Circulating ensembles of tumor-associated cells: A redoubtable new systemic hallmark of cancer.

Circulating ensembles of tumor-associated cells (C-ETACs) which comprise tumor emboli, immune cells and fibroblasts pose well-recognized risks of thrombosis and aggressive metastasis. However, the detection, prevalence and characterization of C-ETACs have been impaired due to methodological difficulties. Our findings show extensive pan-cancer prevalence of C-ETACs on a hitherto unreported scale in cancer patients and virtual undetectability in asymptomatic individuals. Peripheral blood mononuclear cells (PBMCs) were isolated from blood samples of 16,134 subjects including 5,509 patients with epithelial malignancies in various organs and 10,625 asymptomatic individuals with age related higher cancer risk. PBMCs were treated with stabilizing reagents to protect and harvest apoptosis-resistant C-ETACs, which are defined as cell clusters comprising at least three EpCAM+ and CK+ cells irrespective of leucocyte common antigen (CD45) status. All asymptomatic individuals underwent screening investigations for malignancy including PAP smear, mammography, low-dose computed tomography, evaluation of cancer antigen 125, cancer antigen 19-9, alpha fetoprotein, carcinoembryonic antigen, prostate specific antigen (PSA) levels and clinical examination to identify healthy individuals with no indication of cancer. C-ETACs were detected in 4,944 (89.8%, 95% CI: 89.0-90.7%) out of 5,509 cases of cancer. C-ETACs were detected in 255 (3%, 95% CI: 2.7-3.4%) of the 8,493 individuals with no abnormal findings in screening. C-ETACs were detected in 137 (6.4%, 95% CI: 5.4-7.4%) of the 2,132 asymptomatic individuals with abnormal results in one or more screening tests. Our study shows that heterotypic C-ETACs are ubiquitous in epithelial cancers irrespective of radiological, metastatic or therapy status. C-ETACs thus qualify to be a systemic hallmark of cancer.

The hazards of DAPI photoconversion: effects of dye, mounting media and fixative, and how to minimize the problem.

Immunocytochemistry is a powerful tool for detection and visualization of specific molecules in living or fixed cells, their localization and their relative abundance. One of the most commonly used fluorescent DNA dyes in immunocytochemistry applications is 4',6-diamidino-2-phenylindole dihydrochloride, known as DAPI. DAPI binds strongly to DNA and is used extensively for visualizing cell nuclei. It is excited by UV light and emits characteristic blue fluorescence. Here, we report a phenomenon based on an apparent photoconversion of DAPI that results in detection of a DAPI signal using a standard filter set for detection of green emission due to blue excitation. When a sample stained with DAPI only was first imaged with the green filter set (FITC/GFP), only a weak cytoplasmic autofluorescence was observed. Next, we imaged the sample with a DAPI filter set, obtaining a strong nuclear DAPI signal as expected. Upon reimaging the same samples with a FITC/GFP filter set, robust nuclear fluorescence was observed. We conclude that excitation with UV results in a photoconversion of DAPI that leads to detection of DAPI due to excitation and emission in the FITC/GFP channel. This phenomenon can affect data interpretation and lead to false-positive results when used together with fluorochrome-labeled nuclear proteins detected with blue excitation and green emission. In order to avoid misinterpretations, extra precaution should be taken to prepare staining solutions with low DAPI concentration and DAPI (UV excitation) images should be acquired after all other higher wavelength images. Of various DNA dyes tested, Hoechst 33342 exhibited the lowest photoconversion while that for DAPI and Hoechst 33258 was much stronger. Different fixation methods did not substantially affect the strength of photoconversion. We also suggest avoiding the use of mounting medium with high glycerol concentrations since glycerol showed the strongest impact on photoconversion. This photoconversion effect cannot be avoided even when using narrow bandpass filter sets.

Accurate Screening for Early-Stage Breast Cancer by Detection and Profiling of Circulating Tumor Cells.

