| Osteoarthritis(OA)is the most common degenerative joint disability disease.OA is mainly characterized by the irreversible and progressive degradation of articular cartilage.Among the population over 60 years old,9.6%of men and 18.0%of women have OA symptoms,which made OA become a global epidemic disease.Current treatment options for OA,only alleviate the symptoms without attenuating the progression of OA.Therefore,to develop biomaterials or drugs or methods to protect and even promote the cartilage regeneration is a critical and central pursuit of OA research field.Researches have shown that the decreased lubrication performance of articular cartilage directly affects the metabolic behavior of chondrocytes(even causes chondrocyte apoptosis),that is,the metabolic ability of chondrocytes to synthesize matrix decreases while the metabolic ability to degrade matrix increases,thereby inducing OA.With the loss of cartilage matrix,the lubrication performance of articular cartilage further decreases,resulting in further imbalance between chondrocyte anabolism and catabolism and synovial tissue inflammation,accelerating the loss of cartilage matrix and the deterioration of OA.Therefore,the decreased cartilage lubrication performance determines the onset of OA and plays a promoting role in the pathological development of OA.Based on the role of lubrication performance in OA,the following comprehensive studies were conducted in this study after the idea of cartilage regeneration by improving lubrication property was proposed:Firstly,based on the mechanism of the excellent lubricating properties of articular cartilage,that is,synovial molecules cooperate with each other to form lubricating layer on the surface of cartilage,the biomimetic joint lubricant HPA,which is rich in sulfonic acid groups,and HPM,which is rich in phosphate choline groups,were designed and synthesized.~1H-Nuclear magnetic resonance,fourier transform infrared spectrometer,gel permeation chromatography,ultraviolet spectroscopy,atomic force microscopy,zeta potential and rheology were used to study the structure,anti-enzyme degradation of HPA and HPM.Besides,the standard pellet constructed by the chondrocytes and human mesenchymal stem cells(h MSCs)were used to estimate the tissue biocompatibility and chondrogenic differentiation of HPA and HPM.The results showed that HPA and HPM,with brush-like structure and excellent anti-degradation properties,were successfully constructed,the graft efficiency of HPA and HPM were25%and 31.2%,so that the molecular weight of HPA and HPM were 1.4×10~7 Da and9.0×10~6 Da,respectively.Furthermore,HPA and HPM showed good histocompatibility of cells and tissues,but did not show the performance of promoting the chondrogenic differentiation of h MSCs.Secondly,the properties of the constructed biomimetic lubricants HPA and HPM assembly on the outer surface of articular cartilage were studied qualitatively and quantitatively in vitro.The binding ability of HPA and HPM to the major matrix proteins of cartilage,namely type II collagen and fibronectin,was studied by quartz crystal microbalance,isothermal calorimetry,surface plasma resonance and molecular dynamics simulation.Cy5-labeled HPA,HPM and confocal microscopy were used to investigate whether HPA and HPM could be assembled and then bonded to the surface of articular cartilage under the interference of proteins in synovial fluid in vitro.Compared with HA,The results showed that HPA and HPM showed higher affinity to the main proteins in cartilage matrix,and this strong affinity mainly comes from the ionic and hydrophobic interactions between HPA and HPM and type II collagen and fibronectin,and was sufficient to support the selective assembly and binding of HPA and HPM to cartilage matrix proteins under the interference of proteins in synovial fluid,and thus a stable lubricating layer was formed on the outer surface of articular cartilage.These results lay a foundation for the subsequent research on the lubrication properties of HPA and HPM.Then,based on the previous results,the lubrication properties of HPA and HPM were studied at the macroscopic and molecular level.Macroscopically,the lubrication properties and lubrication mechanism of human OA model articular cartilage under the action of HPA and HPM were studied by using the UMT-2 under the reciprocating motion mode(continuous change of contact area);and also,were studied by using rheometer in rotation mode(the contact area was relatively constant).Molecularly,based on the high affinity between HPA or HPM and type II collagen,the surface morphology changes before and after type II collagen interacted with HPA or HPM were studied by atomic force microscope.Cartilage surface model of type II collagen and HPA or HPM were constructed layer by layer on the molecularly smooth sheets of mica,and then the nano-lubrication behaviors of HPA and HPM were studied at the molecular level using the specific surface force balance.On this basis,preliminary exploration was made for the development of bionic joint lubricants with better properties.The results showed that both HPA and HPM can effectively reduce the friction coefficient of human OA model articular cartilage under these two motion modes.Especially when HPA and HPM are used in combination,the friction coefficient of human OA model articular cartilage is the lowest and can be restored to the normal level of articular cartilage.At the molecular level,HPA and HPM showed good hydration lubrication,so that effectively reduce the friction coefficient of the surface.So far,it has been proved that HPA and HPM have lubricating properties at both macro and micro levels,thus laying a foundation for the subsequent study of promoting cartilage regeneration to heal early OA.Finally,in view of the high affinity with cartilage matrix proteins and the lubricating properties of HPA and HPM,the therapeutic effect of HPA and HPM on early OA was further studied,so as to explore the relationship between the restoration of cartilage lubrication and cartilage regeneration and then treatment of OA.The bio-safety of the articular-injection of the HPA and HPM was firstly estimated by normal rats from joint tissue to immune-related tissue.The early OA model rats were used to estimate the distribution of HPA and HPM after articular-injected.The chondroprotection effects and the promotion in cartilage regeneration of HPA and HPM were studied from histological staining to immunohistochemical staining in early OA model rats.The results showed that the intra-articular injection of HPA and HPM did not affect the structure and morphology of normal cartilage at first,and did not stimulate the synovium to produce obvious inflammatory response.HPA and HPM injected into the OA joint were concentrated in the cartilage and only a small amount of them were present in the synovial fluid.The duration of HPA and HPM in the OA joint of rats was up to 31 days,thus avoiding frequent intra-articular injection of HPA an HPM.HPA and HPM,especially used in combination,were injected into the knee joint of early OA model rats.After 8 weeks,the results in vivo showed the degradation of articular cartilage was delayed significantly,which suggested the conditions of OA were alleviated.In addition,the secretion and accumulation of the cartilage matrix were promoted due to the reconstruction of cartilage lubrication when HPA and HPM anchored at the outer surface of cartilage.These results suggested that the cartilage regeneration in OA may reach by restoring the lubrication properties of cartilage in early stage of OA,which,in turn,realized the treatment or heal of early OA. |
PDF Full Text Request