Biology subjects

Zlotnick, H. M.

Publications and source records attributed to Zlotnick, H. M..

5 recordsLinked to original sources

bioRxiv2025

Synovial fibroblasts support vascular function in an acute injury-on-a-chip model

Most patients who sustain an acute joint injury develop degenerative joint disease, or osteoarthritis (OA). Animal models have informed the design of OA therapeutics; however, no disease-modifying therapy has successfully translated to human patients. Thus, there is a strong motivation to develop humanized in vitro platforms to fill a critical gap in knowledge of disease progression post-injury. Here, we develop an acute injury-on-a-chip model of the synovium, a vascularized, joint-lining tissue that has been implicated in OA progression and as a key driver of joint disease. We apply this chip-based system to investigate crosstalk between endothelial cells, lining an engineered vessel, and synovial fibroblasts, embedded within an extracellular matrix hydrogel. Our data indicate that synovial fibroblasts, rather than initiating disease, attempt to support and maintain vascular function in the presence of acute inflammation (i.e., interleukin-1{beta}). Such knowledge may provide new targets for OA therapeutics, preventing the progression from joint injury to disease in patients. TeaserIn the presence of inflammation, a hallmark of acute injury, synovial fibroblasts work to maintain vascular health.

bioengineering↗

bioRxiv2024

Digital Light Processing 3D Printing enables High Throughput Fabrication of Human Engineered Heart Tissues for Disease Modeling

3D in vitro engineered heart tissue (EHT) models recapitulate aspects of native cardiac physiology but are often limited by scalability, cost, and reproducibility. Here, we report a simple, one-step method for rapid ([~]minutes) fabrication of molds using digital light processing (DLP)-based 3D printing that support the formation of EHTs by human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) with high reproducibility (>95% efficiency) and varied designs (e.g., length, aspect ratio). Compared to 2D iPSC-CMs, 3D EHTs display enhanced maturity, including increased expression of {beta}-oxidation genes, higher concentrations of sarcomeric myosins, improved sarcomere density and alignment, and enrichment of cardiac pathways (e.g., upregulation of sodium channels, action potentials, contraction). The technology is applied to model pathological cardiac hypertrophy in vitro, using either (i) acute adrenergic agonism or (ii) chronic culture within stiff hydrogel molds. Treated EHTs exhibit increased levels of pathology-associated gene expression and activation of signaling cascades involved in pathological remodeling compared to untreated controls or treated 2D iPSC-CMs. Thus, our method results in robust yet simpler, cheaper, and faster EHTs to study cardiac disease.

bioengineering↗

bioRxiv2022

Anti-Inflammatory Tension-Activated Repair Patches Improve Repair After Intervertebral Disc Herniation

Conventional treatment for intervertebral disc herniation alleviates pain but does not repair the annulus fibrosus (AF), resulting in a high incidence of recurrent herniation and persistent disfunction. The lack of repair and the acute inflammation that arise after injury further compromises the disc and can result in disc-wide degeneration in the long term. To address this clinical need, we developed tension-activated repair patches (TARPs) for annular repair and the local delivery of bioactive anti-inflammatory factors. TARPs transmit physiologic strains to mechanically-activated microcapsules (MAMCs) embedded within, which activate and release encapsulated biomolecules in response to physiologic loading. Here, we demonstrate that the TARP design modulates implant biomechanical properties and regulates MAMC mechano-activation. Next, the FDA-approved anti-inflammatory molecule, interleukin 1 receptor antagonist, Anakinra, was loaded in TARPs and the effects of TARP-mediated annular repair and Anakinra delivery was evaluated in a model of annular injury in the goat cervical spine. TARPs showed robust integration with the native tissue and provided structural reinforcement at the injury site that prevented disc-wide aberrant remodeling resulting from AF detensioning. The delivery of Anakinra via TARP implantation improved the retention of disc biochemical composition through increased matrix deposition and retention at the site of annular injury. Anakinra delivery additionally attenuated the inflammatory response associated by scaffold implantation, decreasing osteolysis in adjacent vertebrae and preserving disc cellularity and matrix organization throughout the AF. These results demonstrate the translational and therapeutic potential of this novel TARP system for the treatment of intervertebral disc herniations. One Sentence SummaryTension-activated repair patches delivering bioactive anti-inflammatory factors improve healing in an in vivo goat cervical disc injury model.

