Beyond SEP-1 Compliance: Assessing the Impact of Antibiotic Overtreatment and Fluid Overload in Suspected Septic Patients

BACKGROUND

The Centers for Medicare and Medicaid Services (CMS) developed the Severe Sepsis and Septic Shock Performance Measure bundle (SEP-1) metric to improve sepsis care, but evidence supporting this bundle is limited and harms secondary to compliance have not been investigated.

OBJECTIVE

This study investigates the effect of an emergency department (ED) sepsis quality-improvement (QI) effort to improve CMS SEP-1 compliance, looking specifically at antibiotic overtreatment and harm from fluid resuscitation.

METHODS

This was a retrospective observational study conducted between March and July 2021 with patients for whom a sepsis order set was initiated. The primary outcomes included the number of patients treated with antibiotics who were ultimately deemed nonseptic and the number of patients who developed pulmonary edema, with or without need for positive pressure ventilation (PPV), within 48 h of receiving a 30 mL/kg fluid bolus. Data were collected via nonblinded chart reviews, with a free marginal κ-calculation indicating excellent interrater reliability.

RESULTS

The study cohort included 273 patients, 170 (62.3%) who were ultimately determined to be septic and 103 (37.7%) who were nonseptic. Of the 103 nonseptic patients, 82 (79.6%) received antibiotics in the ED. Of the 121 patients (44.3%) who received a 30 mL/kg bolus, 5 patients (4.1%) developed pulmonary edema and 0 of 121 patients required PPV within 48 h.

CONCLUSIONS

The QI effort led to moderate rates of antibiotic overtreatment and very few patients developed pulmonary edema due to a 30 mL/kg fluid bolus.

Accurately evaluating for a small bowel obstruction using an abdominal radiograph, by a new method: The Bowel-Spine Ratio

INTRODUCTION

A well-established method does not exist to rule out a small bowel obstruction using an abdominal xray series with significant accuracy. The hypothesis of the study is that the ratio of an average small bowel diameter to lumbar spine diameter over 0.5 is most likely a small bowel obstruction.

METHODS

An x-ray abdominal series measurement technique was applied to 41 subjects with a chief complaint of "abdominal pain" as part of a randomized retrospective case review to predict an obstruction v. non obstruction. A total number of 81 abdominal pain subjects with a mean age of 46.7 years were selected with 40 excluded due to normal small bowel gas pattern. The subject's medical information was unknown to the authors when reading their images. The measurement technique involved averaging the largest and smallest small bowel short axis diameters with comparison to the lowest clearly visible lumbar body width. The subjects' medical course as described in the medical chart or subsequent computed tomography scans were used as the referencing standard to determine presence of obstruction vs non-obstruction.

RESULTS

This method, called the Bowel-Spine Ratio (BSR), resulted in a sensitivity of 0.882 (0.622-0.979; 95% CI), specificity of 0.957 (0.760-0.998; 95% CI), accuracy of 94.7% (80.9%-99.1%; 95% CI) and a positive likelihood ratio of 21 for predicting a small bowel obstruction.

CONCLUSION

The abdominal series Bowel-Spine Ratio is a simple yet effective technique to screen for a small bowel obstruction using limited resources and to avoid unnecessary computed tomography scans with the potential to reduce health care costs.

IMPLICATIONS FOR PRACTICE

Clinicians could have increased confidence in utilizing abdominal radiographs to evaluate for small bowel obstruction.

Hemodynamic profile effects of PM101 amiodarone formulation in patients with post-operative tachyarrhythmias

Amiodarone may be considered for patients with junctional ectopic tachycardia refractory to treatment with sedation, analgesia, cooling, and electrolyte replacements. There are currently no published pediatric data regarding the hemodynamic effects of the newer amiodarone formulation, PM101, devoid of hypotensive agents used in the original amiodarone formulation. We performed a single-center, retrospective, descriptive study from January 2012 to December 2020 in a pediatric ICU. Thirty-three patients were included (22 male and 11 female) between the ages of 1.1 and 1,460 days who developed post-operative junctional ectopic tachycardia or other tachyarrhythmias requiring PM101. Data analysis was performed on hemodynamic parameters (mean arterial pressures and heart rate) and total PM101 (mg/kg) from hour 0 of amiodarone administration to hour 72. Adverse outcomes were defined as Vasoactive-Inotropic Score >20, patients requiring ECMO or CPR, or patient death. There was no statistically significant decrease in mean arterial pressures within the 6 hours of PM101 administration (p > 0.05), but there was a statistically significant therapeutic decrease in heart rate for resolution of tachyarrhythmia (p < 0.05). Patients received up to 25 mg/kg in an 8-hour time for rate control. Average rate control was achieved within 11.91 hours and average rhythm control within 62 hours. There were four adverse events around the time of PM101 administration, with three determined to not be associated with the medication. PM101 is safe and effective in the pediatric cardiac surgical population. Our study demonstrated that PM101 can be used in a more aggressive dosing regimen than previously reported in pediatric literature with the prior formulation.

