Impact of Intraoperative Hypothermia on Autologous Breast Reconstruction.

OBJECTIVE: Studies have identified perioperative hypothermia as a risk factor for impaired wound healing, increased hospital length of stay, and surgical site infection. This study examines the effect of intraoperative hypothermia on postoperative outcomes in autologous microvascular free flap breast reconstruction. METHODS: This was a retrospective review of 55 patients who experienced intraoperative hypothermia, defined as less than 35.0°C core body temperature and 99 normothermic patients who underwent autologous-based microvascular free flap breast reconstruction from 2013 to 2021. Demographics, comorbidities, smoking status, intraoperative warming devices, type of autologous reconstruction, hypothermia (and its duration), and length of surgery were collected. The outcomes assessed were infection rate, reoperation within 90 days, skin necrosis, wound healing complications, hematoma, seroma, and readmission within 90 days. RESULTS: In the study population of 154 consecutive patients, 8.4% had type 1 or type 2 diabetes and 3.2% were current smokers. A total of 90.3% of patients (139) underwent deep inferior epigastric perforator flap reconstruction, 7.1% (11) superficial inferior epigastric artery flap reconstruction, and 4 (2.6%) another free flap type. A total of 35.7% of the patients (55) experienced intraoperative hypothermia defined as less than 35.0°C. In the hypothermic group, a higher proportion of patients had wound healing complications (52.7% vs 29.3%, P < 0.05), hematoma (16.4% vs 5.1%, P < 0.05), and readmission for postoperative complications (34.5% vs 14.1%, P < 0.05). There was also a trend toward higher incidence of seroma (7.3% vs 5.1%), surgical site infection (12.7% vs 9.1%), skin necrosis (12.7% vs 9.1%), and unplanned reoperation within 90 days (10.9% vs 7.1%). Further analysis via Firth logistic regression demonstrated intraoperative hypothermia predicted postoperative hematoma (odds ratio [OR], 3.68; 95% confidence interval [CI], 1.17-11.60; P < 0.05), readmission within 90 days (OR, 3.20; 95% CI, 1.45-7.08; P < 0.05), and wound healing complications (OR, 2.69; 95% CI, 1.36-5.33; P < 0.05). CONCLUSIONS: This study demonstrates that intraoperative hypothermia is a significant risk factor for postoperative wound healing complications, hematoma, and readmission within 90 days in autologous breast reconstruction. Because of a finite amount of donor sites, it is important to find ways to minimize the risk of postoperative complications. Our results support that maintaining strict normothermia during autologous breast reconstruction can significantly improve patient outcomes and reduce morbidity.

Stopping Traffic: An Analysis of Number of Scrubbed Personnel and Infection in Implant-Based Breast Reconstruction.

BACKGROUND: Postoperative surgical site infection (SSI) is a devastating complication of implant-based breast reconstruction. Its occurrence may require additional hospitalization and ultimately necessitate prosthesis removal. The effect of foot traffic in the operating room has not yet been investigated within plastic surgery. OBJECTIVES: This study analyzed the influence of scrubbed and unscrubbed personnel on postoperative SSI in immediate implant-based breast reconstruction. METHODS: This was a retrospective review of 223 consecutive patients who underwent immediate implant-based reconstruction from 2015 to 2021 at the authors' institution. Patient demographics, comorbidities, smoking status, laterality, number of personnel, use of drains, and length of surgery were collected. The primary outcome assessed was surgical site infection with secondary outcomes of delayed wound healing, skin necrosis, hematoma, seroma, and reoperation within 90 days. RESULTS: Patients who had a postoperative SSI had a mean number of 8.7 scrubbed individuals, whereas those who did not have a postoperative SSI had a mean number of 7.9 individuals scrubbed (P < .05). Univariate analysis demonstrated that increasing number of scrubbed individuals was predictive of SSI (odds ratio [OR]: 1.239, CI: 1.064-1.444, P < .05). A multivariate logistic regression demonstrated increased likelihood of SSI with increasing number of individuals scrubbed (OR: 1.232, CI: 1.027-1.478, P < .05). CONCLUSIONS: This study demonstrates an increased risk of SSI in immediate, implant-based breast reconstruction with an increased number of personnel in the operative field. The findings highlight the importance of reducing foot traffic in the operating room when feasible to reduce risk of postoperative SSI and its associated morbidity.

