Objective: Hyaline cartilage degenerative pathologies induce morphologic and biomechanical changes resulting in cartilage tissue damage. In pursuit of therapeutic options, electrical and mechanical stimulation have been proposed for improving tissue engineering approaches for cartilage repair. The purpose of this review was to highlight the effect of electrical stimulation and mechanical stimuli in chondrocyte behavior. Design: Different information sources and the MEDLINE database were systematically revised to summarize the different contributions for the past 40 years. Results: It has been shown that electric stimulation may increase cell proliferation and stimulate the synthesis of molecules associated with the extracellular matrix of the articular cartilage, such as collagen type II, aggrecan and glycosaminoglycans, while mechanical loads trigger anabolic and catabolic responses in chondrocytes. Conclusion: The biophysical stimuli can increase cell proliferation and stimulate molecules associated with hyaline cartilage extracellular matrix maintenance.

Cell membrane is a lipid bilayer that allows the flow of ions through their ionic pumping proteins. The ionic flow can be stimulated with external stimuli to activate specific signaling pathways intracellularly. Although studies have applied electric and magnetic stimuli to modify the cell function, the parameters to stimulate the cell membrane are unknown. Accordingly, a computational model to simulate the effect of electric and magnetic fields on the cell membrane was developed. Cells were stimulated with electric fields from 45 × 10³ V/m to 12.6 × 10⁵ V/m and magnetic fields of 2 mT, at frequencies of 60 kHz, 10 MHz, and 1 GHz. Results showed that the electric fields applied to the cell membrane tend to increase according to the frequency used, while magnetic fields do not have any effect on it. It was observed that electric fields generate a high voltage concentrator in the cell membrane of ellipsoidal cells when a frequency window from 1 kHz to 1 GHz was applied. These findings demonstrate that depending on the intensity of the field and frequency, it was possible to stimulate different cell membrane zones. This model is a promising tool to establish the adequate parameters to stimulate cells, and accurately predict if the stimulation modifies the cell membrane potential.

This paper aims to construct a general framework of coupling tumor–bone remodeling processes in order to produce plausible outcomes of the effects of tumors on the number of osteoclasts, osteoblasts, and the frequency of the bone turnover cycle. In this document, Komarova’s model has been extended to include the effect of tumors on the bone remodeling processes. Thus, we explored three alternatives for coupling tumor presence into Komarova’s model: first, using a “damage” parameter that depends on the tumor cell concentration. A second model follows the original structure of Komarova, including the tumor presence in those equations powered up to a new parameter, called the paracrine effect of the tumor on osteoclasts and osteoblasts; the last model is replicated from Ayati and collaborators in which the impact of the tumor is included into the paracrine parameters. Through the models, we studied their stability and considered some examples that can reproduce the tumor effects seen in clinic and experimentally. Therefore, this paper has three parts: the exposition of the three models, the results and discussion (where we explore some aspects and examples of the solution of the models), and the conclusion.