BACKGROUND: The early detection of breast cancer (BrC) is associated with improved survival. We describe a blood-based breast cancer detection test based on functional enrichment of breast-adenocarcinoma-associated circulating tumor cells (BrAD-CTCs) and their identification via multiplexed fluorescence immunocytochemistry (ICC) profiling for GCDFP15, GATA3, EpCAM, PanCK, and CD45 status. METHODS: The ability of the test to differentiate BrC cases (N = 548) from healthy women (N = 9632) was evaluated in a case-control clinical study. The ability of the test to differentiate BrC cases from those with benign breast conditions was evaluated in a prospective clinical study of women (N = 141) suspected of BrC. RESULTS: The test accurately detects BrAD-CTCs in breast cancers, irrespective of age, ethnicity, disease stage, grade, or hormone receptor status. Analytical validation established the high accuracy and reliability of the test under intended use conditions. The test detects and differentiates BrC cases from healthy women with 100% specificity and 92.07% overall sensitivity in a case-control study. In a prospective clinical study, the test shows 93.1% specificity and 94.64% overall sensitivity in differentiating breast cancer cases (N = 112) from benign breast conditions (N = 29). CONCLUSION: The findings reported in this manuscript support the clinical potential of this test for blood-based BrC detection.

Circulating tumor cell assay to non-invasively evaluate PD-L1 and other therapeutic targets in multiple cancers.

Biomarker directed selection of targeted anti-neoplastic agents such as immune checkpoint inhibitors, small molecule inhibitors and monoclonal antibodies form an important aspect of cancer treatment. Immunohistochemistry (IHC) analysis of the tumor tissue is the method of choice to evaluate the presence of these biomarkers. However, a significant barrier to biomarker testing on tissue is the availability of an adequate amount of tissue and need for repetitive sampling due to tumor evolution. Also, tumor tissue testing is not immune to inter- and intra-tumor heterogeneity. We describe the analytical and clinical validation of a Circulating Tumor Cell (CTC) assay to accurately assess the presence of PD-L1 22C3 and PD-L1 28.8, ER, PR and HER2, from patients with solid tumors to guide the choice of suitable targeted therapies. Analytically, the test has high sensitivity, specificity, linearity and precision. Based on a blinded case control study, the clinical sensitivity and specificity for PD-L1 (22C3 and 28.8) was determined to be 90% and 100% respectively. The clinical sensitivity and specificity was 83% and 89% for ER; 80% and 94% for PR; 63% and 89% for HER2 (by ICC); and 100% and 92% for HER2 (by FISH), respectively. The performance characteristics of the test support its suitability and adaptability for routine clinical use.

Hallmark Circulating Tumor-Associated Cell Clusters Signify 230 Times Higher One-Year Cancer Risk.

We have previously shown that circulating ensembles of tumor-associated cells (C-ETACs) are a systemic hallmark of cancer based on analysis of blood samples from 16,134 individuals including 10,625 asymptomatic individuals and 5,509 diagnosed cases of cancer. C-ETACs were ubiquitously (90%) detected across all cancer types and were rare (3.6%) among the asymptomatic population. Consequently, we hypothesized that asymptomatic individuals with detectable C-ETACs would have a definitively elevated risk of developing cancer as compared with individuals without C-ETACs. In the present manuscript we present 1-year follow-up data of the asymptomatic cohort which shows that C-ETAC positive individuals have a 230-fold (P < 0.00001) higher 1-year cancer risk as compared with individuals where C-ETACs were undetectable. Simultaneously, we also expanded the study to include 4,419 symptomatic individuals, suspected of cancer, prior to undergoing an invasive biopsy for diagnosis. C-ETACs were detected in 4,101 (92.8%) of these 4,419 cases where cancer was eventually confirmed. We conclude that detection of C-ETACs can identify patients at risk of cancer and can be reliably used to stratify asymptomatic individuals with an elevated 1-year risk of cancer. PREVENTION RELEVANCE: The study evaluated a blood test that can determine if healthy ('asymptomatic') individuals without a history of cancer have an increased risk of developing cancer within the next one year. This test can significantly minimize radiological or invasive screening in the majority individuals who do not have any increased risk.

Improved Treatment Outcomes by Using Patient Specific Drug Combinations in Mammalian Target of Rapamycin Activated Advanced Metastatic Cancers.

