Oncoplastic Augmentation Mastopexy in Breast Conservation Therapy: Retrospective Study and Postoperative Complications.

BACKGROUND: Oncoplastic techniques, in conjunction with lumpectomy and adjuvant radiotherapy, have been demonstrated to achieve good aesthetic results and cancer outcomes in the treatment of patients with macromastia or significant ptosis. This study evaluated a series of patients undergoing breast conservation with concomitant oncoplastic-augmentation-mastopexy and a contralateral augmentation-mastopexy. METHODS: Patients undergoing lumpectomy for breast conservation were identified via a retrospective chart review. Inclusion criteria included patients with ptosis and preexisting breast implants or insufficient breast volume undergoing oncoplastic implant placement/exchange and mastopexy. Demographic characteristics, operative details, and complications were assessed. RESULTS: Thirty-four consecutive patients (64 breasts, 4 unilateral procedures) were included in the study. Average age was 51.4 years, average body mass index was 27, and 38.2% were smokers/former smokers. The average operative time was 2.5 hours. Furthermore, 38.2% of patients received chemotherapy, and 82.4% of patients received breast adjuvant radiotherapy. The average length of follow-up was 11.7 months. In the sample that received radiation, the capsular contracture rate was 25%, with a 7.1% contracture revision rate. For the entire group, a total of 8 patients (23.5%) underwent revisions for either positive margins (8.8%), capsular contracture (8.8%), implant loss (2.9%), or cosmetic concerns (2.9%). One patient developed a pulmonary embolism. CONCLUSIONS: Oncoplastic-augmentation-mastopexy is a safe technique with acceptable complication rates. This technique is best used for breast cancer patients with breast ptosis and a paucity of breast volume or preexisting implants who wish to pursue breast-conserving therapy. The revision rates are acceptable compared with single-stage cosmetic augmentation procedures as well as other oncoplastic techniques described in the literature, but patients must be clearly counseled on contracture risk.

Contralateral Heterotopic Thumb-to-Thumb Replantation With Free Ulnar Forearm Fasciocutaneous Flap and Targeted Muscle Reinnervation.

Mangling hand injuries can be difficult to manage owing to the severity and heterogeneity of the injuries. Outcomes after reconstruction of unique injuries are less well-known but provide valuable insight. We present an unusual spare parts reconstruction of a bilateral upper-extremity mangling injury treated with a heterotopic thumb-to-thumb replantation, an acute forearm fasciocutaneous free flap, and targeted muscle reinnervation. This report highlights the utility of microsurgical reconstruction with available autogenous tissue in the acute setting.

Penis Transplantation: First US Experience.

OBJECTIVE: We describe the first successful penis transplant in the United States in a patient with a history of subtotal penectomy for penile cancer. BACKGROUND: Penis transplantation represents a new paradigm in restoring anatomic appearance, urine conduit, and sexual function after genitourinary tissue loss. To date, only 2 penis transplants have been performed worldwide. METHODS: After institutional review board approval, extensive medical, surgical, and radiological evaluations of the patient were performed. His candidacy was reviewed by a multidisciplinary team of surgeons, physicians, psychiatrists, social workers, and nurse coordinators. After appropriate donor identification and recipient induction with antithymocyte globulin, allograft procurement and recipient preparation took place concurrently. Anastomoses of the urethra, corpora, cavernosal and dorsal arteries, dorsal vein, and dorsal nerves were performed, and also inclusion of a donor skin pedicle as the composite allograft. Maintenance immunosuppression consisted of mycophenolate mofetil, tacrolimus, and methylprednisolone. RESULTS: Intraoperative, the allograft had excellent capillary refill and strong Doppler signals after revascularization. Operative reinterventions on postoperative days (PODs) 2 and 13 were required for hematoma evacuation and skin eschar debridement. At 3 weeks, no anastomotic leaks were detected on urethrogram, and the catheter was removed. Steroid resistant-rejection developed on POD 28 (Banff I), progressed by POD 32 (Banff III), and required a repeat course of methylprednisolone and antithymocyte globulin. At 7 months, the patient has recovered partial sensation of the penile shaft and has spontaneous penile tumescence. Our patient reports increased overall health satisfaction, dramatic improvement of self-image, and optimism for the future. CONCLUSIONS: We have shown that it is feasible to perform penile transplantation with excellent results. Furthermore, this experience demonstrates that penile transplantation can be successfully performed with conventional immunosuppression. We propose that our successful penile transplantation pilot experience represents a proof of concept for an evolution in reconstructive transplantation.