Perceived Value of Osteopathic Recognition

BACKGROUND AND OBJECTIVES

In 2020 the Accreditation Council on Graduate Medical Education (ACGME) became the sole accrediting body for osteopathic and allopathic residency programs, with an option for programs to apply for Osteopathic Recognition (OR) to distinguish their training in osteopathic principles and practice. There is limited research regarding this transition. The goal of our study was to assess the perceived value of OR and perceived difficulty of obtaining OR for family medicine residency programs.

METHODS

We performed analyses regarding the difficulty of obtaining OR status and the value of OR and Osteopathic Principles and Practice (OPP) using questions on the 2020 Council of Academic Family Medicine Educational Research Alliance (CERA) omnibus survey.

RESULTS

Of the 280 program directors (PD) responding, 69 (24.6%) had OR status, 126 (45.0%) were considering applying or would apply if needed resources were available, and 85 (30.4%) were not considering OR. Of the 73 PDs reporting on experience with the OR process, 28 (38.4%) found it "very smooth," 30 (41.1%) found it "a little bumpy," and 15 (20.5%) found it "very bumpy"; 87.0% of PDs (60 of 69) with OR felt it had value in recruiting DO students and 31.8% (22/69) in recruiting MD students; 86.9% of programs with OR status perceived OPP to be somewhat or very valuable in enhancing patient satisfaction compared to 77% of those considering OR and 44.7% not considering OR.

CONCLUSIONS

Program directors perceive value in OR status for recruiting and in osteopathic practice for patient care. Since 75.4% of responding program directors have or are interested in achieving OR status, further research is needed on its benefits and barriers.

176. Topical Antibiotic and Antiseptic Use in the Operating Room: An Opportunity for Antimicrobial Stewardship?

Background

Data suggest that topical antibiotic and antiseptic use in the operating room is common but not commonly monitored by antimicrobial stewardship programs. Although some data suggest a benefit in certain surgical procedures, the CDC and WHO advise against the routine use of topical antibiotics in surgery due to uncertainty and heterogeneity in the overall data.

Methods

We conducted a retrospective 28-day period prevalence study of topical antibiotic and antiseptic use during surgical procedures performed in the operating room by 6 surgical specialties at a tertiary care medical center. For the subset of patients undergoing orthopedic surgeries, we evaluated the types of topical antibiotics received and the rates of surgical site infections (SSI) and adverse drug events within 28 days of the procedure.

Results

Of 744 surgical procedures reviewed, topical antibiotics were used in 127 (17.1%), topical antiseptics in 71 (9.5%), and both in 18 (2.4%) (Table 1). Antiseptic use was higher in orthopedics relative to all other surgical specialties while topical antibiotic use was higher in neurosurgery. Hand, vascular and plastics had distinguishably lower use. In the orthopedic subgroup, after exclusions, 218 procedures were evaluated. Topical antibiotics were used in 42 (19.2%). Topical antibiotic therapy was more likely to be administered if prosthetic material was implanted, the procedure was emergent, or if a Staphylococcus aureus infection was present. Vancomycin was the most commonly used topical antibiotic and powder was the most commonly used type of application. As shown in table 2, SSI occurred more often when both topical antibiotics and antiseptics were applied; however, SSI events were relatively uncommon, and these were more likely to have infection present at the time of surgery. Adverse events were rare.

Conclusion

In our institution we noted significant variability in use of topical antibiotic and antiseptic therapy among surgical specialties as well as within the orthopedic surgical specialty. Although opportunities to standardize use/nonuse of these therapies exist, this may be challenging due to the uncertainty and heterogeneity of currently available data.

