Publications by authors named "Sashank K Reddy"

17 Publications

  • Page 1 of 1

Size-Controlled and Shelf-Stable DNA Particles for Production of Lentiviral Vectors.

Nano Lett 2021 07 6;21(13):5697-5705. Epub 2021 Jul 6.

Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States.

Polyelectrolyte complex particles assembled from plasmid DNA (pDNA) and poly(ethylenimine) (PEI) have been widely used to produce lentiviral vectors (LVVs) for gene therapy. The current batch-mode preparation for pDNA/PEI particles presents limited reproducibility in large-scale LVV manufacturing processes, leading to challenges in tightly controlling particle stability, transfection outcomes, and LVV production yield. Here we identified the size of pDNA/PEI particles as a key determinant for a high transfection efficiency with an optimal size of 400-500 nm, due to a cellular-uptake-related mechanism. We developed a kinetics-based approach to assemble size-controlled and shelf-stable particles using preassembled nanoparticles as building blocks and demonstrated production scalability on a scale of at least 100 mL. The preservation of colloidal stability and transfection efficiency was benchmarked against particles generated using an industry standard protocol. This particle manufacturing method effectively streamlines the viral manufacturing process and improves the production quality and consistency.
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http://dx.doi.org/10.1021/acs.nanolett.1c01421DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8283758PMC
July 2021

Neuroma of The Supraorbital Nerve Following Forehead Flap Reconstruction - Presentation and Surgical Management.

J Craniofac Surg 2021 Jun;32(4):1515-1516

Department of Plastic and Reconstructive Surgery.

Abstract: Localized pain or headache from neuroma formation is a rare and challenging complication of forehead flap surgery. Here the authors present a patient who developed local pain and dysesthesia following iatrogenic injury to the left supraorbital nerve during forehead flap elevation. Following a diagnostic nerve block in clinic, surgical excision of the neuroma was performed through an upper blepharoplasty approach. The patient had immediate postoperative pain relief and remains pain free at fifteen-month follow-up. The authors describe etiology, workup, and surgical management of sensory nerve injury during forehead flap reconstruction.
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http://dx.doi.org/10.1097/SCS.0000000000007566DOI Listing
June 2021

Bacteria induce skin regeneration via IL-1β signaling.

Cell Host Microbe 2021 05 1;29(5):777-791.e6. Epub 2021 Apr 1.

Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, MD 21210, USA; Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21210, USA. Electronic address:

Environmental factors that enhance regeneration are largely unknown. The immune system and microbiome are attributed roles in repairing and regenerating structure but their precise interplay is unclear. Here, we assessed the function of skin bacteria in wound healing and wound-induced hair follicle neogenesis (WIHN), a rare adult organogenesis model. WIHN levels and stem cell markers correlate with bacterial counts, being lowest in germ-free (GF), intermediate in conventional specific pathogen-free (SPF), and highest in wild-type mice, even those infected with pathogenic Staphylococcus aureus. Reducing skin microbiota via cage changes or topical antibiotics decreased WIHN. Inflammatory cytokine IL-1β and keratinocyte-dependent IL-1R-MyD88 signaling are necessary and sufficient for bacteria to promote regeneration. Finally, in a small trial, a topical broad-spectrum antibiotic also slowed skin wound healing in adult volunteers. These results demonstrate a role for IL-1β to control morphogenesis and support the need to reconsider routine applications of topical prophylactic antibiotics.
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http://dx.doi.org/10.1016/j.chom.2021.03.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8122070PMC
May 2021

Wound Induced Hair Neogenesis - A Novel Paradigm for Studying Regeneration and Aging.

Front Cell Dev Biol 2020 15;8:582346. Epub 2020 Oct 15.

Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States.

Hair follicles are the signature dermal appendage of mammals. They can be thought of as mini-organs with defined polarity, distinct constituent cell types, dedicated neurovascular supply, and specific stem cell compartments. Strikingly, some mammals show a capacity for adult hair follicle regeneration in a phenomenon known as wound-induced hair neogenesis (WIHN). In WIHN functional hair follicles reemerge during healing of large cutaneous wounds, and they can be counted to provide an index of regeneration. While age-related decline in hair follicle number and cycling are widely appreciated in normal physiology, it is less clear whether hair follicle regeneration also diminishes with age. WIHN provides an extraordinary quantitative system to address questions of mammalian regeneration and aging. Here we review cellular and molecular underpinnings of WIHN, explore known age-related changes to these elements, and present unanswered questions for future exploration.
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http://dx.doi.org/10.3389/fcell.2020.582346DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593594PMC
October 2020

Tissue Engineering of Axially Vascularized Soft-Tissue Flaps with a Poly-(ɛ-Caprolactone) Nanofiber-Hydrogel Composite.