Background: Activation of the mTOR signaling pathway is ubiquitous in cancers and a favourable therapeutic target. However, presently approved mTOR inhibitor monotherapies have modest benefits in labeled indications while poor outcomes have been reported for mTOR inhibitor monotherapy when administered in a label-agnostic setting based on univariate molecular indications. The present study aimed to determine whether patient-specific combination regimens with mTOR inhibitors and other anticancer agents selected based on multi-analyte molecular and functional tumor interrogation (ETA: Encyclopedic Tumor Analysis) yields significant treatment response and survival benefits in advanced or refractory solid organ cancers. Methods: We evaluated treatment outcomes in 49 patients diagnosed with unresectable or metastatic solid organ cancers, of whom 3 were therapy naïve and 46 were pre-treated in whom the cancer had progressed on 2 or more prior systemic lines. All patients received mTOR inhibitor in combination with other targeted, endocrine or cytotoxic agents as guided by ETA. Patients were followed-up to determine Objective Response Rate (ORR), Progression Free Survival (PFS) and Overall Survival (OS). Results: The Objective Response Rate (ORR) was 57.1%, the disease Control rate (DCR) was 91.8%, median Progression Free Survival (mPFS) was 4.9 months and median Overall Survival (mOS) was 9.4 months. There were no Grade IV treatment related adverse events (AEs) or any treatment related deaths. Conclusion: Patient-specific combination regimens with mTOR inhibition and other anti-neoplastic agents, when selected based on multi-analyte molecular and functional profiling of the tumor can yield meaningful outcomes in advanced or refractory solid organ cancers. Trial Registration: Details of all trials are available at WHO-ICTRP: https://apps.who.int/trialsearch/. RESILIENT ID CTRI/2018/02/011808. ACTPRO ID CTRI/2018/05/014178. LIQUID IMPACT ID CTRI/2019/02/017548.

Clinical utility of circulating tumor-associated cells to predict and monitor chemo-response in solid tumors.

PURPOSE: Selection of cytotoxic chemotherapy agents (CCA) based on pre-treatment evaluation of drug sensitivities is a desirable but unmet goal for personalized anticancer treatment strategies. Prior attempts to correlate in vitro Chemo-Response Profiles (CRP) of tumor explants or Circulating Tumor Cells (CTCs) with clinical outcomes have been largely unsuccessful. METHODS: We present results from a large cohort (n = 5090, three Arms) of patients with various solid organ tumors, where CRP of Circulating Tumor-Associated Cells (C-TACs) was determined against cancer-specific CCA panels to generate a database of 56,466 unique CRP. RESULTS: In Arm 1 (n = 230), 93.7% concordance was observed between CRP of C-TACs and concurrently obtained Tumor tissue Derived Cells (TDCs). In arm 2 (n = 2201, pretreated), resistance of C-TACs to ≥ 1 CCA was observed in 79% of cases. In a blinded subset analysis of 143 pretreated patients with radiologically ascertained disease progression, CRP of C-TACs was 87% concordant with in vivo treatment failure. In Arm 3 (n = 2734, therapy naïve), innate resistance of C-TACs to ≥ 1 CCA was observed in 61% of cases. In a blinded subset analysis of 77 therapy naïve patients, in vitro chemo-sensitivity of C-TACs was concordant with radiologically ascertained treatment response to first line CCA in 97% of cases. CONCLUSION: To our knowledge, this is the first expansive and in-depth study demonstrating that real-time CRP of C-TACs is a viable approach for non-invasive assessment of response to CCA in solid organ cancers.

Evaluation of circulating tumor cell clusters for pan-cancer noninvasive diagnostic triaging.

BACKGROUND: Histopathologic examination (HPE) of tumor tissue obtained by invasive biopsy is the standard for cancer diagnosis but is resource-intensive and has been associated with procedural risks. The authors demonstrate that immunocytochemistry (ICC) profiling of circulating ensembles of tumor-associated cells (C-ETACs) can noninvasively provide diagnostic guidance in solid organ cancers. METHODS: The clinical performance of this approach was tested on blood samples from 30,060 individuals, including 9416 individuals with known cancer; 6725 symptomatic individuals with suspected cancer; and 13,919 asymptomatic individuals with no prior diagnosis of cancer. C-ETACs were harvested from peripheral blood and profiled by ICC for organ-specific and subtype-specific markers relevant to the cancer type. ICC profiles were compared with HPE diagnoses to determine concordance. RESULTS: The presence of malignancy was confirmed by the detection of C-ETACs in 91.8% of the 9416 individuals with previously known cancer. Of the 6725 symptomatic individuals, 6025 were diagnosed with cancer, and 700 were diagnosed with benign conditions; C-ETACs were detected in 92.6% of samples from the 6025 individuals with cancer. In a subset of 3509 samples, ICC profiling of C-ETACs for organ-specific and subtype-specific markers was concordant with HPE findings in 93.1% of cases. C-ETACs were undetectable in 95% of samples from the 700 symptomatic individuals who had benign conditions and in 96.3% of samples from the 13,919 asymptomatic individuals. CONCLUSIONS: C-ETACs were ubiquitous (>90%) in various cancers and provided diagnostically relevant information in the majority (>90%) of cases. This is the first comprehensive report on the feasibility of ICC profiling of C-ETACs to provide pan-cancer diagnostic guidance with accuracy comparable to that of HPE.