Breast reconstruction with superior epigastric artery perforator (SEAP) free flap: Report of two cases.

The deep inferior epigastric artery perforator (DIEP) flap is the gold standard for autologous breast reconstruction. When the DIEP pedicle is damaged, alternative perforator flaps are harvested from sites with less donor tissue, such as the thigh. Pedicled superior epigastric artery perforator (SEAP) flaps have been recently described for reconstruction of inferior partial breast defects. The purpose of this report is to show the surgical technique of the free SEAP flap for reconstruction of the entire breast in two patients. The authors describe two patients where the DIEP pedicle was unavailable. The first patient was 53 years old, with body mass index (BMI) 22.7, while the second patient was 60 with BMI 32.4. The donor site was marked as for a DIEP, and two lateral row perforators were selected in each case. Flaps were designed to cross the midline, with adequate perfusion confirmed via indocyanine green angiography. Both flaps were rotated 90° counterclockwise for inset into the chest. Flap size and weight for the two patients were: 24 × 15 cm and 350 g; and 25 × 15 cm and 400 g. Both patients had a routine postoperative course without complications. Length of follow-up was 155 and 158 days, respectively. We believe that the free SEAP flap is a promising technique in select patients who require an alternative to the DIEP for autologous breast reconstruction.

Perioperative management for microsurgical free tissue transfer: survey of current practices with a comparison to the literature.

BACKGROUND: Free tissue transfer is an important technique in reconstructive surgery. Due to a lack of evidence-based guidelines, a variety of practices are currently implemented by microsurgeons. This motivated the authors to define current practices and identify key areas where these practices can be optimized. METHODS: An anonymous online survey consisting of 40 questions regarding perioperative management for free tissue transfer was generated via an online survey platform. Questions covered topics including patient selection, anesthesia, patient temperature, fluid management, vasoactive agents, and analgesia. Approval was received from the American Society for Reconstructive Microsurgery and the survey was distributed to its members via two emails, in May and June 2013. RESULTS: Survey responses were received from 82/706 microsurgeons (12% response rate): 36% of respondents believed that complications of these cases are "sometimes" or "often" related to anesthesia; 55% of respondents stated they do not use specific goals and protocols to guide fluid management for these cases; 38% of respondents stated that they have no target range for hemoglobin and hematocrit for these procedures; and 70% of respondents stated that they do not permit the use of a vasopressor in nonemergent situations. CONCLUSION: Current practices remain exceedingly diverse and at times differ from best practices, which may be identified from the available literature. Key areas where patient care can be standardized and optimized include anesthesia, patient temperature, fluid management, the use of vasoactive agents, and analgesic medications. Standardized, evidence-based guidelines have the potential to further improve patient care and free flap outcomes.

Modulation of polyplex release from biodegradable microparticles through poly(ethylenimine) modification and varying loading concentration.

PURPOSE: This work investigates the effects of hyaluronic acid (HA) conjugated onto branched poly(ethylenimine) (bPEI) and varying loading concentrations of these polymers complexed with DNA on their release from poly(DL-lactic-co-glycolic acid) (PLGA) microparticles and the transfection of target cells. METHODS: To examine the effect of alteration of the gene delivery polymer on the system, we observed the morphology, size, loading efficiency, polymer and DNA release, and the transfection efficiency for the microparticles formed with three internal phase loading concentrations during microparticle formation. RESULTS: Addition of HA to this vector allowed for increased loading concentration within these systems and significantly altered release kinetics without changing the morphology of the particles. The incorporation of HA onto the bPEI backbone significantly increased the transfection efficiency of the complexes released from the corresponding microparticle formulation. CONCLUSIONS: The results show that the modification of bPEI with HA and the concentration of loaded polymer/DNA complexes can significantly alter the entrapment and release profiles from PLGA microparticles. This is significant in that it offers insight into the effects of modification of gene delivery vectors on a controlled release system designed to achieve a sustained therapeutic response.

Impact of Intraoperative Hypothermia on Incidence of Infection in Implant-Based Breast Reconstruction.

