Alteration of Type I collagen microstructure induced by estrogen depletion can be prevented with drug treatment

Atomic force microscopy imaging for nanoscale and microscale assessments of extracellular matrix in intervertebral disc and degeneration

Degeneration of the intervertebral disc (IVD) is a condition that is often associated with debilitating back pain. There are no disease-modifying treatments available to halt the progression of this ubiquitous disorder. This is partly due to a lack of understanding of extracellular matrix (ECM) changes that occur at the micro- and nanometer size scales as the disease progresses. Over the past decade, atomic force microscopy (AFM) has been utilized as a tool to investigate the impact of disease on nanoscale structure of ECM in bone, skin, tendon, and dentin. We have expanded this methodology to include the IVD and report the first quantitative analysis of ECM structure at submicron size scales in a murine model for progressive IVD degeneration. Collagen D-spacing, a metric of nanoscale structure at the fibril level, was observed as a distribution of values with an overall average value of 62.5 ± 2.5 nm. In degenerative discs, the fibril D-spacing distribution shifted towards higher values in both the annulus fibrosus and nucleus pulposus (NP) (P < .05). A novel microstructural feature, collagen toroids, defined by a topographical pit enclosed by fibril-forming matrix was observed in the NP. With degeneration, these microstructures became more numerous and the morphology was altered from circular (aspect ratio 1.0 ± 0.1) to oval (aspect ratio 1.5 ± 0.4), P < .005. These analyses provide ECM structural details of the IVD at size scales that have historically been missing in studies of disc degeneration. Knowledge gained from these insights may aid the development of novel disease-modifying therapeutics.

Topical Deferoxamine Alleviates Skin Injury and Normalizes Atomic Force Microscopy Patterns Following Radiation in a Murine Breast Reconstruction Model

BACKGROUND

Breast cancer is most commonly managed with a combination of tumor ablation, radiation, and/or chemotherapy. Despite the oncologic benefit of these treatments, the detrimental effect of radiation on surrounding tissue challenges the attainment of ideal breast reconstruction outcomes. The purpose of this study was to determine the ability of topical deferoxamine (DFO) to reduce cutaneous ulceration and collagen disorganization following radiotherapy in a murine model of expander-based breast reconstruction.

METHODS

Female Sprague-Dawley rats (n = 15) were divided into 3 groups: control (expander), XRT (expander + radiation), and DFO (expander + radiation + deferoxamine [DFO]). Expanders were placed in a submusculocutaneous plane in the right upper back and ultimately filled to 15 mL. Radiation was administered via a fractionated dose of 28 Gy. Deferoxamine was delivered topically for 10 days following radiation. After a 20-day recovery period, skin ulceration and dermal type I collagen organization were analyzed.

RESULTS

Compared with control, the XRT group demonstrated a significant increase in skin ulceration (3.7% vs 43.3%, P = 0.00) and collagen fibril disorganization (26.3% vs 81.8%, P = 0.00). Compared with the XRT group, treatment with topical DFO resulted in a significant reduction in ulceration (43.3% vs 7.0%, P = 0.00) and fibril disorganization (81.8% vs 15.3%, P = 0.00). There were no statistical differences between the control and DFO groups in skin ulceration or collagen disorganization.

CONCLUSIONS

This study suggests topical DFO is capable of reducing skin ulceration and type I collagen fibril disorganization following radiotherapy. This novel application of DFO has potential to enhance expander-based breast reconstruction outcomes and improve quality of life for women suffering the devastating effects of breast cancer.

Distributions: The Importance of the Chemist's Molecular View for Biological Materials

Characterization of materials with biological applications and assessment of physiological effects of therapeutic interventions are critical for translating research to the clinic and preventing adverse reactions. Analytical techniques typically used to characterize targeted nanomaterials and tissues rely on bulk measurement. Therefore, the resulting data represent an average structure of the sample, masking stochastic (randomly generated) distributions that are commonly present. In this Perspective, we examine almost 20 years of work our group has done in different fields to characterize and control distributions. We discuss the analytical techniques and statistical methods we use and illustrate how we leverage them in tandem with other bulk techniques. We also discuss the challenges and time investment associated with taking such a detailed view of distributions as well as the risks of not fully appreciating the extent of heterogeneity present in many systems. Through three case studies showcasing our research on conjugated polymers for drug delivery, collagen in bone, and endogenous protein nanoparticles, we discuss how identification and characterization of distributions, i.e., a molecular view of the system, was critical for understanding the observed biological effects. In all three cases, data would have been misinterpreted and insights missed if we had only relied upon spatially averaged data. Finally, we discuss how new techniques are starting to bridge the gap between bulk and molecular level analysis, bringing more opportunity and capacity to the research community to address the challenges of distributions and their roles in biology, chemistry, and the translation of science and engineering to societal challenges.

The Relationship of Collagen Structural and Compositional Heterogeneity to Tissue Mechanical Properties: A Chemical Perspective

Collagen is the primary protein component in mammalian connective tissues. Over the last 20 years, evidence has mounted that collagen matrices exhibit substantial heterogeneity in their hierarchical structures and that this heterogeneity plays important roles in both structure and function. Herein, an overview of studies addressing the nanoscale compositional and structural heterogeneity is provided and connected to work exploring the mechanical implications for a number of tissues.

Estrogen depletion and drug treatment alter the microstructure of type I collagen in bone

The impact of estrogen depletion and drug treatment on type I collagen fibril nanomorphology and collagen fibril packing (microstructure) was evaluated by atomic force microscopy (AFM) using an ovariectomized (OVX) rabbit model of estrogen deficiency induced bone loss. Nine month-old New Zealand white female rabbits were treated as follows: sham-operated (Sham; n = 11), OVX + vehicle (OVX + Veh; n = 12), OVX + alendronate (ALN, 600 μg/kg/wk., s.c.; n = 12), and OVX + cathepsin-K inhibitor L-235 (CatKI, 10 mg/kg, daily, p.o.; n = 13) in prevention mode for 27 weeks. Samples from the cortical femur and trabecular lumbar vertebrae were polished, demineralized, and imaged using AFM. Auto-correlation of image patches was used to generate a vector field for each image that mathematically approximated the collagen fibril alignment. This vector field was used to compute an information-theoretic entropy that was employed as a quantitative fibril alignment parameter (FAP) to allow image-to-image and sample-to-sample comparison. For all samples, no change was observed in the average FAP values; however significant differences in the distribution of FAP values were observed. In particular, OVX + Veh lumbar vertebrae samples contained a tail of lower FAP values representing regions of greater fibril alignment. OVX + ALN treatment resulted in a FAP distribution with a tail indicating greater alignment for cortical femur and less alignment for trabecular lumbar vertebrae. OVX + CatKI treatment gave a distribution of FAP values with a tail indicating less alignment for cortical femur and no change for trabecular lumbar vertebrae. Fibril alignment was also evaluated by considering when a fibril was part of discrete bundles or sheets (classified as parallel) or not (classified as oblique). For this analysis, the percentage of parallel fibrils in cortical femur for the OVX group was 17% lower than the Sham group. OVX + ALN treatment partially prevented the proportion of parallel fibrils from decreasing and OVX + CatKI treatment completely prevented a change. In trabecular lumbar vertebrae, there was no difference in the percentage of parallel fibrils between Sham and any of the other treatment groups.