Biology subjects

Miclau, T.

Publications and source records attributed to Miclau, T..

4 recordsLinked to original sources

bioRxiv2026

Age-related Delays in Osteochondral Remodeling of Fracture Healing Illustrated by Mass Spectrometry Imaging

Age-related delays in fracture healing are prevalent and contribute to morbidity and mortality in elderly populations. Clinical and preclinical studies demonstrate that aging is associated with slower and less complete fracture repair characterized by delayed cartilage and bone formation, impaired matrix resorption, and an increased risk of delayed union or non-union. Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI MSI) enables spatially resolved, in situ molecular analysis of proteins directly from murine fracture tissues. We applied collagenase type III (MMP-13) mediated proteolytic digestion to formalin-fixed, paraffin-embedded (FFPE) tibia fracture callus sections harvested 10 days post-tibial fracture from young (3-month-old) and aged (18-month-old) mice to perform spatially resolved proteomic profiling. Spatial MS Imaging revealed pronounced age-dependent differences in extracellular matrix protein composition and remodeling within the fracture callus. We identified upregulation of canonical bone and matrix proteins, including Col1a1 and Col1a2 specifically in the young fracture callus demonstrating advancement into harden callus formation. Conversely, Col2a1 and other soft callus proteins were only seen in the aged callus tissues. Further, protein indicators of tissue state, such as fibronectin (upregulated) and calreticulin (downregulated) were selectively regulated aged tissues, demonstrating a failure for aged tissues to fully progress into harden calluses. Spatial proteomic patterns demonstrated a marked delay in progression from cartilaginous to osseous callus in aged mice, consistent with impaired matrix remodeling during fracture repair. Together, these findings establish spatial MS Imaging based proteomics as a powerful approach to elucidate age-related alterations in fracture healing and to identify molecular regulators of impaired skeletal regeneration. Lay SummaryUsing spatially-resolved proteomics via mass spectrometry imaging on fracture callus tissues from young and aged mice, we observed delayed healing in aged animals based on the composition of the extracellular matrices. Higher levels of bone specific collagens were detected in young animals, whereas cartilage specific collagens were detected in aged animals at higher levels. Further, detection of novel, non-canonical callus proteins revealed critical transitional steps that are delayed in aged-callus tissues, and these may also contribute to the delayed healing aged animals.

biochemistry↗

bioRxiv2021

Localized delivery of β-NGF via injectable microrods accelerates endochondral fracture repair

Currently, there are no biological approaches to accelerate bone fracture repair. Osteobiologics that promote endochondral ossification are an exciting alternative to surgically implanted bone grafts, however, the translation of osteobiologics remains elusive because of the need for localized and sustained delivery that is both safe and effective. In this regard, an injectable system composed of hydrogel-based microparticles designed to release osteobiologics in a controlled and localized manner is ideal in the context of bone fracture repair. Here, we describe poly (ethylene glycol) dimethacrylate (PEGDMA)-based microparticles, in the form of microrods, engineered to be loaded with beta nerve growth factor ({beta}-NGF) for use in a murine tibial fracture model. In-vitro studies demonstrated that protein-loading efficiency is readily altered by varying PEGDMA macromer concentration and that {beta}-NGF loaded onto PEGDMA microrods exhibited sustained release over a period of 7 days. In-vitro bioactivity of {beta}-NGF was confirmed using a tyrosine receptor kinase A (Trk-A) expressing cell line, TF-1. Moreover, TF-1 cell proliferation significantly increased when incubated with {beta}-NGF loaded PEGDMA microrods versus {beta}-NGF in media. In-vivo studies show that PEGDMA microrods injected into the fracture calluses of mice remained in the callus for over 7 days. Importantly, a single injection of {beta}-NGF-loaded PEGDMA microrods resulted in significantly improved fracture healing as indicated by significant increases in bone volume, trabecular connective density, and bone mineral density and a significant decrease in cartilage despite a remarkably lower dose ([~]111 fold) than the {beta}-NGF in media. In conclusion, we demonstrate a novel and translational method of delivering {beta}-NGF via injectable PEGDMA microrods to improve bone fracture repair.

bioengineering↗

bioRxiv2020

β-catenin Signaling Regulates Cell Fate Decisions at the Transition Zone of the Chondro-Osseous Junction During Fracture Healing

Chondrocytes within the fracture callus transform into osteoblasts during bone regeneration, but the molecular mechanisms regulating this process are unknown. Wnt ligands are expressed within the fracture callus, and hypertrophic chondrocytes undergoing transformation to osteoblasts exhibit nuclear localization of {beta}-catenin, indicating active Wnt signaling in these cells. Here, we show that conditional knock out (cKO) of {beta}-catenin in chondrocytes inhibits the transformation of chondrocytes to osteoblasts, while stabilization of {beta}-catenin in chondrocytes accelerates this process. After cKO, chondrocyte-derived cells were located in the bone marrow cavity and upon re-fracture formed cartilage. Lineage tracing in wild type mice revealed that in addition to osteoblasts, chondrocytes give rise to stem cells that contribute to repair of subsequent fractures. These data indicate that Wnt signaling directs cell fate choices of chondrocytes during fracture healing by stimulating transformation of chondrocytes to osteoblasts, and provide a framework for developing Wnt-therapies to stimulate repair.

developmental biology↗

bioRxiv2019

Age-related changes to macrophages are detrimental to fracture healing

The elderly population suffers from higher rates of complications during fracture healing that result in increased morbidity and mortality. Inflammatory dysregulation is associated with increased age and is a contributing factor to the myriad of age-related diseases. Therefore, we investigated age-related changes to an important cellular regulator of inflammation, the macrophage, and the impact on fracture healing outcomes. We demonstrated that old mice (24 months) have delayed fracture healing with significantly less bone and more cartilage compared to young mice (3 months). The quantity of infiltrating macrophages into the fracture callus was similar in old and young mice. However, RNA-seq analysis demonstrated distinct differences in the transcriptomes of macrophages derived from the fracture callus of old and young mice, with an upregulation of M1/pro-inflammatory genes in macrophages from old mice as well as dysregulation of other immune-related genes. Preventing infiltration of the fracture site by macrophages in old mice improved healing outcomes, with significantly more bone in the calluses of treated mice compared to age-matched controls. After preventing infiltration by macrophages, the macrophages within the fracture callus were collected and examined via RNA-seq analysis, and their transcriptome resembled macrophages from young calluses. Taken together, infiltrating macrophages from old mice demonstrate detrimental age-related changes, and depleting infiltrating macrophages can improve fracture healing in old mice.

immunology↗