Technique to Promote Symmetry in 2-Staged Bilateral Breast Reconstruction in the Setting of Unilateral Postmastectomy Radiation.

BACKGROUND: Bilateral breast reconstruction in the setting of unilateral postmastectomy radiation therapy (PMRT) remains one of the most difficult reconstructive challenges due to significant radiation-induced asymmetry from capsular contracture and superior migration of the irradiated reconstructed breast. We describe a novel and straightforward intraoperative technique for creating compensatory asymmetry to maximize postradiation symmetry in immediate bilateral tissue expander (TE) and acellular dermal matrix (ADM) reconstruction requiring unilateral PMRT. METHODS: A cohort of 25 bilateral TE/ADM breast reconstructions with planned unilateral PMRT was performed using this approach, and outcomes were reviewed. On the PMRT side, the ADM edge was inset to a lower inframammary fold (IMF) position resulting in a near "bottoming-out" effect. On the non-PMRT side, the ADM was inset using a triple point stitch onto the IMF in a higher chest wall location. The planned PMRT side TE was overexpanded and second-stage exchanges were performed 6+ months post-PMRT. RESULTS: Post-PMRT results showed improved symmetry as the PMRT side migrated superiorly to match the contralateral non-irradiated side. Minimal pocket or IMF adjustments were required during second-stage procedures, with just 6 patients (24%) requiring minor lowering and 1 patient (4%) requiring elevation of the PMRT side IMF. Thus, most (72%) patients undergoing bilateral mastectomy and unilateral PMRT did not require any IMF modifications during the second-stage procedure. CONCLUSIONS: A differential ADM inset and TE pocket creation for bilateral TE/ADM breast reconstructions with planned unilateral PMRT can minimize the typical adverse aesthetic effects of PMRT on reconstruction results and maximize symmetry.

Cytoskeleton-based forecasting of stem cell lineage fates.

Stem cells that adopt distinct lineages cannot be distinguished based on traditional cell shape. This study reports that higher-order variations in cell shape and cytoskeletal organization that occur within hours of stimulation forecast the lineage commitment fates of human mesenchymal stem cells (hMSCs). The unique approach captures numerous early (24 h), quantitative features of actin fluororeporter shapes, intensities, textures, and spatial distributions (collectively termed morphometric descriptors). The large number of descriptors are reduced into "combinations" through which distinct subpopulations of cells featuring unique combinations are identified. We demonstrate that hMSCs cultured on fibronectin-treated glass substrates under environments permissive to bone lineage induction could be readily discerned within the first 24 h from those cultured in basal- or fat-inductive conditions by such cytoskeletal feature groupings. We extend the utility of this approach to forecast osteogenic stem cell lineage fates across a series of synthetic polymeric materials of diverse physicochemical properties. Within the first 24 h following stem cell seeding, we could successfully "profile" the substrate responsiveness prospectively in terms of the degree of bone versus nonbone predisposition. The morphometric methodology also provided insights into how substrates may modulate the pace of osteogenic lineage specification. Cells on glass substrates deficient in fibronectin showed a similar divergence of lineage fates, but delayed beyond 48 h. In summary, this high-content imaging and single cell modeling approach offers a framework to elucidate and manipulate determinants of stem cell behaviors, as well as to screen stem cell lineage modulating materials and environments.

Use of Plain Radiography of Uninjured Wrists as Patient-Specific Markers of Successful Reduction of Unilateral Distal Radius Fractures.

