected to a 1.2 Gy total body irradiation by exposure to a 6 MV X-ray linear accelerator followed by ∼10 cm2 full thickness burns (pre-heated brass block with calibrated spring). Three days after injury, wounds were excised to the underlying fascia and each animal was randomized to receive treatment with autologous adipose-derived regenerative cells (ADRC) delivered by local or intravenous injection, or vehicle control. Blood counts were used to assess radiation-induced marrow suppression. All animals were followed using digital imaging to assess wound healing. Full-thickness biopsies were obtained at 7, 14, 21 and 30 days' post-treatment. RESULTS: Compared to animals receiving burn injury alone, significant transient neutropenia and thrombocytopenia were observed in irradiated subjects with average neutrophil nadir of 0.79 × 103/µl (day 15) and platelet nadir of 60 × 103/µl (day 12). Wound closure through a combination of contraction and epithelialization from the wound edges occurred over a period of approximately 28 days' post excision and treatment. Re-epithelialization was accelerated in wounds treated with ADRC (mean 3.5-fold increase at 2 weeks post-treatment relative to control). This acceleration was accompanied by an average 67% increase in blood vessel density and 30% increase in matrix (collagen) deposition. Similar results were observed when ADRC were injected either directly into the wound or by intravenous administration. CONCLUSIONS: Although preliminary, this study provides a reproducible minipig model of thermal burn injury complicated by myelosuppressive total body irradiation that utilizes standardized procedures to evaluate novel countermeasures for potential use following attack by an improvised nuclear device.

Uncultured adipose-derived regenerative cells (ADRCs) seeded in collagen scaffold improves dermal regeneration, enhancing early vascularization and structural organization following thermal burns.

OBJECTIVE: Advances in tissue engineering have yielded a range of both natural and synthetic skin substitutes for burn wound healing application. Long-term viability of tissue-engineered skin substitutes requires the formation and maturation of neo-vessels to optimize survival and biointegration after implantation. A number of studies have demonstrated the capacity of Adipose Derived Regenerative Cells (ADRCs) to promote angiogenesis and modulate inflammation. On this basis, it was hypothesized that adding ADRCs to a collagen-based matrix (CBM) (i.e. Integra) would enhance formation and maturation of well-organized wound tissue in the setting of acute thermal burns. The purpose of this study was to evaluate whether seeding uncultured ADRCs onto CBM would improve matrix properties and enhance healing of the grafted wound. METHODS: Full thickness thermal burns were created on the backs of 8 Gottingen mini-swine. Two days post-injury wounds underwent fascial excision and animals were randomized to receive either Integra seeded with either uncultured ADRCs or control vehicle. Wound healing assessment was performed by digital wound imaging, histopathological and immunohistochemical analyses. RESULTS: In vitro analysis demonstrated that freshly isolated ADRCs adhered and propagated on the CBM. Histological scoring revealed accelerated maturation of wound bed tissue in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM. This was associated with a significant increase in depth of the wound bed tissue and collagen deposition (p<0.05). Blood vessel density in the wound bed was 50% to 69.6% greater in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM (p=0.05) at day 14 and 21. In addition, ADRCs delivered with CBM showed increased blood vessel lumen area and blood vessel maturation at day 21(p=0.05). Interestingly, vascularity and overall cellularity within the CBM were 50% and 45% greater in animals receiving ADRC loaded scaffolds compared to CBM alone (p<0.05). CONCLUSIONS: These data demonstrate that seeding uncultured ADRCs onto CBM dermal substitute enhances wound angiogenesis, blood vessel maturation and matrix remodeling.

Adipose-derived stem cells: methods for isolation and applications for clinical use.

Adipose tissue sciences have rapidly expanded since the identification of regenerative cells contained within the stromal vascular fraction (SVF) of fat. Isolation of the SVF, containing adipose-derived stem cells (ADSC), can be accomplished efficiently in the operating room or in the laboratory through enzymatic digestion of the adipose tissue and concentration of SVF. Cells can be directly re-injected as a mesotherapeutic agent, recombined with a tissue scaffold (e.g., cell-enriched fat grafts) or expanded in culture for tissue-engineered cell therapeutics. The potential for cell therapy is under current investigation by researchers around the world. This chapter reviews laboratory methods for isolating ADSCs and the ongoing clinical trials evaluating cell therapeutic efficacy across many specialties, including cardiology, neurology, immunology, tissue engineering, sports medicine, and plastic and reconstructive surgery.

