Initiating versus delaying treatment-dose anticoagulation in suspected venous thromboembolism (VTE) in post-operative hip and knee arthroplasty patients: Outcomes and risks.

Background: Hip and knee arthroplasty is a risk factor for venous thromboembolism (VTE). Initiation of treatment-dose anticoagulation in the post-operative period in suspected cases prior to confirmed diagnosis involves balancing increased bleeding risk to VTE-associated morbidity. Methods: A single-centre retrospective cohort study was undertaken comparing outcomes of empirical treatment of suspected VTE in post-operative elective lower-limb arthroplasty patients as opposed to delaying treatment until diagnosis is confirmed. All patients undergoing ultrasonography (US) or CT-pulmonary-angiogram (CTPA) for suspected VTE following elective total hip arthroplasty (THA) or total knee arthroplasty (TKA) between 05/05/17 and 19/07/21 were identified. Primary outcomes were surgical site infection (SSI), readmission, and other wound problems within 30-days of surgery. Results: 107 patients were included for analysis. 93 patients had suspected deep venous thrombosis (DVT), 21 had suspected pulmonary embolism (PE), and 7 were investigated for both DVT and PE. Empirical treatment-dose anticoagulation was initiated in 4 patients with suspected pulmonary embolism (PE) prior to CTPA, and 34 patients with suspected deep venous thrombosis (DVT) prior to US. No significant differences were noted in 30-day readmission rate ([DVT: 12 % vs 23 %, p = 0.41], [PE: 50 % vs 33 %, p = 1.00]), SSI rate ([DVT: 6 % vs 3 %, p = 1.00], [PE: 0 % vs 11 %, p = 1.00]) or other wound complication rate ([DVT: 3 % vs 3 %, p = 1.00), [PE 0 % vs 11 %, p = 1.00]) between empirically and non-empirically treated groups respectively. Conclusion: Empirical initiation of therapeutic anticoagulation in post-operative lower limb arthroplasty patients with suspected VTE appears to be safe practice prior to a definitive diagnosis.

Evaluating Interaction of Cord Blood Hematopoietic Stem/Progenitor Cells with Functionally Integrated Three-Dimensional Microenvironments.

Despite advances in ex vivo expansion of cord blood-derived hematopoietic stem/progenitor cells (CB-HSPC), challenges still remain regarding the ability to obtain, from a single unit, sufficient numbers of cells to treat an adolescent or adult patient. We and others have shown that CB-HSPC can be expanded ex vivo in two-dimensional (2D) cultures, but the absolute percentage of the more primitive stem cells decreases with time. During development, the fetal liver is the main site of HSPC expansion. Therefore, here we investigated, in vitro, the outcome of interactions of primitive HSPC with surrogate fetal liver environments. We compared bioengineered liver constructs made from a natural three-dimensional-liver-extracellular-matrix (3D-ECM) seeded with hepatoblasts, fetal liver-derived (LvSt), or bone marrow-derived stromal cells, to their respective 2D culture counterparts. We showed that the inclusion of cellular components within the 3D-ECM scaffolds was necessary for maintenance of HSPC viability in culture, and that irrespective of the microenvironment used, the 3D-ECM structures led to the maintenance of a more primitive subpopulation of HSPC, as determined by flow cytometry and colony forming assays. In addition, we showed that the timing and extent of expansion depends upon the biological component used, with LvSt providing the optimal balance between preservation of primitive CB HSPC and cellular differentiation. Stem Cells Translational Medicine 2018;7:271-282.

Shear stress upregulates regeneration-related immediate early genes in liver progenitors in 3D ECM-like microenvironments.

The role of fluid stresses in activating the hepatic stem/progenitor cell regenerative response is not well understood. This study hypothesized that immediate early genes (IEGs) with known links to liver regeneration will be upregulated in liver progenitor cells (LPCs) exposed to in vitro shear stresses on the order of those produced from elevated interstitial flow after partial hepatectomy. The objectives were: (1) to develop a shear flow chamber for application of fluid stress to LPCs in 3D culture; and (2) to determine the effects of fluid stress on IEG expression in LPCs. Two hours of shear stress exposure at ∼4 dyn/cm2 was applied to LPCs embedded individually or as 3D spheroids within a hyaluronic acid/collagen I hydrogel. Results were compared against static controls. Quantitative reverse transcriptase polymerase chain reaction was used to evaluate the effect of experimental treatments on gene expression. Twenty-nine genes were analyzed, including IEGs and other genes linked to liver regeneration. Four IEGs (CFOS, IP10, MKP1, ALB) and three other regeneration-related genes (WNT, VEGF, EpCAM) were significantly upregulated in LPCs in response to fluid mechanical stress. LPCs maintained an early to intermediate stage of differentiation in spheroid culture in the absence of the hydrogel, and addition of the gel initiated cholangiocyte differentiation programs which were abrogated by the onset of flow. Collectively the flow-upregulated genes fit the pattern of an LPC-mediated proliferative/regenerative response. These results suggest that fluid stresses are potentially important regulators of the LPC-mediated regeneration response in liver.