BACKGROUND: Infection following implant-based breast reconstruction can lead to devastating complications. Risk factors for infection include smoking, diabetes, and obesity. Intraoperative hypothermia may represent another modifiable risk factor. This study analyzed the effect of hypothermia in postmastectomy immediate implant-based reconstruction on postoperative surgical-site infection (SSI). METHODS: This was a retrospective review of 122 patients with intraoperative hypothermia, defined as less than 35.5°C, and 106 normothermic patients who underwent postmastectomy implant-based reconstruction between 2015 and 2021. Demographics, comorbidities, smoking status, hypothermia (and its duration), and length of surgery were collected. The primary outcome was SSI. Secondary outcomes included reoperation and delayed wound healing. RESULTS: A total of 185 patients (81%) underwent staged reconstruction with tissue expander placement and 43 patients (18.9%) had a direct-to-implant procedure. Over half (53%) of the patients experienced intraoperative hypothermia. In the hypothermic group, a higher proportion of patients had SSIs (34.4% versus 17% of normothermic patients; P < 0.05) and wound healing complications (27.9% versus 16%; P < 0.05). Intraoperative hypothermia predicted SSI (OR, 2.567; 95% CI, 1.367 to 4.818; P < 0.05) and delayed wound healing (OR, 2.023; 95% CI, 1.053 to 3.884; P < 0.05). Longer duration of hypothermia significantly correlated with SSI, with an average 103 minutes versus 77 minutes ( P < 0.05). CONCLUSIONS: This study demonstrates that intraoperative hypothermia is a significant risk factor for postoperative infection in postmastectomy implant-based breast reconstruction. Maintaining strict normothermia during implant-based breast reconstruction procedures may improve patient outcomes by reducing the risk of postoperative infection and delayed wound healing. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Invasive stage III breast implant-associated anaplastic large cell lymphoma successfully treated with incomplete resection.

A woman with history of bilateral breast augmentation 15 years prior presented with right breast swelling, peri-implant effusion and a palpable inferomedial mass. Effusion aspiration demonstrated pleiomorphic cells consistent with breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). Further diagnostic studies confirmed stage III disease with a 4.7 cm right breast mass and fluorodeoxyglucose uptake in an internal mammary chain lymph node. The patient underwent surgery with incomplete resection due to invasion of the chest wall followed by chemotherapy and radiation therapy. BIA-ALCL typically presents as an indolent effusion, however advanced disease carries a worse prognosis. This case highlights successful treatment without recurrence past the one-year mark as well as the need for multidisciplinary management when dealing with advanced disease.

It's not all White: Implicit Racial Bias in Imagery Used in Plastic Surgery Resident Education.

OBJECTIVE: Plastic surgery education relies heavily on images featuring patient skin tone; while images can be useful representations, it is highly susceptible to implicit bias, a known contributor to healthcare disparities. Using skin tone as a proxy, this study evaluates patient representation in images used in the American Society of Plastic Surgery Resident Education Curriculum. DESIGN: Color photographs, graphics, and videos featured in the American Society of Plastic Surgery "Course Materials" for each module were categorized using the Fitzpatrick scale (I-II, III-IV, or V-VI) by six reviewers. Proportional data and average number ± standard deviation of photos and graphics for each category were reported. Significant difference between Fitzpatrick I to II and V to VI was investigated via a one-way analysis of variance with a Tukey's post-test to adjust for multiple comparisons. RESULTS: An average of 1861 photographs and 237 graphics were assessed with 82% (1518 ± 25.11) of photos and 97% (231 ± 24.45) of graphics categorized as Fitzpatrick I to II. A one-way analysis of variance with a Tukey's post-test demonstrates a statistical difference between images and graphics categorized as Fitzpatrick I to II and Fitzpatrick V to VI (p < 0.001). CONCLUSIONS: Our data reveals an opportunity to improve racial representation in resident education. When 76% of patients in the United States are white and 13% are Black, our findings demonstrate both an unequal and unrepresentative distribution of photos and graphics of non-white patients. Residency is a formative time in a surgeon's career and therefore, exposure to accurate representation of a diverse patient population is of the utmost importance.

Systematic Review and Guidelines for Perioperative Management of Pediatric Patients Undergoing Major Plastic Surgery Procedures, with a Focus on Free Tissue Transfer.