Disclosures

All Authors: No reported disclosures

Safety of Inpatient Dofetilide Initiation per Cardiology Services: A Retrospective Review

INTRODUCTION

Dofetilide is an antiarrhythmic medication that has the potential to cause life threatening arrhythmias, such as Torsade de pointes. The 2014 ACC/AHA/HRS guidelines for the management of patients with atrial fibrillation state that patients need to meet certain criteria to be initiated on dofetilide. Patients who are not initiated on this therapy according to the guideline criteria are likely to be at higher risk of adverse reactions.

METHODS

This is a single center, retrospective chart review of patients who were initiated on dofetilide from July 2016-December 2019. Patients included in the study were initiated on dofetilide as a new antiarrhythmic and monitored inpatient for 3 days. The primary outcome was a composite of incidence of cardiac arrhythmias, cardiac arrest, cardiac death, and cardiac related hospital readmission.

RESULTS

There were 224 patients included in the analysis: 190 patients who were initiated on dofetilide inappropriately and 34 that were initiated appropriately. The primary outcome (composite of cardiac arrhythmia, cardiac arrest, cardiac death, and hospital readmission) was statistically significant with more patients experiencing an outcome in the group initiated inappropriately.

CONCLUSIONS

Patients are placed at a higher risk of adverse reactions when this potentially dangerous antiarrhythmic medication is not used according to the protocol set forth by the guidelines. Practitioners should use caution when prescribing dofetilide. Other antiarrhythmic medications or non-pharmacologic options should be considered due to the incidence of these dangerous adverse reactions.

Simulation-based Training Curriculum for the Management of Vaginal Cuff Dehiscence and Evisceration

Objective

Vaginal cuff dehiscence with evisceration (VCDE) is a serious, life-threatening complication of hysterectomy. Due to the high volume of hysterectomies performed in the U.S each year, it is likely that a practitioner will encounter VCDE during their career. Due to its infrequent occurrence, residents receive little exposure to it during training. Delayed diagnosis of VCDE can impede proper management and lead to severe, long-term complications or death. Our goal was to provide an opportunity for resident physicians to identify VCDE and practice performing a reduction of prolapsed bowel and vaginal cuff repair through hands-on simulation in hopes that the simulation would improve the residents’ confidence and knowledge in recognizing and managing future VCDE cases.

Methods

Obstetrics and Gynecology residents postgraduate year (PGY) 1-4 participated in this study (n=13). Before and after the simulated case, a knowledge test covering VCDE recognition and management and a confidence survey were given to the participants. A gynecologic mannequin was modified by placing simulated bowel into the abdominal cavity with a portion extending through a vaginal cuff and protruding from the vaginal introitus. For the simulation, a hemodynamically unstable patient presented with findings consistent with a VCDE. Once the decision to proceed to surgery was made, participants were transferred to a simulated operating room where they performed a reduction of prolapsed bowel and vaginal cuff closure either laparoscopically or vaginally on the mannequin. A debriefing session was held post-simulation to discuss management and thought processes, as well as reflect on their performance and discuss improvement strategies for future cases. Finally, the residents participated in a brief didactic lecture on education about the incidence, presentation, and management of VCDE.

Results

Analysis of the knowledge questionnaires showed the median score and interquartile range (IQR) pre- and post-simulation was 15(12-28) and 20(19-22) respectively, with a median score increase (and IQR) of 5(3.5-8.5) (p=0.001). The confidence score had pre- and post-simulation median scores (and IQRs) of 28(20-34.5) and 40(37.5-46) respectively, with a median score increase (and IQR) of 15(8-20.5) (p=0.001).

Conclusions

Our intervention improved residents’ knowledge and confidence in recognizing VCDE, identifying the need for surgical management, and performing a reduction of prolapsed bowel and vaginal cuff repair.

Type 2 Diabetes Prescribing Habits amongst Providers to an Underserved Population

Introduction:

Type 2 diabetes mellitus (T2DM) affected over 30 million individuals in the United States as of 2015. Due to the national diabetes guidelines recommending drug selection based on several patient specific factors and varying formulary restrictions, prescribers are often inundated when selecting treatment. Currently, limited evidence is available regarding the primary factors influencing prescribers’ drug therapy selection.