BACKGROUND: The standard of care of distal radius fractures requiring operative intervention involves restoration of anatomical alignment radiologically by comparing preoperative films and intraoperative fluoroscopy with established values based on population norms. The objective of this study is to evaluate the use of plain radiographs obtained from the uninjured wrist of patients who present with unilateral displaced distal radius fractures as a measure of successful achievement of anatomical realignment. METHODS: A retrospective review was performed on 133 consecutive patients who presented from August 2020 to August 2021 with a diagnosis of unilateral distal radius fracture as confirmed on 3-view plain radiography. Patients who had bilateral radiographs and underwent open reduction and internal fixation were included. The primary outcome measure was comparison of radial inclination, radial height, tilt, and ulnar variance measured by 3 observers on preoperative, 1-week postoperative, and uninjured contralateral wrist films. RESULTS: Twenty-one patients were included for analysis. Comparison of postoperative radiologic parameters with the contralateral uninjured extremity revealed a mean radial inclination difference of 3.8°, radial height difference of 2.0 mm, volar tilt difference of 6.3°, and ulnar variance difference of 0.9 mm. The average postreduction radial height was found to deviate from contralateral radial height significantly more than from the historic radial height parameter (2.0 vs 0.6 mm, P < .001). CONCLUSION: Attempts at achieving distal radius fracture reduction to within historical normal limits may result in an increased deviation from patient-specific anatomical parameters, especially with respect to radial height.

Long-Term Patency and Fluid Dynamics of Recipient Artery after End-to-Side Anastomosis for Free Tissue Transfer.

BACKGROUND: End-to-end microvascular anastomoses sacrifice downstream inline perfusion of the recipient vessels. End-to-side anastomoses, in theory, maintain distal inline flow of the recipient vessel. The proposed benefit of the end-to-side technique depends on patency of the distal vessels and subsequent flow parameters, but maintenance of distal perfusion has not been conclusively demonstrated. METHODS: Fifteen patients who underwent a successful extremity free flap procedure via end-to-side anastomoses to a noncritical vessel between 2003 and 2017 were enrolled. Recipient artery patency distal to the anastomosis was assessed using pulse volume recordings and duplex ultrasound imaging. Resistance indices, flow velocities, vessel diameters, volumetric flow, and turbulent flow dimensionless number (Reynolds number) were measured. Comparisons were made to the ipsilateral collateral vessel as well as to the vessels on the nonoperative contralateral limb using paired t tests. RESULTS: Downstream flow was identified in 14 of 15 patients (93 percent patency). There was no statistical difference in resistive indices comparing the anastomotic vessel (0.859 ± 0.300) and the collateral vessel (0.853 ± 0.179) of the ipsilateral extremity. Ultrasound flows were similar; the anastomotic vessel demonstrated downstream volumetric flows of 139 ± 92.0 cm3/min versus 137 ± 41.6 cm3/min within the same vessel of the nonoperative contralateral limb. The anastomotic vessel had Reynolds numbers well below the turbulent threshold (448 ± 202 and 493 ± 127 for the anastomotic and nonoperative contralateral limb, respectively). CONCLUSION: End-to-side anastomosis to noncritical vessels resulted in a 93 percent long-term recipient vessel patency rate, with no statistically significant changes in volumetric flows, resistive indices, or fluid dynamics in the vessels that remained patent.

Synthetic polymeric substrates as potent pro-oxidant versus anti-oxidant regulators of cytoskeletal remodeling and cell apoptosis.

The role of reactive oxygen species (ROS)-mediated cell signal transduction pathways emanating from engineered cell substrates remains unclear. To elucidate the role, polymers derived from the amino acid L-tyrosine were used as synthetic matrix substrates. Variations in their chemical properties were created by co-polymerizing hydrophobic L-tyrosine derivatives with uncharged hydrophilic poly(ethylene glycol) (PEG, Mw = 1,000 Da), and negatively charged desaminotyrosyl-tyrosine (DT). These substrates were characterized for their intrinsic ability to generate ROS, as well as their ability to elicit Saos-2 cell responses in terms of intracellular ROS production, actin remodeling, and apoptosis. PEG-containing substrates induced both exogenous and intracellular ROS production, whereas the charged substrates reduced production of both types, indicating a coupling of exogenous ROS generation and intracellular ROS production. Furthermore, PEG-mediated ROS induction caused nuclear translocation of glyceraldehyde-3-phosphate dehydrogenase and an increase in caspase-3 activity, confirming a link with apoptosis. PEG-rich pro-oxidant substrates caused cytoskeletal actin remodeling through beta-actin cleavage by caspase-3 into fractins. The fractins co-localized to the mitochondria and reduced the mitochondrial membrane potential. The remnant cytosolic beta-actin was polymerized and condensed, events consistent with apoptotic cell shrinkage. The cytoskeletal remodeling was integral to the further augmentation of intracellular ROS production. Conversely, the anti-oxidant DT-containing charged substrates suppressed the entire cascade of apoptotic progression. We demonstrate that ROS activity serves an important role in "outside-in" signaling for cells grown on substrates: the ROS activity couples exogenous stress, driven by substrate composition, to changes in intracellular signaling. This signaling causes cell apoptosis, which is mediated by actin remodeling.

