title: Preformed gelatin microcryogels as injectable cell carriers for enhanced skin wound healing.
abstract: Wound dressings of cell-laden bulk hydrogel or scaffold were mainly applied for enhanced cell engraftment in contrast to free cell injection. However, dressing of cells laden in biomaterials on wound surface might not effectively and timely exert functions on deep or chronic wounds where insufficient blood supply exists. Previously, we developed injectable gelatin microcryogels (GMs) which could load cells for enhanced cell delivery and cell therapy. In this study, biological changes of human adipose-derived stem cells (hASCs) laden in GMs were compared in varied aspects with traditional two dimensional (2D) cell culture, such as cell phenotype markers, stemness genes, differentiation, secretion of growth factors, cell apoptosis and cell memory by FACS, QRT-PCR and ELISA, that demonstrated the priming effects of GMs on upregulation of stemness genes and improved secretion of growth factors of hASCs for potential augmented wound healing. In a full-thickness skin wound model in nude mice, multisite injection and dressing of hASCs-laden GMs could significantly accelerate the healing compared to free cell injection. Bioluminescence imaging and protein analysis indicated improved cell retention and secretion of multiple growth factors. Our study suggests that GMs as primed injectable 3D micro-niches represent a new cell delivery methodology for skin wound healing which could not only benefit on the recovery of wound bed but also play direct effects on wound basal layer for healing enhancement. Injectable GMs as facile multisite cell delivery approach potentially provide new minimally-invasive therapeutic strategy for refractory wounds such as diabetic ulcer or radiative skin wound.
  
  
  CONCLUSIONS
  This work applied a type of elastic micro-scaffold (GMs) to load and prime hMSCs for skin wound healing. Due to the injectability of GMs, the 3D cellular micro-niches could simply realize minimally-invasive and multisite cell delivery approach for accelerating the wound healing process superior to free cell injection. The biological features of MSCs has been thoroughly characterized during 3D culture in GMs (i.e. cell proliferation, characterization of cell surface markers, stemness of MSCs in GMs, differentiation of MSCs in GMs, secretion of MSCs in GMs, induced apoptosis of MSCs in GMs). Multiple methods such as bioluminescent imaging, immunohistochemistry, immunofluorescence, qRT-PCR, ELSA and western blot were used to assess the in vivo results between groups.
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Tsinghua University, Beijing 100084, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Division of Plastic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Center of Excellence in Tissue Engineering, Institute of Basic Medical Sciences and School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Han
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Tsinghua University, Beijing 100084, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Center of Excellence in Tissue Engineering, Institute of Basic Medical Sciences and School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Mao
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Tsinghua University, Beijing 100084, China.
authors.forename: Yaqian
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Plastic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Nanze
authors.initials: N
authors.lastname: Yu
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
authors.forename: Siyu
authors.initials: S
authors.lastname: Feng
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
authors.forename: Qinyouen
authors.initials: Q
authors.lastname: Fu
authors.affiliation: Division of Plastic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China. Electronic address: xjwang100@hotmail.com.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Tsinghua University, Beijing 100084, China. Electronic address: duyanan@tsinghua.edu.cn.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Du
authors.affiliation: Center of Excellence in Tissue Engineering, Institute of Basic Medical Sciences and School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China; Center of Translational Medicine Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China. Electronic address: zhaochunhua@vip.163.com.
authors.forename: Robert Chunhua
authors.initials: RC
authors.lastname: Zhao
mesh_terms: D000273:Adipose Tissue / Q000166:cytology; D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology; D015415:Biomarkers / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D059985:Cryogels / Q000737:chemistry*; D019610:Cytoprotection / Q000187:drug effects; D004195:Disease Models, Animal; D004337:Drug Carriers / Q000737:chemistry*; D005399:Fishes; D005780:Gelatin / Q000737:chemistry*; D006801:Humans; D007267:Injections; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D012867:Skin / Q000187:drug effects / Q000473:pathology*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D014945:Wound Healing / Q000187:drug effects
chemical_list: D001672:Biocompatible Materials; D015415:Biomarkers; D059985:Cryogels; D004337:Drug Carriers; D005780:Gelatin
keywords: Adipose-derived stromal/stem cells; Gelatin microcryogels; Injectable; Skin wound healing