Objectives:

The purpose of this study was to identify factors that influence providers during T2DM medication selection.

Methods:

The study was conducted with providers at a large, academic, safety net health system. All prescribers were sent an electronic, optional and anonymous survey. Prescribers treating T2DM in non-pregnant adult patients were the only prescribers assessed. Factors evaluated were: cost, A1c, comorbidities, adherence, weight, tolerability, patient limitations, and use of guidelines.

Results:

A total of 86 prescribers responded, yielding a response rate of 31%. The respondents included physicians (56.3%), nurse practitioners (21.8%), medical residents (18.4%), and fellows (3.4%); with the majority practicing in internal or family medicine (47.1%). The most frequently prescribed T2DM medications included: metformin (83.8%), insulin (78.1%), and sulfonylureas (64.8%). Cost and A1c elevation were two of the major factors influencing prescribing of metformin (94.1% and 81.2%), insulin (57.4% and 69.6%), and sulfonylureas (81.2% and 89.9%) respectively. Due to cost concerns, respondents reported rarely or never prescribing glucagon-like peptide-1 agonists (GLP-1RA) and sodium-glucose co-transporter-2 inhibitors (SGLT2i) despite recognizing benefits on diabetes related comorbidities.

Conclusion:

Although current literature from the national guidelines encourages the use of GLP-1RA and SGLT2i as first-line options after metformin in T2DM, these classes of medications were not reported among the most commonly prescribed despite providers correctly identifying positive medication attributes such as cardio- and nephroprotection and weight loss. However, cost of these medications appears to outweigh the benefits when selecting medication therapy.

Simulation-based Training in Ectopic Pregnancy and Salpingostomy

Objective Ectopic pregnancy leads to approximately 3% of deaths in pregnancy. Surgical management is indicated when patients are hemodynamically unstable or have signs of a ruptured ectopic pregnancy. Salpingectomy is more commonly performed, but salpingostomy is preferred in a patient with prior salpingectomy with a desire for future pregnancy. Due to the lack of exposure, salpingostomy is not frequently performed and most residents do not feel adequately trained. Our goal was to provide a hands-on simulation about ectopic pregnancy and salpingostomy in hopes that the simulation will improve the resident's confidence and knowledge in recognizing an ectopic pregnancy, identifying an appropriate candidate for surgical management, and performing a salpingostomy. Methods The educational initiative was aimed towards postgraduate year (PGY) 1-4 OB/GYN residents (n=11). Knowledge and confidence questionnaires were given to participants prior to and post-simulation. A gynecologic mannequin was modified by taking the existing pelvic organs and creating a tubal pregnancy. In the first part of the simulation, a hemodynamically unstable patient presented with lab and imaging findings consistent with an ectopic pregnancy. Once recognized and the decision made for surgical intervention, participants were transferred to a simulated operating room where they performed salpingostomy or salpingectomy on the mannequin. The simulation was followed by a debriefing session to discuss the actions and thought processes of participants, provide reflection, and incorporate improvement opportunities for future cases. Finally, participants engaged in a didactic lecture where they were educated about the incidence, presentation, and management of tubal ectopic pregnancy. Results Analysis of the knowledge questionnaires showed the median score pre- and post-intervention was 9 and 12, respectively, with a median change of 3 (p=0.001). The median confidence value pre- and post-intervention were 28 and 42, respectively, with a median value change of 12 (p<0.001). Conclusion Our intervention improved residents' confidence and knowledge in recognizing an ectopic pregnancy, identifying an appropriate candidate for surgical management, and performing a salpingostomy.

Emergency Undocking Curriculum in Robotic Surgery

Introduction

Traditional instruction for robotic surgery is typically devoid of training that addresses the delineation of interprofessional roles for operating room personnel. An emergency undocking scenario was developed for robotic surgeons with the objectives of improving time to access the patient, provider knowledge of and confidence in emergency undocking, completion of predetermined critical actions, and delineation of operating room personnel roles.