Fresh and cryopreserved, uncultured adipose tissue-derived stem and regenerative cells ameliorate ischemia-reperfusion-induced acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) represents a major clinical problem with high mortality and limited causal treatments. The use of cell therapy has been suggested as a potential modality to improve the course and outcome of AKI. METHODS: We investigated the possible renoprotection of freshly isolated, uncultured adipose tissue-derived stem and regenerative cells (ADRCs) before and after cryopreservation in a rat ischemia-reperfusion (I-R) model of AKI. RESULTS: We demonstrated that ADRC therapy drastically reduced mortality (survival 100% vs. 57%, ADRC vs. controls, respectively) and significantly reduced serum creatinine (sCr on Day 3: 3.03 ± 1.58 vs. 7.37 ± 2.32 mg/dL, ADRC vs. controls, respectively). Histological analysis further validated a significantly reduced intratubular cast formation, ameliorated acute tubular epithelial cell necrosis and mitigated macrophage infiltration. Furthermore, a reduced RNA expression of CXCL2 and IL-6 was found in the ADRC group which could explain the reduced macrophage recruitment. Use of cryopreserved ADRCs resulted in an equally high survival (90% vs. 33% in the control group) and similarly improved renal function (sCr on Day 3: 4.64 ± 2.43 vs. 7.24 ± 1.40 mg/dL in controls). CONCLUSIONS: Collectively, these results suggest a potential clinical role for ADRC therapy in patients with AKI. Importantly, cryopreservation of ADRCs could offer an autologous treatment strategy for patients who are at high risk for AKI during planned interventions.

Adipose-derived stem cells.

Human adipose tissue has been shown to contain a population of cells that possesses extensive proliferative capacity and the ability to differentiate into multiple cell lineages. These cells are referred to as adipose tissue-derived stem cells (ADSCs) and are generally similar, though not identical, to mesenchymal stem cells (also referred to as marrow stromal cells). ADSCs for research are most conveniently extracted from tissue removed during an elective cosmetic liposuction procedure but may also be obtained from resected adipose tissue. This chapter describes surgical procedures associated with improved ADSC recovery and the processes by which aspirated adipose tissue is washed and digested with collagenase to yield a heterogeneous population from which ADSCs can be expanded. The large volume of tissue obtained from a liposuction procedure (average approximately 2 L), combined with the relatively high frequency of ADSC within the digestate, yields substantially more stem cells than can be realized from marrow without extensive expansion in culture.

Clonogenic multipotent stem cells in human adipose tissue differentiate into functional smooth muscle cells.

Smooth muscle is a major component of human tissues and is essential for the normal function of a multitude of organs including the intestine, urinary tract and the vascular system. The use of stem cells for cell-based tissue engineering and regeneration strategies represents a promising alternative for smooth muscle repair. For such strategies to succeed, a reliable source of smooth muscle precursor cells must be identified. Adipose tissue provides an abundant source of multipotent cells. In this study, the capacity of processed lipoaspirate (PLA) and adipose-derived stem cells to differentiate into phenotypic and functional smooth muscle cells was evaluated. To induce differentiation, PLA cells were cultured in smooth muscle differentiation medium. Smooth muscle differentiation of PLA cells induced genetic expression of all smooth muscle markers and further confirmed by increased protein expression of smooth muscle cell-specific alpha actin (ASMA), calponin, caldesmon, SM22, myosin heavy chain (MHC), and smoothelin. Clonal studies of adipose derived multipotent cells demonstrated differentiation of these cells into smooth muscle cells in addition to trilineage differentiation capacity. Importantly, smooth muscle-differentiated cells, but not their precursors, exhibit the functional ability to contract and relax in direct response to pharmacologic agents. In conclusion, adipose-derived cells have the potential to differentiate into functional smooth muscle cells and, thus, adipose tissue can be a useful source of cells for treatment of injured tissues where smooth muscle plays an important role.

Fat tissue: an underappreciated source of stem cells for biotechnology.

Adipose tissue can be harvested in large amounts with minimal morbidity. It contains numerous cells types, including adipocytes, preadipocytes, vascular endothelial cells and vascular smooth muscle cells; it also contains cells that have the ability to differentiate into several lineages, such as fat, bone, cartilage, skeletal, smooth, and cardiac muscle, endothelium, hematopoietic cells, hepatocytes and neuronal cells. Cloning studies have shown that some adipose-derived stem cells (ADSCs) have multilineage differentiation potential. ADSCs are also capable of expressing multiple growth factors, including vascular endothelial growth factor and hepatocyte growth factor. Early, uncontrolled, non-randomized clinical research, applying fresh adipose-derived cells into a cranial defect or undifferentiated ADSCs into fistulas in Crohn's disease, has shown healing and an absence of side effects. The combination of these properties, and the large quantity of cells that can be obtained from fat, suggests that this tissue will be a useful tool in biotechnology.

Plasticity of human adipose stem cells toward endothelial cells and cardiomyocytes.

