News & Events
Killian and Abraham Labs presenting research at 2025 Orthopaedic Research Society Annual Meeting
We are looking forward to traveling to Phoenix in February to share our work!
Dr. Adam Abraham: moderator for Tendon Disease and Treatment podium session
Dr. Megan Killian: presenter in Tendon Growth and Development podium session
Dr. Nicole Migotsky: presenter in Late Breaking podium session and poster session 1
Stephanie Steltzer: presenter in Tendon and Ligament Healing podium session and poster session 1
Allie Risha: ORS Underrepresented in STEM Undergraduate Travel Award winner
January 2025
Graphical abstract from Lamia et al. 2024
Paper published in The FASEB Journal describes a new mouse model for skeletal-muscle optogenetics
Authors: Syeda N. Lamia, Carol S. Davis, Peter C. D. Macpherson, T. Brad Willingham, Yingfan Zhang, Chengyu Liu, Leanne Iannucci, Elahe Ganji, Desmond Harden, Iman Bhattacharya, Adam C. Abraham, Susan V. Brooks, Brian Glancy, and Megan L. Killian
Abstract: Skeletal muscle activation using optogenetics has emerged as a promising technique for inducing noninvasive muscle contraction and assessing muscle function both in vivo and in vitro. Transgenic mice overexpressing the optogenetic fusion protein, Channelrhodopsin 2-EYFP (ChR2-EYFP) in skeletal muscle are widely used; however, overexpression of fluorescent proteins can negatively impact the functionality of activable tissues. In this study, we characterized the contractile properties of ChR2-EYFP skeletal muscle and introduced the ChR2-only mouse model that expresses light-responsive ChR2 without the fluorescent EYFP in their skeletal muscles. We found a significant reduction in the contractile ability of ChR2-EYFP muscles compared with ChR2-only and WT mice, observed under both electrical and optogenetic stimulation paradigms. Bulk RNAseq identified the downregulation of genes associated with transmembrane transport and metabolism in ChR2-EYFP muscle, while the ChR2-only muscle did not demonstrate any notable deviations from WT muscle. The RNAseq results were further corroborated by a reduced protein-level expression of ion channel-related HCN2 in ChR2-EYFP muscles and gluconeogenesis-modulating FBP2 in both ChR2-EYFP and ChR2-only muscles. Overall, this study reveals an intrinsic skeletal dysfunction in the widely used ChR2-EYFP mice model and underscores the importance of considering alternative optogenetic models, such as the ChR2-only, for future research in skeletal muscle optogenetics.
November 2024
HIF-1a is a transcription factor recognized by the von Hippel-Lindau (VHL) tumor suppressor protein and is degraded under normoxic conditions. Under hypoxic conditions, HIF-1a is translocated to the nucleus leading to the transcription of downstream genes such as those affiliated with cell proliferation, ECM deposition, and ECM organization. Knockdown (LOF) and stabilization of HIF-1a (GOF) can be driven genetically using Cre recombination.
R01 awarded to Dr. Megan Killian
Regulation of Tendon Enthesis Development and Healing via HIF1
Achilles tendon ruptures are common musculoskeletal injuries, and the rate of rupture is rising with increased participation in sports. Vascular irregularities and degenerative changes to extracellular matrix (ECM) result in poor biomechanical properties that increase risk of tendon rupture. We have discovered that, following Achilles tendon rupture in mice, the tendon-bone enthesis exhibits profound cell loss, which impairs remodeling and further increases susceptibility to degeneration. This focal cell loss within the enthesis motivated our work to study enthesis cell survival during growth and following tendon injury. Our preliminary studies in mice have established the Achilles enthesis maintains a hypoxic niche during perinatal growth and depends on Hypoxia Inducible Factor-1a (HIF1a) for enthesis cell survival. Targeted loss of Hif1a in tendon and enthesis progenitor cells leads to focal cell death, disruption of enthesis ECM, and failed integration of tendon into bone. Conversely, overexpression of Hif1a rescues cell within the enthesis following Achilles tendon injury, suggesting its potential role in guiding tendon and enthesis regeneration. Therefore, we hypothesize hypoxia is critical for establishing the enthesis progenitor cell/ECM niche, and cell survival in this niche depends on and is enhanced by Hif1a. Our central goal is to define HIF1-dependent mechanisms of cell function and ECM production during growth and repair of the fibrocartilage enthesis. We hypothesize that HIF1a drives enthesis cell differentiation in part by regulating cell survival and ECM deposition. We will use innovative approaches (e.g., in vivo reporters; subcellular spatial RNA-sequencing; synthetic hydrogels; nascent protein labeling) to establish the role of HIF1a and hypoxia in maintaining, establishing, and protecting enthesis progenitors. Our long-term goal is to develop druggable therapeutics to prevent Achilles tendon rupture and improve tendon and enthesis healing. In Aim 1, we will establish the time course of progenitor cell survival, differentiation, and ECM deposition in the mouse Achilles enthesis using inducible and tissue-specific Hif1a-loss and gain of function models. Additionally, we will use synthetic 3D hydrogels to study the effects of HIF1a and hypoxia on tendon/enthesis progenitor cell survival, nascent ECM deposition, and mechanotransduction. In Aim 2, we will use parallel approaches to determine if and how HIF1a contributes to functional healing of Achilles tendon and enthesis using inducible HIF1a LOF and GOF mice with HIF (HIF1a- GFP and HIF2a-mCherry) reporters and structural/functional testing. We will also use novel HIF-targeting drugs to determine the therapeutic potential of HIF-agonists in tendon and enthesis healing. Together, we will identify the emergent role of HIF1a and hypoxia during tendon and enthesis development and repair following injury. Ultimately, this work will establish the potential therapeutic role of HIF1a in tendon and enthesis repair following injury, improving clinical care for the prevention and treatment of common musculoskeletal injuries.