TFCC Injuries: Meta-Analysis and Comparison of Diagnostic Imaging Modalities.

Background Imaging of the triangular fibrocartilaginous complex (TFCC) remains difficult, as no single imaging modality demonstrates perfect sensitivity and specificity. Purpose This study performs a meta-analysis of multiple previous publications to guide noninvasive imaging selection for the diagnosis of TFCC injuries. Methods A literature search was performed and conducted. Studies were included that compared the diagnostic accuracy of magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA), and computed tomography (CT)/computed tomographic arthrography (CTA) for the evaluation of TFCC injuries. All studies included either arthroscopic or open surgical findings as the "gold standard." A meta-analysis was performed comparing the diagnostic accuracy of MRA, MRI, and CT for the detection of TFCC injuries. Results Initial search returned 2,568 candidate articles. Studies were then reviewed and narrowed yielding a total of 28 independent studies (20 MRI, 9 MRA, 4 CT/CTA with some studies including multiple modalities) considered in the qualitative data synthesis. Pooling of the raw data in a meta-analysis demonstrated sensitivities of 0.76 (0.72-0.80), 0.78(0.70-0.84), and 0.89 (0.81-0.95) for MRI, MRA, and CT arthrogram, respectively, with specificities of 0.82 (0.77-0.86), 0.85 (0.77-0.92), and 0.89 (0.81-0.95), respectively. Additionally, across all imaging modalities, diagnostic accuracy was highest for central TFCC lesions versus peripheral lesions. Conclusion This study represents the largest meta-analysis to date to compare multiple imaging modalities for the diagnosis of TFCC injuries. Pooled data demonstrated that CTA and MRA had statistically equivalent sensitivity and specificity for the diagnosis of TFCC injuries. Diagnostic accuracy was highest for central TFCC injuries.

Profiling cell-biomaterial interactions via cell-based fluororeporter imaging.

Cell-based, high-throughput screening has revolutionized the development of small-molecule pharmaceuticals. A similar paradigm for the accelerated development of biomaterials for cell and tissue engineering involves the iterative use of combinatorial biomaterial synthesis, rapid cellular response screens, and computational modeling methods. However assays to probe cell responses to biomaterials are frequently subjective, lack dynamic responsiveness, and are limited to low-throughput experimentation. In this report, we highlight the use of high-resolution imaging of cell-based fluororeporters to establish and correlate quantifiable metrics of cell functional endpoints (e.g., cell growth, cell adhesion, cell attachment strength), as well as of intracellular cytoskeletalfeatures (e.g., descriptors of actin organization) on a set of model biomaterial substrates synthesized by combinatorial variations. Selected mammalian cell lines were genetically engineered with a series of green fluorescent protein (GFP)fusion genes to allow for live cell imaging on biomaterials. We demonstrate that high-content imaging yields a large number of quantifiable morphometric descriptors of ultrastructural cell features (e.g., cell cytoskeleton) in conjunction with densitometric descriptors of cell behaviors (e.g., cell apoptosis). We illustrate how such descriptors can be used to discern combinatorial variations in substrate composition, and how living GFP reporters are uniquely suited to generate such descriptors unlike fixed tissue preparations. This quantitative approach of live fluororeporter cell imaging could be valuable for metrology of cell-material interactions.

Quantitative biorelevant profiling of material microstructure within 3D porous scaffolds via multiphoton fluorescence microscopy.