Methods

Over one month, participants joined in three sessions: Session 1 - formative, Session 2 - review, and Session 3 - summative. Embedded standardized participants (ESPs) represented members of the interprofessional team. Prior to entering the operating room for Sessions 1 and 3, trainees were asked to complete a confidence survey and multiple choice questionnaire (MCQ) for knowledge assessment. Participants were randomized to one of two cases and participated in the reciprocal case for the final session four weeks later. Following Session 1, participants underwent an educational intervention, including the proper technique for emergency undocking, emphasis on operating room personnel roles, and hands-on practice. Obstetrics and Gynecology (OBGYN) residents in post-graduate Years 2-4 and attending physicians with robotics privileges at Summa Health Akron Campus or Cleveland Clinic Akron General Medical Center were invited to participate. A total of 21 participants enrolled and finished the study.

Results

Among the 21 participants, there was a significant increase in the baseline level of knowledge (p-value=0.001) and in the confidence of surgeons when faced with an emergency undocking after the completion of our curriculum (p-value=0.003). Additionally, an improvement in the undocking times (p-value<0.001) and an increase in the critical actions performed (p-value=0.002) were observed.

Conclusion

The results of this study demonstrate that incorporating this curriculum into the training programs of robotic surgeons is an effective way to improve the surgical skill of emergency undocking.

Regionally-derived cell populations and skeletal stem cells from human foetal femora exhibit specific osteochondral and multi-lineage differentiation capacity in vitro and ex vivo

Background

Adult skeletal stem cells (SSCs) often exhibit limited in vitro expansion with undesirable phenotypic changes and loss of differentiation capacity. Foetal tissues offer an alternative cell source, providing SSCs which exhibit desirable differentiation capacity over prolonged periods, ideal for extensive in vitro and ex vivo investigation of fundamental bone biology and skeletal development.

Methods

We have examined the derivation of distinct cell populations from human foetal femora. Regionally isolated populations including epiphyseal and diaphyseal cells were carefully dissected. Expression of the SSC marker Stro-1 was also found in human foetal femora over a range of developmental stages and subsequently utilised for immuno-selection.

Results

Regional populations exhibited chondrogenic (epiphyseal) and osteogenic (diaphyseal) phenotypes following in vitro and ex vivo characterisation and molecular analysis, indicative of native SSC maturation during skeletal development. However, each population exhibited potential for induced multi-lineage differentiation towards bone (bone nodule formation), cartilage (proteoglycan and mucopolysaccharide deposition) and fat (lipid deposition), suggesting the presence of a shared stem cell sub-population. This shared sub-population may be comprised of Stro-1+ cells, which were later identified and immuno-selected from whole foetal femora exhibiting multi-lineage differentiation capacity in vitro and ex vivo.

Conclusions

Distinct populations were isolated from human foetal femora expressing osteochondral differentiation capacity. Stro-1 immuno-selected SSCs were isolated from whole femora expressing desirable multi-lineage differentiation capacity over prolonged in vitro expansion, superior to their adult-derived counterparts, providing a valuable cell source with which to study bone biology and skeletal development.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0247-2) contains supplementary material, which is available to authorized users.

In Vivo Assessment of Bone Regeneration in Alginate/Bone ECM Hydrogels with Incorporated Skeletal Stem Cells and Single Growth Factors

The current study has investigated the use of decellularised, demineralised bone extracellular matrix (ECM) hydrogel constructs for in vivo tissue mineralisation and bone formation. Stro-1-enriched human bone marrow stromal cells were incorporated together with select growth factors including VEGF, TGF-β3, BMP-2, PTHrP and VitD3, to augment bone formation, and mixed with alginate for structural support. Growth factors were delivered through fast (non-osteogenic factors) and slow (osteogenic factors) release PLGA microparticles. Constructs of 5 mm length were implanted in vivo for 28 days within mice. Dense tissue assessed by micro-CT correlated with histologically assessed mineralised bone formation in all constructs. Exogenous growth factor addition did not enhance bone formation further compared to alginate/bone ECM (ALG/ECM) hydrogels alone. UV irradiation reduced bone formation through degradation of intrinsic growth factors within the bone ECM component and possibly also ECM cross-linking. BMP-2 and VitD3 rescued osteogenic induction. ALG/ECM hydrogels appeared highly osteoinductive and delivery of angiogenic or chondrogenic growth factors led to altered bone formation. All constructs demonstrated extensive host tissue invasion and vascularisation aiding integration and implant longevity. The proposed hydrogel system functioned without the need for growth factor incorporation or an exogenous inducible cell source. Optimal growth factor concentrations and spatiotemporal release profiles require further assessment, as the bone ECM component may suffer batch variability between donor materials. In summary, ALG/ECM hydrogels provide a versatile biomaterial scaffold for utilisation within regenerative medicine which may be tailored, ultimately, to form the tissue of choice through incorporation of select growth factors.