Fluid Flow Regulation of Revascularization and Cellular Organization in a Bioengineered Liver Platform.

OBJECTIVE: Modeling of human liver development, especially cellular organization and the mechanisms underlying it, is fundamental for studying liver organogenesis and congenital diseases, yet there are no reliable models that mimic these processes ex vivo. DESIGN: Using an organ engineering approach and relevant cell lines, we designed a perfusion system that delivers discrete mechanical forces inside an acellular liver extracellular matrix scaffold to study the effects of mechanical stimulation in hepatic tissue organization. RESULTS: We observed a fluid flow rate-dependent response in cell distribution within the liver scaffold. Next, we determined the role of nitric oxide (NO) as a mediator of fluid flow effects on endothelial cells. We observed impairment of both neovascularization and liver tissue organization in the presence of selective inhibition of endothelial NO synthase. Similar results were observed in bioengineered livers grown under static conditions. CONCLUSION: Overall, we were able to unveil the potential central role of discrete mechanical stimulation through the NO pathway in the revascularization and cellular organization of a bioengineered liver. Last, we propose that this organ bioengineering platform can contribute significantly to the identification of physiological mechanisms of liver organogenesis and regeneration and improve our ability to bioengineer livers for transplantation.

Whole-organ bioengineering: current tales of modern alchemy.

End-stage organ disease affects millions of people around the world, to whom organ transplantation is the only definitive cure available. However, persistent organ shortage and the resulting widespread transplant backlog are part of a disturbing reality and a common burden felt by thousands of patients on waiting lists in almost every country where organ transplants are performed. Several alternatives and potential solutions to this problem have been sought in past decades, but one seems particularly promising now: whole-organ bioengineering. This review describes briefly the evolution of organ transplantation and the development of decellularized organ scaffolds and their application to organ bioengineering. This modern alchemy of generating whole-organ scaffolds and recellularizing them with multiple cell types in perfusion bioreactors is paving the way for a new revolution in transplantation medicine. Furthermore, although the first generation of bioengineered organs still lacks true clinical value, it has created a number of novel tissue and organ model platforms with direct application in other areas of science (eg, developmental biology and stem cell biology, drug discovery, physiology and metabolism). In this review, we describe the current status and numerous applications of whole-organ bioengineering, focusing also on the multiple challenges that researchers have to overcome to translate these novel technologies fully into transplantation medicine.

Production and implantation of renal extracellular matrix scaffolds from porcine kidneys as a platform for renal bioengineering investigations.

BACKGROUND: It is important to identify new sources of transplantable organs because of the critical shortage of donor organs. Tissue engineering holds the potential to address this issue through the implementation of decellularization-recellularization technology. OBJECTIVE: To produce and examine acellular renal extracellular matrix (ECM) scaffolds as a platform for kidney bioengineering. METHODS: Porcine kidneys were decellularized with distilled water and sodium dodecyl sulfate-based solution. After rinsing with buffer solution to remove the sodium dodecyl sulfate, the so-obtained renal ECM scaffolds were processed for vascular imaging, histology, and cell seeding to investigate the vascular patency, degree of decellularization, and scaffold biocompatibility in vitro. Four whole renal scaffolds were implanted in pigs to assess whether these constructs would sustain normal blood pressure and to determine their biocompatibility in vivo. Pigs were sacrificed after 2 weeks and the explanted scaffolds were processed for histology. RESULTS: Renal ECM scaffolds were successfully produced from porcine kidneys. Scaffolds retained their essential ECM architecture and an intact vascular tree and allowed cell growth. On implantation, unseeded scaffolds were easily reperfused, sustained blood pressure, and were tolerated throughout the study period. No blood extravasation occurred. Pathology of explanted scaffolds showed maintenance of renal ultrastructure. Presence of inflammatory cells in the pericapsular region and complete thrombosis of the vascular tree were evident. CONCLUSIONS: Our investigations show that pig kidneys can be successfully decellularized to produce renal ECM scaffolds. These scaffolds maintain their basic components, are biocompatible, and show intact, though thrombosed, vasculature.