This study presents a novel approach, based on fluorescence multiphoton microscopy (MPM), to image and quantitatively characterize the microstructure and cell-substrate interactions within microporous scaffold substrates fabricated from synthetic biodegradable polymers. Using fluorescently dyed scaffolds fabricated from poly(DTE carbonate)/poly(DTO carbonate) blends of varying porosity and complementary green fluorescent protein-engineered fibroblasts, we reconstructed the three-dimensional distribution of the microporous and macroporous regions in 3D scaffolds, as well as cellular morphological patterns. The porosity, pore size and distribution, strut size, pore interconnectivity, and orientation of both macroscale and microscale pores of 3D scaffolds were effectively quantified and validated using complementary imaging techniques. Compared to other scaffold characterizing techniques such as confocal imaging and scanning electron microscopy (SEM), MPM enables the acquisition of images from scaffold thicknesses greater than a hundred microns with high signal-to-noise ratio, reduced bulk photobleaching, and the elimination of the need for deconvolution. In our study, the morphology and cytoskeletal organization of cells within the scaffold interior could be tracked with high resolution within the limits of penetration of MPM. Thus, MPM affords a promising integrated platform for imaging cell-material interactions within the interior of polymeric biomaterials.

Tissue Expander Overfilling: Achieving New Dimensions of Customization in Breast Reconstruction.

UNLABELLED: Overfill of tissue expanders is a commonly used modality to achieve customized dimensions in breast reconstruction. Little formal study of the dynamics of hyperexpansion of these devices has been performed to date, however. METHODS: Overfill trials were performed using both Natrelle 133 MV and Mentor 8200 tissue expanders of indicated capacities ranging from 250 to 800 mL. Each expander was initially filled to its indicated capacity with normal water and then injected in regular increments to 400% overfill. Measurements of each expander's width, height, and projection were made at indicated capacity and with each successive incremental overfill injection, and these results were then recorded, collated, and analyzed. RESULTS: Over the first 50% overfill, all expanders demonstrated a logarithmic increase in projection (mean increase, 143 ± 9%) while maintaining essentially stable base dimensions. Overfill levels in excess of 50% were accompanied by linear increases in height, width, and projection, during which projection approached, but never equaled, base dimensions. Stress versus strain analyses demonstrated nonlinear biomechanical dynamics during the first 50% overfill, followed by standard elastic dynamics up to 400% overfill. At no point during the study, did expander tensions outstrip elastic properties, thereby explaining the lack of device rupture. CONCLUSIONS: Through overfilling, tunable geometries of tissue expanders can be accessed that may provide for increasing customization of reconstructions, particularly at overfill volumes up to 50% over indicated capacity. This study should serve to guide tissue expander selection and fill volumes that surgeons may implement in obtaining ideal reconstructed breast shapes.

Predictors of Complications and Comparison of Outcomes Using SurgiMend Fetal Bovine and AlloDerm Human Cadaveric Acellular Dermal Matrices in Implant-Based Breast Reconstruction.

BACKGROUND: Implant-based breast reconstruction with an acellular dermal matrix is one of the most common procedures performed by plastic surgeons. Although numerous matrices are available, there is little literature comparing them. This study compares the rates of complications between two commonly used products: AlloDerm (human cadaveric) and SurgiMend (fetal bovine) acellular dermal matrices. METHODS: A retrospective review of a single center's 6-year experience was performed for consecutive, immediate breast reconstructions with acellular dermal matrix from 2009 to 2014. The authors compared demographics and surgical characteristics between patients receiving AlloDerm versus SurgiMend. Multivariate logistic regression was used to determine any association between type of matrix and surgical complications and to identify other clinical predictors for complications. RESULTS: A total of 640 patients underwent 952 reconstructions using AlloDerm [578 breasts (61 percent)] or SurgiMend [374 breasts (39 percent)]. The average follow-up was 587 days. Multivariate analysis revealed that type of matrix was not an independent risk factor for the development of complications. However, smoking, age, radiotherapy, and initial tissue expander fill volume were associated with increased risk of postoperative complications. CONCLUSIONS: Both AlloDerm and SurgiMend acellular dermal matrices demonstrate similar rates of major complications when used in immediate implant-based breast reconstruction. In contrast, preoperative radiation therapy, smoking, increasing age, and initial tissue expander fill volume are independent risk factors for postoperative complications. Reconstructive surgeons should take these findings into consideration when performing implant-based breast reconstruction with a dermal matrix.