Tissue engineered bone using select growth factors: A comprehensive review of animal studies and clinical translation studies in man

There is a growing socio-economic need for effective strategies to repair damaged bone resulting from disease, trauma and surgical intervention. Bone tissue engineering has received substantial investment over the last few decades as a result. A multitude of studies have sought to examine the efficacy of multiple growth factors, delivery systems and biomaterials within in vivo animal models for the repair of critical-sized bone defects. Defect repair requires recapitulation of in vivo signalling cascades, including osteogenesis, chondrogenesis and angiogenesis, in an orchestrated spatiotemporal manner. Strategies to drive parallel, synergistic and consecutive signalling of factors including BMP-2, BMP-7/OP-1, FGF, PDGF, PTH, PTHrP, TGF-β3, VEGF and Wnts have demonstrated improved bone healing within animal models. Enhanced bone repair has also been demonstrated in the clinic following European Medicines Agency and Food and Drug Administration approval of BMP-2, BMP-7/OP-1, PDGF, PTH and PTHrP. The current review assesses the in vivo and clinical data surrounding the application of growth factors for bone regeneration. This review has examined data published between 1965 and 2013. All bone tissue engineering studies investigating in vivo response of the growth factors listed above, or combinations thereof, utilising animal models or human trials were included. All studies were compiled from PubMed-NCBI using search terms including 'growth factor name', 'in vivo', 'model/animal', 'human', and 'bone tissue engineering'. Focus is drawn to the in vivo success of osteoinductive growth factors incorporated within material implants both in animals and humans, and identifies the unmet challenges within the skeletal regenerative area.

Evaluation of skeletal tissue repair, part 1: assessment of novel growth-factor-releasing hydrogels in an ex vivo chick femur defect model

Current clinical treatments for skeletal conditions resulting in large-scale bone loss include autograft or allograft, both of which have limited effectiveness. In seeking to address bone regeneration, several tissue engineering strategies have come to the fore, including the development of growth factor releasing technologies and appropriate animal models to evaluate repair. Ex vivo models represent a promising alternative to simple in vitro systems or complex, ethically challenging in vivo models. We have developed an ex vivo culture system of whole embryonic chick femora, adapted in this study as a critical size defect model to investigate the effects of novel bone extracellular matrix (bECM) hydrogel scaffolds containing spatio-temporal growth factor-releasing microparticles and skeletal stem cells on bone regeneration, to develop a viable alternative treatment for skeletal degeneration. Alginate/bECM hydrogels combined with poly (d,l-lactic-co-glycolic acid) (PDLLGA)/triblock copolymer (10-30% PDLLGA-PEG-PDLLGA) microparticles releasing VEGF, TGF-β3 or BMP-2 were placed, with human adult Stro-1+ bone marrow stromal cells, into 2mm central segmental defects in embryonic chick femurs. Alginate/bECM hydrogels loaded with HSA/VEGF or HSA/TGF-β3 demonstrated a cartilage-like phenotype, with minimal collagen I deposition, comparable to HSA-only control hydrogels. The addition of BMP-2 releasing microparticles resulted in enhanced structured bone matrix formation, evidenced by increased Sirius red-stained matrix and collagen expression within hydrogels. This study demonstrates delivery of bioactive growth factors from a novel alginate/bECM hydrogel to augment skeletal tissue formation and the use of an organotypic chick femur defect culture system as a high-throughput test model for scaffold/cell/growth factor therapies for regenerative medicine.