Adv Wound Care (New Rochelle) 2020 07 10;9(7):365-377. Epub 2020 Jun 10.

Department of Hand, Plastic, and Reconstructive Surgery, BG Trauma Center Ludwigshafen, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

To develop a novel approach for tissue engineering of soft-tissue flaps suitable for free microsurgical transfer, using an injectable nanofiber hydrogel composite (NHC) vascularized by an arteriovenous (AV) loop. A rat AV loop model was used for tissue engineering of vascularized soft-tissue flaps. NHC or collagen-elastin (CE) scaffolds were implanted into isolation chambers together with an AV loop and explanted after 15 days. Saphenous veins were implanted into the scaffolds as controls. Neoangiogenesis, ultrastructure, and protein expression of SYNJ2BP, EPHA2, and FOXC1 were analyzed by immunohistochemistry and compared between the groups. Rheological properties were compared between the two scaffolds and native human adipose tissue. A functional neovascularization was evident in NHC flaps with its amount being comparable with CE flaps. Scanning electron microscopy revealed a strong mononuclear cell infiltration along the nanofibers in NHC flaps and a trend toward higher fiber alignment compared with CE flaps. SYNJ2BP and EPHA2 expression in endothelial cells (ECs) was lower in NHC flaps compared with CE flaps, whereas FOXC1 expression was increased in NHC flaps. Compared with the stiffer CE flaps, the NHC flaps showed similar rheological properties to native human adipose tissue. This is the first study to demonstrate the feasibility of tissue engineering of soft-tissue flaps with similar rheological properties as human fat, suitable for microsurgical transfer using an injectable nanofiber hydrogel composite. The injectable NHC scaffold is suitable for tissue engineering of axially vascularized soft-tissue flaps with a solid neovascularization, strong cellular infiltration, and biomechanical properties similar to human fat. Our data indicate that SYNJ2BP, EPHA2, and FOXC1 are involved in AV loop-associated angiogenesis and that the scaffold material has an impact on protein expression in ECs.
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http://dx.doi.org/10.1089/wound.2019.0975DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307685PMC
July 2020

Nasolabial and forehead flap reconstruction of contiguous alar-upper lip defects.

J Plast Reconstr Aesthet Surg 2017 Mar 11;70(3):330-335. Epub 2016 Nov 11.

Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Taipei, Taiwan. Electronic address:

Background: Defects of the nasal ala and upper lip aesthetic subunits can be challenging to reconstruct when they occur in isolation. When defects incorporate both the subunits, the challenge is compounded as subunit boundaries also require reconstruction, and local soft tissue reservoirs alone may provide inadequate coverage. In such cases, we used nasolabial flaps for upper lip reconstruction and a forehead flap for alar reconstruction.

Methods: Three men and three women aged 21-79 years (average, 55 years) were treated for defects of the nasal ala and upper lip that resulted from cancer (n = 4) and trauma (n = 2). Unaffected contralateral subunits dictated the flap design. The upper lip subunit was excised and replaced with a nasolabial flap. The flap, depending on the contralateral reference, determined accurate alar base position. A forehead flap resurfaced or replaced the nasal ala. Autologous cartilage was used in every case to fortify the forehead flap reconstruction.

Results: Patients were followed for 25.6 months (range, 1-4 years). All the flaps survived, and there were no complications. Satisfactory aesthetic results were achieved in every case. With the exception of a small vertical cheek scar and a vertical forehead scar, all incisions were concealed within the subunit borders.

Conclusion: From preliminary experience, we advocate combining nasolabial flap reconstruction of the upper lip with a forehead flap reconstruction of the ala to preserve normal facial appearance. This combination addresses an important void in the algorithmic approach to central facial reconstruction.
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http://dx.doi.org/10.1016/j.bjps.2016.10.027DOI Listing
March 2017

Double forehead flap reconstruction of composite nasal defects.

J Plast Reconstr Aesthet Surg 2016 Sep 3;69(9):1280-4. Epub 2016 Jun 3.

Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Taipei, Taiwan. Electronic address:

Background And Aim: Composite nasal defects require skin, framework, and lining reconstruction. The forehead flap is an ideal donor for skin coverage because of good color match and excellent donor-site healing. Intranasal flaps and grafts are reserved for lining reconstruction of small defects. Locoregional and free flaps are used for larger lining defects, but these may not be ideal or safe. The authors advocate the double forehead flap for large composite defects of the nose in a subset of patients.

Methods: Three men and three women aged 55-87 years (average 74.7 years) were treated for composite nasal defects that resulted from cancer (n = 5) and trauma (n = 1). Skin and lining defects were >2 cm in every dimension. Double forehead flaps were raised in stages (n = 1) or simultaneously (n = 5), and nasal reconstruction was performed in two (n = 1) or three stages (n = 5).

Results: Patients were followed for 19.3 months (range 13-24 months). Donor sites of flaps raised in stages healed after 3 months. When flaps were raised together, healing required 5-13 months (average 7.6 months). There were no partial or complete flap losses. None of the patients had infection, hematoma, or nerve injury. Satisfactory aesthetic results were achieved in every case.

Conclusion: The authors advocate the double forehead flap for large composite nasal defects in patients who are not suitable candidates for nasolabial flaps and those who may not tolerate free tissue transfer. The advantages of this method must be weighed against the drawbacks, which include prolonged donor-site healing and elimination of the contralateral forehead flap.
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http://dx.doi.org/10.1016/j.bjps.2016.05.026DOI Listing
September 2016

dsRNA Released by Tissue Damage Activates TLR3 to Drive Skin Regeneration.

Cell Stem Cell 2015 Aug;17(2):139-51

Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA. Electronic address:

Regeneration of skin and hair follicles after wounding--a process known as wound-induced hair neogenesis (WIHN)--is a rare example of adult organogenesis in mammals. As such, WIHN provides a unique model system for deciphering mechanisms underlying mammalian regeneration. Here, we show that dsRNA, which is released from damaged skin, activates Toll-Like Receptor 3 (TLR3) and its downstream effectors IL-6 and STAT3 to promote hair follicle regeneration. Conversely, TLR3-deficient animals fail to initiate WIHN. TLR3 activation promotes expression of hair follicle stem cell markers and induces elements of the core hair morphogenetic program, including ectodysplasin A receptor (EDAR) and the Wnt and Shh pathways. Our results therefore show that dsRNA and TLR3 link the earliest events of mammalian skin wounding to regeneration and suggest potential therapeutic approaches for promoting hair neogenesis.
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http://dx.doi.org/10.1016/j.stem.2015.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529957PMC
August 2015

The thinning top: why old people have less hair.

J Invest Dermatol 2014 Aug;134(8):2068-2069

Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Electronic address:

Changes in the hair cycle underlie age-related alopecia, but the causative mechanisms have remained unclear. Chen et al. point to an imbalance between stem cell-activating and -inhibitory signals as the key determinant of age-related regenerative decline. Further, they identify a secreted protein, follistatin, that may be able to shift the balance toward renewal.
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http://dx.doi.org/10.1038/jid.2014.172DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4101907PMC
August 2014

Pyoderma Gangrenosum After Breast Surgery: Diagnostic Pearls and Treatment Recommendations Based on a Systematic Literature Review.

Ann Plast Surg 2016 Aug;77(2):e39-44

From the Department of Plastic and Reconstructive Surgery, Johns Hopkins Medical Institutions, Baltimore, MD.

Background: Pyoderma gangrenosum (PG) is a rare cutaneous disorder that poses a diagnostic challenge in the postoperative period. A systematic literature review was performed to determine distinguishing characteristics of PG in the setting of breast surgery that can facilitate timely diagnosis and appropriate treatment.

Methods: PubMed, EMBASE, Scopus, and Web of Science databases were systematically searched for articles with cases of PG occurring after breast surgery. Forty-three relevant articles, including 49 case reports, were identified.

Results: PG manifested bilaterally in 30 of 34 cases (88%) in which bilateral surgery was performed. Abdominal wounds were present in 6 of 7 cases in which an abdominal donor site was used for breast reconstruction. Nipples were spared from wound involvement in 33 of 37 cases (89%) in which nipples were present after surgery. Presence of fever was noted in 27 cases (55%) and leukocytosis in 21 cases (43%). A total of 33 patients (67%) underwent wound debridement. Successful medical treatment most commonly involved steroids (41 cases, 84%) and cyclosporine (10 cases, 20%).