Management of hidradenitis suppurativa wounds with an internal vacuum-assisted closure device.

BACKGROUND: Hidradenitis suppurativa is a chronic, debilitating disease that is difficult to treat. Once medical management fails, wide local excision offers the best chance for cure. However, the resultant wound often proves too large or contaminated for immediate closure. METHODS: The authors performed a retrospective chart review of hidradenitis cases managed surgically between 2005 and 2010. Data collected included patient characteristics, management method, and outcomes. Approximately half of the patients received internal vacuum-assisted closure therapy using the vacuum-assisted closure system and delayed closure and half of the patients received immediate primary closure at the time of their excision. Delayed closure consisted of closing the majority of the wound in a linear fashion following internal vacuum-assisted closure while accepting healing by means of secondary intention for small wound areas. RESULTS: Patients managed with internal vacuum-assisted closure had wounds on average four times larger in area than patients managed without internal vacuum-assisted closure. In both groups, all wounds were eventually closed primarily. Healing times averaged 2.2 months with internal vacuum-assisted closure and 2.7 months without. At an average follow-up time of 2.3 months, all patients with internal vacuum-assisted closure had no recurrence of their local disease. CONCLUSIONS: Severe hidradenitis presents a treatment challenge, as surgical excisions are often complicated by difficult closures and unsatisfactory recurrence rates. This study demonstrates that wide local excision with reasonable outcomes can be achieved using accelerated delayed primary closure. This method uses internal vacuum-assisted closure as a bridge between excision and delayed primary closure, facilitating closure without recurrence in large, heavily contaminated wounds. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Parsing the early cytoskeletal and nuclear organizational cues that demarcate stem cell lineages.

Our recent report suggests that subtle changes in early cytoskeletal protein-level organization correlate with long-term stem cell lineage commitment. In this extra-view, we dissect changes in the expression of both cytoskeletal and nuclear-regulating genes that may precede and, possibly, govern the formative lineage-specific organizational cues. Human mesenchymal stem cells cultured on glass under basal, osteogenic, and adipogenic induction media were analyzed for gene expression profiles within the first 24 hours. Several key actin organization regulating genes and nuclear and cell cycle regulatory genes were found to be upregulated in osteogenic media compared to adipogenic and basal conditions. Given the role of both cytoskeletal and nuclear genes, we examined the possibility of classifying stem cell subpopulations using high content imaging approaches based on the organization of both actin, as previously proposed, as well as nuclear organization and distribution of a nuclear organizational protein, the nuclear mitotic apparatus (NuMA). A pool of combined cytoskeletal and nuclear descriptors were merged into a composite feature space via dimensionality reduction, data fusion, and classification methodologies. This composite approach enabled feature-based identification of specific lineage committed as well as non-differentiating cell populations. Using the improved classification of this high-content imaging-based profiling tool, we demonstrate that MSCs induced to differentiate to either osteogenic or adipogenic lineages are discernable within the first 24 hours from each other and from non-differentiating cells.

Interplay of anionic charge, poly(ethylene glycol), and iodinated tyrosine incorporation within tyrosine-derived polycarbonates: Effects on vascular smooth muscle cell adhesion, proliferation, and motility.