Gene expression profiling of single bovine embryos uncovers significant effects of in vitro maturation, fertilization and culture.

In vitro production (IVP) has been shown to affect embryonic gene expression and often result in large offspring syndrome (LOS) in cattle and sheep. To dissect the effects of in vitro maturation, fertilization and culture on bovine embryos, we compared the expression profiles of single blastocysts generated by: (1) in vitro maturation, fertilization and culture (IVF); (2) in vivo maturation, fertilization and in vitro culture (IVD); and (3) in vivo maturation, fertilization and development (AI). To conduct expression profiling, total RNA was isolated from individual embryos, linearly amplified and hybridized to a custom bovine cDNA microarray containing approximately 6,300 unique genes. There were 306, 367, and 200 genes differentially expressed between the AI and IVD, IVF and IVD, and AI and IVF comparisons, respectively. Interestingly, 44 differentially expressed genes were identified between the AI embryos and both the IVF and IVD embryos, making these potential candidates for LOS. There were 60 genes differentially expressed between the IVF embryos and the AI and IVD embryos. The Gene Ontology category "RNA processing" was over-represented among the genes that were down-regulated in the IVF embryos, indicating an effect of in vitro oocyte maturation/fertilization on the ability to transcribe maternal RNA stores. A culture effect on the expression of genes involved in translation was also observed by the comparison of AI with IVD embryos.

Encyclopedic tumor analysis for guiding treatment of advanced, broadly refractory cancers: results from the RESILIENT trial.

RESILIENT (CTRI/2018/02/011808) was a single arm, open label, phase II/III study to test if label agnostic therapy regimens guided by Encyclopedic Tumor Analysis (ETA) can offer meaningful clinical benefit for patients with relapsed refractory metastatic (r/r-m) malignancies. Patients with advanced refractory solid organ malignancies where disease had progressed following ≥2 lines of systemic treatments were enrolled in the trial. Patients received personalized treatment recommendations based on integrational comprehensive analysis of freshly biopsied tumor tissue and blood. The primary end points were Objective Response Rate (ORR), Progression Free Survival (PFS) and Quality of Life (QoL). Objective Response (Complete Response + Partial Response) was observed in 54 of 126 patients evaluable per protocol (ORR = 42.9%; 95% CI: 34.3%-51.4%, p < 0.0001). At study completion, Disease Control (Complete Response + Partial Response + Stable Disease) was observed in 114 out of 126 patients evaluable per protocol (CBR = 90.5%; 95% CI: 83.9% - 95.0%, p < 0.00001) and Disease Progression in 12 patients. Median duration of follow-up was 138 days (range 31 to 379). Median PFS at study termination was 134 days (range 31 to 379). PFS rate at 90 days and 180 days were 93.9% and 82.5% respectively. The study demonstrated that tumors have latent vulnerabilities that can be identified via integrational multi-analyte investigations such as ETA. This approach identified viable treatment options that could yield meaningful clinical benefit in this cohort of patients with advanced refractory cancers.

* Design of an In Vitro Model of Cell Recruitment for Skeletal Muscle Regeneration Using Hepatocyte Growth Factor-Loaded Fibrin Microthreads.