bioengineering↗

bioRxiv2021

Fabrication and delivery of mechano-activedmicrocapsules containing osteogenic factors in alarge animal model of osteochondral injury

Chondral and osteochondral repair strategies are limited by adverse bony changes that occur after injury. Bone resorption can cause entire scaffolds, engineered tissues, or even endogenous repair tissues to subside below the cartilage surface. To address this translational issue, we fabricated poly(D,L-lactide-co-glycolide) (PLGA) microcapsules containing the pro-osteogenic agents triiodothyronine and {beta}-glycerophosphate, and delivered these microcapsules in a large animal model of osteochondral injury to preserve bone structure. We demonstrate that developed microcapsules ruptured in vitro under increasing mechanical loads, and readily sink within a liquid solution, allowing for gravity-based positioning onto the osteochondral surface. In a large animal, these mechano-active microcapsules (MAMCs) were assessed through two different delivery strategies. Intra-articular injection of control MAMCs enabled fluorescent quantification of MAMC rupture and cargo release in a synovial joint setting over time in vivo. This joint-wide injection also confirmed that the MAMCs do not elicit an inflammatory response. In the contralateral hindlimbs, chondral defects were created, MAMCs were locally administered, and nanofracture (Nfx), a clinically utilized method to promote cartilage repair, was performed. The NFx holes enabled marrow-derived stromal cells to enter the defect area and served as repeatable bone injury sites to monitor over time. Animals were evaluated 1 and 2 weeks after injection and surgery. Analysis of injected MAMCs showed that bioactive cargo was released in a controlled fashion over 2 weeks. A bone fluorochrome label injected at the time of surgery displayed maintenance of mineral labeling in the therapeutic group, but resorption in both control groups. Alkaline phosphatase (AP) staining at the osteochondral interface revealed higher AP activity in defects treated with therapeutic MAMCs. Overall, this study establishes a new micro-fluidically generated delivery platform that releases therapeutic factors in an articulating joint, and reduces this to practice in the delivery of therapeutics that preserve bone structure after osteochondral injury.

bioengineering↗

bioRxiv2021

Marked differences in local bone remodeling in response to different marrow stimulation techniques in a large animal

Marrow stimulation, including subchondral drilling and microfracture, is the most commonly performed cartilage repair strategy, whereby the subchondral bone plate is perforated to release marrow-derived cells into a cartilage defect to initiate repair. Novel scaffolds and therapeutics are being designed to enhance and extend the positive short-term outcomes of this marrow stimulation. However, the translation of these newer treatments is hindered by bony abnormalities, including bone resorption, intralesional osteophytes, and bone cysts, that can arise after marrow stimulation. In this study, three different marrow stimulation approaches -- microfracture, subchondral drilling, and needle-puncture - were evaluated in a translationally relevant large animal model, the Yucatan minipig. The objective of this study was to determine which method of marrow access (malleted awl, drilled Kirschner wire, or spring-loaded needle) best preserved the underlying subchondral bone. Fluorochrome labels were injected at the time of surgery and 2 weeks post-surgery to capture bone remodeling over the first 4 weeks. Comprehensive outcome measures included cartilage indentation testing, histological grading, microcomputed tomography, and fluorochrome imaging. Our findings indicated that needle-puncture devices best preserved the underlying subchondral bone relative to other marrow access approaches. This may relate to the degree of bony compaction occurring with marrow access, as the Kirschner wire approach, which consolidated bone most, induced the most significant bone damage with marrow stimulation. This study provides basic science evidence in support of updated marrow stimulation techniques for preclinical and clinical practice.

bioengineering↗