BACKGROUND: Microsurgical free tissue transfer has been successfully implemented for various reconstructive applications in children. The goal of this study was to identify the best available evidence on perioperative management of pediatric patients undergoing free tissue transfer and to use it to develop evidence-based care guidelines. METHODS: A systematic review was conducted in the PubMed, Embase, Scopus, and Cochrane Library databases. Because a preliminary search of the pediatric microsurgical literature yielded scant data with a low level of evidence, pediatric anesthesia guidelines for healthy children undergoing major operations were also included. Exclusion criteria included vague descriptions of perioperative care, case reports, and studies of syndromic or chronically ill children. RESULTS: Two hundred four articles were identified, and 53 met inclusion criteria. Management approaches specific to the pediatric population were used to formulate recommendations. High-quality data were found for anesthesia, analgesia, fluid administration/blood transfusion, and anticoagulation (Level I Evidence). Lower quality evidence was identified for patient temperature (Level III Evidence) and vasodilator use (Level IV Evidence). Key recommendations include administering sevoflurane for general anesthesia, implementing a multimodal analgesia strategy, limiting preoperative fasting, restricting blood transfusions until hemoglobin level is less than 7 g/dl unless the patient is symptomatic, and reserving chemical venous thromboembolism prophylaxis for high-risk patients. CONCLUSIONS: Pediatric-specific guidelines are important, as they acknowledge physiologic differences in children, which may be overlooked when extrapolating from adult studies. These evidence-based recommendations are a key first step toward standardization of perioperative care of pediatric patients undergoing plastic surgical procedures, including free tissue transfer, to improve outcomes and minimize complications.

Controlled release of anti-inflammatory siRNA from biodegradable polymeric microparticles intended for intra-articular delivery to the temporomandibular joint.

PURPOSE: As the next step in the development of an intra-articular controlled release system to treat painful temporomandibular joint (TMJ) inflammation, we developed several biodegradable poly(DL-lactic-co-glycolic acid) (PLGA)-based microparticle (MP) formulations encapsulating a model anti-inflammatory small interfering RNA (siRNA) together with branched poly(ethylenimine) (PEI) as a transfecting agent. The effect of siRNA loading and N:P ratio on the release kinetics of siRNA-PEI polyplexes was determined, and the size and N:P ratio of the polyplexes released over time was characterized. METHODS: Polyplex-loaded PLGA MPs were prepared using an established double emulsion technique. Increasing the pH of the release samples enabled siRNA-PEI dissociation and subsequent measurement of the release of each component over 28 days. Polyplex diameter was measured for all release samples and compared to freshly prepared siRNA-PEI under simulated physiologic conditions. RESULTS: Systematic variation of siRNA loading and N:P ratio resulted in distinct siRNA and PEI release profiles. Polyplex diameter remained constant despite large variations in the relative amounts of siRNA and PEI. Excess PEI was sequestered through complexation with 500-1,000 nm diameter PLGA MP-derived particles, including small MPs and PLGA degradation products. CONCLUSIONS: These PLGA MP formulations show exciting potential as the first intra-articular TMJ controlled release system.

An Effective, Reproducible, and Cost-Effective Approach for Achieving Symmetry in Bicoronal Incisions in Pediatric Patients Undergoing Craniofacial Surgery.

SUMMARY: Bicoronal incisions are frequently used for exposure and access to the craniofacial skeleton. A zigzag design is often used to camouflage the resultant scar. Often, free-hand zigzag drawings require several correction attempts to ensure symmetry because of the need for replication of multiple limbs of the bicoronal incision that need to be similar lengths, distance, and angles from each other. The authors present a novel technique using a template that rapidly and consistently achieves symmetric zigzag bicoronal incisions. The device is a hairstyling device that is inherently geometric in its design. Retrospective results of pediatric craniofacial patients from 2010 to 2018 are presented. Patients undergoing endoscopic reconstructions and patients who had prior operations at other institutions were excluded from the study. Fifty-two patients met inclusion criteria, with age at surgery ranging from 3 to 207 months (mean, 17 months). Follow-up ranged from 1 to 66 months (mean, 26 months). Data collected included demographics, type of surgery, and operative outcomes, including incision-related complications. Using this dynamic hairstyling device in a novel application as a template results in a fast, effective, and easily reproducible symmetric bicoronal zigzag incision in all cases. This technique eliminates the need for adjusting the length and angles of bicoronal incisions, and it can be adapted across a variety of head sizes and shapes in both pediatric and adult populations.