Large skeletal muscle defects that result in volumetric muscle loss (VML) result in the destruction of the basal lamina, which removes key signaling molecules such as hepatocyte growth factor (HGF) from the wound site, eliminating the endogenous capacity of these injuries to regenerate. We recently showed that HGF-loaded fibrin microthreads increased the force production in muscle tissues after 60 days in a mouse VML model. In this study, we created an in vitro, three-dimensional (3D) microscale outgrowth assay system designed to mimic cell recruitment in vivo, and investigated the effect of HGF-loaded, cross-linked fibrin microthreads on myoblast recruitment to predict the results observed in vivo. This outgrowth assay discretely separated the cellular and molecular functions (migration, proliferation, and chemotaxis) that direct outgrowth from the wound margin, creating a powerful platform to model cell recruitment in axially aligned tissues, such as skeletal muscle. The degree of cross-linking was controlled by pH and microthreads cross-linked using physiologically neutral pH (EDCn) facilitated the release of active HGF; increasing the two-dimensional migration and 3D outgrowth of myoblasts twofold. While HGF adsorbed to uncross-linked microthreads, it did not enhance myoblast migration, possibly due to the low concentrations that were adsorbed. Regardless of the amount of HGF adsorbed on the microthreads, myoblast proliferation increased significantly on stiffer, cross-linked microthreads. Together, the results of these studies show that HGF loaded onto EDCn microthreads supported enhanced myoblast migration and recruitment and suggest that our novel outgrowth assay system is a robust in vitro screening tool that predicts the performance of fibrin microthreads in vivo.

Intracytoplasmic sperm injection in the bovine induces abnormal [Ca2+]i responses and oocyte activation.

Fertilisation by intracytoplasmic sperm injection (ICSI), a technique that bypasses the membrane fusion of the gametes, has been widely used to produce offspring in humans and mice. Success with this technique has lent support to the hypothesis that in mammalian fertilisation, a factor from the sperm, the so-called sperm factor, is responsible for oocyte activation and that the fusion process is not involved in the generation of the hallmark [Ca2+]i signalling seen following fertilisation. However, the success of ICSI has largely eluded large domestic species, such as the bovine, porcine and equine, casting doubt on the current model of oocyte activation at fertilisation in these species. Using Ca2+ imagery and a series of treatments to manipulate the chemical structure of the sperm, we have investigated the early events of oocyte activation in response to ICSI in the bovine. Our results demonstrate, for the first time, that following ICSI, the majority of bovine oocytes are unable to mount [Ca2+]i oscillations, although, in few cases, the initiation of [Ca2+]i oscillations can occur in a manner indistinguishable from in vitro fertilisation. We also show that bull sperm possess a full complement of sperm factor. However, either the release and/or activation of the sperm factor are compromised after ICSI, leading to the delivery of a defective Ca2+ stimulus, which results in premature termination of embryo development.

Designing Biopolymer Microthreads for Tissue Engineering and Regenerative Medicine.

Native tissue structures possess elaborate extracellular matrix (ECM) architectures that inspire the design of fibrous structures in the field of regenerative medicine. We review the literature with respect to the successes and failures, as well as the future promise of biopolymer microthreads as scaffolds to promote endogenous and exogenous tissue regeneration. Biomimetic microthread tissue constructs have been proposed for the functional regeneration of tendon, ligament, skeletal muscle, and ventricular myocardial tissues. To date, biopolymer microthreads have demonstrated promising results as materials to recapitulate the hierarchical structure of simple and complex tissues and well as biochemical signaling cues to direct cell-mediated tissue regeneration. Biopolymer microthreads have also demonstrated exciting potential as a platform technology for the targeted delivery of stem cells and therapeutic molecules. Future studies will focus on the design of microthread-based tissue analogs that strategically integrate growth factors and progenitor cells to temporally direct cell-mediated processes that promote enhanced functional tissue regeneration.

Rapid release of growth factors regenerates force output in volumetric muscle loss injuries.

