Ostheoarthritis in cartilage
Clinical applications of multiphoton microscopy
Nonlinear optical microscopy (NLOM) provides many opportunities for minimally invasive investigating tissues without exogenous staining. We try to integrate the process from image interpretion, through image analysis and biophysical model to maximize the information which can be presented to the clinician.
The information acquired may provide insight into diagnosis, improved therapeutics and better understanding of disease progression. Basically any tissue may be examined but we are focusing on three main areas: ostheoarthritis in cartilage, atherosclerosis in heart vessels as well as breast cancer. Nonlinear optical microscopy
Research topics
Ostheoarthritis in cartilage
Cartilage is the tissue which covers articular surfaces in the joints providing a smooth, low friction surface and cushioning for the subchondral bone. It has remarkable mechanical properties in its healthy state, but can, if damaged, lead to painful and disabling diseases like osteoarthritis.
Cartilage consists of hydrated proteoglycan rich gel which is densely reinforced with collagen fibres. Second harmonic generation imaging can be used to image these fibres, providing information on how the structure imparts the mechanical properties on the tissue and what changes occur in the tissue in various disease states.
With the advent of in vivo NLOM it will be possible to image the structure of diseased cartilage which can be used to guide interventional procedures and give the clinician information for making the right choice for management of the patient.
NLOM using SHG can be used to visualize many different structures in cartilage. E.g. the difference in the collagen structure in the superficial and the middle layer of the cartilage can clearly be seen in figure 1 and 2. In the middle layer the collagen fibrils are too small to be resolved in the microscope. We are working with Mueller matrix ellipsometry to image these structures. The chondrocytes gives a moderately strong TPEF signal and can be visualized (fig. 1 and 2). Their size and shape can be quantified and their relationship to the pericondral matrix can be seen.
A large part of our work is aimed at finding quantitative methods for analyzing NLOM images. An example can be seen in figure 4 where the direction of the fibres have been found by a method employing Fourier analysis. We are also working towards the clinic to find areas in clinical practice where NLOM can provide a practical tool to improve the healthcare of people suffering from osteoarthritis and similar diseases.
Figure 1. Surface layer of cartilage. Collagen fibers in magenta (SHG) and chondrocytes in green (TPEF)
Figure 2. Middel layer of cartilage. Collagen fibers in magenta (SHG) and chondrocytes residing in their lacuna seenn in green (TPEF). Photos: Magnus B. LilledahlContact: Magnus Borstad Lilledahl