Factors Influencing the Dissemination of Tweets at the American College of Surgeons Clinical Congress 2018.

BACKGROUND: Social media is increasingly used in surgery, facilitating the dissemination of knowledge. Social media can potentially aid networking, education, and information exchange. This study explored the impact of tweet components and tweeter characteristics during a large surgical congress to inform recommendations for optimizing social media use at future surgical conferences. METHODS: Twitter activity was monitored during the American College of Surgeons Clinical Congress 2018 using NodeXL to extract tweets containing the conference hashtag #ACSCC18 (or #ACSCC2018). Multivariable logistic regression analysis was performed to identify independent predictors of retweet activity, also testing for multicollinearity and interactions among variables. RESULTS: There were 4386 tweets that contained #ACSCC18 (or #ACSCC2018) posted from 1023 Twitter accounts. A larger group of Twitter accounts just retweeted. Other Twitter accounts with a stake in the conference neither tweeted nor retweeted. In a multivariable analysis of original tweets, the following were all independently associated with retweets, in decreasing order of effect size: mention of other tweeters, multimedia, inclusion of other hashtags, and the number of followers. In contrast with other conferences, the inclusion of a weblink (URL)-for example, link to paper or blog-was not associated with retweets. DISCUSSION: This study helps understand social media impact at surgical conferences. Engage by tweeting and retweeting. Mention other tweeters, add multimedia, include congress hashtags and topic-specific hashtags, and build your followers. Although not associated with retweet activity in this study, the inclusion of URLs can still contribute in substantiating the disseminated content based on findings at other conferences.

Emerging intra-articular drug delivery systems for the temporomandibular joint.

Temporomandibular joint (TMJ) disorders are a heterogeneous group of diseases that cause progressive joint degeneration leading to chronic pain and reduced quality of life. Both effective pain reduction and restoration of TMJ function remain unmet challenges. Intra-articular injections of corticosteroids and hyaluronic acid are currently used to treat chronic pain, but these methods require multiple injections that increase the risk of iatrogenic joint damage and other complications. The small and emerging field of TMJ tissue engineering aims to reduce pain and disability through novel strategies that induce joint tissue regeneration. Development of methods for sustained, intra-articular release of growth factors and other pro-regenerative signals will be critical for the success of TMJ tissue engineering strategies. This review discusses methods of intra-articular drug delivery to the TMJ, as well as emerging injectable controlled release systems with potential to improve TMJ drug delivery, to encourage further research in the development of sustained release systems for both long-term pain management and to enhance tissue engineering strategies for TMJ regeneration.

Use of Innovative Technologies in Pediatric Lower Extremity Reconstruction.

The anterolateral thigh (ALT) free flap has proven to be a reliable option for the coverage of soft tissue defects in adults and more recently in the pediatric population. When considering the use of the ALT flap in the pediatric patient, there are few studies that detail techniques specific to pediatric free flap management. We present a unique case of a 14- × 8-cm ALT flap used for traumatic wound coverage in a distal tibial injury in a 6-year-old girl. This case highlights innovative techniques in pediatric perioperative free flap monitoring and the use of continuous external tissue expansion to achieve delayed primary closure of the donor site.

Emerging paradigms in perioperative management for microsurgical free tissue transfer: review of the literature and evidence-based guidelines.

