Pores are vital for functioning of avascular tissues. Laser-induced pores play an important role in the process of cartilage regeneration. The aim of any treatment for osteoarthritis is to repair hyaline-type cartilage. The aims of this study are to answer two questions: (1) How do laser-assisted pores affect the cartilaginous cells to synthesize hyaline cartilage (HC)? and (2) How can the size distribution of pores arising in the course of laser radiation be controlled? We have shown that in cartilage, the pores arise predominately near chondrocytes, which promote nutrition of cells and signal molecular transfer that activates regeneration of cartilage. In vivo laser treatment of damaged cartilage of miniature pig joints provides cellular transformation and formation of HC. We propose a simple model of pore formation in biopolymers that paves the way for going beyond the trial-and-error approach when choosing an optimal laser treatment regime. Our findings support the approach toward laser healing of osteoarthritis.

Laser modelling of costal cartilage implants (grafts) of a given shape is a new promising technology in laser medicine. When the final shape of an implant is formed with a surgical scalpel, residual stresses lead to the distortion of the implant and decrease its survivability after the surgery. Laser-induced relaxation of the interstitial residual stresses without disturbing tissue functionality opens new possibilities for a wide range of implantology problems. This article is devoted to a new laser method of treatment of laryngeal stenosis using laser-modelled costal cartilage grafts for the closure of laryngotracheal defect in patients. The paper discusses the physical ground of the applied laser modes when the stresses at the graft borders are minimal which provides positive impact on the survival of the laser-modelled cartilage. The results of the first clinical application of this method are presented.

Lasers offer new possibilities in the treatment of such widespread diseases as osteoarthritis, with both direct and indirect effects on cell metabolism. Cyclic hydrostatic pressure is one of the main natural stimuli of cartilage chondrocytes. The present work shows that hydrostatic stimulation with magnitudes of up to 20 MPa can be realized locally through infrared impact on the neighboring media of chondrocytes. We compare indirect (thermomechanical, λ = 1560 nm) and direct (photo-modulation, λ 1 = 1560 nm, λ 2 = 670 nm) laser effects on the synthetic activity of chondrocytes in cultures within a 1 min exposure time limit, to study separately the photo-modulation and thermomechanical components of laser impact. The chondrocyte activity was monitored by immunohistochemical analysis in normoxic and hypoxic conditions. Collagen II and proteoglycan accumulation increased significantly (up to 70%) after a pulsed thermomechanical laser impact. Thermomechanical laser irradiation showed the more pronounced stimulation in both normoxic and hypoxic conditions, while the effect of photo-modulation was inhibited by oxygen concentration increase. Theoretical calculations of the laser-induced temperature and stress fields show that the spreading of the stress field with a maximum at 19.2 MPa is approximately three times greater than that of appreciable (>1 °C) heating. Thus, thermomechanical infrared stimulation of chondrocytes can be a perspective method for the restoration of hyaline-type cartilage.

This paper presents a recently developed variant of phase-resolved Optical Coherence Elastography (OCE) enabling non-contact visualization of transient local strains of various origins in biological tissues and other materials. In this work, we demonstrate the possibilities of this new technique for studying dynamics of osmotically-induced strains in cartilaginous tissue impregnated with optical clearing agents (OCA). For poroelastic water-containing biological tissues, application of non-isotonic OCAs, various contrast additives, as well as drug solutions administration, may excite transient spatially-inhomogeneous strain fields of high magnitude in the tissue bulk, initiating mechanical and structural alterations. The range of the strain reliably observed by OCE varied from ±10⁻³ to ±0.4 for diluted and pure glycerol, correspondingly. The OCE-technique used made it possible to reveal previously inaccessible details of the complex spatio-temporal evolution of alternating-sign osmotic strains at the initial stages of agent diffusion. Qualitatively different effects produced by particular hydrophilic OCAs, such as glycerol and iohexol, are discussed, as well as concentration-dependent differences. Overall, the work demonstrates the unique abilities of the new OCE-modality in providing a deeper insight in real-time kinetics of osmotically-induced strains relevant to a broad range of biomedical applications.