April 2024
Microphysiological systems, like the ones developed by Dr. Abraham, allow for the controlled study and visualization of cell/matrix responses. We use microphysiological systems, like the ones shown above and below, to study self-assembly and cell behavior within tendon-like tissues in vitro.
Katz R01 awarded to Dr. Adam Abraham
Extracellular Matrix Regulation of Inflammatory Signaling in Tendon
Twenty percent of all primary care consults are related to musculoskeletal diseases; 30% of these are associated with tendinopathies. Pathogenesis of tendinopathy includes increased inflammatory signaling and extracellular matrix (ECM) remodeling. This remodeling leads to softer tendinopathic tendons, increasing the risk of tearing. Yet the relative roles of chronic inflammation and ECM stiffness in the initiation and progression of tendon disease remain controversial and are difficult to decouple in patient populations. We and others have shown that, in 2D cell culture using interleukin-1β (IL-1β) as a stimulant, patient-derived tendinopathic fibroblasts exhibit a stronger inflammatory response that is further enhanced on soft substrates. This inflammatory response is dependent on NF-κB signaling, which we have previously established as a critical regulator of tendon disease and healing. Yet these studies are limited by the use of classical 2D culture approaches and fail to recapitulate in vivo cell behavior or provide insight into ECM remodeling. The ability to visualize cytokine receptor clustering in 3D environments has further demonstrated that cellular sensitivity to cytokines is based on the properties of the ECM. Although these studies suggest physicochemical coupling between ECM stiffness (physical) and inflammatory signaling (chemical) that sustains chronic loss of tendon mechanical function, the mechanisms of how ECM drives cell behavior in 3D tissues like tendon remain unknown. Therefore, there remains a critical need to define the physicochemical cell-ECM interactions that regulate tendon function to discover the mechanisms underlying tendinopathies and treatments. Our long-term goal is to develop therapeutic strategies for the clinical treatment of tendinopathy by identifying key cell-ECM mechanisms driving chronic inflammatory tendon disease. Our overall objective in this application is to develop a novel approach to studying the physicochemical coupling between ECM stiffness and inflammatory signaling by developing a tendon specific microphysiological system (MPS) with tunable stiffness. In Aim 1 we will establish a tendon specific MPS with tunable ECM stiffness that quantifies mechanical function in situ. We will quantify tendon function by measuring micro-cantilever displacement in situ and tune ECM stiffness using light- induced matrix polymerization. In Aim 2 we will demonstrate that inflammatory signaling in primary human tendon fibroblasts is modulated by ECM stiffness via inflammatory receptor clustering. In Aim 3 we will evaluate if and how pathogenic tendon fibroblast phenotype is regulated by ECM stiffness. At the completion of this proposed work, our expected outcomes are to develop an MPS relevant to tendon function and deliver new insight into tendon cell-ECM interactions that govern tendon pathogenesis. These results will have a positive impact by providing the field with a repeatable and tunable platform to improve our understanding of tendon pathology, ultimately leading to new opportunities for the development of novel therapies.
April 2024
Dr. Syeda Lamia celebrates after defending her dissertation work.
Congratulations to Syeda Lamia for successfully defending your PhD dissertation!
Syeda Lamia successfully defended her PhD dissertation titled "Transcriptomics and Functionality of Optogenetic Skeletal Muscle" in the Department of Mechanical Engineering on Tuesday, Oct 24th, 2023 at the University of Michigan.