BACKGROUND: Microsurgical free tissue transfer has become an increasingly valuable technique in reconstructive surgery. However, there is a paucity of evidence-based guidelines to direct management. A systematic review was performed to define strategies to optimize perioperative management. METHODS: A systematic review of the literature was performed using key search terms. Strategies to guide patient management were identified, classified according to level of evidence, and used to devise recommendations in seven categories: patient temperature, anesthesia, fluid administration/blood transfusion, vasodilators, vasopressors, and anticoagulation. RESULTS: A total of 106 articles were selected and reviewed. High-level evidence was identified to guide practices in several key areas, including patient temperature, fluid management, vasopressor use, anticoagulation, and analgesic use. CONCLUSIONS: Current practices remain exceedingly diverse. Key strategies to improve patient outcomes can be defined from the available literature. Key evidence-based guidelines included that normothermia should be maintained perioperatively to improve outcomes (level of evidence 2b), and volume replacement should be maintained between 3.5 and 6.0 ml/kg per hour (level of evidence 2b). Vasopressors do not harm outcomes and may improve flap flow (level of evidence 1b), with most evidence supporting the use of norepinephrine over other vasopressors (level of evidence 1b). Dextran should be avoided (level of evidence 1b), and pump systems for local anesthetic infusion are beneficial following free flap breast reconstruction (level of evidence 1b). Further prospective studies will improve the quality of available evidence.

Cell-derived polymer/extracellular matrix composite scaffolds for cartilage regeneration, Part 1: investigation of cocultures and seeding densities for improved extracellular matrix deposition.

This study investigated the coculture of chondrocytes and mesenchymal stem cells (MSCs) on electrospun fibrous polymer scaffolds to produce polymer/extracellular matrix (ECM) hybrid constructs with the objective of reducing the number of chondrocytes necessary to produce ample cartilage-like ECM within the scaffolds. To generate these hybrid constructs, electrospun poly(ɛ-caprolactone) fibrous scaffolds were seeded at both high and low initial densities with five different ratios of chondrocytes to MSCs: 1:0, 1:1, 1:3, 1:5, and 0:1, and cultured for 7, 14, and 21 days. Glycosaminoglycan production and distribution within the three coculture groups was similar to quantities generated by chondrocyte-only controls. Conversely, as the concentration of chondrocytes was increased, the collagen content of the constructs also increased at each time point, with a 1:1 chondrocyte to MSC ratio approximating the collagen production of chondrocytes alone. Histological staining suggested that cocultured constructs mimicked the well-distributed ECM patterns of chondrocyte generated constructs, while improving greatly over the restricted distribution of matrix within MSC-only constructs. These results support the capacity of cocultures of chondrocytes and MSCs to generate cartilaginous matrix within a polymeric scaffold. Further, the inclusion of MSCs in these cocultures enables the reduction of chondrocytes needed to produce cell-generated ECM.

Cell-derived polymer/extracellular matrix composite scaffolds for cartilage regeneration, Part 2: construct devitalization and determination of chondroinductive capacity.

This work examined the chondrogenic potential of chondrocyte and mesenchymal stem cell (MSC) coculture generated poly(ɛ-caprolactone) (PCL)/extracellular matrix (ECM) hybrid scaffolds. Five different ratios of chondrocytes and MSCs were cocultured to generate cartilage-like ECM within electrospun fibrous scaffolds for 7, 14, and 21 days. These constructs were then devitalized to isolate the chondrogenic effects of the ECM alone. Devitalization was successful at removing cellular matter from the scaffolds, yet did reduce the amount of matrix present in the scaffolds. Following devitalization, the PCL/ECM scaffolds were then cultured with MSCs in serum-free conditions with or without TGF-ß3 treatment for 21 days. TGF-ß3 supplemented culture caused an induction of chondrogenesis in each scaffold type, but also somewhat masked the subtle differences of the different ECM coatings. Without TGF-ß3, the cartilaginous matrix generated by 1:1 cocultures of chondrocytes to MSCs for 14 days supported similar chondrogenic gene expression patterns of MSCs cultured on scaffolds generated by chondrocytes alone. These scaffold formulations had a positive chondrogenic effect on aggrecan, collagen type II, and collagen II/I expression when compared to PCL controls. This study demonstrates that it is possible to utilize cocultures of chondrocytes and MSCs to coat a polymer scaffold with cartilage-like ECM capable of supporting chondrogenic differentiation of MSCs.

Open-source three-dimensional printing of biodegradable polymer scaffolds for tissue engineering.