Conclusions: Pertinent clinical features were identified that may aid in timely diagnosis and treatment of PG after breast surgery. Appearance of discrete wounds involving multiple surgical sites that surround but spare the nipples should raise suspicion for PG rather than infection or ischemia, even with concomitant fever and leukocytosis. Wound debridement should be minimized and skin grafting considered only after medical therapy is initiated. Cognizance of these features may enable prompt therapeutic intervention that minimizes morbidity and improves outcomes.
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http://dx.doi.org/10.1097/SAP.0000000000000248DOI Listing
August 2016

Facial fractures of the upper craniofacial skeleton predict mortality and occult intracranial injury after blunt trauma: an analysis.

J Craniofac Surg 2013 Nov;24(6):1922-6

From the *Johns Hopkins School of Medicine; †Division of Plastic and Reconstructive Surgery, R. Adams Cowley Shock Trauma Center, University of Maryland School of Medicine; and ‡Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland; and §Division of Plastic and Reconstructive Surgery, Duke University, Durham, North Carolina.

Purpose: The aim of this article was to assess how regional facial fracture patterns predict mortality and occult intracranial injury after blunt trauma.

Methods: Retrospective chart review was performed for blunt-mechanism craniofacial fracture patients who presented to an urban trauma center from 1998 to 2010. Fractures were confirmed by author review of computed tomographic imaging and then grouped into 1 of 5 patterns of regional involvement representing all possible permutations of facial-third injury. Mortality and the presence of occult intracranial injury, defined as those occurring in patients at low risk at presentation for head injury by Canadian CT Head Rule criteria, were evaluated. Relative risk estimates were obtained using multivariable regression.

Results: Of 4540 patients identified, 338 (7.4%) died, and 171 (8.1%) had intracranial injury despite normal Glasgow Coma Scale at presentation. Cumulative mortality reached 18.8% for isolated upper face fractures, compared with 6.9% and 4.0% for middle and lower face fractures (P < 0.001), respectively. Upper face fractures were independently associated with 4.06-, 3.46-, and 3.59-fold increased risk of death for the following fracture patterns: isolated upper, combined upper, panfacial, respectively (P < 0.001). Patients who were at low risk for head injury remained 4 to 6 times more likely to suffer an occult intracranial injury if they had involvement of the upper face.

Conclusions: The association between facial fractures, intracranial injury, and death varies by regional involvement, with increasing insult in those with upper face fractures. Cognizance of the increased risk for intracranial injury in patients with upper face fractures may supplement existing triage tools and should increase suspicion for underlying or impending neuropathology, regardless of clinical picture at presentation.
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http://dx.doi.org/10.1097/SCS.0b013e3182a30544DOI Listing
November 2013

Le Fort II fractures are associated with death: a comparison of simple and complex midface fractures.

J Oral Maxillofac Surg 2013 Sep 15;71(9):1556-62. Epub 2013 Jul 15.

Johns Hopkins School of Medicine, Baltimore, MD 21201, USA.

Purpose: To investigate whether complex midface fractures have a greater association with death and intracranial injury than simple midface fractures.

Materials And Methods: A retrospective chart review was performed for patients with blunt-mechanism midface fractures who had presented to an urban trauma center from 1998 to 2010. The survival and intracranial injury status was evaluated for patients with simple and complex midface fractures, including Le Fort, naso-orbitoethmoid, and/or zygomaticomaxillary fractures. Intracranial injury included hemorrhage and brainstem injury. Patients with upper face fractures were excluded to minimize confounding. Adjusted relative risk estimates were obtained using multivariate regression analysis.

Results: Of 3,291 patients with midface fractures, 213 (6.3%) died and 693 (21.3%) had an intracranial injury. The cumulative mortality reached 11.6% in patients with complex midface fractures and 5.1% in those with simple midface fractures (P < .001). Patients with complex midface fractures were 57% more likely to die (relative risk = 1.57; P < .005). Specifically, Le Fort II fractures independently conferred a 94% increased risk of death (relative risk = 1.94; P < .01), but Le Fort I and III fractures were not significantly associated with death. Among patients presenting without neurologic impairment, those with Le Fort II and III fractures remained 2.88-fold (P < .01) and 2.54-fold (P < .001) more likely to have an underlying intracranial injury, respectively.