Her committee included:
Dr Killian (co-chair)
Dr Allen Liu (co-chair)
Dr Susan Brooks (cognate)
Dr Talia Moore
Congratulations, Syeda!! We are so proud of you!
October 2023
In this paper, we used optogenetics as a noninvasive tool for direct and precise induction of muscle contraction for in vivo tendon loading in growing mice.
Recent optogenetics publication in Science Advances
Our recent paper using optogenetics to control tendon and enthesis loading has been published in Science Advances ! This work was led by Elahe Ganji, PhD, and Syeda Lamia.
Abstract: Skeletal shape depends on the transmission of contractile muscle forces from tendon to bone across the enthesis. Loss of muscle loading impairs enthesis development, yet little is known if and how the postnatal enthesis adapts to increased loading. Here, we studied adaptations in enthesis structure and function in response to increased loading, using optogenetically induced muscle contraction in young (i.e., growth) and adult (i.e., mature) mice. Daily bouts of unilateral optogenetic loading in young mice led to radial calcaneal expansion and warping. This also led to a weaker enthesis with increased collagen damage in young tendon and enthisis, with little change in adult mice. We then used RNA sequencing to identify the pathways associated with increased mechanical loading during growth. In tendon, we found enrichment of glycolysis, focal adhesion, and cell-matrix interactions. In bone, we found enrichment of inflammation and cell cycle. Together, we demonstrate the utility of optogenetic-induced muscle contraction to elicit in vivo adaptation of the enthesis.
This work was supported by funding from the NSF CAREER and NIH R01 (NIAMS) and R03 (NICHD).
June 2023
Syeda presented her research as a podium talk at the SB3C2023.
Syeda presented her dissertation work at the SB3C conference in the PhD level student paper competition in Vail.
In June, Syeda competed as one of 36 finalists in the PhD level student paper competition at the SB3C meeting in Vail. There were >200 abstracts submitted to the competition this year. Syeda also helped organize a meetup for BUET alumni at the SB3C meeting and went on several hikes in the Rockies.
June 2023
MiMHC Symposium 2023 recap + Steph wins a travel award!
This year's MiMHC Symposium was a hit, with excellent scientific presentations and high caliber posters.
Our laboratory presented five posters, including:
-Brandon's study assessing bone morphometry of a mouse model for gender-affirming hormone therapy
-Syeda's study assessing skeletal muscle contractility using e-stim and optogenetics of mouse muscle with and without eYFP
-Steph's *award winning* poster (and first-ever podium talk!) on her study of extracellular matrix associated gene expression in tendon fibroblasts and its dependence on Hif1a. Steph won a MiMHC travel award!
-LeeAnn's study investigating the role of AMPKa1 on tendon homeostasis and matrix remodeling in vivo.
-LeeAnn's study (presented by Dr. Abraham) on tendon cell-matrix interactions (not pictured).
May 2023
LeeAnn presents her dissertation work at the APS Summit in Long Beach!
LeeAnn (Hold) Flowers presented her dissertation work as a poster ("AMPKα1 is necessary for extracellular matrix homeostasis in mouse Achilles tendon") at the APS Summit in Long Beach this April. Her abstract was selected as an Abstract of Distinction ! Congratulations, LeeAnn!
April 2023
The growth and adaptation of the enthesis depends on FGF signaling. In these two studies, we used transgenic mouse models to interrogate the role of FGF ligand (FGF9) and receptors (FGFR1 and FGFR2) in Scx-lineage cells during postnatal growth. Schematic created with BioRender.com.
Two papers related to our FGF signaling work have been recently accepted in Developmental Dynamics and The FASEB J
Two publications from our FGF signaling projects were recently accepted for publication in the journals Developmental Dynamics and The FASEB Journal. These include:
"Loss of Fgfr1 and Fgfr2 in Scleraxis-lineage cells leads to enlarged bone eminences and attachment cell death," led by Killian lab alumni Kendra Wernle and Michael Sonnenfelt with Connor Leek, Elahe Ganji, Anna Lia Sullivan, and our collaborators at WashU, and "Targeted deletion of Fgf9 in tendon disrupts mineralization of the developing enthesis," led by Elahe Ganji with Connor Leek and our WashU collaborators, Drs. David Ornitz and Deb Patra.
April 2023
Syeda presented her research as a poster at the ORS2022.
Members of the Killian Lab at ORS2022
Syeda, Tessa, and Megan headed to Tampa for this year's ORS Annual Meeting. Read more here!