A significant challenge in the design and development of biomaterial scaffolds is to incorporate mechanical and biochemical cues to direct organized tissue growth. In this study, we investigated the effect of hepatocyte growth factor (HGF) loaded, crosslinked fibrin (EDCn-HGF) microthread scaffolds on skeletal muscle regeneration in a mouse model of volumetric muscle loss (VML). The rapid, sustained release of HGF significantly enhanced the force production of muscle tissue 60 days after injury, recovering more than 200% of the force output relative to measurements recorded immediately after injury. HGF delivery increased the number of differentiating myoblasts 14 days after injury, and supported an enhanced angiogenic response. The architectural morphology of microthread scaffolds supported the ingrowth of nascent myofibers into the wound site, in contrast to fibrin gel implants which did not support functional regeneration. Together, these data suggest that EDCn-HGF microthreads recapitulate several of the regenerative cues lost in VML injuries, promote remodeling of functional muscle tissue, and enhance the functional regeneration of skeletal muscle. Further, by strategically incorporating specific biochemical factors and precisely tuning the structural and mechanical properties of fibrin microthreads, we have developed a powerful platform technology that may enhance regeneration in other axially aligned tissues.

Biomimetic scaffolds for regeneration of volumetric muscle loss in skeletal muscle injuries.

Skeletal muscle injuries typically result from traumatic incidents such as combat injuries where soft-tissue extremity injuries are present in one of four cases. Further, about 4.5 million reconstructive surgical procedures are performed annually as a result of car accidents, cancer ablation, or cosmetic procedures. These combat- and trauma-induced skeletal muscle injuries are characterized by volumetric muscle loss (VML), which significantly reduces the functionality of the injured muscle. While skeletal muscle has an innate repair mechanism, it is unable to compensate for VML injuries because large amounts of tissue including connective tissue and basement membrane are removed or destroyed. This results in a significant need to develop off-the-shelf biomimetic scaffolds to direct skeletal muscle regeneration. Here, the structure and organization of native skeletal muscle tissue is described in order to reveal clear design parameters that are necessary for scaffolds to mimic in order to successfully regenerate muscular tissue. We review the literature with respect to the materials and methodologies used to develop scaffolds for skeletal muscle tissue regeneration as well as the limitations of these materials. We further discuss the variety of cell sources and different injury models to provide some context for the multiple approaches used to evaluate these scaffold materials. Recent findings are highlighted to address the state of the field and directions are outlined for future strategies, both in scaffold design and in the use of different injury models to evaluate these materials, for regenerating functional skeletal muscle. STATEMENT OF SIGNIFICANCE: Volumetric muscle loss (VML) injuries result from traumatic incidents such as those presented from combat missions, where soft-tissue extremity injuries are represented in one of four cases. These injuries remove or destroy large amounts of skeletal muscle including the basement membrane and connective tissue, removing the structural, mechanical, and biochemical cues that usually direct its repair. This results in a significant need to develop off-the-shelf biomimetic scaffolds to direct skeletal muscle regeneration. In this review, we examine current strategies for the development of scaffold materials designed for skeletal muscle regeneration, highlighting advances and limitations associated with these methodologies. Finally, we identify future approaches to enhance skeletal muscle regeneration.

Maintenance of multipotency in human dermal fibroblasts treated with Xenopus laevis egg extract requires exogenous fibroblast growth factor-2.

Direct reprogramming of a differentiated somatic cell into a developmentally more plastic cell would offer an alternative to applications in regenerative medicine that currently depend on either embryonic stem cells (ESCs), adult stem cells, or induced pluripotent stem cells (iPSCs). Here we report the potential of select Xenopus laevis egg extract fractions, in combination with exogenous fibroblast growth factor-2 (FGF2), to affect life span, morphology, gene expression, protein translation, and cellular localization of OCT4 and NANOG transcription factors, and the developmental potential of human dermal fibroblasts in vitro. A gradual change in morphology is accompanied by translation of embryonic transcription factors and their nuclear localization and a life span exceeding 60 population doublings. Cells acquire the ability to follow adipogenic, neuronal, and osteogenic differentiation under appropriate induction conditions in vitro. Analysis of active extract fractions reveals that Xenopus egg protein and RNAs as well as exogenously supplemented FGF2 are required and sufficient for induction and maintenance of this phenotypic change. Factors so far identified in the active fractions include FGF2 itself, transforming growth factor-ß, maskin, and nucleoplasmin. Identification of critical factors needed for reprogramming may allow for nonviral, chemically defined derivation of human-induced multipotent cells that can be maintained by exogenous FGF2.

Crosslinking strategies facilitate tunable structural properties of fibrin microthreads.