Evaluation of skeletal tissue repair, part 2: enhancement of skeletal tissue repair through dual-growth-factor-releasing hydrogels within an ex vivo chick femur defect model

There is an unmet need for improved, effective tissue engineering strategies to replace or repair bone damaged through disease or injury. Recent research has focused on developing biomaterial scaffolds capable of spatially and temporally releasing combinations of bioactive growth factors, rather than individual molecules, to recapitulate repair pathways present in vivo. We have developed an ex vivo embryonic chick femur critical size defect model and applied the model in the study of novel extracellular matrix (ECM) hydrogel scaffolds containing spatio-temporal combinatorial growth factor-releasing microparticles and skeletal stem cells for bone regeneration. Alginate/bovine bone ECM (bECM) hydrogels combined with poly(d,l-lactic-co-glycolic acid) (PDLLGA)/triblock copolymer (10-30% PDLLGA-PEG-PLDLGA) microparticles releasing dual combinations of vascular endothelial growth factor (VEGF), chondrogenic transforming growth factor beta 3 (TGF-β3) and the bone morphogenetic protein BMP2, with human adult Stro-1+bone marrow stromal cells (HBMSCs), were placed into 2mm central segmental defects in embryonic day 11 chick femurs and organotypically cultured. Hydrogels loaded with VEGF combinations induced host cell migration and type I collagen deposition. Combinations of TGF-β3/BMP2, particularly with Stro-1+HBMSCs, induced significant formation of structured bone matrix, evidenced by increased Sirius red-stained matrix together with collagen expression demonstrating birefringent alignment within hydrogels. This study demonstrates the successful use of the chick femur organotypic culture system as a high-throughput test model for scaffold/cell/growth factor therapies in regenerative medicine. Temporal release of dual growth factors, combined with enriched Stro-1+HBMSCs, improved the formation of a highly structured bone matrix compared to single release modalities. These studies highlight the potential of a unique alginate/bECM hydrogel dual growth factor release platform for bone repair.

Prospective isolation of human bone marrow stromal cell subsets: A comparative study between Stro-1-, CD146- and CD105-enriched populations

Stro-1 has proved an efficacious marker for enrichment of skeletal stem and progenitor cells although isolated populations remain heterogeneous, exhibiting variable colony-forming efficiency and osteogenic differentiation potential. The emerging findings that skeletal stem cells originate from adventitial reticular cells have brought two further markers to the fore including CD146 and CD105 (both primarily endothelial and perivascular). This study has compared CD146-, CD105- and Stro-1 (individual and in combination)-enriched human bone marrow stromal cell subsets and assessed whether these endothelial/perivascular markers offer further selection over conventional Stro-1. Fluorescent cell sorting quantification showed that CD146 and CD105 both targeted smaller (2.22% ± 0.59% and 6.94% ± 1.34%, respectively) and potentially different human bone marrow stromal cell fractions compared to Stro-1 (16.29% ± 0.78%). CD146+, but not CD105+, cells exhibited similar alkaline phosphatase-positive colony-forming efficiency in vitro and collagen/proteoglycan deposition in vivo to Stro-1+ cells. Molecular analysis of a number of select osteogenic and potential osteo-predictive genes including ALP, CADM1, CLEC3B, DCN, LOXL4, OPN, POSTN and SATB2 showed Stro-1+ and CD146+ populations possessed similar expression profiles. A discrete human bone marrow stromal cell fraction (2.04% ± 0.41%) exhibited positive immuno-labelling for both Stro-1 and CD146. The data presented here show that CD146+ populations are comparable but not superior to Stro-1+ populations. However, this study demonstrates the critical need for new candidate markers with which to isolate homogeneous skeletal stem cell populations or skeletal stem cell populations which exhibit homogeneous in vitro/in vivo characteristics, for implementation within tissue engineering and regenerative medicine strategies.

Assessing the potential of colony morphology for dissecting the CFU-F population from human bone marrow stromal cells

Mesenchymal stem cells (MSCs) provide an ideal cell source for bone tissue engineering strategies. However, bone marrow stromal cell (BMSC) populations that contain MSCs are highly heterogeneous expressing a wide variety of proliferative and differentiation potentials. Current MSC isolation methods employing magnetic-activated and fluorescent-activated cell sorting can be expensive and time consuming and, in the absence of specific MSC markers, fail to generate homogeneous populations. We have investigated the potential of various colony morphology descriptors to provide correlations with cell growth potential. Density-independent colony forming unit-fibroblastic (CFU-F) capacity is a MSC prerequisite and resultant colonies display an array of shapes and sizes that might be representative of cell function. Parent colonies were initially categorised according to their diameter and cell density and grouped before passage for the subsequent assessment of progeny colonies. Whereas significant morphological differences between distinct parent populations indicated a correlation with immunophenotype, enhanced CFU-F capacity was not observed when individual colonies were isolated according to these morphological parameters. Colony circularity, an alternative morphological measure, displayed a strong correlation with subsequent cell growth potential. The current study indicates the potential of morphological descriptors for predicting cell growth rate and suggests new directions for research into dissection of human BMSC CFU-F populations.