Regulation of smooth muscle cell adhesion, proliferation, and motility on biomaterials is critical to the performance of blood-contacting implants and vascular tissue engineering scaffolds. The goal of this study was to examine the underlying substrate-smooth muscle cell response relations, using a selection of polymers representative of an expansive library of multifunctional, tyrosine-derived polycarbonates. Three chemical components within the polymer structure were selectively varied through copolymerization: (1) the content of iodinated tyrosine to achieve X-ray visibility; (2) the content of poly(ethylene glycol) (PEG) to decrease protein adsorption and cell adhesivity; and (3) the content of desaminotyrosyl-tyrosine (DT), which regulates the rate of polymer degradation. Using quartz crystal microbalance with dissipation, we quantified differential serum protein adsorption behavior because of the chemical components DT, iodinated tyrosine, and PEG: increased PEG content within the polymer structure progressively decreased protein adsorption but the simultaneous presence of both DT and iodinated tyrosine reversed the effects of PEG. The complex interplay of these components was next tested on the adhesion, proliferation, and motility behavior cultured human aortic smooth muscle cells. The incorporation of PEG into the polymer reduced cell attachment, which was reversed in the presence of iodinated tyrosine. Further, we found that as little as 10% DT content was sufficient to negate the PEG effect in polymers containing iodinated tyrosine, whereas in non-iodinated polymers, the PEG effect on cell attachment was reversed. Cross-functional analysis of motility and proliferation revealed divergent substrate chemistry related cell response regimes. For instance, within the series of polymers containing both iodinated tyrosine and 10% of DT, increasing PEG levels lowered smooth muscle cell motility without a change in the rate of cell proliferation. In contrast, for non-iodinated tyrosine and 10% of DT, increasing PEG levels increased cell proliferation significantly while reducing cell motility. Clearly, the polycarbonate polymer library offers a sensitive platform to modulate cell adhesion, proliferation, and motility responses, which, in turn, may have implications for controlling vascular remodeling in vivo. Additionally, our data suggests unique biorelevant properties following the incorporation of iodinated subunits in a polymeric biomaterial as a potential platform for X-ray visible devices.

Osteogenic differentiation of human mesenchymal stem cells on poly(ethylene glycol)-variant biomaterials.

This study evaluated the osteogenic differentiation of human mesenchymal stem cells (MSCs), on tyrosine-derived polycarbonates copolymerized with poly(ethylene glycol) (PEG) to determine their potential as a scaffold for bone tissue engineering applications. The addition of PEG in the backbone of polycarbonates has been shown to alter mechanical properties, degradation rates, degree of protein adsorption, and subsequent cell adhesion and motility in mature cell phenotypes. Its effect on MSC behavior is unknown. MSC morphology, motility, proliferation, and osteogenic differentiation were evaluated on polycarbonates containing 0-5% PEG over a 14 day culture. MSCs on polycarbonates containing 0% or 3% PEG content upregulated the expression of osteogenic markers as demonstrated by alkaline phosphatase activity and osteocalcin expression although at different stages in the 14 day culture. Cells on polycarbonates containing no PEG were characterized as having early onset of cell spreading and osteogenic differentiation. Cells on 3% PEG surfaces were delayed in cell spreading and osteogenic differentiation, but had the highest motility as compared with cells on substrates containing no PEG and substrates containing 5% PEG at early time points. Throughout the culture, cells on polycarbonates containing 5% PEG had the lowest levels of osteogenic markers, displayed poor cell-substrate adhesion, and established cell-cell aggregates. Thus, designing substrates with minute variations in PEG may serve as a tool to guide MSC adhesion and motility accompanying osteogenic differentiation, and may be beneficial for abundant bone tissue formation in vivo.

High-content profiling of cell responsiveness to graded substrates based on combinyatorially variant polymers.

We have developed a novel approach combining high information and high throughput analysis to characterize cell adhesive responses to biomaterial substrates possessing gradients in surface topography. These gradients were fabricated by subjecting thin film blends of tyrosine-derived polycarbonates, i.e. poly(DTE carbonate) and poly(DTO carbonate) to a gradient temperature annealing protocol. Saos-2 cells engineered with a green fluorescent protein (GFP) reporter for farnesylation (GFP-f) were cultured on the gradient substrates to assess the effects of nanoscale surface topology and roughness that arise during the phase separation process on cell attachment and adhesion strength. The high throughput imaging approach allowed us to rapidly identify the "global" and "high content" structure-property relationships between cell adhesion and biomaterial properties such as polymer chemistry and topography. This study found that cell attachment and spreading increased monotonically with DTE content and were significantly elevated at the position with intermediate regions corresponding to the highest "gradient" of surface roughness, while GFP-f farnesylation intensity descriptors were sensitively altered by surface roughness, even in cells with comparable levels of spreading.