Conclusions: Le Fort II fractures are associated with increased mortality. Furthermore, Le Fort II and III fractures are associated with serious intracranial injury, even in the absence of alterations in consciousness. These patients should be monitored with heightened vigilance and followed up closely during hospitalization, regardless of the presenting clinical findings.
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http://dx.doi.org/10.1016/j.joms.2013.04.007DOI Listing
September 2013

Severe infectious complications following frontal sinus fracture: the impact of operative delay and perioperative antibiotic use.

Plast Reconstr Surg 2013 Jul;132(1):154-162

Baltimore, Md. From the Johns Hopkins School of Medicine; the Division of Plastic and Reconstructive Surgery, R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine; and the Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University.

Background: The purpose of this study was to investigate whether a delay in operative management of frontal sinus fractures is associated with increased risk of serious infections.

Methods: Retrospective chart review was performed of 242 consecutive patients with surgically managed frontal sinus fractures who presented to the R Adams Cowley Shock Trauma Center between 1996 and 2011. Collected patient characteristics included demographics, surgical management, hospital course, and complications. All computed tomographic imaging was reviewed to evaluate involvement of the posterior table and nasofrontal outflow tract. Serious infections included meningitis, encephalitis, brain abscess, frontal sinus abscess, and osteomyelitis. Delayed operative interventions were defined as procedures performed more than 48 hours after admission. Adjusted relative risk estimates were obtained using multivariable regression.

Results: There were 14 serious infections (5.8 percent). All patients with serious infections had both involvement of the posterior table and nasofrontal outflow tract injury. The cumulative incidence of serious infection in these patients was 10.8 percent. After adjustments for confounding, multivariable regression showed that operative delay beyond 48 hours was independently associated with a 4.03-fold (p < 0.05) increased risk for serious infection; external cerebrospinal fluid drainage catheter use and local soft-tissue infection conferred a 4.09-fold (p < 0.05) and 5.10-fold (p < 0.001) increased risk, respectively. Antibiotic use beyond 48 hours postoperatively was not associated with fewer infections.

Conclusions: Delay in operative management of frontal sinus fractures in patients requiring operative intervention is associated with an increased risk for serious infections. Continued antibiotic prophylaxis beyond the perioperative period provides little benefit in preventing serious infections.

Clinical Question/level Of Evidence: Risk, II.
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http://dx.doi.org/10.1097/PRS.0b013e3182910b9bDOI Listing
July 2013

Hoofbeats.

Plast Reconstr Surg 2011 Aug;128(2):94e-95e

Massachusetts General Hospital, Harvard Medical School, Boston, Mass.

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http://dx.doi.org/10.1097/PRS.0b013e31821ef358DOI Listing
August 2011

Bilateral autologous reconstruction from different sites: indications and outcomes after DIEP and SGAP flaps.

Plast Reconstr Surg 2011 Jun;127(6):151e-153e

Department of Surgery, Division of Plastic and Reconstructive Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass.

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http://dx.doi.org/10.1097/PRS.0b013e318213a1eaDOI Listing
June 2011

Central fusion disruption following irradiation of neoplasms in the pineal region.

Arch Ophthalmol 2009 Mar;127(3):337-8

Department of Ophthalmology, Children's Hospital Boston, 300 Longwood Ave, Fegan 4, Boston, MA 02115, USA.

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http://dx.doi.org/10.1001/archophthalmol.2008.605DOI Listing
March 2009

The processivity of multiubiquitination by the APC determines the order of substrate degradation.

Cell 2006 Jan;124(1):89-103

Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.

The anaphase-promoting complex (APC) coordinates mitosis and G1 by sequentially promoting the degradation of key cell-cycle regulators. Following the degradation of its substrates in G1, the APC catalyzes the autoubiquitination of its E2 UbcH10. This stabilizes cyclin A and allows it to inactivate APC(Cdh1). How the APC establishes this complex temporal sequence of ubiquitinations, referred to as substrate ordering, is not understood. Here we show that substrate ordering depends on the relative processivity of substrate multiubiquitination by the APC. Processive substrates obtain ubiquitin chains in a single APC binding event. The multiubiquitination of distributive substrates requires multiple rounds of APC binding, which render it sensitive to lower APC concentrations, competition by processive substrates, and deubiquitination. Consequently, more processive substrates are preferentially multiubiquitinated in vitro and degraded earlier in vivo. The processivity of multiubiquitination is strongly influenced by the D box within the substrate, suggesting that substrate ordering is established by a mechanism intrinsic to APC and its substrates and similar to kinetic proofreading.
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http://dx.doi.org/10.1016/j.cell.2005.10.032DOI Listing
January 2006
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