In search of the skeletal stem cell: isolation and separation strategies at the macro/micro scale for skeletal regeneration

Skeletal stem cells (SSCs) show great capacity for bone and cartilage repair however, current in vitro cultures are heterogeneous displaying a hierarchy of differentiation potential. SSCs represent the diminutive true multipotent stem cell fraction of bone marrow mononuclear cell (BMMNC) populations. Endeavours to isolate SSCs have generated a multitude of separation methodologies. SSCs were first identified and isolated by their ability to adhere to culture plastic. Once isolated, further separation is achieved via culture in selective or conditioned media (CM). Indeed, preferential SSC growth has been demonstrated through selective in vitro culture conditions. Other approaches have utilised cell morphology (size and shape) as selection criteria. Studies have also targeted SSCs based on their preferential adhesion to specified compounds, individually or in combination, on both macro and microscale platforms. Nevertheless, most of these methods which represent macroscale function with relatively high throughput, yield insufficient purity. Consequently, research has sought to downsize isolation methodologies to the microscale for single cell analysis. The central approach is identification of the requisite cell populations of SSC-specific surface markers that can be targeted for isolation by either positive or negative selection. SELEX and phage display technology provide apt means to sift through substantial numbers of candidate markers. In contrast, single cell analysis is the paramount advantage of microfluidics, a relatively new field for cell biology. Here cells can be separated under continuous or discontinuous flow according to intrinsic phenotypic and physicochemical properties. The combination of macroscale quantity with microscale specificity to generate robust high-throughput (HT) technology for pure SSC sorting, isolation and enrichment offers significant implications therein for skeletal regenerative strategies as a consequence of lab on chip derived methodology.

Engineering embryonic stem-cell aggregation allows an enhanced osteogenic differentiation in vitro

Pluripotent embryonic stem (ES) cells hold great promise for the field of tissue engineering, with numerous studies investigating differentiation into various cell types including cardiomyocytes, chondrocytes, and osteoblasts. Previous studies have detailed osteogenic differentiation via dissociated embryoid body (EB) culture in osteoinductive media comprising of ascorbic acid, beta-glycerophosphate, and dexamethasone. It is hoped that these osteogenic cultures will have clinical application in bone tissue repair and regeneration and pharmacological testing. However, differentiation remains highly inefficient and generates heterogeneous populations. We have previously reported an engineered three-dimensional culture system for controlled ES cell-ES cell interaction via the avidin-biotin binding complex. Here we investigate the effect of such engineering on ES cell differentiation. Engineered EBs exhibit enhanced osteogenic differentiation assessed by cadherin-11, Runx2, and osteopontin expression, alkaline phosphatase activity, and bone nodule formation. Results show that cultures produced from intact EBs aggregated for 3 days generated the greatest levels of osteogenic differentiation when cultured in osteoinductive media. However, when cultured in control media, only engineered samples appeared to exhibit bone nodule formation. In addition, polymerase chain reaction analysis revealed a decrease in endoderm and ectoderm expression within engineered samples. This suggests that engineered ES cell aggregation has increased mesoderm homogeneity, contributing to enhanced osteogenic differentiation.

Controlled embryoid body formation via surface modification and avidin-biotin cross-linking

Cell-cell interaction is an integral part of embryoid body (EB) formation controlling 3D aggregation. Manipulation of embryonic stem (ES) cell interactions could provide control over EB formation. Studies have shown a direct relationship between EB formation and ES cell differentiation. We have previously described a cell surface modification and cross-linking method for influencing cell-cell interaction and formation of multicellular constructs. Here we show further characterisation of this engineered aggregation. We demonstrate that engineering accelerates ES cell aggregation, forming larger, denser and more stable EBs than control samples, with no significant decrease in constituent ES cell viability. However, extended culture >/=5 days reveals significant core necrosis creating a layered EB structure. Accelerated aggregation through engineering circumvents this problem as EB formation time is reduced. We conclude that the proposed engineering method influences initial ES cell-ES cell interactions and EB formation. This methodology could be employed to further our understanding of intrinsic EB properties and their effect on ES cell differentiation.