A significant challenge in the design of biomimetic scaffolds is combining morphologic, mechanical, and biochemical cues into a single construct to promote tissue regeneration. In this study, we analyzed the effects of different crosslinking conditions on fibrin biopolymer microthreads to create morphologic scaffolds with tunable mechanical properties that are designed for directional cell guidance. Fibrin microthreads were crosslinked using carbodiimides in either acidic or neutral buffer, and the mechanical, structural, and biochemical responses of the microthreads were investigated. Crosslinking in the presence of acidic buffer (EDCa) created microthreads that had significantly higher tensile strengths and moduli than all other microthreads, and failed at lower strains than all other microthreads. Microthreads crosslinked in neutral buffer (EDCn) were also significantly stronger and stiffer than uncrosslinked threads and were comparable to contracting muscle in stiffness. Swelling ratios of crosslinked microthreads were significantly different from each other and uncrosslinked controls, suggesting a difference in the internal organization and compaction of the microthreads. Using an in vitro degradation assay, we observed that EDCn microthreads degraded within 24h, six times slower than uncrosslinked control threads, but EDCa microthreads did not show any significant indication of degradation within the 7-day assay period. Microthreads with higher stiffnesses supported significantly increased attachment of C2C12 cells, as well as increases in cell proliferation without a decrease in cell viability. Taken together, these data demonstrate the ability to create microthreads with tunable mechanical and structural properties that differentially direct cellular functions. Ultimately, we anticipate that we can strategically exploit these properties to promote site-specific tissue regeneration.

Restoration of skeletal muscle defects with adult human cells delivered on fibrin microthreads.

Large-scale musculoskeletal wounds, such as those seen in trauma injuries, present poor functional healing prognoses. In severe trauma, when the native tissue architecture is destroyed or lost, the regenerative capacity of skeletal muscle is diminished by scar formation. Here we demonstrate that a scaffold system composed of fibrin microthreads can provide an efficient delivery system for cell-based therapies and improve regeneration of a large defect in the tibialis anterior of the mouse. Cell-loaded fibrin microthread bundles implanted into a skeletal muscle resection reduced the overall fibroplasia-associated deposition of collagen in the wound bed and promoted in-growth of new muscle tissue. When fibrin microthreads were seeded with adult human cells, implanted cells contributed to the nascent host tissue architecture by forming skeletal muscle fibers, connective tissue, and PAX7-positive cells. Stable engraftment was observed at 10 weeks postimplant and was accompanied by reduced levels of collagen deposition. Taken together, these data support the design and development of a platform for microthread-based delivery of autologous cells that, when coupled to an in vitro cellular reprogramming process, has the potential to improve healing outcomes in large skeletal muscle wounds.

Expression of NANOG and NANOGP8 in a variety of undifferentiated and differentiated human cells.

The transcription factor NANOG is essential for maintaining pluripotency in embryonic stem cells. We have previously reported the expression of NANOG in adult human fibroblasts; here we present a more thorough investigation into the expression of NANOG in a panel of both differentiated and undifferentiated human cells. We utilize RT-PCR, qRT-PCR, cloning and sequencing, sequence alignment, restriction digestion, immunocytochemistry, Western blotting, and EMSA to investigate expression of NANOG in a variety of somatic, transformed and stem cell phenotypes. RT-PCR and qRT-PCR analysis revealed the presence of NANOG transcripts in all the cell types examined, albeit at magnitudes lower than human embryonic stem cells. Further investigation by single nucleotide polymorphism analysis of expressed transcripts in several cell types detected a NANOG pseudogene, NANOGP8, one of only two NANOG pseudogenes with the potential of encoding a similar size protein to embryonic NANOG (eNANOG). Our analysis demonstrates that although the NANOG protein is detected in nearly all cells examined, expression of the eNANOG and/or NANOGP8 transcript as well as the sub-cellular localization of the protein is cell type-specific. Additionally, smooth muscle cells, which express exclusively NANOGP8, display nuclear localization of NANOG protein, indicating that NANOGP8 is a protein coding gene possibly functioning as a transcription factor. Lastly, all cell types expressing eNANOG and/or NANOGP8 were found to be capable of binding a NANOG consensus sequence in vitro. We conclude that eNANOG is not exclusively expressed in undifferentiated cells and that both eNANOG and NANOGP8 may function as transcription factors in a cell type-specific manner.