The fabrication of scaffolds for tissue engineering requires elements of customization depending on the application and is often limited due to the flexibility of the processing technique. This investigation seeks to address this obstacle by utilizing an open-source three-dimensional printing (3DP) system that allows vast customizability and facilitates reproduction of experiments. The effects of processing parameters on printed poly(ε-caprolactone) scaffolds with uniform and gradient pore architectures have been characterized with respect to fiber and pore morphology and mechanical properties. The results demonstrate the ability to tailor the fiber diameter, pore size, and porosity through modification of pressure, printing speed, and programmed fiber spacing. A model was also used to predict the compressive mechanical properties of uniform and gradient scaffolds, and it was found that modulus and yield strength declined with increasing porosity. The use of open-source 3DP technologies for printing tissue-engineering scaffolds provides a flexible system that can be readily modified at a low cost and is supported by community documentation. In this manner, the 3DP system is more accessible to the scientific community, which further facilitates the translation of these technologies toward successful tissue-engineering strategies.

Effect of temporally patterned TNF-α delivery on in vitro osteogenic differentiation of mesenchymal stem cells cultured on biodegradable polymer scaffolds.

Recent insight into the critical role of pro-inflammatory cytokines, particularly tumor necrosis factor-α (TNF-α), in bone regeneration has heralded a new direction in the design of tissue engineering constructs. Previous studies have demonstrated that continuous delivery of 50 ng/ml TNF-α to mesenchymal stem cells (MSCs) cultured on three-dimensional (3D) biodegradable electrospun poly(ϵ-caprolactone) (PCL) microfiber meshes stimulates mineralized matrix deposition, a marker of osteogenic differentiation. Since TNF-α exhibits a biphasic pattern of expression following bone fracture in vivo, this study aimed to investigate the effects of temporal patterns of TNF-α delivery on in vitro osteogenic differentiation of MSCs cultured on 3D electrospun PCL scaffolds. MSCs were cultured for 16 days and exposed to continuous, early, intermediate, or late TNF-α delivery. To further elucidate the effects of TNF-α on osteogenic differentiation, the study design included MSCs precultured both in the presence and absence of typically required osteogenic supplement dexamethasone. Mineralized matrix deposition was not observed in constructs with dexamethasone-naïve MSCs, suggesting that TNF-α is not sufficient to trigger in vitro osteogenic differentiation of MSCs. For MSCs precultured with dexamethasone, TNF-α suppressed alkaline phosphatase activity, an early marker of osteogenic differentiation, and stimulated mineralized matrix deposition, a late stage marker of MSC osteogenic differentiation. By elucidating the impact of temporal variations in TNF-α delivery on MSC osteogenic differentiation, our results offer insight into the regenerative mechanism of TNF-α and provide the design parameters for a novel tissue engineering strategy that rationally controls TNF-α signaling to stimulate bone regeneration.

Student Award for Outstanding Research Winner in the Ph.D. Category for the 9th World Biomaterials Congress, Chengdu, China, June 1-5, 2012: The interplay of bone-like extracellular matrix and TNF-α signaling on in vitro osteogenic differentiation of mesenchymal stem cells.

As an initial step in the development of a bone tissue engineering strategy to rationally control inflammation, we investigated the interplay of bone-like extracellular matrix (ECM) and varying doses of the inflammatory cytokine tumor necrosis factor alpha (TNF-α) on osteogenically differentiating mesenchymal stem cells (MSCs) cultured in vitro on 3D poly(ε-caprolactone) (PCL) microfiber scaffolds containing pregenerated bone-like ECM. To generate the ECM, PCL scaffolds were seeded with MSCs and cultured in medium containing the typically required osteogenic supplement dexamethasone. However, since dexamethasone antagonizes TNF-α, the interplay of ECM and TNF-α was investigated by culturing naïve MSCs on the decellularized scaffolds in the absence of dexamethasone. MSCs cultured on ECM-coated scaffolds continued to deposit mineralized matrix, a late stage marker of osteogenic differentiation. Mineralized matrix deposition was not adversely affected by exposure to TNF-α for 4-8 days, but was significantly reduced after continuous exposure to TNF-α over 16 days, which simulates the in vivo response, where brief TNF-α signaling stimulates bone regeneration, while prolonged exposure has damaging effects. This underscores the exciting potential of PCL/ECM constructs as a more clinically realistic in vitro culture model to facilitate the design of new bone tissue engineering strategies that rationally control inflammation to promote regeneration.