February 2022
The enthesis is a transitionally graded tissue positioned between bone and tendon. The primordial enthesis develops from bi-fated progenitor cells expressing chondrogenic and tenogenic factors (i.e., Scx, Sox9, and Gli1). Created with BioRender.com.
Review published in Seminars in Cell and Developmental Biology
Our recent review paper, "Growth and mechanobiology of the tendon-bone enthesis," is now published as part of the Special Issue on Musculoskeletal Physiology, edited by Dr. Ryan Riddle. This manuscript highlights much of our current understanding of enthesis research, and highlights some new directions towards which the field is headed.
Abstract: Tendons are cable-like connective tissues that transfer both active and passive forces generated by skeletal muscle to bone. In the mature skeleton, the tendon-bone enthesis is an interfacial zone of transitional tissue located between two mechanically dissimilar tissues: compliant, fibrous tendon to rigid, dense mineralized bone. In this review, we focus on emerging areas in enthesis development related to its structure, function, and mechanobiology, as well as highlight established and emerging signaling pathways and physiological processes that influence the formation and adaptation of this important transitional tissue.
February 2022
Schematic of biomaterial design for musculoskeletal regeneration, from HarleyLab.org
NIH NIAMS R01 subcontract with Dr. Brendan Harley at University of Illinois awarded!
We recently received R01 funding from the NIAMS (PI: Brendan Harley at the University of Illinois-Urbana Champaign) to translate spatially-graded biomaterials for improving enthesis regeneration in vivo! This five-year programmatic grant is an extension of an R56 that Dr. Harley received in 2020. We are excited to continue this collaborative work with folks here at Michigan Medicine (including Dr. James Carpenter) and at UIUC (including Dr. Simon Rogers). Also, this is our first multi-uni B1G funding!
November 2021
The organization of the growth plate of long bones (left) resembles that of the tendon-bone interface (right).
NIH NIAMS R01 funded!
Dr. Killian is the PI on a recently awarded R01 titled: FGF signaling during growth and mechanical adaptation of tendon-bone interfaces. This project includes collaborations with Dr. David Ornitz (WUSTL) and Drs. Ken Kozloff, Sue Brooks, and Kurt Hankenson (University of Michigan).
August 2021
Congratulations, Dr. Ganji!
Elahe Ganji successfully defended her PhD work on Growth and mechanobiology of the Achilles enthesis in mice. Read more here
July 2021
Congratulations, Dr. Leek!
Connor Leek successfully defended his PhD work on The Role of Fibroblast Growth Factor Signaling During Superstructure Development and in Muscle-Bone Crosstalk. Read more here
June 2021
Elahe awarded the Beckman Postdoctoral Fellowship!
PhD student, Elahe Ganji, was awarded the Beckman Postdoctoral Fellowship, which will support 3 years of postdoctoral training at the University of Illinois with Drs. Mariana Kersh and Kate Clancy.
March 2021
Welcome, LeeAnn Flowers!
LeeAnn is a PhD student in Molecular and Integrative Physiology and joined the Killian lab this year for her doctoral work.
March 2021
Congratulations to Iman Bhattacharya!
MS student, Iman Bhattacharya, successfully defended his MS thesis.
November 2020
Congratulations to Ryan Locke, PhD!
Congratulations to Ryan Locke on successfully defending your dissertation work!
Aug 2020
Review in TMIR published!
PhD student, Connor Leek, and undergraduate students, Jaclyn Soulas and Anna Lia Sullivan, each contributed equally to a recent review entitled: Using Tools in Mechanobiology to Repair Tendons, which was published in a special issue (Cell Behavior Manipulation) in the new open-access journal, Current Tissue Microenvironment Reports.
March 2020
Elahe Ganji awarded the University Doctoral Fellowship
Congratulations to Elahe Ganji, a fourth year PhD student in Mechanical Engineering (University of Delaware) on being selected for the University Doctoral Fellowship Award from the University of Delaware! This award will support Elahe for her doctoral research over the next academic year and is a competitive award. Elahe was one of two students nominated from her home department.
March 2020
Professor Killian receives the prestigious NSF CAREER Award
In this CAREER project, Professor Killian will use an in vivo optogenetic platform to measure structural, mechanical, and molecular changes induced by remodeling and damage of the tendon attachment that are driven by frequency-, magnitude-, and duration-dependent changes in muscle loading, both during postnatal growth and in the mature and aging attachment.
March 2020
Killian Lab at #ORS2020
The Killian Lab had a record attendance at this year's Orthopaedic Research Society Annual meeting in Phoenix, where three undergraduate and three graduate students presented their orthopaedic research.
February 2020