Recent preclinical and clinical studies have suggested that adult stem cells have the ability to promote the retention or restoration of cardiac function in acute and chronic ischemia. Published clinical studies have used autologous donor cells, including skeletal muscle myoblasts, cultured peripheral blood cells, or bone marrow cells. However, our research and that of others indicates that human adipose tissue is an alternative source of cells with potential for cardiac cell therapy. These findings include the presence of cells within adipose tissue that can differentiate into cells expressing a cardiomyocytic or endothelial phenotype, as well as angiogenic and antiapoptotic growth factors. This potential is supported by preclinical studies in large animals.

Processed lipoaspirate cells for tissue engineering of the lower urinary tract: implications for the treatment of stress urinary incontinence and bladder reconstruction.

PURPOSE: We performed a pilot study to investigate the ability of human adipose derived, multipotent stem cells to be delivered to and survive within bladder and urethral smooth muscle. MATERIALS AND METHODS: Lipoaspirate was acquired from female patients undergoing liposuction. The lipoaspirate was processed to yield a pluripotent population of processed lipoaspirate (PLA) cells. For tissue delivery PLA cells were fluorescent labeled and suspended in Hanks' balanced salt solution (Sigma Chemical Co., St. Louis, Missouri). To assess PLA viability in multiple animal models 8 Rnu athymic rats (Charles River, Wilmington, Massachusetts) and 6 SCID mice (Taconic Farms, Oxnard, California) underwent laparotomy and injection of PLA cells into the bladder and urethra. An additional 8 rats underwent sham injection of Hanks' balanced salt solution alone. Experimental and control animals were sacrificed 2, 4, 8 and 12 weeks after injection, and the bladders and urethras were analyzed. RESULTS: Self-regenerating, pluripotent PLA cells were easily isolated from human adipose tissue. Evaluation 2, 4, 8 and 12 weeks after injection demonstrated PLA cell viability and incorporation into the recipient smooth muscle. Eight weeks following injection PLA cells demonstrated in vivo expression of alpha-smooth muscle actin, an early marker of smooth muscle differentiation. CONCLUSIONS: PLA cells are an easily accessible source of pluripotent cells, making them ideal for tissue regeneration. PLA cells remain viable up to 12 weeks in the lower urinary tract. Human PLA cells injected into the urinary tract show morphological and phenotypic evidence of smooth muscle incorporation and differentiation with time. PLA cells may provide a feasible and cost-effective cell source for urinary tract reconstruction.

Multipotential differentiation of adipose tissue-derived stem cells.

Tissue engineering offers considerable promise in the repair or replacement of diseased and/or damaged tissues. The cellular component of this regenerative approach will play a key role in bringing these tissue engineered constructs from the laboratory bench to the clinical bedside. However, the ideal source of cells still remains unclear and may differ depending upon the application. Current research for many applications is focused on the use of adult stem cells. The properties of adult stem cells that make them well-suited for regenerative medicine are (1) ease of harvest for autologous transplantation, (2) high proliferation rates for ex vivo expansion and (3) multilineage differentiation capacity. This review will highlight the use of adipose tissue as a reservoir of adult stem cells and draw conclusions based upon comparisons with bone marrow stromal cells.

Multilineage potential of cells from the artery wall.

BACKGROUND: In diabetes or atherosclerosis, ectopic bone, fat, cartilage, and marrow often develop in arteries. However the mechanism is unknown. We have previously identified a subpopulation of vascular cells (calcifying vascular cells, CVC), derived by dilutional cloning of bovine aortic medial cells, and showed that they undergo osteoblastic differentiation and mineralization. We now show that CVC have the potential to differentiate along other mesenchymal lineages. METHODS AND RESULTS: To determine the multilineage potential of CVC, molecular and functional markers of multiple mesenchymal lineages were assessed. Chondrogenic potential of CVC was evidenced by expression of types II and IX collagen and cytochemical staining for Alcian blue. Leiomyogenic potential of CVC was evidenced by the expression of smooth muscle-alpha actin, calponin, caldesmon, and myosin heavy chain. Stromogenic potential of CVC was evidenced by the ability to support growth of colony-forming units of hematopoietic progenitor cells from human CD34+ umbilical cord blood cells for a period of 5 weeks. Adipogenic potential was not observed. CVC were immunopositive to antigens to CD29 and CD44 but not to CD14 or CD45, consistent with other mesenchymal stem cells. CVC retained multipotentiality despite passaging and expansion through more than 20 to 25 population triplings, indicating a capacity for self-renewal. CONCLUSIONS: These results suggest that the artery wall contains cells that have the potential for multiple lineages similar to mesenchymal stem cells but with a unique differentiation repertoire.

Differential expression of stem cell mobilization-associated molecules on multi-lineage cells from adipose tissue and bone marrow.

