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Introduction: Osteogenesis imperfecta (OI) is a rare genetic bone disorder, mainly caused by autosomal dominant mutations of the COL1A1 or COL1A2 genes that encode the alpha chains of type 1 collagen. In severe forms and in nonambulatory patients, for whom physical exercise is difficult, exposing the bone to mechanical stimuli by promoting movement, especially with physiotherapy and mobility aids, is an essential part of clinical practice. However, the effects of mechanical stimulation at the cellular level remain unknown for this disease., Hypothesis: The study hypothesis was that human mesenchymal stem cells (hMSCs) from patients with OI were as sensitive to mechanical stimulation as those from healthy patients, validating the current clinical practice., Materials and Methods: hMSCs were harvested from 3 healthy control subjects and 3 patients with OI during an elective osteotomy of a long bone of the lower limb. The healthy and OI hMSCs were then exposed to mechanical stimuli, such as intermittent shear stress of 0, 0.7, 1.5, and 3 Pascal (Pa) at a frequency of 2.8 Hertz (Hz) for 30 min using a commercial ibidi system. The immediate early gene expression of themechanosensitive prostaglandin-endoperoxide synthase 2 (PTGS2) was examined 1 h after stimulation to determine the best level of mechanical stimulation. The expression of 7 other mechanosensitive genes was also examined for this level of mechanical stimulation after applying intermittent shear stress at 1.5 Pa., Results: In all hMSCs, mechanical stimulation induced PTGS2 gene overexpression with a maximum after exposure to intermittent shear stress of 1.5 Pa and without significant differences between OI and healthy donors. Except for fibroblast growth factor 2, gene expression in OI donors was found to be significantly different from that in hMSCs not exposed to shear stress. Moreover, the relative expression associated with mechanical stimulation was not significantly different between healthy and OI donors for most other genes., Discussion: This is the first study to demonstrate that hMSCs from patients with OI are as sensitive to mechanical shear stress as those from healthy donors. The mechanical stress that resulted in the greatest change in the expression of PTGS2 in patients with OI was similar to that previously reported in the literature for healthy subjects. These findings are an important step toward further fundamental research aimed at confirming the effects of mechanical stress at the cellular level over the long term and, more importantly, toward developing clinical protocols for delivering mechanical stimuli to these patients., Level of Evidence: III; comparative case-control study., Competing Interests: Declaration of competing interest None., (Copyright © 2024. Published by Elsevier Masson SAS.)

Management of the upper limb in children with cerebral palsy is often complex and must be carried out by a team experienced in this field. Several clinical parameters must be taken into consideration, such as higher functions, visual problems, overall upper limb function, motor control, sensitivity, presence of hemineglect or synkinesis, limb position at rest and during walking. And last but not least, a complete analysis of the upper limb is required. It is only after this exhaustive assessment - which often includes occupational therapy, physiotherapy and in some cases, video and electromyography evaluations - that a treatment indication can be discussed with the patient's family. Other than baseline treatment consisting of rehabilitation, occupational therapy and bracing, botulinum toxin injections could be an option, targeting specific muscle groups. Surgical treatments, which are often indicated in severe forms with contractures, are proposed after the patient's case is presented at a multidisciplinary meeting. These include selective neurotomy, muscle-tendon release, transfer or lengthening, and procedures on bone and joints (osteotomy, arthrodesis). LEVEL OF EVIDENCE: Expert opinion., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)