Our laboratory has characterized a population of stromal cells obtained from adipose tissue termed processed lipoaspirate cells (PLAs). PLAs, like bone-marrow derived mesenchymal stem cells (BM-MSCs), have the capacity to differentiate along the adipogenic, osteogenic, chondrogenic, and myogenic lineages, In order to better characterize these two multi-lineage populations, we examined the surface phenotype of both bone marrow and adipose tissue-derived cells from five patients undergoing surgery. PLA and BM-MSC cells were isolated, subcultivated, and evaluated for cell surface marker expression using flow cytometry. PLA and BM-MSC cells both expressed CD13, CD29, CD44, CD90, CD105, SH-3, and STRO-1. Differences in expression were noted for cell adhesion molecules CD49d (Integrin alpha4), CD54 (ICAM-1), CD34, and CD106 (VCAM-1). While markedly similar, the surface phenotypes of PLA and BM-MSC cells are distinct for several cell adhesion molecules implicated in hematopoietic stem cell homing, mobilization, and proliferation.

Comparison of multi-lineage cells from human adipose tissue and bone marrow.

Our laboratory has recently characterized a population of cells from adipose tissue, termed processed lipoaspirate (PLA) cells, which have multi-lineage potential similar to bone-marrow-derived mesenchymal stem cells (MSCs). This study is the first comparison of PLA cells and MSCs isolated from the same patient. No significant differences were observed for yield of adherent stromal cells, growth kinetics, cell senescence, multi-lineage differentiation capacity, and gene transduction efficiency. Adipose tissue is an abundant and easily procured source of PLA cells, which have a potential like MSCs for use in tissue-engineering applications and as gene delivery vehicles.

Human adipose tissue is a source of multipotent stem cells.

Much of the work conducted on adult stem cells has focused on mesenchymal stem cells (MSCs) found within the bone marrow stroma. Adipose tissue, like bone marrow, is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. Preliminary studies have recently identified a putative stem cell population within the adipose stromal compartment. This cell population, termed processed lipoaspirate (PLA) cells, can be isolated from human lipoaspirates and, like MSCs, differentiate toward the osteogenic, adipogenic, myogenic, and chondrogenic lineages. To confirm whether adipose tissue contains stem cells, the PLA population and multiple clonal isolates were analyzed using several molecular and biochemical approaches. PLA cells expressed multiple CD marker antigens similar to those observed on MSCs. Mesodermal lineage induction of PLA cells and clones resulted in the expression of multiple lineage-specific genes and proteins. Furthermore, biochemical analysis also confirmed lineage-specific activity. In addition to mesodermal capacity, PLA cells and clones differentiated into putative neurogenic cells, exhibiting a neuronal-like morphology and expressing several proteins consistent with the neuronal phenotype. Finally, PLA cells exhibited unique characteristics distinct from those seen in MSCs, including differences in CD marker profile and gene expression.

Establishment of an adherent cell layer from human umbilical cord blood

As células-mäe säo encontradas no sangue do cordäo umbilical humano (HUCB), além de na medula óssea e no sangue periférico, e há um crescente interesse no uso desse material como uma fonte alternativa para transplante de medula óssea e terapia gênica. A hematopoiese in vitro tem sido mantida por até 16 semanas em culturas de HUCB, mas o estabelecimento de uma camada estromal aderente tem invariavelmente falhado. Precursores de células aderentes foram pesquisados entre células mononucleares do HUCB em culturas a longo prazo. Células mononucleares obtidas do sangue do cordäo depois de partos normais a termo foram cultivadas em diferentes concentraçöes em meio Dulbecco modificado por Iscove, com alimentaçäo semanal. Uma camada aderente foi detectada em 16 de 30 culturas, 12 das quais em concentraçöes celulares maiores que 2 x 10(potência 6) células/ml. Ao contrário das culturas de medula óssea, em que o estroma é detectado precocemente, na maioria (10/16) das culturas positivas do HUCB a camada aderente foi identificada apenas depois da quarta semana de cultura. As células nunca atingiram a confluência e se destacaram da placa aproximadamente quatro semanas após sua detecçäo. A coloraçäo de culturas positivas por May-Grünwald-Giemsa revelou células aderentes semelhantes a fibroblastos ou semelhantes a células endoteliais em um arranjo diferente daquele do estroma da medula óssea em 13 amostras. Em duas dessas, as células aderentes estavam organizadas em cordöes característicos e delimitados de células. Ao contrário das culturas de medula óssea, células gordurosas nunca foram observadas nas camadas aderentes. Um rápido desenvolvimento de grandes células mielóides na primeira semana de cultura foi característico de culturas negativas e essas células mantiveram-se por até 12 semanas. HUCB contém precursores de células aderentes que ocorrem em números menores do que na medula óssea e podem estar em um estágio diferente (possivelmente menos maduro) de diferenciaçäo.